Settings

* add healthcheck to simple failover

* update comment

* update comment

* add another test

.circleci/config.yml

@@ -4,7 +4,7 @@ version: 2.1
 setup: true
 
 orbs:
-  path-filtering: circleci/path-filtering@0.1.1
+  path-filtering: circleci/path-filtering@1.0.0
 
 workflows:
   check-updated-files:
@@ -20,6 +20,9 @@ workflows:
             proxyd/.* run-build-proxyd true
             .circleci/.* run-all true
             .github/.* run-all true
+          filters:
+            tags:
+              only: /.*/
 
           base-revision: main
           # this is the path of the configuration we should trigger once

.circleci/continue_config.yml

@@ -4,7 +4,7 @@ orbs:
   go: circleci/go@1.9.0
   gcp-cli: circleci/gcp-cli@2.4.1
   shellcheck: circleci/shellcheck@3.1.2
-  path-filtering: circleci/path-filtering@0.1.1
+  path-filtering: circleci/path-filtering@1.0.0
 
 parameters:
   run-build-op-conductor-mon:
@@ -64,6 +64,47 @@ commands:
 
 
 jobs:
+  log-config-results:
+    docker:
+      - image: us-docker.pkg.dev/oplabs-tools-artifacts/images/ci-builder:latest # only used to enable codecov.
+    environment:
+      CURRENT_TAG: << pipeline.git.tag >>
+    steps:
+      - checkout
+      - run:
+          name: Log Configuration Results
+          command: |
+            echo "Configuration Results:"
+            echo "run-build-op-conductor-mon: << pipeline.parameters.run-build-op-conductor-mon >>"
+            echo "run-build-op-ufm: << pipeline.parameters.run-build-op-ufm >>"
+            echo "run-build-proxyd: << pipeline.parameters.run-build-proxyd >>"
+            echo "run-all: << pipeline.parameters.run-all >>"
+            echo ""
+            echo "Pipeline Trigger Information:"
+            echo "pipeline.trigger_source: << pipeline.trigger_source >>"
+            echo "Is not a scheduled pipeline: $([ "<< pipeline.trigger_source >>" != "scheduled_pipeline" ] && echo "true" || echo "false")"
+            echo ""
+            echo "Tag Information:"
+            echo "Current tag: $CURRENT_TAG"
+
+            # Use the same regex patterns as defined in the YAML anchors
+            if [[ $CURRENT_TAG =~ ^proxyd/v.* ]]; then
+              echo "proxyd tag regex match: true"
+            else
+              echo "proxyd tag regex match: false"
+            fi
+
+            if [[ $CURRENT_TAG =~ ^op-conductor-mon/v.* ]]; then
+              echo "op-conductor-mon tag regex match: true"
+            else
+              echo "op-conductor-mon tag regex match: false"
+            fi
+
+            if [[ $CURRENT_TAG =~ ^op-ufm/v.* ]]; then
+              echo "op-ufm tag regex match: true"
+            else
+              echo "op-ufm tag regex match: false"
+            fi
   docker-build:
     environment:
       DOCKER_BUILDKIT: 1
@@ -206,7 +247,7 @@ jobs:
           name: Tag
           command: |
             gcloud auth configure-docker <<parameters.registry>>
-            ./ops/scripts/ci-docker-tag-op-stack-release.sh <<parameters.registry>>/<<parameters.repo>> $CIRCLE_TAG $CIRCLE_SHA1
+            ./ops/ci-tag-docker-release/ci-docker-tag-op-stack-release.sh <<parameters.registry>>/<<parameters.repo>> $CIRCLE_TAG $CIRCLE_SHA1
 
   go-lint:
     parameters:
@@ -343,6 +384,14 @@ jobs:
             ghr -t "$GITHUB_TOKEN" -u "$CIRCLE_PROJECT_USERNAME" -r "$CIRCLE_PROJECT_REPONAME" -c "$CIRCLE_SHA1" -delete "$CIRCLE_TAG" <<parameters.package_name>>/<<parameters.artifact_path>>
 
 workflows:
+  logging:
+    jobs:
+      - log-config-results:
+          filters:
+            tags:
+              only: /.*/
+            branches:
+              ignore: /.*/
   op-conductor-mon:
     when:
       or: [<< pipeline.parameters.run-build-op-conductor-mon >>, << pipeline.parameters.run-all >>]
@@ -392,10 +441,13 @@ workflows:
           docker_tags: <<pipeline.git.revision>>,<<pipeline.git.branch>>
           docker_context: .
   release:
-    when:
-      not:
-        equal: [ scheduled_pipeline, << pipeline.trigger_source >> ]
     jobs:
+      - log-config-results:
+          filters:
+            tags:
+              only: /^(proxyd|ufm-[a-z0-9\-]*|op-[a-z0-9\-]*)\/v.*/
+            branches:
+              ignore: /.*/
       - hold:
           type: approval
           filters:
@@ -408,8 +460,6 @@ workflows:
           filters:
             tags:
               only: /^op-ufm\/v.*/
-            branches:
-              ignore: /.*/
           docker_name: op-ufm
           docker_tags: <<pipeline.git.revision>>
           docker_context: .
@@ -423,17 +473,25 @@ workflows:
           docker_name: op-ufm
           docker_tags: <<pipeline.git.revision>>
           context:
-            - oplabs-gcr
+            - oplabs-gcr-release
           requires:
             - op-ufm-docker-build
-
+      - docker-tag-op-stack-release:
+          name: docker-tag-op-ufm-release
+          filters:
+            tags:
+              only: /^op-ufm\/v.*/
+            branches:
+              ignore: /.*/
+          context:
+            - oplabs-gcr-release
+          requires:
+            - op-ufm-docker-publish
       - docker-build:
           name: proxyd-docker-build
           filters:
             tags:
               only: /^proxyd\/v.*/
-            branches:
-              ignore: /.*/
           docker_name: proxyd
           docker_tags: <<pipeline.git.revision>>
           docker_context: .
@@ -447,26 +505,52 @@ workflows:
           filters:
             tags:
               only: /^proxyd\/v.*/
-            branches:
-              ignore: /.*/
           docker_name: proxyd
           docker_tags: <<pipeline.git.revision>>
           context:
             - oplabs-gcr-release
           requires:
             - proxyd-docker-build
-
+      - docker-tag-op-stack-release:
+          name: docker-tag-op-stack-release
+          filters:
+            tags:
+              only: /^proxyd\/v.*/
+            branches:
+              ignore: /.*/
+          context:
+            - oplabs-gcr-release
+          requires:
+            - proxyd-docker-release
       - docker-build:
           name: op-conductor-mon-docker-build
+          filters:
+            tags:
+              only: /^op-conductor-mon\/v.*/
           docker_file: op-conductor-mon/Dockerfile
           docker_name: op-conductor-mon
           docker_tags: <<pipeline.git.revision>>,<<pipeline.git.branch>>
           docker_context: .
+          context:
+            - oplabs-gcr-release
+          requires:
+            - hold
       - docker-publish:
           name: op-conductor-mon-docker-publish
           docker_name: op-conductor-mon
           docker_tags: <<pipeline.git.revision>>,<<pipeline.git.branch>>
           context:
-            - oplabs-gcr
+            - oplabs-gcr-release
           requires:
             - op-conductor-mon-docker-build
+      - docker-tag-op-stack-release:
+          name: docker-tag-op-stack-release
+          filters:
+            tags:
+              only: /^op-conductor-mon\/v.*/
+            branches:
+              ignore: /.*/
+          context:
+            - oplabs-gcr-release
+          requires:
+            - op-conductor-mon-docker-publish

ops/ci-tag-docker-release/ci-docker-tag-op-stack-release.sh

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+DOCKER_REPO=$1
+GIT_TAG=$2
+GIT_SHA=$3
+
+IMAGE_NAME=$(echo "$GIT_TAG" | grep -Eow '^(proxyd|ufm-[a-z0-9\-]*|op-[a-z0-9\-]*)' || true)
+if [ -z "$IMAGE_NAME" ]; then
+  echo "image name could not be parsed from git tag '$GIT_TAG'"
+  exit 1
+fi
+IMAGE_TAG=$(echo "$GIT_TAG" | grep -Eow 'v.*' || true)
+if [ -z "$IMAGE_TAG" ]; then
+  echo "image tag could not be parsed from git tag '$GIT_TAG'"
+  exit 1
+fi
+
+SOURCE_IMAGE_TAG="$DOCKER_REPO/$IMAGE_NAME:$GIT_SHA"
+TARGET_IMAGE_TAG="$DOCKER_REPO/$IMAGE_NAME:$IMAGE_TAG"
+TARGET_IMAGE_TAG_LATEST="$DOCKER_REPO/$IMAGE_NAME:latest"
+
+echo "Checking if docker images exist for '$IMAGE_NAME'"
+echo ""
+tags=$(gcloud container images list-tags "$DOCKER_REPO/$IMAGE_NAME" --limit 1 --format json)
+if [ "$tags" = "[]" ]; then
+  echo "No existing docker images were found for '$IMAGE_NAME'. The code tagged with '$GIT_TAG' may not have an associated dockerfile or docker build job."
+  echo "If this service has a dockerfile, add a docker-publish job for it in the circleci config."
+  echo ""
+  echo "Exiting"
+  exit 0
+fi
+
+echo "Tagging $SOURCE_IMAGE_TAG with '$IMAGE_TAG'"
+gcloud container images add-tag -q "$SOURCE_IMAGE_TAG" "$TARGET_IMAGE_TAG"
+
+# Do not tag with latest if the release is a release candidate.
+if [[ "$IMAGE_TAG" == *"rc"* ]]; then
+  echo "Not tagging with 'latest' because the release is a release candidate."
+  exit 0
+fi
+
+echo "Tagging $SOURCE_IMAGE_TAG with 'latest'"
+gcloud container images add-tag -q "$SOURCE_IMAGE_TAG" "$TARGET_IMAGE_TAG_LATEST"

proxyd/Makefile

@@ -20,6 +20,6 @@ lint:
 	go vet ./...
 .PHONY: test
 
-test-fallback:
+test-%:
-	go test -v ./... -test.run ^TestFallback$
+	go test -v ./... -test.run ^Test$*$$
-.PHONY: test-fallback
+.PHONY: test-%

proxyd/backend.go

@@ -160,7 +160,7 @@ type Backend struct {
 
 	latencySlidingWindow            *sw.AvgSlidingWindow
 	networkRequestsSlidingWindow    *sw.AvgSlidingWindow
-	networkErrorsSlidingWindow   *sw.AvgSlidingWindow
+	intermittentErrorsSlidingWindow *sw.AvgSlidingWindow
 
 	weight int
 }
@@ -279,6 +279,12 @@ func WithConsensusReceiptTarget(receiptsTarget string) BackendOpt {
 	}
 }
 
