Merge pull request #5794 from ethereum-optimism/felipe/consensus-finalized-safe

feat(proxyd): track consensus for {safe,finalized} blocks and rewrite tags

proxyd/Dockerfile

-FROM golang:1.18.0-alpine3.15 as builder
+FROM golang:1.20.4-alpine3.18 as builder
 
 ARG GITCOMMIT=docker
 ARG GITDATE=docker
@@ -12,7 +12,7 @@ WORKDIR /app
 
 RUN make proxyd
 
-FROM alpine:3.15
+FROM alpine:3.18
 
 COPY ./proxyd/entrypoint.sh /bin/entrypoint.sh
 

proxyd/backend.go

@@ -374,7 +374,6 @@ func (b *Backend) ForwardRPC(ctx context.Context, res *RPCRes, id string, method
 func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool) ([]*RPCRes, error) {
 	// we are concerned about network error rates, so we record 1 request independently of how many are in the batch
 	b.networkRequestsSlidingWindow.Incr()
-	RecordBackendNetworkRequestCountSlidingWindow(b, b.networkRequestsSlidingWindow.Count())
 
 	isSingleElementBatch := len(rpcReqs) == 1
 
@@ -391,7 +390,7 @@ 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()
-		RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error creating backend request")
 	}
 
@@ -413,7 +412,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 	httpRes, err := b.client.DoLimited(httpReq)
 	if err != nil {
 		b.networkErrorsSlidingWindow.Incr()
-		RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error in backend request")
 	}
 
@@ -432,7 +431,7 @@ 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()
-		RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, fmt.Errorf("response code %d", httpRes.StatusCode)
 	}
 
@@ -440,7 +439,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 	resB, err := io.ReadAll(io.LimitReader(httpRes.Body, b.maxResponseSize))
 	if err != nil {
 		b.networkErrorsSlidingWindow.Incr()
-		RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, wrapErr(err, "error reading response body")
 	}
 
@@ -458,18 +457,18 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 			// 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()
-				RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+				RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 				return nil, ErrBackendUnexpectedJSONRPC
 			}
 			b.networkErrorsSlidingWindow.Incr()
-			RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+			RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 			return nil, ErrBackendBadResponse
 		}
 	}
 
 	if len(rpcReqs) != len(res) {
 		b.networkErrorsSlidingWindow.Incr()
-		RecordBackendNetworkErrorCountSlidingWindow(b, b.networkErrorsSlidingWindow.Count())
+		RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 		return nil, ErrBackendUnexpectedJSONRPC
 	}
 
@@ -483,6 +482,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 	duration := time.Since(start)
 	b.latencySlidingWindow.Add(float64(duration))
 	RecordBackendNetworkLatencyAverageSlidingWindow(b, time.Duration(b.latencySlidingWindow.Avg()))
+	RecordBackendNetworkErrorRateSlidingWindow(b, b.ErrorRate())
 
 	sortBatchRPCResponse(rpcReqs, res)
 	return res, nil
@@ -490,11 +490,7 @@ func (b *Backend) doForward(ctx context.Context, rpcReqs []*RPCReq, isBatch bool
 
 // IsHealthy checks if the backend is able to serve traffic, based on dynamic parameters
 func (b *Backend) IsHealthy() bool {
-	errorRate := float64(0)
-	// avoid division-by-zero when the window is empty
-	if b.networkRequestsSlidingWindow.Sum() >= 10 {
-		errorRate = b.networkErrorsSlidingWindow.Sum() / b.networkRequestsSlidingWindow.Sum()
-	}
+	errorRate := b.ErrorRate()
 	avgLatency := time.Duration(b.latencySlidingWindow.Avg())
 	if errorRate >= b.maxErrorRateThreshold {
 		return false
@@ -505,6 +501,16 @@ func (b *Backend) IsHealthy() bool {
 	return true
 }
 
+// ErrorRate returns the instant error rate of the backend
+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()
+	}
+	return errorRate
+}
+
 // IsDegraded checks if the backend is serving traffic in a degraded state (i.e. used as a last resource)
 func (b *Backend) IsDegraded() bool {
 	avgLatency := time.Duration(b.latencySlidingWindow.Avg())
@@ -556,7 +562,11 @@ func (bg *BackendGroup) Forward(ctx context.Context, rpcReqs []*RPCReq, isBatch
 		backends = bg.loadBalancedConsensusGroup()
 
