Feature/bci 2996 local finality violation

.changeset/dull-ants-collect.md

@@ -0,0 +1,9 @@
+---
+"chainlink": patch
+---
+
+Fixed local finality violation caused by an RPC lagging behind on latest finalized block.
+
+Added `EVM.FinalizedBlockOffset` and `EVM.NodePool.EnforceRepeatableRead` config options.
+With `EnforceRepeatableRead = true`, RPC is considered healthy only if its most recent finalized block is larger or equal to the highest finalized block observed by the Node minus `FinalizedBlockOffset`.
+#bugfix

common/client/ctx.go

@@ -0,0 +1,17 @@
+package client
+
+import "context"
+
+type multiNodeContextKey int
+
+const (
+	contextKeyHeathCheckRequest multiNodeContextKey = iota + 1
+)
+
+func CtxAddHealthCheckFlag(ctx context.Context) context.Context {
+	return context.WithValue(ctx, contextKeyHeathCheckRequest, struct{}{})
+}
+
+func CtxIsHeathCheckRequest(ctx context.Context) bool {
+	return ctx.Value(contextKeyHeathCheckRequest) != nil
+}

common/client/ctx_test.go

@@ -0,0 +1,16 @@
+package client
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/smartcontractkit/chainlink-common/pkg/utils/tests"
+)
+
+func TestContext(t *testing.T) {
+	ctx := tests.Context(t)
+	assert.False(t, CtxIsHeathCheckRequest(ctx), "expected false for test context")
+	ctx = CtxAddHealthCheckFlag(ctx)
+	assert.True(t, CtxIsHeathCheckRequest(ctx), "expected context to contain the healthcheck flag")
+}

common/client/mocks/config.go

@@ -3,9 +3,10 @@ package mocks
 import "time"
 
 type ChainConfig struct {
-	IsFinalityTagEnabled   bool
-	FinalityDepthVal       uint32
-	NoNewHeadsThresholdVal time.Duration
+	IsFinalityTagEnabled    bool
+	FinalityDepthVal        uint32
+	NoNewHeadsThresholdVal  time.Duration
+	FinalizedBlockOffsetVal uint32
 }
 
 func (t ChainConfig) NodeNoNewHeadsThreshold() time.Duration {
@@ -19,3 +20,7 @@ func (t ChainConfig) FinalityDepth() uint32 {
 func (t ChainConfig) FinalityTagEnabled() bool {
 	return t.IsFinalityTagEnabled
 }
+
+func (t ChainConfig) FinalizedBlockOffset() uint32 {
+	return t.FinalizedBlockOffsetVal
+}