+func WithIntermittentNetworkErrorSlidingWindow(sw *sw.AvgSlidingWindow) BackendOpt {
+	return func(b *Backend) {
+		b.intermittentErrorsSlidingWindow = sw
+	}
+}
+
 type indexedReqRes struct {
 	index int
 	req   *RPCReq
@@ -330,7 +336,7 @@ func NewBackend(
 
 		latencySlidingWindow:            sw.NewSlidingWindow(),
 		networkRequestsSlidingWindow:    sw.NewSlidingWindow(),
-		networkErrorsSlidingWindow:   sw.NewSlidingWindow(),
+		intermittentErrorsSlidingWindow: sw.NewSlidingWindow(),
 	}
 
 	backend.Override(opts...)
@@ -366,6 +372,14 @@ func (b *Backend) Forward(ctx context.Context, reqs []*RPCReq, isBatch bool) ([]
 			),
 		)
 
+		log.Trace(
+			"forwarding request to backend",
+			"name", b.Name,
+			"req_id", GetReqID(ctx),
+			"attempt_count", i+1,
+			"max_attempts", b.maxRetries+1,
+			"method", metricLabelMethod,
+		)
 		res, err := b.doForward(ctx, reqs, isBatch)
 		switch err {
 		case nil: // do nothing
@@ -375,6 +389,7 @@ func (b *Backend) Forward(ctx context.Context, reqs []*RPCReq, isBatch bool) ([]
 				"name", b.Name,
 				"req_id", GetReqID(ctx),
 				"max", b.maxResponseSize,
+				"method", metricLabelMethod,
 			)
 			RecordBatchRPCError(ctx, b.Name, reqs, err)
 		case ErrConsensusGetReceiptsCantBeBatched:
@@ -409,6 +424,9 @@ func (b *Backend) Forward(ctx context.Context, reqs []*RPCReq, isBatch bool) ([]
 				"name", b.Name,
 				"req_id", GetReqID(ctx),
 				"err", err,
+				"method", metricLabelMethod,
+				"attempt_count", i+1,
+				"max_retries", b.maxRetries+1,
 			)
 			timer.ObserveDuration()
 			RecordBatchRPCError(ctx, b.Name, reqs, err)
@@ -534,7 +552,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 
 	httpReq, err := http.NewRequestWithContext(ctx, "POST", b.rpcURL, bytes.NewReader(body))
 	if err != nil {
-		b.networkErrorsSlidingWindow.Incr()
+		b.intermittentErrorsSlidingWindow.Incr()
 		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error creating backend request")
 	}
@@ -560,7 +578,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 	start := time.Now()
 	httpRes, err := b.client.DoLimited(httpReq)
 	if err != nil {
-		b.networkErrorsSlidingWindow.Incr()
+		b.intermittentErrorsSlidingWindow.Incr()
 		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error in backend request")
 	}
@@ -579,7 +597,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 
 	// Alchemy returns a 400 on bad JSONs, so handle that case
 	if httpRes.StatusCode != 200 && httpRes.StatusCode != 400 {
-		b.networkErrorsSlidingWindow.Incr()
+		b.intermittentErrorsSlidingWindow.Incr()
 		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, fmt.Errorf("response code %d", httpRes.StatusCode)
 	}
@@ -590,7 +608,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 		return nil, ErrBackendResponseTooLarge
 	}
 	if err != nil {
-		b.networkErrorsSlidingWindow.Incr()
+		b.intermittentErrorsSlidingWindow.Incr()
 		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error reading response body")
 	}
@@ -608,18 +626,18 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 		if err := json.Unmarshal(resB, &rpcRes); err != nil {
 			// Infura may return a single JSON-RPC response if, for example, the batch contains a request for an unsupported method
 			if responseIsNotBatched(resB) {
-				b.networkErrorsSlidingWindow.Incr()
+				b.intermittentErrorsSlidingWindow.Incr()
 				RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 				return nil, ErrBackendUnexpectedJSONRPC
 			}
-			b.networkErrorsSlidingWindow.Incr()
+			b.intermittentErrorsSlidingWindow.Incr()
 			RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 			return nil, ErrBackendBadResponse
 		}
 	}
 
 	if len(rpcReqs) != len(rpcRes) {
-		b.networkErrorsSlidingWindow.Incr()
+		b.intermittentErrorsSlidingWindow.Incr()
 		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, ErrBackendUnexpectedJSONRPC
 	}
@@ -670,7 +688,7 @@ func (b *Backend) ErrorRate() (errorRate float64) {
 	// we only really start counting the error rate after a minimum of 10 requests
 	// this is to avoid false positives when the backend is just starting up
 	if b.networkRequestsSlidingWindow.Sum() >= 10 {
-		errorRate = b.networkErrorsSlidingWindow.Sum() / b.networkRequestsSlidingWindow.Sum()
+		errorRate = b.intermittentErrorsSlidingWindow.Sum() / b.networkRequestsSlidingWindow.Sum()
 	}
 	return errorRate
 }
@@ -710,6 +728,11 @@ type BackendGroup struct {
 	WeightedRouting  bool
 	Consensus        *ConsensusPoller
 	FallbackBackends map[string]bool
+	routingStrategy  RoutingStrategy
+}
+
+func (bg *BackendGroup) GetRoutingStrategy() RoutingStrategy {
+	return bg.routingStrategy
 }
 
 func (bg *BackendGroup) Fallbacks() []*Backend {
@@ -744,113 +767,178 @@ func (bg *BackendGroup) Forward(ctx context.Context, rpcReqs []*RPCReq, isBatch
 	overriddenResponses := make([]*indexedReqRes, 0)
 	rewrittenReqs := make([]*RPCReq, 0, len(rpcReqs))
 
-	if bg.Consensus != nil {
+	// When routing_strategy is set to `consensus_aware` the backend group acts as a load balancer
-		// When `consensus_aware` is set to `true`, the backend group acts as a load balancer
 	// serving traffic from any backend that agrees in the consensus group
-
 	// We also rewrite block tags to enforce compliance with consensus
-		rctx := RewriteContext{
+	if bg.Consensus != nil {
-			latest:        bg.Consensus.GetLatestBlockNumber(),
+		rpcReqs, overriddenResponses = bg.OverwriteConsensusResponses(rpcReqs, overriddenResponses, rewrittenReqs)
-			safe:          bg.Consensus.GetSafeBlockNumber(),
-			finalized:     bg.Consensus.GetFinalizedBlockNumber(),
-			maxBlockRange: bg.Consensus.maxBlockRange,
 	}
 
-		for i, req := range rpcReqs {
+	// When routing_strategy is set to 'multicall' the request will be forward to all backends
-			res := RPCRes{JSONRPC: JSONRPCVersion, ID: req.ID}
+	// and return the first successful response
-			result, err := RewriteTags(rctx, req, &res)
+	if bg.GetRoutingStrategy() == MulticallRoutingStrategy && isValidMulticallTx(rpcReqs) && !isBatch {
-			switch result {
+		backendResp := bg.ExecuteMulticall(ctx, rpcReqs)
-			case RewriteOverrideError:
+		return backendResp.RPCRes, backendResp.ServedBy, backendResp.error
-				overriddenResponses = append(overriddenResponses, &indexedReqRes{
-					index: i,
-					req:   req,
-					res:   &res,
-				})
-				if errors.Is(err, ErrRewriteBlockOutOfRange) {
-					res.Error = ErrBlockOutOfRange
-				} else if errors.Is(err, ErrRewriteRangeTooLarge) {
-					res.Error = ErrInvalidParams(
-						fmt.Sprintf("block range greater than %d max", rctx.maxBlockRange),
-					)
-				} else {
-					res.Error = ErrParseErr
-				}
-			case RewriteOverrideResponse:
-				overriddenResponses = append(overriddenResponses, &indexedReqRes{
-					index: i,
-					req:   req,
-					res:   &res,
-				})
-			case RewriteOverrideRequest, RewriteNone:
-				rewrittenReqs = append(rewrittenReqs, req)
-			}
-		}
-		rpcReqs = rewrittenReqs
 	}
 
 	rpcRequestsTotal.Inc()
 
-	for _, back := range backends {
+	ch := make(chan BackendGroupRPCResponse)
-		res := make([]*RPCRes, 0)
+	go func() {
-		var err error
+		defer close(ch)
+		backendResp := bg.ForwardRequestToBackendGroup(rpcReqs, backends, ctx, isBatch)
+		ch <- *backendResp
+	}()
+	backendResp := <-ch
 
-		servedBy := fmt.Sprintf("%s/%s", bg.Name, back.Name)
+	if backendResp.error != nil {
-
+		log.Error("error serving requests",
-		if len(rpcReqs) > 0 {
-			res, err = back.Forward(ctx, rpcReqs, isBatch)
-			if errors.Is(err, ErrConsensusGetReceiptsCantBeBatched) ||
-				errors.Is(err, ErrConsensusGetReceiptsInvalidTarget) ||
-				errors.Is(err, ErrMethodNotWhitelisted) {
-				return nil, "", err
-			}
-			if errors.Is(err, ErrBackendResponseTooLarge) {
-				return nil, servedBy, err
-			}
-			if errors.Is(err, ErrBackendOffline) {
-				log.Warn(
-					"skipping offline backend",
-					"name", back.Name,
-					"auth", GetAuthCtx(ctx),
-					"req_id", GetReqID(ctx),
-				)
-				continue
-			}
-			if errors.Is(err, ErrBackendOverCapacity) {
-				log.Warn(
-					"skipping over-capacity backend",
-					"name", back.Name,
-					"auth", GetAuthCtx(ctx),
-					"req_id", GetReqID(ctx),
-				)
-				continue
-			}
-			if err != nil {
-				log.Error(
-					"error forwarding request to backend",
-					"name", back.Name,
 			"req_id", GetReqID(ctx),
 			"auth", GetAuthCtx(ctx),
-					"err", err,
+			"err", backendResp.error,
 		)
-				continue
+		return backendResp.RPCRes, backendResp.ServedBy, backendResp.error
-			}
 	}
 
