Merge pull request #7977 from danyalprout/proxyd-weighting

feat(proxyd): add weighting feature to node selection

proxyd/proxyd/backend.go

@@ -22,6 +22,7 @@ import (
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/gorilla/websocket"
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/xaionaro-go/weightedshuffle"
 	"golang.org/x/sync/semaphore"
 
 	sw "github.com/ethereum-optimism/optimism/proxyd/pkg/avg-sliding-window"
@@ -160,6 +161,8 @@ type Backend struct {
 	latencySlidingWindow         *sw.AvgSlidingWindow
 	networkRequestsSlidingWindow *sw.AvgSlidingWindow
 	networkErrorsSlidingWindow   *sw.AvgSlidingWindow
+
+	weight int
 }
 
 type BackendOpt func(b *Backend)
@@ -246,6 +249,12 @@ func WithConsensusForcedCandidate(forcedCandidate bool) BackendOpt {
 	}
 }
 
+func WithWeight(weight int) BackendOpt {
+	return func(b *Backend) {
+		b.weight = weight
+	}
+}
+
 func WithMaxDegradedLatencyThreshold(maxDegradedLatencyThreshold time.Duration) BackendOpt {
 	return func(b *Backend) {
 		b.maxDegradedLatencyThreshold = maxDegradedLatencyThreshold
@@ -694,9 +703,10 @@ func sortBatchRPCResponse(req []*RPCReq, res []*RPCRes) {
 }
 
 type BackendGroup struct {
-	Name      string
-	Backends  []*Backend
-	Consensus *ConsensusPoller
+	Name            string
+	Backends        []*Backend
+	WeightedRouting bool
+	Consensus       *ConsensusPoller
 }
 
 func (bg *BackendGroup) Forward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool) ([]*RPCRes, string, error) {
@@ -704,7 +714,7 @@ func (bg *BackendGroup) Forward(ctx context.Context, rpcReqs []*RPCReq, isBatch
 		return nil, "", nil
 	}
 
-	backends := bg.Backends
+	backends := bg.orderedBackendsForRequest()
 
 	overriddenResponses := make([]*indexedReqRes, 0)
 	rewrittenReqs := make([]*RPCReq, 0, len(rpcReqs))
@@ -712,7 +722,6 @@ func (bg *BackendGroup) Forward(ctx context.Context, rpcReqs []*RPCReq, isBatch
 	if bg.Consensus != nil {
 		// 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
-		backends = bg.loadBalancedConsensusGroup()
 
 		// We also rewrite block tags to enforce compliance with consensus
 		rctx := RewriteContext{
@@ -856,6 +865,27 @@ func (bg *BackendGroup) ProxyWS(ctx context.Context, clientConn *websocket.Conn,
 	return nil, ErrNoBackends
 }
 
+func weightedShuffle(backends []*Backend) {
+	weight := func(i int) float64 {
+		return float64(backends[i].weight)
+	}
+
+	weightedshuffle.ShuffleInplace(backends, weight, nil)
+}
+
+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
+	}
+}
+
 func (bg *BackendGroup) loadBalancedConsensusGroup() []*Backend {
 	cg := bg.Consensus.GetConsensusGroup()
 
@@ -883,6 +913,10 @@ func (bg *BackendGroup) loadBalancedConsensusGroup() []*Backend {
 		backendsDegraded[i], backendsDegraded[j] = backendsDegraded[j], backendsDegraded[i]
 	})
 
+	if bg.WeightedRouting {
+		weightedShuffle(backendsHealthy)
+	}
+
 	// healthy are put into a priority position
 	// degraded backends are used as fallback
 	backendsHealthy = append(backendsHealthy, backendsDegraded...)

proxyd/proxyd/config.go

@@ -96,6 +96,8 @@ type BackendConfig struct {
 	StripTrailingXFF bool              `toml:"strip_trailing_xff"`
 	Headers          map[string]string `toml:"headers"`
 
+	Weight int `toml:"weight"`
+
 	ConsensusSkipPeerCountCheck bool   `toml:"consensus_skip_peer_count"`
 	ConsensusForcedCandidate    bool   `toml:"consensus_forced_candidate"`
 	ConsensusReceiptsTarget     string `toml:"consensus_receipts_target"`
@@ -106,6 +108,8 @@ type BackendsConfig map[string]*BackendConfig
 type BackendGroupConfig struct {
 	Backends []string `toml:"backends"`
 
+	WeightedRouting bool `toml:"weighted_routing"`
+
 	ConsensusAware        bool   `toml:"consensus_aware"`
 	ConsensusAsyncHandler string `toml:"consensus_handler"`
 

proxyd/proxyd/go.mod

@@ -18,6 +18,7 @@ require (
 	github.com/rs/cors v1.10.1
 	github.com/stretchr/testify v1.8.4
 	github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7
+	github.com/xaionaro-go/weightedshuffle v0.0.0-20211213010739-6a74fbc7d24a
 	golang.org/x/sync v0.4.0
 	gopkg.in/yaml.v3 v3.0.1
 )

proxyd/proxyd/go.sum

@@ -198,6 +198,8 @@ github.com/tklauser/go-sysconf v0.3.12 h1:0QaGUFOdQaIVdPgfITYzaTegZvdCjmYO52cSFA
 github.com/tklauser/go-sysconf v0.3.12/go.mod h1:Ho14jnntGE1fpdOqQEEaiKRpvIavV0hSfmBq8nJbHYI=
 github.com/tklauser/numcpus v0.6.1 h1:ng9scYS7az0Bk4OZLvrNXNSAO2Pxr1XXRAPyjhIx+Fk=
 github.com/tklauser/numcpus v0.6.1/go.mod h1:1XfjsgE2zo8GVw7POkMbHENHzVg3GzmoZ9fESEdAacY=
+github.com/xaionaro-go/weightedshuffle v0.0.0-20211213010739-6a74fbc7d24a h1:WS5nQycV+82Ndezq0UcMcGVG416PZgcJPqI/bLM824A=
+github.com/xaionaro-go/weightedshuffle v0.0.0-20211213010739-6a74fbc7d24a/go.mod h1:0KAUfC65le2kMu4fnBxm7Xj3PkQ3MBpJbF5oMmqufBc=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/gopher-lua v1.1.0 h1:BojcDhfyDWgU2f2TOzYK/g5p2gxMrku8oupLDqlnSqE=

proxyd/proxyd/proxyd.go

@@ -156,6 +156,7 @@ func Start(config *Config) (*Server, func(), error) {
 		opts = append(opts, WithProxydIP(os.Getenv("PROXYD_IP")))
 		opts = append(opts, WithConsensusSkipPeerCountCheck(cfg.ConsensusSkipPeerCountCheck))
 		opts = append(opts, WithConsensusForcedCandidate(cfg.ConsensusForcedCandidate))
+		opts = append(opts, WithWeight(cfg.Weight))
 
 		receiptsTarget, err := ReadFromEnvOrConfig(cfg.ConsensusReceiptsTarget)
 		if err != nil {
@@ -186,11 +187,12 @@ func Start(config *Config) (*Server, func(), error) {
 			}
 			backends = append(backends, backendsByName[bName])
 		}
-		group := &BackendGroup{
-			Name:     bgName,
-			Backends: backends,
+
+		backendGroups[bgName] = &BackendGroup{
+			Name:            bgName,
+			Backends:        backends,
+			WeightedRouting: bg.WeightedRouting,
 		}
-		backendGroups[bgName] = group
 	}
 
 	var wsBackendGroup *BackendGroup