From 8a624bb2ca2ef2ce56c3b57f3253fc9b5f6da6ac Mon Sep 17 00:00:00 2001
From: Matthew Slipper <me@matthewslipper.com>
Date: Thu, 13 Oct 2022 14:54:30 -0500
Subject: [PATCH] proxyd: Allow disabling backend rate limiting

The backend rate limiter is in place to protect upstreams like the sequencer. However, in many cases it isn't needed and it causes unnecessary requests to Redis. This PR allows this to be disabled, and disables this by default.
---
 proxyd/proxyd/backend_rate_limiter.go         | 28 ++++++++++++++++++-
 proxyd/proxyd/config.go                       | 15 +++++-----
 .../testdata/backend_rate_limit.toml          |  5 +++-
 proxyd/proxyd/proxyd.go                       | 12 +++++---
 4 files changed, 47 insertions(+), 13 deletions(-)

diff --git a/proxyd/proxyd/backend_rate_limiter.go b/proxyd/proxyd/backend_rate_limiter.go
index 03c6436..3cc6fae 100644
--- a/proxyd/proxyd/backend_rate_limiter.go
+++ b/proxyd/proxyd/backend_rate_limiter.go
@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"fmt"
+	"math"
 	"sync"
 	"time"
 
@@ -256,5 +257,30 @@ func randStr(l int) string {
 	return hex.EncodeToString(b)
 }
 
-type ServerRateLimiter struct {
+type NoopBackendRateLimiter struct{}
+
+var noopBackendRateLimiter = &NoopBackendRateLimiter{}
+
+func (n *NoopBackendRateLimiter) IsBackendOnline(name string) (bool, error) {
+	return true, nil
+}
+
+func (n *NoopBackendRateLimiter) SetBackendOffline(name string, duration time.Duration) error {
+	return nil
+}
+
+func (n *NoopBackendRateLimiter) IncBackendRPS(name string) (int, error) {
+	return math.MaxInt, nil
+}
+
+func (n *NoopBackendRateLimiter) IncBackendWSConns(name string, max int) (bool, error) {
+	return true, nil
+}
+
+func (n *NoopBackendRateLimiter) DecBackendWSConns(name string) error {
+	return nil
+}
+
+func (n *NoopBackendRateLimiter) FlushBackendWSConns(names []string) error {
+	return nil
 }
diff --git a/proxyd/proxyd/config.go b/proxyd/proxyd/config.go
index d0a32d6..de221d9 100644
--- a/proxyd/proxyd/config.go
+++ b/proxyd/proxyd/config.go
@@ -41,13 +41,14 @@ type MetricsConfig struct {
 }
 
 type RateLimitConfig struct {
-	UseRedis         bool                                `toml:"use_redis"`
-	BaseRate         int                                 `toml:"base_rate"`
-	BaseInterval     TOMLDuration                        `toml:"base_interval"`
-	ExemptOrigins    []string                            `toml:"exempt_origins"`
-	ExemptUserAgents []string                            `toml:"exempt_user_agents"`
-	ErrorMessage     string                              `toml:"error_message"`
-	MethodOverrides  map[string]*RateLimitMethodOverride `toml:"method_overrides"`
+	UseRedis                 bool                                `toml:"use_redis"`
+	EnableBackendRateLimiter bool                                `toml:"enable_backend_rate_limiter"`
+	BaseRate                 int                                 `toml:"base_rate"`
+	BaseInterval             TOMLDuration                        `toml:"base_interval"`
+	ExemptOrigins            []string                            `toml:"exempt_origins"`
+	ExemptUserAgents         []string                            `toml:"exempt_user_agents"`
+	ErrorMessage             string                              `toml:"error_message"`
+	MethodOverrides          map[string]*RateLimitMethodOverride `toml:"method_overrides"`
 }
 
 type RateLimitMethodOverride struct {
diff --git a/proxyd/proxyd/integration_tests/testdata/backend_rate_limit.toml b/proxyd/proxyd/integration_tests/testdata/backend_rate_limit.toml
index eca6580..e29bb19 100644
--- a/proxyd/proxyd/integration_tests/testdata/backend_rate_limit.toml
+++ b/proxyd/proxyd/integration_tests/testdata/backend_rate_limit.toml
@@ -15,4 +15,7 @@ max_rps = 2
 backends = ["good"]
 
 [rpc_method_mappings]
-eth_chainId = "main"
\ No newline at end of file
+eth_chainId = "main"
+
+[rate_limit]
+enable_backend_limiter = true
\ No newline at end of file
diff --git a/proxyd/proxyd/proxyd.go b/proxyd/proxyd/proxyd.go
index 5685633..3e21d71 100644
--- a/proxyd/proxyd/proxyd.go
+++ b/proxyd/proxyd/proxyd.go
@@ -53,11 +53,15 @@ func Start(config *Config) (func(), error) {
 
 	var lim BackendRateLimiter
 	var err error
-	if redisClient == nil {
-		log.Warn("redis is not configured, using local rate limiter")
-		lim = NewLocalBackendRateLimiter()
+	if config.RateLimit.EnableBackendRateLimiter {
+		if redisClient != nil {
+			lim = NewRedisRateLimiter(redisClient)
+		} else {
+			log.Warn("redis is not configured, using local rate limiter")
+			lim = NewLocalBackendRateLimiter()
+		}
 	} else {
-		lim = NewRedisRateLimiter(redisClient)
+		lim = noopBackendRateLimiter
 	}
 
 	// While modifying shared globals is a bad practice, the alternative