 	// re-apply overridden responses
-		for _, ov := range overriddenResponses {
+	log.Trace("successfully served request overriding responses",
-			if len(res) > 0 {
+		"req_id", GetReqID(ctx),
-				// insert ov.res at position ov.index
+		"auth", GetAuthCtx(ctx),
-				res = append(res[:ov.index], append([]*RPCRes{ov.res}, res[ov.index:]...)...)
+	)
+	res := OverrideResponses(backendResp.RPCRes, overriddenResponses)
+	return res, backendResp.ServedBy, backendResp.error
+}
+
+func isValidMulticallTx(rpcReqs []*RPCReq) bool {
+	if len(rpcReqs) == 1 {
+		if rpcReqs[0].Method == "eth_sendRawTransaction" {
+			return true
+		}
+	}
+	return false
+}
+
+// Using special struct since servedBy may not be populated if error occurs
+type multicallTuple struct {
+	response    *BackendGroupRPCResponse
+	backendName string
+}
+
+func (bg *BackendGroup) ExecuteMulticall(ctx context.Context, rpcReqs []*RPCReq) *BackendGroupRPCResponse {
+
+	// Create ctx without cancel so background tasks process
+	// after original request returns
+	bgCtx := context.WithoutCancel(ctx)
+
+	log.Info("executing multicall routing strategy",
+		"req_id", GetReqID(bgCtx),
+		"auth", GetAuthCtx(bgCtx),
+	)
+	var wg sync.WaitGroup
+	ch := make(chan *multicallTuple, len(bg.Backends))
+	for _, backend := range bg.Backends {
+		wg.Add(1)
+		go bg.MulticallRequest(backend, rpcReqs, &wg, bgCtx, ch)
+	}
+
+	go func() {
+		wg.Wait()
+		log.Debug("closing multicall channel",
+			"req_id", GetReqID(bgCtx),
+			"auth", GetAuthCtx(bgCtx),
+		)
+		close(ch)
+	}()
+
+	return bg.ProcessMulticallResponses(ch, bgCtx)
+}
+
+func (bg *BackendGroup) MulticallRequest(backend *Backend, rpcReqs []*RPCReq, wg *sync.WaitGroup, ctx context.Context, ch chan *multicallTuple) {
+	defer wg.Done()
+	log.Debug("forwarding multicall request to backend",
+		"req_id", GetReqID(ctx),
+		"auth", GetAuthCtx(ctx),
+		"backend", backend.Name,
+	)
+
+	RecordBackendGroupMulticallRequest(bg, backend.Name)
+	backendResp := bg.ForwardRequestToBackendGroup(rpcReqs, []*Backend{backend}, ctx, false)
+
+	multicallResp := &multicallTuple{
+		response:    backendResp,
+		backendName: backend.Name,
+	}
+
+	log.Debug("placing multicall response into channel",
+		"req_id", GetReqID(ctx),
+		"auth", GetAuthCtx(ctx),
+		"backend", backend.Name,
+	)
+
+	ch <- multicallResp
+
+	log.Trace("placed multicall response into channel",
+		"req_id", GetReqID(ctx),
+		"auth", GetAuthCtx(ctx),
+		"backend", backend.Name,
+	)
+
+	if backendResp.error != nil {
+		log.Error("received multicall error response from backend",
+			"req_id", GetReqID(ctx),
+			"auth", GetAuthCtx(ctx),
+			"backend", backend.Name,
+			"error", backendResp.error.Error(),
+		)
+		RecordBackendGroupMulticallCompletion(bg, backend.Name, backendResp.error.Error())
 	} else {
-				res = append(res, ov.res)
+		RecordBackendGroupMulticallCompletion(bg, backend.Name, "nil")
 	}
 }
 
-		return res, servedBy, nil
+func (bg *BackendGroup) ProcessMulticallResponses(ch chan *multicallTuple, ctx context.Context) *BackendGroupRPCResponse {
+	var finalResp *BackendGroupRPCResponse
+	i := 0
+	for {
+		multicallResp, ok := <-ch
+		if !ok {
+			log.Trace("multicall response channel closed",
+				"req_id", GetReqID(ctx),
+				"auth", GetAuthCtx(ctx),
+				"response_count", i,
+			)
+			if i > 0 {
+				return finalResp
+			}
+			return &BackendGroupRPCResponse{
+				RPCRes:   nil,
+				ServedBy: "",
+				error:    errors.New("no multicall response received"),
+			}
 		}
 
-	RecordUnserviceableRequest(ctx, RPCRequestSourceHTTP)
+		i++
-	return nil, "", ErrNoBackends
+		resp := multicallResp.response
+		backendName := multicallResp.backendName
+
+		if resp.error != nil {
+			log.Error("received error response from multicall channel",
+				"req_id", GetReqID(ctx),
+				"auth", GetAuthCtx(ctx),
+				"err", resp.error,
+				"backend", backendName,
+			)
+			finalResp = resp
+			continue
+		}
+		log.Info("received successful response from multicall channel",
+			"req_id", GetReqID(ctx),
+			"auth", GetAuthCtx(ctx),
+			"served_by", resp.ServedBy,
+			"backend", backendName,
+		)
+		return resp
+	}
 }
 
 func (bg *BackendGroup) ProxyWS(ctx context.Context, clientConn *websocket.Conn, methodWhitelist *StringSet) (*WSProxier, error) {
@@ -901,13 +989,21 @@ func weightedShuffle(backends []*Backend) {
 func (bg *BackendGroup) orderedBackendsForRequest() []*Backend {
 	if bg.Consensus != nil {
 		return bg.loadBalancedConsensusGroup()
-	} else if bg.WeightedRouting {
-		result := make([]*Backend, len(bg.Backends))
-		copy(result, bg.Backends)
-		weightedShuffle(result)
-		return result
 	} else {
-		return bg.Backends
+		healthy := make([]*Backend, 0, len(bg.Backends))
+		unhealthy := make([]*Backend, 0, len(bg.Backends))
+		for _, be := range bg.Backends {
+			if be.IsHealthy() {
+				healthy = append(healthy, be)
+			} else {
+				unhealthy = append(unhealthy, be)
+			}
+		}
+		if bg.WeightedRouting {
+			weightedShuffle(healthy)
+			weightedShuffle(unhealthy)
+		}
+		return append(healthy, unhealthy...)
 	}
 }
 
@@ -1232,7 +1328,7 @@ func RecordBatchRPCError(ctx context.Context, backendName string, reqs []*RPCReq
 }
 
 func MaybeRecordErrorsInRPCRes(ctx context.Context, backendName string, reqs []*RPCReq, resBatch []*RPCRes) {
-	log.Info("forwarded RPC request",
+	log.Debug("forwarded RPC request",
 		"backend", backendName,
 		"auth", GetAuthCtx(ctx),
 		"req_id", GetReqID(ctx),
@@ -1266,7 +1362,148 @@ func RecordBatchRPCForward(ctx context.Context, backendName string, reqs []*RPCR
 	}
 }
 
+func (b *Backend) ClearSlidingWindows() {
+	b.intermittentErrorsSlidingWindow.Clear()
+	b.networkRequestsSlidingWindow.Clear()
+}
+
 func stripXFF(xff string) string {
 	ipList := strings.Split(xff, ",")
 	return strings.TrimSpace(ipList[0])
 }
+
+type BackendGroupRPCResponse struct {
+	RPCRes   []*RPCRes
+	ServedBy string
+	error    error
+}
+
+func (bg *BackendGroup) ForwardRequestToBackendGroup(
+	rpcReqs []*RPCReq,
+	backends []*Backend,
+	ctx context.Context,
+	isBatch bool,
+) *BackendGroupRPCResponse {
+	for _, back := range backends {
+		res := make([]*RPCRes, 0)
+		var err error
+
+		servedBy := fmt.Sprintf("%s/%s", bg.Name, back.Name)
+
+		if len(rpcReqs) > 0 {
+
+			res, err = back.Forward(ctx, rpcReqs, isBatch)
+
+			if errors.Is(err, ErrConsensusGetReceiptsCantBeBatched) ||
+				errors.Is(err, ErrConsensusGetReceiptsInvalidTarget) ||
+				errors.Is(err, ErrMethodNotWhitelisted) {
+				return &BackendGroupRPCResponse{
+					RPCRes:   nil,
+					ServedBy: "",
+					error:    err,
+				}
+			}
+			if errors.Is(err, ErrBackendResponseTooLarge) {
+				return &BackendGroupRPCResponse{
+					RPCRes:   nil,
+					ServedBy: "",
+					error:    err,
+				}
+			}
+			if errors.Is(err, ErrBackendOffline) {
+				log.Warn(
+					"skipping offline backend",
+					"name", back.Name,
+					"auth", GetAuthCtx(ctx),
+					"req_id", GetReqID(ctx),
+				)
+				continue
+			}
+			if errors.Is(err, ErrBackendOverCapacity) {
+				log.Warn(
+					"skipping over-capacity backend",
+					"name", back.Name,
+					"auth", GetAuthCtx(ctx),
+					"req_id", GetReqID(ctx),
+				)
+				continue
+			}
+			if err != nil {
+				log.Error(
+					"error forwarding request to backend",
+					"name", back.Name,
+					"req_id", GetReqID(ctx),
+					"auth", GetAuthCtx(ctx),
+					"err", err,
+				)
+				continue
+			}
+		}
+
+		return &BackendGroupRPCResponse{
+			RPCRes:   res,
+			ServedBy: servedBy,
+			error:    nil,
+		}
+	}
+
+	RecordUnserviceableRequest(ctx, RPCRequestSourceHTTP)
+	return &BackendGroupRPCResponse{
+		RPCRes:   nil,
+		ServedBy: "",
+		error:    ErrNoBackends,
+	}
+
+}
+
+func OverrideResponses(res []*RPCRes, overriddenResponses []*indexedReqRes) []*RPCRes {
+	for _, ov := range overriddenResponses {
+		if len(res) > 0 {
+			// insert ov.res at position ov.index
+			res = append(res[:ov.index], append([]*RPCRes{ov.res}, res[ov.index:]...)...)
+		} else {
+			res = append(res, ov.res)
+		}
+	}
+	return res
+}
+
+func (bg *BackendGroup) OverwriteConsensusResponses(rpcReqs []*RPCReq, overriddenResponses []*indexedReqRes, rewrittenReqs []*RPCReq) ([]*RPCReq, []*indexedReqRes) {
+	rctx := RewriteContext{
+		latest:        bg.Consensus.GetLatestBlockNumber(),
+		safe:          bg.Consensus.GetSafeBlockNumber(),
+		finalized:     bg.Consensus.GetFinalizedBlockNumber(),
+		maxBlockRange: bg.Consensus.maxBlockRange,
+	}
+
+	for i, req := range rpcReqs {
+		res := RPCRes{JSONRPC: JSONRPCVersion, ID: req.ID}
+		result, err := RewriteTags(rctx, req, &res)
+		switch result {
+		case RewriteOverrideError:
+			overriddenResponses = append(overriddenResponses, &indexedReqRes{
+				index: i,
+				req:   req,
+				res:   &res,
+			})
+			if errors.Is(err, ErrRewriteBlockOutOfRange) {
+				res.Error = ErrBlockOutOfRange
+			} else if errors.Is(err, ErrRewriteRangeTooLarge) {
+				res.Error = ErrInvalidParams(
+					fmt.Sprintf("block range greater than %d max", rctx.maxBlockRange),
+				)
+			} else {
+				res.Error = ErrParseErr
+			}
+		case RewriteOverrideResponse:
+			overriddenResponses = append(overriddenResponses, &indexedReqRes{
+				index: i,
+				req:   req,
+				res:   &res,
+			})
+		case RewriteOverrideRequest, RewriteNone:
+			rewrittenReqs = append(rewrittenReqs, req)
+		}
+	}
+	return rewrittenReqs, overriddenResponses
+}