 		// We also rewrite block tags to enforce compliance with consensus
-		rctx := RewriteContext{latest: bg.Consensus.GetConsensusBlockNumber()}
+		rctx := RewriteContext{
+			latest:    bg.Consensus.GetLatestBlockNumber(),
+			finalized: bg.Consensus.GetFinalizedBlockNumber(),
+			safe:      bg.Consensus.GetSafeBlockNumber(),
+		}
 
 		for i, req := range rpcReqs {
 			res := RPCRes{JSONRPC: JSONRPCVersion, ID: req.ID}

proxyd/consensus_tracker.go

@@ -13,35 +13,68 @@ import (
 // ConsensusTracker abstracts how we store and retrieve the current consensus
 // allowing it to be stored locally in-memory or in a shared Redis cluster
 type ConsensusTracker interface {
-	GetConsensusBlockNumber() hexutil.Uint64
-	SetConsensusBlockNumber(blockNumber hexutil.Uint64)
+	GetLatestBlockNumber() hexutil.Uint64
+	SetLatestBlockNumber(blockNumber hexutil.Uint64)
+	GetFinalizedBlockNumber() hexutil.Uint64
+	SetFinalizedBlockNumber(blockNumber hexutil.Uint64)
+	GetSafeBlockNumber() hexutil.Uint64
+	SetSafeBlockNumber(blockNumber hexutil.Uint64)
 }
 
 // InMemoryConsensusTracker store and retrieve in memory, async-safe
 type InMemoryConsensusTracker struct {
-	consensusBlockNumber hexutil.Uint64
+	latestBlockNumber    hexutil.Uint64
+	finalizedBlockNumber hexutil.Uint64
+	safeBlockNumber      hexutil.Uint64
 	mutex                sync.Mutex
 }
 
 func NewInMemoryConsensusTracker() ConsensusTracker {
 	return &InMemoryConsensusTracker{
-		consensusBlockNumber: 0,
 		mutex: sync.Mutex{},
 	}
 }
 
-func (ct *InMemoryConsensusTracker) GetConsensusBlockNumber() hexutil.Uint64 {
+func (ct *InMemoryConsensusTracker) GetLatestBlockNumber() hexutil.Uint64 {
 	defer ct.mutex.Unlock()
 	ct.mutex.Lock()
 
-	return ct.consensusBlockNumber
+	return ct.latestBlockNumber
 }
 
-func (ct *InMemoryConsensusTracker) SetConsensusBlockNumber(blockNumber hexutil.Uint64) {
+func (ct *InMemoryConsensusTracker) SetLatestBlockNumber(blockNumber hexutil.Uint64) {
 	defer ct.mutex.Unlock()
 	ct.mutex.Lock()
 
-	ct.consensusBlockNumber = blockNumber
+	ct.latestBlockNumber = blockNumber
+}
+
+func (ct *InMemoryConsensusTracker) GetFinalizedBlockNumber() hexutil.Uint64 {
+	defer ct.mutex.Unlock()
+	ct.mutex.Lock()
+
+	return ct.finalizedBlockNumber
+}
+
+func (ct *InMemoryConsensusTracker) SetFinalizedBlockNumber(blockNumber hexutil.Uint64) {
+	defer ct.mutex.Unlock()
+	ct.mutex.Lock()
+
+	ct.finalizedBlockNumber = blockNumber
+}
+
+func (ct *InMemoryConsensusTracker) GetSafeBlockNumber() hexutil.Uint64 {
+	defer ct.mutex.Unlock()
+	ct.mutex.Lock()
+
+	return ct.safeBlockNumber
+}
+
+func (ct *InMemoryConsensusTracker) SetSafeBlockNumber(blockNumber hexutil.Uint64) {
+	defer ct.mutex.Unlock()
+	ct.mutex.Lock()
+
+	ct.safeBlockNumber = blockNumber
 }
 
 // RedisConsensusTracker uses a Redis `client` to store and retrieve consensus, async-safe
@@ -59,14 +92,29 @@ func NewRedisConsensusTracker(ctx context.Context, r *redis.Client, namespace st
 	}
 }
 
