From 911cb56f4c4177fa44e9b15314a3d758d5b586a0 Mon Sep 17 00:00:00 2001
From: artem_danilov <artem_danilov@airbnb.com>
Date: Mon, 25 Nov 2024 22:06:10 -0800
Subject: [PATCH] add default circuit breaker

Signed-off-by: artem_danilov <artem_danilov@airbnb.com>
---
 client/circuit_breaker/circuit_breaker.go      | 8 ++++++++
 client/circuit_breaker/circuit_breaker_test.go | 8 +++-----
 client/http/client.go                          | 2 +-
 client/opt/option.go                           | 9 +++++----
 4 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/client/circuit_breaker/circuit_breaker.go b/client/circuit_breaker/circuit_breaker.go
index 38a88a7cb36..c24b894071b 100644
--- a/client/circuit_breaker/circuit_breaker.go
+++ b/client/circuit_breaker/circuit_breaker.go
@@ -53,6 +53,14 @@ type Settings struct {
 	HalfOpenSuccessCount uint32
 }
 
+var AlwaysOpenSettings = Settings{
+	ErrorRateThresholdPct: 0,                // never trips
+	ErrorRateWindow:       10 * time.Second, // effectively results in testing for new settings every 10 seconds
+	MinQPSForOpen:         10,
+	CoolDownInterval:      10 * time.Second,
+	HalfOpenSuccessCount:  1,
+}
+
 // CircuitBreaker is a state machine to prevent sending requests that are likely to fail.
 type CircuitBreaker[T any] struct {
 	config *Settings
diff --git a/client/circuit_breaker/circuit_breaker_test.go b/client/circuit_breaker/circuit_breaker_test.go
index 84b60c30f89..1c47b6c1327 100644
--- a/client/circuit_breaker/circuit_breaker_test.go
+++ b/client/circuit_breaker/circuit_breaker_test.go
@@ -156,12 +156,10 @@ func TestCircuitBreaker_Half_Open_Fail_Over_Pending_Count(t *testing.T) {
 
 func TestCircuitBreaker_ChangeSettings(t *testing.T) {
 	re := require.New(t)
-	disabledSettings := settings
-	disabledSettings.ErrorRateThresholdPct = 0
 
-	cb := NewCircuitBreaker[int]("test_cb", disabledSettings)
-	driveQPS(cb, minCountToOpen, Yes, re)
-	cb.advance(settings.ErrorRateWindow)
+	cb := NewCircuitBreaker[int]("test_cb", AlwaysOpenSettings)
+	driveQPS(cb, int(AlwaysOpenSettings.MinQPSForOpen*uint32(AlwaysOpenSettings.ErrorRateWindow.Seconds())), Yes, re)
+	cb.advance(AlwaysOpenSettings.ErrorRateWindow)
 	assertSucceeds(cb, re)
 	re.Equal(StateClosed, cb.state.stateType)
 
diff --git a/client/http/client.go b/client/http/client.go
index 5195005d2d9..31836c1f0c5 100644
--- a/client/http/client.go
+++ b/client/http/client.go
@@ -230,7 +230,7 @@ func (ci *clientInner) doRequest(
 	req.Header.Set(xCallerIDKey, callerID)
 	start := time.Now()
 	var resp *http.Response
-	if _, exists := regionRequestNames[reqInfo.name]; exists {
+	if _, exists := regionRequestNames[reqInfo.name]; exists && ci.regionMetaCircuitBreaker != nil {
 		resp, err = ci.regionMetaCircuitBreaker.Execute(func() (*http.Response, error, cb.Overloading) {
 			resp, err := ci.cli.Do(req)
 			return resp, err, isOverloaded(resp)
diff --git a/client/opt/option.go b/client/opt/option.go
index 8be77e4660f..73f7a3a440d 100644
--- a/client/opt/option.go
+++ b/client/opt/option.go
@@ -75,10 +75,11 @@ type Option struct {
 // NewOption creates a new PD client option with the default values set.
 func NewOption() *Option {
 	co := &Option{
-		Timeout:                  defaultPDTimeout,
-		MaxRetryTimes:            maxInitClusterRetries,
-		EnableTSOFollowerProxyCh: make(chan struct{}, 1),
-		InitMetrics:              true,
+		Timeout:                          defaultPDTimeout,
+		MaxRetryTimes:                    maxInitClusterRetries,
+		EnableTSOFollowerProxyCh:         make(chan struct{}, 1),
+		InitMetrics:                      true,
+		RegionMetaCircuitBreakerSettings: cb.AlwaysOpenSettings,
 	}
 
 	co.dynamicOptions[MaxTSOBatchWaitInterval].Store(defaultMaxTSOBatchWaitInterval)