proxyd/config.go

@@ -6,6 +6,8 @@ import (
 	"os"
 	"strings"
 	"time"
+
+	"github.com/ethereum/go-ethereum/log"
 )
 
 type ServerConfig struct {
@@ -111,11 +113,54 @@ type BackendConfig struct {
 
 type BackendsConfig map[string]*BackendConfig
 
+type RoutingStrategy string
+
+func (b *BackendGroupConfig) ValidateRoutingStrategy(bgName string) bool {
+
+	// If Consensus Aware is Set and Routing RoutingStrategy is populated fail
+	if b.ConsensusAware && b.RoutingStrategy != "" {
+		log.Warn("consensus_aware is now deprecated, please use routing_strategy = consensus_aware")
+		log.Crit("Exiting consensus_aware and routing strategy are mutually exclusive, they cannot both be defined")
+	}
+
+	// If Consensus Aware is Set set RoutingStrategy to consensus_aware
+	if b.ConsensusAware {
+		b.RoutingStrategy = ConsensusAwareRoutingStrategy
+		log.Info("consensus_aware is now deprecated, please use routing_strategy = consenus_aware in the future")
+	}
+
+	switch b.RoutingStrategy {
+	case ConsensusAwareRoutingStrategy:
+		return true
+	case MulticallRoutingStrategy:
+		return true
+	case FallbackRoutingStrategy:
+		return true
+	case "":
+		log.Info("Empty routing strategy provided for backend_group, using fallback strategy ", "name", bgName)
+		b.RoutingStrategy = FallbackRoutingStrategy
+		return true
+	default:
+		return false
+	}
+}
+
+const (
+	ConsensusAwareRoutingStrategy RoutingStrategy = "consensus_aware"
+	MulticallRoutingStrategy      RoutingStrategy = "multicall"
+	FallbackRoutingStrategy       RoutingStrategy = "fallback"
+)
+
 type BackendGroupConfig struct {
 	Backends []string `toml:"backends"`
 
 	WeightedRouting bool `toml:"weighted_routing"`
 
+	RoutingStrategy RoutingStrategy `toml:"routing_strategy"`
+
+	/*
+		Deprecated: Use routing_strategy config to create a consensus_aware proxyd instance
+	*/
 	ConsensusAware          bool         `toml:"consensus_aware"`
 	ConsensusAsyncHandler   string       `toml:"consensus_handler"`
 	ConsensusPollerInterval TOMLDuration `toml:"consensus_poller_interval"`

proxyd/consensus_poller.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common/hexutil"
-
 	"github.com/ethereum/go-ethereum/log"
 )
 
@@ -63,6 +62,24 @@ func (bs *backendState) IsBanned() bool {
 	return time.Now().Before(bs.bannedUntil)
 }
 
+func (bs *backendState) GetLatestBlock() (hexutil.Uint64, string) {
+	bs.backendStateMux.Lock()
+	defer bs.backendStateMux.Unlock()
+	return bs.latestBlockNumber, bs.latestBlockHash
+}
+
+func (bs *backendState) GetSafeBlockNumber() hexutil.Uint64 {
+	bs.backendStateMux.Lock()
+	defer bs.backendStateMux.Unlock()
+	return bs.safeBlockNumber
+}
+
+func (bs *backendState) GetFinalizedBlockNumber() hexutil.Uint64 {
+	bs.backendStateMux.Lock()
+	defer bs.backendStateMux.Unlock()
+	return bs.finalizedBlockNumber
+}
+
 // GetConsensusGroup returns the backend members that are agreeing in a consensus
 func (cp *ConsensusPoller) GetConsensusGroup() []*Backend {
 	defer cp.consensusGroupMux.Unlock()
@@ -287,7 +304,7 @@ func NewConsensusPoller(bg *BackendGroup, opts ...ConsensusOpt) *ConsensusPoller
 
 // UpdateBackend refreshes the consensus state of a single backend
 func (cp *ConsensusPoller) UpdateBackend(ctx context.Context, be *Backend) {
-	bs := cp.getBackendState(be)
+	bs := cp.GetBackendState(be)
 	RecordConsensusBackendBanned(be, bs.IsBanned())
 
 	if bs.IsBanned() {
@@ -306,6 +323,7 @@ func (cp *ConsensusPoller) UpdateBackend(ctx context.Context, be *Backend) {
 	RecordConsensusBackendInSync(be, err == nil && inSync)
 	if err != nil {
 		log.Warn("error updating backend sync state", "name", be.Name, "err", err)
+		return
 	}
 
 	var peerCount uint64
@@ -313,23 +331,49 @@ func (cp *ConsensusPoller) UpdateBackend(ctx context.Context, be *Backend) {
 		peerCount, err = cp.getPeerCount(ctx, be)
 		if err != nil {
 			log.Warn("error updating backend peer count", "name", be.Name, "err", err)
+			return
+		}
+		if peerCount == 0 {
+			log.Warn("peer count responded with 200 and 0 peers", "name", be.Name)
+			be.intermittentErrorsSlidingWindow.Incr()
+			return
 		}
 		RecordConsensusBackendPeerCount(be, peerCount)
 	}
 
 	latestBlockNumber, latestBlockHash, err := cp.fetchBlock(ctx, be, "latest")
 	if err != nil {
-		log.Warn("error updating backend - latest block", "name", be.Name, "err", err)
+		log.Warn("error updating backend - latest block will not be updated", "name", be.Name, "err", err)
+		return
+	}
+	if latestBlockNumber == 0 {
+		log.Warn("error backend responded a 200 with blockheight 0 for latest block", "name", be.Name)
+		be.intermittentErrorsSlidingWindow.Incr()
+		return
 	}
 
 	safeBlockNumber, _, err := cp.fetchBlock(ctx, be, "safe")
 	if err != nil {
-		log.Warn("error updating backend - safe block", "name", be.Name, "err", err)
+		log.Warn("error updating backend - safe block will not be updated", "name", be.Name, "err", err)
+		return
+	}
+
+	if safeBlockNumber == 0 {
+		log.Warn("error backend responded a 200 with blockheight 0 for safe block", "name", be.Name)
+		be.intermittentErrorsSlidingWindow.Incr()
+		return
 	}
 
 	finalizedBlockNumber, _, err := cp.fetchBlock(ctx, be, "finalized")
 	if err != nil {
-		log.Warn("error updating backend - finalized block", "name", be.Name, "err", err)
+		log.Warn("error updating backend - finalized block will not be updated", "name", be.Name, "err", err)
+		return
+	}
+
+	if finalizedBlockNumber == 0 {
+		log.Warn("error backend responded a 200 with blockheight 0 for finalized block", "name", be.Name)
+		be.intermittentErrorsSlidingWindow.Incr()
+		return
 	}
 
 	RecordConsensusBackendUpdateDelay(be, bs.lastUpdate)
@@ -523,6 +567,14 @@ func (cp *ConsensusPoller) IsBanned(be *Backend) bool {
 	return bs.IsBanned()
 }
 
+// IsBanned checks if a specific backend is banned
+func (cp *ConsensusPoller) BannedUntil(be *Backend) time.Time {
+	bs := cp.backendState[be]
+	defer bs.backendStateMux.Unlock()
+	bs.backendStateMux.Lock()
+	return bs.bannedUntil
+}
+
 // Ban bans a specific backend
 func (cp *ConsensusPoller) Ban(be *Backend) {
 	if be.forcedCandidate {
@@ -618,8 +670,8 @@ func (cp *ConsensusPoller) isInSync(ctx context.Context, be *Backend) (result bo
 	return res, nil
 }
 
-// getBackendState creates a copy of backend state so that the caller can use it without locking
+// GetBackendState creates a copy of backend state so that the caller can use it without locking
-func (cp *ConsensusPoller) getBackendState(be *Backend) *backendState {
+func (cp *ConsensusPoller) GetBackendState(be *Backend) *backendState {
 	bs := cp.backendState[be]
 	defer bs.backendStateMux.Unlock()
 	bs.backendStateMux.Lock()
@@ -691,7 +743,7 @@ func (cp *ConsensusPoller) FilterCandidates(backends []*Backend) map[*Backend]*b
 
 	for _, be := range backends {
 
-		bs := cp.getBackendState(be)
+		bs := cp.GetBackendState(be)
 		if be.forcedCandidate {
 			candidates[be] = bs
 			continue