-func (ct *RedisConsensusTracker) key() string {
-	return fmt.Sprintf("consensus_latest_block:%s", ct.backendGroup)
+func (ct *RedisConsensusTracker) key(tag string) string {
+	return fmt.Sprintf("consensus:%s:%s", ct.backendGroup, tag)
 }
 
-func (ct *RedisConsensusTracker) GetConsensusBlockNumber() hexutil.Uint64 {
-	return hexutil.Uint64(hexutil.MustDecodeUint64(ct.client.Get(ct.ctx, ct.key()).Val()))
+func (ct *RedisConsensusTracker) GetLatestBlockNumber() hexutil.Uint64 {
+	return hexutil.Uint64(hexutil.MustDecodeUint64(ct.client.Get(ct.ctx, ct.key("latest")).Val()))
+}
+
+func (ct *RedisConsensusTracker) SetLatestBlockNumber(blockNumber hexutil.Uint64) {
+	ct.client.Set(ct.ctx, ct.key("latest"), blockNumber, 0)
+}
+
+func (ct *RedisConsensusTracker) GetFinalizedBlockNumber() hexutil.Uint64 {
+	return hexutil.Uint64(hexutil.MustDecodeUint64(ct.client.Get(ct.ctx, ct.key("finalized")).Val()))
+}
+
+func (ct *RedisConsensusTracker) SetFinalizedBlockNumber(blockNumber hexutil.Uint64) {
+	ct.client.Set(ct.ctx, ct.key("finalized"), blockNumber, 0)
+}
+func (ct *RedisConsensusTracker) GetSafeBlockNumber() hexutil.Uint64 {
+	return hexutil.Uint64(hexutil.MustDecodeUint64(ct.client.Get(ct.ctx, ct.key("safe")).Val()))
 }
 
-func (ct *RedisConsensusTracker) SetConsensusBlockNumber(blockNumber hexutil.Uint64) {
-	ct.client.Set(ct.ctx, ct.key(), blockNumber, 0)
+func (ct *RedisConsensusTracker) SetSafeBlockNumber(blockNumber hexutil.Uint64) {
+	ct.client.Set(ct.ctx, ct.key("safe"), blockNumber, 0)
 }

proxyd/example.config.toml

@@ -93,8 +93,8 @@ backends = ["infura"]
 # consensus_ban_period = "1m"
 # Maximum delay for update the backend, default 30s
 # consensus_max_update_threshold = "20s"
-# Maximum block lag, default 50
-# consensus_max_block_lag = 10
+# Maximum block lag, default 8
+# consensus_max_block_lag = 16
 # Minimum peer count, default 3
 # consensus_min_peer_count = 4
 

proxyd/integration_tests/testdata/consensus.toml

@@ -18,7 +18,7 @@ consensus_aware = true
 consensus_handler = "noop" # allow more control over the consensus poller for tests
 consensus_ban_period = "1m"
 consensus_max_update_threshold = "2m"
-consensus_max_block_lag = 50
+consensus_max_block_lag = 8
 consensus_min_peer_count = 4
 
 [rpc_method_mappings]

proxyd/integration_tests/testdata/consensus_responses.yml

@@ -26,40 +26,161 @@
       "jsonrpc": "2.0",
       "id": 67,
       "result": {
-        "hash": "hash1",
-        "number": "0x1"
+        "hash": "hash_0x101",
+        "number": "0x101"
       }
     }
 - method: eth_getBlockByNumber
-  block: 0x1
+  block: 0x101
   response: >
     {
       "jsonrpc": "2.0",
       "id": 67,
       "result": {
-        "hash": "hash1",
-        "number": "0x1"
+        "hash": "hash_0x101",
+        "number": "0x101"
       }
     }
 - method: eth_getBlockByNumber
-  block: 0x2
+  block: 0x102
   response: >
     {
       "jsonrpc": "2.0",
       "id": 67,
       "result": {
-        "hash": "hash2",
-        "number": "0x2"
+        "hash": "hash_0x102",
+        "number": "0x102"
       }
     }
 - method: eth_getBlockByNumber
-  block: 0x3
+  block: 0x103
   response: >
     {
       "jsonrpc": "2.0",
       "id": 67,
       "result": {
-        "hash": "hash3",
-        "number": "0x3"
+        "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"
       }
     }

proxyd/metrics.go

@@ -246,6 +246,22 @@ var (
 		"backend_group_name",
 	})
 