proxyd/integration_tests/block_height_zero_and_network_errors_test.go

@@ -0,0 +1,353 @@
+package integration_tests
+
+import (
+	"context"
+	"net/http"
+	"os"
+	"path"
+	"testing"
+
+	"time"
+
+	"github.com/ethereum-optimism/optimism/proxyd"
+	sw "github.com/ethereum-optimism/optimism/proxyd/pkg/avg-sliding-window"
+	ms "github.com/ethereum-optimism/optimism/proxyd/tools/mockserver/handler"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/stretchr/testify/require"
+)
+
+type bhZeroNodeContext struct {
+	backend                    *proxyd.Backend   // this is the actual backend impl in proxyd
+	mockBackend                *MockBackend      // this is the fake backend that we can use to mock responses
+	handler                    *ms.MockedHandler // this is where we control the state of mocked responses
+	intermittentNetErrorWindow *sw.AvgSlidingWindow
+	clock                      *sw.AdjustableClock // this is where we control backend time
+}
+
+// ts is a convenient method that must parse a time.Time from a string in format `"2006-01-02 15:04:05"`
+func ts(s string) time.Time {
+	t, err := time.Parse(time.DateTime, s)
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+func setupBlockHeightZero(t *testing.T) (map[string]*bhZeroNodeContext, *proxyd.BackendGroup, *ProxydHTTPClient, func()) {
+	// setup mock servers
+	node1 := NewMockBackend(nil)
+	node2 := NewMockBackend(nil)
+
+	dir, err := os.Getwd()
+	require.NoError(t, err)
+
+	responses := path.Join(dir, "testdata/block_height_zero_and_network_errors_responses.yaml")
+
+	h1 := ms.MockedHandler{
+		Overrides:    []*ms.MethodTemplate{},
+		Autoload:     true,
+		AutoloadFile: responses,
+	}
+	h2 := ms.MockedHandler{
+		Overrides:    []*ms.MethodTemplate{},
+		Autoload:     true,
+		AutoloadFile: responses,
+	}
+
+	require.NoError(t, os.Setenv("NODE1_URL", node1.URL()))
+	require.NoError(t, os.Setenv("NODE2_URL", node2.URL()))
+
+	node1.SetHandler(http.HandlerFunc(h1.Handler))
+	node2.SetHandler(http.HandlerFunc(h2.Handler))
+
+	// setup proxyd
+	config := ReadConfig("block_height_zero_and_network_errors")
+	svr, shutdown, err := proxyd.Start(config)
+	require.NoError(t, err)
+
+	// expose the proxyd client
+	client := NewProxydClient("http://127.0.0.1:8545")
+
+	// expose the backend group
+	bg := svr.BackendGroups["node"]
+
+	require.NotNil(t, bg)
+	require.NotNil(t, bg.Consensus, "Expected Consenus Poller to be intialized")
+	require.Equal(t, 2, len(bg.Backends))
+
+	// convenient mapping to access the nodes
+	nodes := map[string]*bhZeroNodeContext{
+		"node1": {
+			mockBackend: node1,
+			backend:     bg.Backends[0],
+			handler:     &h1,
+		},
+		"node2": {
+			mockBackend: node2,
+			backend:     bg.Backends[1],
+			handler:     &h2,
+		},
+	}
+
+	return nodes, bg, client, shutdown
+}
+
+func TestBlockHeightZero(t *testing.T) {
+	nodes, bg, _, shutdown := setupBlockHeightZero(t)
+	defer nodes["node1"].mockBackend.Close()
+	defer nodes["node2"].mockBackend.Close()
+	defer shutdown()
+
+	ctx := context.Background()
+
+	addTimeToBackend := func(node string, ts time.Duration) {
+		mockBackend, ok := nodes[node]
+		require.True(t, ok, "Fatal error bad node key for override clock")
+		mockBackend.clock.Set(mockBackend.clock.Now().Add(ts))
+	}
+
+	// poll for updated consensus
+	update := func() {
+		for _, be := range bg.Backends {
+			bg.Consensus.UpdateBackend(ctx, be)
+		}
+		bg.Consensus.UpdateBackendGroupConsensus(ctx)
+		addTimeToBackend("node1", 3*time.Second)
+		addTimeToBackend("node2", 3*time.Second)
+	}
+
+	// convenient methods to manipulate state and mock responses
+	reset := func() {
+		for _, node := range nodes {
+			node.handler.ResetOverrides()
+			node.mockBackend.Reset()
+			node.backend.ClearSlidingWindows()
+		}
+		bg.Consensus.ClearListeners()
+		bg.Consensus.Reset()
+
+		require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+		now := ts("2023-04-21 15:00:00")
+		clock := sw.NewAdjustableClock(now)
+		b1 := nodes["node1"]
+		b2 := nodes["node2"]
+		b1.intermittentNetErrorWindow = sw.NewSlidingWindow(
+			sw.WithWindowLength(5*time.Minute),
+			sw.WithBucketSize(time.Second),
+			sw.WithClock(clock))
+
+		b2.intermittentNetErrorWindow = sw.NewSlidingWindow(
+			sw.WithWindowLength(5*time.Minute),
+			sw.WithBucketSize(time.Second),
+			sw.WithClock(clock))
+
+		b1.clock = clock
+		b2.clock = clock
+		b1.backend.Override(proxyd.WithIntermittentNetworkErrorSlidingWindow(b1.intermittentNetErrorWindow))
+		b2.backend.Override(proxyd.WithIntermittentNetworkErrorSlidingWindow(b2.intermittentNetErrorWindow))
+		nodes["node1"] = b1
+		nodes["node2"] = b2
+
+		require.Zero(t, nodes["node1"].intermittentNetErrorWindow.Count())
+		require.Zero(t, nodes["node2"].intermittentNetErrorWindow.Count())
+
+	}
+
+	override := func(node string, method string, block string, response string, responseCode int) {
+		if _, ok := nodes[node]; !ok {
+			t.Fatalf("node %s does not exist in the nodes map", node)
+		}
+		nodes[node].handler.AddOverride(&ms.MethodTemplate{
+			Method:       method,
+			Block:        block,
+			Response:     response,
+			ResponseCode: responseCode,
+		})
+	}
+
+	overrideBlock := func(node string, blockRequest string, blockResponse string, responseCode int) {
+		override(node,
+			"eth_getBlockByNumber",
+			blockRequest,
+			buildResponse(map[string]string{
+				"number": blockResponse,
+				"hash":   "hash_" + blockResponse,
+			}),
+			responseCode,
+		)
+	}
+
+	overridePeerCount := func(node string, count int, responseCode int) {
+		override(node, "net_peerCount", "", buildResponse(hexutil.Uint64(count).String()), responseCode)
+	}
+
+	type blockHeights struct {
+		latestBlockNumber    hexutil.Uint64
+		latestBlockHash      string
+		safeBlockNumber      hexutil.Uint64
+		finalizedBlockNumber hexutil.Uint64
+	}
+
+	getBlockHeights := func(node string) blockHeights {
+		bs := bg.Consensus.GetBackendState(nodes[node].backend)
+		lB, lHash := bs.GetLatestBlock()
+		sB := bs.GetSafeBlockNumber()
+		fB := bs.GetFinalizedBlockNumber()
+		return blockHeights{
+			latestBlockNumber:    lB,
+			latestBlockHash:      lHash,
+			safeBlockNumber:      sB,
+			finalizedBlockNumber: fB,
+		}
+	}
+
+	for _, blockState := range []string{"latest", "finalized", "safe"} {
+
+		t.Run("Test that the backend will not be banned if "+blockState+" responds 429", func(t *testing.T) {
+			reset()
+			update()
+			bh1 := getBlockHeights("node1")
+			overrideBlock("node1", blockState, "0x101", 429)
+			update()
+			bh2 := getBlockHeights("node1")
+			require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+			require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+			require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+			require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+			require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+			require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(1))
+			require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+		})
+
+		// Write  a test which will check the sliding window increments each time by one
+		t.Run("Test that the backend will not be banned and single increment of window if "+blockState+" responds 500", func(t *testing.T) {
+			reset()
+			update()
+			bh1 := getBlockHeights("node1")
+			overrideBlock("node1", blockState, "0x101", 500)
+			update()
+			bh2 := getBlockHeights("node1")
+			require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+			require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+			require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+			require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+			require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+			require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(1))
+			require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+		})
+
+		t.Run("Test that the backend will not be banned and single increment of window if "+blockState+" responds 0 and 200", func(t *testing.T) {
+			reset()
+			update()
+			bh1 := getBlockHeights("node2")
+			overrideBlock("node2", blockState, "0x0", 200)
+			update()
+			bh2 := getBlockHeights("node2")
+			require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+			require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+			require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+			require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+			require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+			require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(0))
+			require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(1))
+		})
+
+	}
+
+	t.Run("Test that the backend will not be banned and single increment of window if latest responds 200 with block height zero", func(t *testing.T) {
+		reset()
+		update()
+		overrideBlock("node1", "latest", "0x0", 200)
+		bh1 := getBlockHeights("node1")
+		update()
+		bh2 := getBlockHeights("node1")
+		require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+		require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+		require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+		require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+		require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(1))
+		require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+	})
+
+	t.Run("Test that the backend will not be banned if latest responds 5xx for peer count", func(t *testing.T) {
+		reset()
+		update()
+		overridePeerCount("node2", 59, 500)
+		bh1 := getBlockHeights("node2")
+		update()
+		bh2 := getBlockHeights("node2")
+		require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+		require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+		require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+		require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+
+		require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(0))
+		require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(1))
+	})
+
+	t.Run("Test that the backend will not be banned if latest responds 4xx for peer count", func(t *testing.T) {
+		reset()
+		update()
+		overridePeerCount("node1", 59, 429)
+		bh1 := getBlockHeights("node1")
+		update()
+		bh2 := getBlockHeights("node1")
+		require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+		require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+		require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+		require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+
+		require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(1))
+		require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+	})
+
+	t.Run("Test that the backend will not be banned if latest responds 200 and 0 for peer count", func(t *testing.T) {
+		reset()
+		update()
+		bh1 := getBlockHeights("node1")
+		overridePeerCount("node1", 0, 200)
+		update()
+		bh2 := getBlockHeights("node1")
+		require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+
+		require.Equal(t, bh1.latestBlockNumber.String(), bh2.latestBlockNumber.String())
+		require.Equal(t, bh1.safeBlockNumber.String(), bh2.safeBlockNumber.String())
+		require.Equal(t, bh1.finalizedBlockNumber.String(), bh2.finalizedBlockNumber.String())
+
+		require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(1))
+		require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+	})
+
+	t.Run("Test that if it breaches the network error threshold the node will be banned", func(t *testing.T) {
+		reset()
+		update()
+		overrideBlock("node1", "latest", "0x0", 500)
+		overrideBlock("node1", "safe", "0x0", 429)
+		overrideBlock("node1", "finalized", "0x0", 403)
+		overridePeerCount("node1", 0, 500)
+
+		for i := 1; i < 7; i++ {
+			require.False(t, bg.Consensus.IsBanned(nodes["node1"].backend), "Execpted node 1 to be not banned on iteration ", i)
+			require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend), "Execpted node 2 to be not banned on iteration ", i)
+			update()
+			// On the 5th update (i=6), node 1 will be banned due to error rate and not increment window
+			if i < 6 {
+				require.Equal(t, nodes["node1"].intermittentNetErrorWindow.Count(), uint(i))
+			}
+			require.Equal(t, nodes["node2"].intermittentNetErrorWindow.Count(), uint(0))
+		}
+		require.True(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.False(t, bg.Consensus.IsBanned(nodes["node2"].backend))
+	})
+
+}

proxyd/integration_tests/consensus_test.go

@@ -102,9 +102,11 @@ func TestConsensus(t *testing.T) {
 		for _, node := range nodes {
 			node.handler.ResetOverrides()
 			node.mockBackend.Reset()
+			node.backend.ClearSlidingWindows()
 		}
 		bg.Consensus.ClearListeners()
 		bg.Consensus.Reset()
+
 	}
 
 	override := func(node string, method string, block string, response string) {
@@ -311,7 +313,11 @@ func TestConsensus(t *testing.T) {
 
 		consensusGroup := bg.Consensus.GetConsensusGroup()
 		require.NotContains(t, consensusGroup, nodes["node1"].backend)
-		require.True(t, bg.Consensus.IsBanned(nodes["node1"].backend))
+		require.True(t, bg.Consensus.IsBanned(nodes["node1"].backend),
+			fmt.Sprintf("Expected Node to be banned. \n\tCurrent Time: %s \n\tBanned Until: %s",
+				time.Now().Format("01-02-2006 15:04:05"),
+				bg.Consensus.BannedUntil(nodes["node1"].backend).Format("01-02-2006 15:04:05")),
+		)
 		require.Equal(t, 0, len(consensusGroup))
 	})
 

proxyd/integration_tests/failover_test.go

@@ -87,6 +87,52 @@ func TestFailover(t *testing.T) {
 		})
 	}
 
+	// the bad endpoint has had 10 requests with 8 error (3xx/4xx/5xx) responses, it should be marked as unhealthy and deprioritized
+	t.Run("bad endpoint marked as unhealthy", func(t *testing.T) {
+		res, statusCode, err := client.SendRPC("eth_chainId", nil)
+		require.NoError(t, err)
+		require.Equal(t, 200, statusCode)
+		RequireEqualJSON(t, []byte(goodResponse), res)
+		require.Equal(t, 1, len(goodBackend.Requests()))
+		require.Equal(t, 0, len(badBackend.Requests())) // bad backend is not called anymore
+		goodBackend.Reset()
+		badBackend.Reset()
+	})
+
+	t.Run("bad endpoint is still called if good endpoint also went bad", func(t *testing.T) {
+		goodBackend.SetHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			time.Sleep(2 * time.Second)
+			_, _ = w.Write([]byte("[{}]"))
+		}))
+		badBackend.SetHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(503)
+			_, _ = w.Write([]byte(unexpectedResponse))
+		}))
+		res, statusCode, _ := client.SendRPC("eth_chainId", nil)
+		require.Equal(t, 503, statusCode)
+		RequireEqualJSON(t, []byte(noBackendsResponse), res) // return no backend available since both failed
+		require.Equal(t, 1, len(goodBackend.Requests()))
+		require.Equal(t, 1, len(badBackend.Requests())) // bad backend is still called
+		goodBackend.Reset()
+		badBackend.Reset()
+	})
+}
+
+func TestFailoverMore(t *testing.T) {
+	goodBackend := NewMockBackend(BatchedResponseHandler(200, goodResponse))
+	defer goodBackend.Close()
+	badBackend := NewMockBackend(nil)
+	defer badBackend.Close()
+
+	require.NoError(t, os.Setenv("GOOD_BACKEND_RPC_URL", goodBackend.URL()))
+	require.NoError(t, os.Setenv("BAD_BACKEND_RPC_URL", badBackend.URL()))
+
+	config := ReadConfig("failover")
+	client := NewProxydClient("http://127.0.0.1:8545")
+	_, shutdown, err := proxyd.Start(config)
+	require.NoError(t, err)
+	defer shutdown()
+
 	t.Run("backend times out and falls back to another", func(t *testing.T) {
 		badBackend.SetHandler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			time.Sleep(2 * time.Second)

proxyd/integration_tests/fallback_test.go

@@ -182,7 +182,7 @@ func TestFallback(t *testing.T) {
 		Fallback will be returned subsequent update
 	*/
 	triggerFirstNormalFailure := func() {
-		overridePeerCount("normal", 0)
+		overridePeerCount("normal", 1)
 		update()
 		require.True(t, containsNode(bg.Consensus.GetConsensusGroup(), "fallback"))
 		require.False(t, containsNode(bg.Consensus.GetConsensusGroup(), "normal"))