+	consensusSafeBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: MetricsNamespace,
+		Name:      "group_consensus_safe_block",
+		Help:      "Consensus safe block",
+	}, []string{
+		"backend_group_name",
+	})
+
+	consensusFinalizedBlock = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: MetricsNamespace,
+		Name:      "group_consensus_finalized_block",
+		Help:      "Consensus finalized block",
+	}, []string{
+		"backend_group_name",
+	})
+
 	backendLatestBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: MetricsNamespace,
 		Name:      "backend_latest_block",
@@ -254,6 +270,30 @@ var (
 		"backend_name",
 	})
 
+	backendSafeBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: MetricsNamespace,
+		Name:      "backend_safe_block",
+		Help:      "Current safe block observed per backend",
+	}, []string{
+		"backend_name",
+	})
+
+	backendFinalizedBlockBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: MetricsNamespace,
+		Name:      "backend_finalized_block",
+		Help:      "Current finalized block observed per backend",
+	}, []string{
+		"backend_name",
+	})
+
+	backendUnexpectedBlockTagsBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: MetricsNamespace,
+		Name:      "backend_unexpected_block_tags",
+		Help:      "Bool gauge for unexpected block tags",
+	}, []string{
+		"backend_name",
+	})
+
 	consensusGroupCount = promauto.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: MetricsNamespace,
 		Name:      "group_consensus_count",
@@ -318,18 +358,10 @@ var (
 		"backend_name",
 	})
 
-	networkErrorCountBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
+	networkErrorRateBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: MetricsNamespace,
-		Name:      "backend_net_error_count",
-		Help:      "Network error count per backend",
-	}, []string{
-		"backend_name",
-	})
-
-	requestCountBackend = promauto.NewGaugeVec(prometheus.GaugeOpts{
-		Namespace: MetricsNamespace,
-		Name:      "backend_request_count",
-		Help:      "Request count per backend",
+		Name:      "backend_error_rate",
+		Help:      "Request error rate per backend",
 	}, []string{
 		"backend_name",
 	})
@@ -402,6 +434,14 @@ func RecordGroupConsensusLatestBlock(group *BackendGroup, blockNumber hexutil.Ui
 	consensusLatestBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
 }
 
+func RecordGroupConsensusSafeBlock(group *BackendGroup, blockNumber hexutil.Uint64) {
+	consensusSafeBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
+}
+
+func RecordGroupConsensusFinalizedBlock(group *BackendGroup, blockNumber hexutil.Uint64) {
+	consensusFinalizedBlock.WithLabelValues(group.Name).Set(float64(blockNumber))
+}
+
 func RecordGroupConsensusCount(group *BackendGroup, count int) {
 	consensusGroupCount.WithLabelValues(group.Name).Set(float64(count))
 }
@@ -418,12 +458,20 @@ func RecordBackendLatestBlock(b *Backend, blockNumber hexutil.Uint64) {
 	backendLatestBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
 }
 
+func RecordBackendSafeBlock(b *Backend, blockNumber hexutil.Uint64) {
+	backendSafeBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
+}
+
+func RecordBackendFinalizedBlock(b *Backend, blockNumber hexutil.Uint64) {
+	backendFinalizedBlockBackend.WithLabelValues(b.Name).Set(float64(blockNumber))
+}
+
+func RecordBackendUnexpectedBlockTags(b *Backend, unexpected bool) {
+	backendUnexpectedBlockTagsBackend.WithLabelValues(b.Name).Set(boolToFloat64(unexpected))
+}
+
 func RecordConsensusBackendBanned(b *Backend, banned bool) {
-	v := float64(0)
-	if banned {
-		v = float64(1)
-	}
-	consensusBannedBackends.WithLabelValues(b.Name).Set(v)
+	consensusBannedBackends.WithLabelValues(b.Name).Set(boolToFloat64(banned))
 }
 
 func RecordConsensusBackendPeerCount(b *Backend, peerCount uint64) {
@@ -431,11 +479,7 @@ func RecordConsensusBackendPeerCount(b *Backend, peerCount uint64) {
 }
 
 func RecordConsensusBackendInSync(b *Backend, inSync bool) {
-	v := float64(0)
-	if inSync {
-		v = float64(1)
-	}
-	consensusInSyncBackend.WithLabelValues(b.Name).Set(v)
+	consensusInSyncBackend.WithLabelValues(b.Name).Set(boolToFloat64(inSync))
 }
 
 func RecordConsensusBackendUpdateDelay(b *Backend, delay time.Duration) {
@@ -446,10 +490,13 @@ func RecordBackendNetworkLatencyAverageSlidingWindow(b *Backend, avgLatency time
 	avgLatencyBackend.WithLabelValues(b.Name).Set(float64(avgLatency.Milliseconds()))
 }
 