proxyd/integration_tests/multicall_test.go

@@ -0,0 +1,500 @@
+package integration_tests
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/ethereum-optimism/optimism/proxyd"
+	ms "github.com/ethereum-optimism/optimism/proxyd/tools/mockserver/handler"
+	"github.com/stretchr/testify/require"
+)
+
+const nonceErrorResponse = `{"jsonrpc": "2.0","error": {"code": -32000, "message": "nonce too low"},"id": 1}`
+const txAccepted = `{"jsonrpc": "2.0","result": "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef","id": 1}`
+
+func setupMulticall(t *testing.T) (map[string]nodeContext, *proxyd.BackendGroup, *ProxydHTTPClient, func(), *proxyd.Server, []*ms.MockedHandler) {
+	// setup mock servers
+	node1 := NewMockBackend(nil)
+	node2 := NewMockBackend(nil)
+	node3 := NewMockBackend(nil)
+
+	dir, err := os.Getwd()
+	require.NoError(t, err)
+
+	responses := path.Join(dir, "testdata/multicall_responses.yml")
+	emptyResponses := path.Join(dir, "testdata/empty_responses.yml")
+
+	h1 := ms.MockedHandler{
+		Overrides:    []*ms.MethodTemplate{},
+		Autoload:     true,
+		AutoloadFile: responses,
+	}
+	h2 := ms.MockedHandler{
+		Overrides:    []*ms.MethodTemplate{},
+		Autoload:     true,
+		AutoloadFile: "",
+	}
+	h3 := ms.MockedHandler{
+		Overrides:    []*ms.MethodTemplate{},
+		Autoload:     true,
+		AutoloadFile: emptyResponses,
+	}
+
+	require.NoError(t, os.Setenv("NODE1_URL", node1.URL()))
+	require.NoError(t, os.Setenv("NODE2_URL", node2.URL()))
+	require.NoError(t, os.Setenv("NODE3_URL", node3.URL()))
+
+	node1.SetHandler(http.HandlerFunc(h1.Handler))
+	node2.SetHandler(SingleResponseHandler(200, txAccepted))
+	node3.SetHandler(SingleResponseHandler(429, dummyRes))
+
+	// setup proxyd
+	config := ReadConfig("multicall")
+	fmt.Printf("[SetupMulticall] Using Timeout of %d \n", config.Server.TimeoutSeconds)
+	svr, shutdown, err := proxyd.Start(config)
+	require.NoError(t, err)
+
+	// expose the proxyd client
+	client := NewProxydClient("http://127.0.0.1:8545")
+
+	// expose the backend group
+	bg := svr.BackendGroups["node"]
+	require.NotNil(t, bg)
+	require.Nil(t, bg.Consensus, "Expeceted consensus not to be initialized")
+	require.Equal(t, 3, len(bg.Backends))
+	require.Equal(t, bg.GetRoutingStrategy(), proxyd.MulticallRoutingStrategy)
+
+	// convenient mapping to access the nodes by name
+	nodes := map[string]nodeContext{
+		"node1": {
+			mockBackend: node1,
+			backend:     bg.Backends[0],
+			handler:     &h1,
+		},
+		"node2": {
+			mockBackend: node2,
+			backend:     bg.Backends[1],
+			handler:     &h2,
+		},
+		"node3": {
+			mockBackend: node3,
+			backend:     bg.Backends[2],
+			handler:     &h3,
+		},
+	}
+
+	handlers := []*ms.MockedHandler{&h1, &h2, &h3}
+
+	nodes["node1"].mockBackend.SetHandler(SingleResponseHandler(200, txAccepted))
+	nodes["node2"].mockBackend.SetHandler(http.HandlerFunc(handlers[1].Handler))
+	//Node 3 has no handler empty handler never respondes should always context timeout
+	nodes["node3"].mockBackend.SetHandler(http.HandlerFunc(handlers[2].Handler))
+
+	require.Equal(t, 0, nodeBackendRequestCount(nodes, "node1"))
+	require.Equal(t, 0, nodeBackendRequestCount(nodes, "node2"))
+	require.Equal(t, 0, nodeBackendRequestCount(nodes, "node3"))
+
+	return nodes, bg, client, shutdown, svr, handlers
+}
+
+func setServerBackend(s *proxyd.Server, nm map[string]nodeContext) *proxyd.Server {
+	bg := s.BackendGroups
+	bg["node"].Backends = []*proxyd.Backend{
+		nm["node1"].backend,
+		nm["node2"].backend,
+		nm["node3"].backend,
+	}
+	s.BackendGroups = bg
+	return s
+}
+
+func nodeBackendRequestCount(nodes map[string]nodeContext, node string) int {
+	return len(nodes[node].mockBackend.requests)
+}
+
+func TestMulticall(t *testing.T) {
+
+	t.Run("Multicall will request all backends", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandler(401, dummyRes))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandler(500, dummyRes))
+		nodes["node3"].mockBackend.SetHandler(SingleResponseHandler(200, txAccepted))
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+		svr.HandleRPC(rr, req)
+		resp := rr.Result()
+		defer resp.Body.Close()
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 200, resp.StatusCode)
+		require.Equal(t, resp.Header["X-Served-By"], []string{"node/node3"})
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.False(t, rpcRes.IsError())
+
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("When all of the backends return non 200, multicall should return 503", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandler(429, dummyRes))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandler(429, dummyRes))
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		localSvr.HandleRPC(rr, req)
+
+		resp := rr.Result()
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 503, resp.StatusCode)
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.True(t, rpcRes.IsError())
+		require.Equal(t, proxyd.ErrNoBackends.Code, rpcRes.Error.Code)
+		require.Equal(t, proxyd.ErrNoBackends.Message, rpcRes.Error.Message)
+
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("It should return the first 200 response", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleep(200, txAccepted, 3*time.Second))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandler(200, txAccepted))
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		localSvr.HandleRPC(rr, req)
+
+		resp := rr.Result()
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 200, resp.StatusCode)
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.False(t, rpcRes.IsError())
+		require.Equal(t, "2.0", rpcRes.JSONRPC)
+
+		require.Equal(t, resp.Header["X-Served-By"], []string{"node/node2"})
+		require.False(t, rpcRes.IsError())
+
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("Ensure application level error is returned to caller if its first", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+
+		defer shutdown()
+
+		shutdownChan1 := make(chan struct{})
+		shutdownChan2 := make(chan struct{})
+
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, nonceErrorResponse, shutdownChan1, 4*time.Second))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, nonceErrorResponse, shutdownChan2, 1*time.Second))
+		nodes["node3"].mockBackend.SetHandler(SingleResponseHandler(403, dummyRes))
+
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			shutdownChan2 <- struct{}{}
+			shutdownChan1 <- struct{}{}
+			wg.Done()
+		}()
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		localSvr.HandleRPC(rr, req)
+
+		resp := rr.Result()
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 200, resp.StatusCode)
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.Equal(t, "2.0", rpcRes.JSONRPC)
+		require.Equal(t, resp.Header["X-Served-By"], []string{"node/node2"})
+		require.True(t, rpcRes.IsError())
+
+		wg.Wait()
+
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("It should ignore network errors and return a 200 from a slower request", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		// We should ignore node2 first response cause 429, and return node 1 because 200
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleep(200, txAccepted, 3*time.Second))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandler(429, txAccepted))
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		localSvr.HandleRPC(rr, req)
+
+		resp := rr.Result()
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 200, resp.StatusCode)
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.False(t, rpcRes.IsError())
+		require.Equal(t, "2.0", rpcRes.JSONRPC)
+
+		require.Equal(t, resp.Header["X-Served-By"], []string{"node/node1"})
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("When one of the backends times out", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		shutdownChan := make(chan struct{})
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandler(200, dummyRes))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, dummyRes, shutdownChan, 7*time.Second))
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		localSvr.HandleRPC(rr, req)
+		resp := rr.Result()
+		shutdownChan <- struct{}{}
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		servedBy := "node/node1"
+		require.Equal(t, 200, resp.StatusCode, "expected 200 response from node1")
+
+		require.Equal(t, resp.Header["X-Served-By"], []string{servedBy}, "Error incorrect node served the request")
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.False(t, rpcRes.IsError())
+
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("allBackends times out", func(t *testing.T) {
+
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		shutdownChan1 := make(chan struct{})
+		shutdownChan2 := make(chan struct{})
+		nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, dummyRes, shutdownChan1, 7*time.Second))
+		nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, dummyRes, shutdownChan2, 7*time.Second))
+
+		localSvr := setServerBackend(svr, nodes)
+
+		body := makeSendRawTransaction(txHex1)
+		req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+		req.Header.Set("X-Forwarded-For", "203.0.113.1")
+		rr := httptest.NewRecorder()
+
+		var wg sync.WaitGroup
+		wg.Add(1)
+		go func() {
+			shutdownChan1 <- struct{}{}
+			shutdownChan2 <- struct{}{}
+			wg.Done()
+		}()
+
+		fmt.Println("sending request")
+		localSvr.HandleRPC(rr, req)
+
+		resp := rr.Result()
+		defer resp.Body.Close()
+
+		require.NotNil(t, resp.Body)
+		require.Equal(t, 503, resp.StatusCode, "expected no response")
+		rpcRes := &proxyd.RPCRes{}
+		require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+		require.True(t, rpcRes.IsError())
+		require.Equal(t, rpcRes.Error.Code, proxyd.ErrNoBackends.Code)
+
+		// Wait for test response to complete before checking query count
+		wg.Wait()
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node1"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node2"))
+		require.Equal(t, 1, nodeBackendRequestCount(nodes, "node3"))
+	})
+
+	t.Run("Test with many multi-calls in without resetting", func(t *testing.T) {
+		nodes, _, _, shutdown, svr, _ := setupMulticall(t)
+		defer nodes["node1"].mockBackend.Close()
+		defer nodes["node2"].mockBackend.Close()
+		defer nodes["node3"].mockBackend.Close()
+		defer shutdown()
+
+		for i := 1; i < 4; i++ {
+			shutdownChan1 := make(chan struct{})
+			shutdownChan2 := make(chan struct{})
+			shutdownChan3 := make(chan struct{})
+
+			switch {
+			case i == 1:
+				nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, txAccepted, shutdownChan1, 1*time.Second))
+				nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(429, dummyRes, shutdownChan2, 1*time.Second))
+				nodes["node3"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(503, dummyRes, shutdownChan3, 1*time.Second))
+			case i == 2:
+				nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(404, dummyRes, shutdownChan1, 1*time.Second))
+				nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, nonceErrorResponse, shutdownChan2, 1*time.Second))
+				nodes["node3"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(405, dummyRes, shutdownChan3, 1*time.Second))
+			case i == 3:
+				// Return the quickest response
+				nodes["node1"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(404, dummyRes, shutdownChan1, 1*time.Second))
+				nodes["node2"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(500, dummyRes, shutdownChan2, 1*time.Second))
+				nodes["node3"].mockBackend.SetHandler(SingleResponseHandlerWithSleepShutdown(200, nonceErrorResponse, shutdownChan3, 1*time.Second))
+			}
+
+			localSvr := setServerBackend(svr, nodes)
+
+			body := makeSendRawTransaction(txHex1)
+			req, _ := http.NewRequest("POST", "https://1.1.1.1:8080", bytes.NewReader(body))
+			req.Header.Set("X-Forwarded-For", "203.0.113.1")
+			rr := httptest.NewRecorder()
+
+			var wg sync.WaitGroup
+			wg.Add(1)
+			go func() {
+				shutdownChan1 <- struct{}{}
+				shutdownChan2 <- struct{}{}
+				shutdownChan3 <- struct{}{}
+				wg.Done()
+			}()
+
+			localSvr.HandleRPC(rr, req)
+
+			resp := rr.Result()
+			defer resp.Body.Close()
+
+			require.NotNil(t, resp.Body)
+			rpcRes := &proxyd.RPCRes{}
+			require.NoError(t, json.NewDecoder(resp.Body).Decode(rpcRes))
+
+			switch {
+			case i == 1:
+				servedBy := "node/node1"
+				require.NotNil(t, rpcRes.Result)
+				require.Equal(t, 200, resp.StatusCode, "expected 200 response from node1")
+				require.Equal(t, resp.Header["X-Served-By"], []string{servedBy}, "Error incorrect node served the request")
+				require.False(t, rpcRes.IsError())
+			case i == 2:
+				servedBy := "node/node2"
+				require.Nil(t, rpcRes.Result)
+				require.Equal(t, 200, resp.StatusCode, "expected 200 response from node2")
+				require.Equal(t, resp.Header["X-Served-By"], []string{servedBy}, "Error incorrect node served the request")
+				require.True(t, rpcRes.IsError())
+			case i == 3:
+				servedBy := "node/node3"
+				require.Nil(t, rpcRes.Result)
+				require.Equal(t, 200, resp.StatusCode, "expected 200 response from node3")
+				require.Equal(t, resp.Header["X-Served-By"], []string{servedBy}, "Error incorrect node served the request")
+				require.True(t, rpcRes.IsError())
+			}
+			// Wait for test response to complete before checking query count
+			wg.Wait()
+			require.Equal(t, i, nodeBackendRequestCount(nodes, "node1"))
+			require.Equal(t, i, nodeBackendRequestCount(nodes, "node2"))
+			require.Equal(t, i, nodeBackendRequestCount(nodes, "node3"))
+		}
+	})
+
+}
+
+func SingleResponseHandlerWithSleep(code int, response string, duration time.Duration) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		fmt.Println("sleeping")
+		time.Sleep(duration)
+		fmt.Println("Shutting down Single Response Handler")
+		w.WriteHeader(code)
+		_, _ = w.Write([]byte(response))
+	}
+}
+
+func SingleResponseHandlerWithSleepShutdown(code int, response string, shutdownServer chan struct{}, duration time.Duration) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		fmt.Println("sleeping")
+		time.Sleep(duration)
+		<-shutdownServer
+		fmt.Println("Shutting down Single Response Handler")
+		w.WriteHeader(code)
+		_, _ = w.Write([]byte(response))
+	}
+}

proxyd/integration_tests/rate_limit_test.go

@@ -16,7 +16,6 @@ type resWithCode struct {
 	res  []byte
 }
 
-const frontendOverLimitResponse = `{"error":{"code":-32016,"message":"over rate limit with special message"},"id":null,"jsonrpc":"2.0"}`
 const frontendOverLimitResponseWithID = `{"error":{"code":-32016,"message":"over rate limit with special message"},"id":999,"jsonrpc":"2.0"}`
 
 var ethChainID = "eth_chainId"
@@ -37,7 +36,7 @@ func TestFrontendMaxRPSLimit(t *testing.T) {
 		limitedRes, codes := spamReqs(t, client, ethChainID, 429, 3)
 		require.Equal(t, 1, codes[429])
 		require.Equal(t, 2, codes[200])
-		RequireEqualJSON(t, []byte(frontendOverLimitResponse), limitedRes)
+		RequireEqualJSON(t, []byte(frontendOverLimitResponseWithID), limitedRes)
 	})
 
 	t.Run("exempt user agent over limit", func(t *testing.T) {
@@ -106,6 +105,25 @@ func TestFrontendMaxRPSLimit(t *testing.T) {
 
 	time.Sleep(time.Second)
 
+	t.Run("Batch RPC with some requests rate limited", func(t *testing.T) {
+		client := NewProxydClient("http://127.0.0.1:8545")
+		req := NewRPCReq("123", "eth_chainId", nil)
+		out, code, err := client.SendBatchRPC(req, req, req)
+		require.NoError(t, err)
+		var res []proxyd.RPCRes
+		require.NoError(t, json.Unmarshal(out, &res))
+
+		expCode := proxyd.ErrOverRateLimit.Code
+		require.Equal(t, 200, code)
+		require.Equal(t, 3, len(res))
+		require.Nil(t, res[0].Error)
+		require.Nil(t, res[1].Error)
+		// base rate = 2, so the third request should be rate limited
+		require.Equal(t, expCode, res[2].Error.Code)
+	})
+
+	time.Sleep(time.Second)
+
 	t.Run("RPC override in batch exempt", func(t *testing.T) {
 		h := make(http.Header)
 		h.Set("User-Agent", "exempt_agent")

proxyd/integration_tests/testdata/block_height_zero_and_network_errors.toml

@@ -0,0 +1,35 @@
+[server]
+rpc_port = 8545
+
+[backend]
+response_timeout_seconds = 1
+max_degraded_latency_threshold = "30ms"
+max_error_rate_threshold = 0.25
+
+[backends]
+[backends.node1]
+rpc_url = "$NODE1_URL"
+
+[backends.node2]
+rpc_url = "$NODE2_URL"
+
+[backend_groups]
+[backend_groups.node]
+backends = ["node1", "node2"]
+routing_strategy = "consensus_aware"
+consensus_handler = "noop"    # allow more control over the consensus poller for tests
+
+## Consensus Ban Need to set very large, becaue consensus poller uses system clock, not adjustable clock
+## if a certain test case takes longer than 15m it may break
+consensus_ban_period = "15m"
+
+consensus_max_update_threshold = "2m"
+consensus_max_block_lag = 8
+consensus_min_peer_count = 4
+
+[rpc_method_mappings]
+eth_call = "node"
+eth_chainId = "node"
+eth_blockNumber = "node"
+eth_getBlockByNumber = "node"
+consensus_getReceipts = "node"

proxyd/integration_tests/testdata/block_height_zero_and_network_errors_responses.yaml

@@ -0,0 +1,234 @@
+- method: eth_chainId
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": "hello",
+    }
+- method: net_peerCount
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": "0x10"
+    }
+- method: eth_syncing
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": false
+    }
+- method: eth_getBlockByNumber
+  block: latest
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x101",
+        "number": "0x101"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x101
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x101",
+        "number": "0x101"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x102
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x102",
+        "number": "0x102"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x103
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x103",
+        "number": "0x103"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x10a
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x10a",
+        "number": "0x10a"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x132
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x132",
+        "number": "0x132"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x133
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x133",
+        "number": "0x133"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x134
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x134",
+        "number": "0x134"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x200
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x200",
+        "number": "0x200"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x91
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x91",
+        "number": "0x91"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: safe
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xe1",
+        "number": "0xe1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xe1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xe1",
+        "number": "0xe1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: finalized
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xc1",
+        "number": "0xc1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xc1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xc1",
+        "number": "0xc1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xd1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xd1",
+        "number": "0xd1"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0x55
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0xc6ef2fc5426d6ad6fd9e2a26abeab0aa2411b7ab17f30a99d3cb96aed1d1055b
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0x101
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: eth_getTransactionReceipt
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "eth_getTransactionReceipt"
+      }
+    }
+- method: alchemy_getTransactionReceipts
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "alchemy_getTransactionReceipts"
+      }
+    }

proxyd/integration_tests/testdata/consensus.toml

@@ -15,7 +15,7 @@ rpc_url = "$NODE2_URL"
 [backend_groups]
 [backend_groups.node]
 backends = ["node1", "node2"]
-consensus_aware = true
+routing_strategy = "consensus_aware"
 consensus_handler = "noop" # allow more control over the consensus poller for tests
 consensus_ban_period = "1m"
 consensus_max_update_threshold = "2m"

proxyd/integration_tests/testdata/empty_responses.yml

@@ -0,0 +1,7 @@
+- method: bad_method
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": "nope",
+    }

proxyd/integration_tests/testdata/fallback.toml

@@ -15,7 +15,7 @@ rpc_url = "$NODE2_URL"
 [backend_groups]
 [backend_groups.node]
 backends = ["normal", "fallback"]
-consensus_aware = true
+routing_strategy = "consensus_aware"
 consensus_handler = "noop"            # allow more control over the consensus poller for tests
 consensus_ban_period = "1m"
 consensus_max_update_threshold = "2m"

proxyd/integration_tests/testdata/multicall.toml

@@ -0,0 +1,27 @@
+[server]
+rpc_port = 8545
+enable_served_by_header = true
+timeout_seconds = 7
+
+[backend]
+response_timeout_seconds = 4
+max_degraded_latency_threshold = "30ms"
+
+[backends]
+[backends.node1]
+rpc_url = "$NODE1_URL"
+
+[backends.node2]
+rpc_url = "$NODE2_URL"
+
+[backends.node3]
+rpc_url = "$NODE3_URL"
+
+[backend_groups]
+[backend_groups.node]
+backends = ["node1", "node2", "node3"]
+routing_strategy = "multicall"
+
+[rpc_method_mappings]
+eth_call = "node"
+eth_sendRawTransaction = "node"

proxyd/integration_tests/testdata/multicall_responses.yml

@@ -0,0 +1,234 @@
+- method: eth_chainId
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": "hello",
+    }
+- method: net_peerCount
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": "0x10"
+    }
+- method: eth_syncing
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": false
+    }
+- method: eth_getBlockByNumber
+  block: latest
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x101",
+        "number": "0x101"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x101
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x101",
+        "number": "0x101"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x102
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x102",
+        "number": "0x102"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x103
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x103",
+        "number": "0x103"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x10a
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x10a",
+        "number": "0x10a"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x132
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x132",
+        "number": "0x132"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x133
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x133",
+        "number": "0x133"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x134
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x134",
+        "number": "0x134"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x200
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x200",
+        "number": "0x200"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0x91
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0x91",
+        "number": "0x91"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: safe
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xe1",
+        "number": "0xe1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xe1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xe1",
+        "number": "0xe1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: finalized
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xc1",
+        "number": "0xc1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xc1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xc1",
+        "number": "0xc1"
+      }
+    }
+- method: eth_getBlockByNumber
+  block: 0xd1
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "hash": "hash_0xd1",
+        "number": "0xd1"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0x55
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0xc6ef2fc5426d6ad6fd9e2a26abeab0aa2411b7ab17f30a99d3cb96aed1d1055b
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: debug_getRawReceipts
+  block: 0x101
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "debug_getRawReceipts"
+      }
+    }
+- method: eth_getTransactionReceipt
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "eth_getTransactionReceipt"
+      }
+    }
+- method: alchemy_getTransactionReceipts
+  response: >
+    {
+      "jsonrpc": "2.0",
+      "id": 67,
+      "result": {
+        "_": "alchemy_getTransactionReceipts"
+      }
+    }

proxyd/metrics.go

@@ -428,6 +428,25 @@ var (
 		"backend_name",
 		"fallback",
 	})
+
+	backendGroupMulticallCounter = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: MetricsNamespace,
+		Name:      "backend_group_multicall_request_counter",
+		Help:      "Record the amount of multicall requests",
+	}, []string{
+		"backend_group",
+		"backend_name",
+	})
+
+	backendGroupMulticallCompletionCounter = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: MetricsNamespace,
+		Name:      "backend_group_multicall_completion_counter",
+		Help:      "Record the amount of completed multicall requests",
+	}, []string{
+		"backend_group",
+		"backend_name",
+		"error",
+	})
 )
 
 func RecordRedisError(source string) {
@@ -593,6 +612,14 @@ func RecordBackendGroupFallbacks(bg *BackendGroup, name string, fallback bool) {
 	backendGroupFallbackBackend.WithLabelValues(bg.Name, name, strconv.FormatBool(fallback)).Set(boolToFloat64(fallback))
 }
 
+func RecordBackendGroupMulticallRequest(bg *BackendGroup, backendName string) {
+	backendGroupMulticallCounter.WithLabelValues(bg.Name, backendName).Inc()
+}
+
+func RecordBackendGroupMulticallCompletion(bg *BackendGroup, backendName string, error string) {
+	backendGroupMulticallCompletionCounter.WithLabelValues(bg.Name, backendName, error).Inc()
+}
+
 func boolToFloat64(b bool) float64 {
 	if b {
 		return 1

proxyd/pkg/avg-sliding-window/sliding.go

@@ -186,3 +186,11 @@ func (sw *AvgSlidingWindow) Count() uint {
 	sw.advance()
 	return sw.qty
 }
+
+// advance evicts old data points
+func (sw *AvgSlidingWindow) Clear() {
+	defer sw.mux.Unlock()
+	sw.mux.Lock()
+	sw.qty = 0
+	sw.sum = 0.0
+}

proxyd/proxyd.go

@@ -228,6 +228,7 @@ func Start(config *Config) (*Server, func(), error) {
 			Backends:         backends,
 			WeightedRouting:  bg.WeightedRouting,
 			FallbackBackends: fallbackBackends,
+			routingStrategy:  bg.RoutingStrategy,
 		}
 	}
 
@@ -353,7 +354,14 @@ func Start(config *Config) (*Server, func(), error) {
 
 	for bgName, bg := range backendGroups {
 		bgcfg := config.BackendGroups[bgName]
-		if bgcfg.ConsensusAware {
+
+		if !bgcfg.ValidateRoutingStrategy(bgName) {
+			log.Crit("Invalid routing strategy provided. Valid options: fallback, multicall, consensus_aware, \"\"", "name", bgName)
+		}
+
+		log.Info("configuring routing strategy for backend_group", "name", bgName, "routing_strategy", bgcfg.RoutingStrategy)
+
+		if bgcfg.RoutingStrategy == ConsensusAwareRoutingStrategy {
 			log.Info("creating poller for consensus aware backend_group", "name", bgName)
 
 			copts := make([]ConsensusOpt, 0)

proxyd/server.go

@@ -330,21 +330,7 @@ func (s *Server) HandleRPC(w http.ResponseWriter, r *http.Request, serverConfig
 		return !ok
 	}
 
-	if isLimited("") {
+	log.Debug(
-		RecordRPCError(ctx, BackendProxyd, "unknown", ErrOverRateLimit)
-		log.Warn(
-			"rate limited request",
-			"req_id", GetReqID(ctx),
-			"auth", GetAuthCtx(ctx),
-			"user_agent", userAgent,
-			"origin", origin,
-			"remote_ip", xff,
-		)
-		writeRPCError(ctx, w, nil, ErrOverRateLimit)
-		return
-	}
-
-	log.Info(
 		"received RPC request",
 		"req_id", GetReqID(ctx),
 		"auth", GetAuthCtx(ctx),
@@ -514,12 +500,22 @@ func (s *Server) handleBatchRPC(xff string, r *http.Request, ctx context.Context
 			continue
 		}
 
+		// Take base rate limit first
+		if isLimited("") {
+			log.Debug(
+				"rate limited individual RPC in a batch request",
+				"source", "rpc",
+				"req_id", parsedReq.ID,
+				"method", parsedReq.Method,
+			)
+			RecordRPCError(ctx, BackendProxyd, parsedReq.Method, ErrOverRateLimit)
+			responses[i] = NewRPCErrorRes(parsedReq.ID, ErrOverRateLimit)
+			continue
+		}
+
 		// Take rate limit for specific methods.
-		// NOTE: eventually, this should apply to all batch requests. However,
-		// since we don't have data right now on the size of each batch, we
-		// only apply this to the methods that have an additional rate limit.
 		if _, ok := s.overrideLims[parsedReq.Method]; ok && isLimited(parsedReq.Method) {
-			log.Info(
+			log.Debug(
 				"rate limited specific RPC",
 				"source", "rpc",
 				"req_id", GetReqID(ctx),

proxyd/tools/mockserver/handler/handler.go

@@ -19,6 +19,7 @@ type MethodTemplate struct {
 	Method       string `yaml:"method"`
 	Block        string `yaml:"block"`
 	Response     string `yaml:"response"`
+	ResponseCode int    `yaml:"response_code"`
 }
 
 type MockedHandler struct {
@@ -85,6 +86,9 @@ func (mh *MockedHandler) Handler(w http.ResponseWriter, req *http.Request) {
 		for _, r := range template {
 			if r.Method == method && r.Block == block {
 				selectedResponse = r.Response
+				if r.ResponseCode != 0 {
+					w.WriteHeader(r.ResponseCode)
+				}
 			}
 		}
 		if selectedResponse != "" {