-func RecordBackendNetworkRequestCountSlidingWindow(b *Backend, count uint) {
-	requestCountBackend.WithLabelValues(b.Name).Set(float64(count))
+func RecordBackendNetworkErrorRateSlidingWindow(b *Backend, rate float64) {
+	networkErrorRateBackend.WithLabelValues(b.Name).Set(rate)
 }
 
-func RecordBackendNetworkErrorCountSlidingWindow(b *Backend, count uint) {
-	networkErrorCountBackend.WithLabelValues(b.Name).Set(float64(count))
+func boolToFloat64(b bool) float64 {
+	if b {
+		return 1
+	}
+	return 0
 }

proxyd/rewriter.go

@@ -10,6 +10,8 @@ import (
 
 type RewriteContext struct {
 	latest    hexutil.Uint64
+	safe      hexutil.Uint64
+	finalized hexutil.Uint64
 }
 
 type RewriteResult uint8
@@ -180,11 +182,13 @@ func rewriteTag(rctx RewriteContext, current string) (string, bool, error) {
 	}
 
 	switch *bnh.BlockNumber {
-	case rpc.SafeBlockNumber,
-		rpc.FinalizedBlockNumber,
-		rpc.PendingBlockNumber,
+	case rpc.PendingBlockNumber,
 		rpc.EarliestBlockNumber:
 		return current, false, nil
+	case rpc.FinalizedBlockNumber:
+		return rctx.finalized.String(), true, nil
+	case rpc.SafeBlockNumber:
+		return rctx.safe.String(), true, nil
 	case rpc.LatestBlockNumber:
 		return rctx.latest.String(), true, nil
 	default:

proxyd/rewriter_test.go

@@ -326,33 +326,33 @@ func TestRewriteRequest(t *testing.T) {
 		{
 			name: "eth_getBlockByNumber finalized",
 			args: args{
-				rctx: RewriteContext{latest: hexutil.Uint64(100)},
+				rctx: RewriteContext{latest: hexutil.Uint64(100), finalized: hexutil.Uint64(55)},
 				req:  &RPCReq{Method: "eth_getBlockByNumber", Params: mustMarshalJSON([]string{"finalized"})},
 				res:  nil,
 			},
-			expected: RewriteNone,
+			expected: RewriteOverrideRequest,
 			check: func(t *testing.T, args args) {
 				var p []string
 				err := json.Unmarshal(args.req.Params, &p)
 				require.Nil(t, err)
 				require.Equal(t, 1, len(p))
-				require.Equal(t, "finalized", p[0])
+				require.Equal(t, hexutil.Uint64(55).String(), p[0])
 			},
 		},
 		{
 			name: "eth_getBlockByNumber safe",
 			args: args{
-				rctx: RewriteContext{latest: hexutil.Uint64(100)},
+				rctx: RewriteContext{latest: hexutil.Uint64(100), safe: hexutil.Uint64(50)},
 				req:  &RPCReq{Method: "eth_getBlockByNumber", Params: mustMarshalJSON([]string{"safe"})},
 				res:  nil,
 			},
-			expected: RewriteNone,
+			expected: RewriteOverrideRequest,
 			check: func(t *testing.T, args args) {
 				var p []string
 				err := json.Unmarshal(args.req.Params, &p)
 				require.Nil(t, err)
 				require.Equal(t, 1, len(p))
-				require.Equal(t, "safe", p[0])
+				require.Equal(t, hexutil.Uint64(50).String(), p[0])
 			},
 		},
 		{

proxyd/tools/mockserver/handler/handler.go

@@ -95,7 +95,7 @@ func (mh *MockedHandler) Handler(w http.ResponseWriter, req *http.Request) {
 	resBody := ""
 	if batched {
 		resBody = "[" + strings.Join(responses, ",") + "]"
-	} else {
+	} else if len(responses) > 0 {
 		resBody = responses[0]
 	}