Merge pull request #20 from WJQSERVER-STUDIO/feat/httpc-split

fix: 改进重试抖动实现

Author: satomitouka

client.go

@@ -1,6 +1,7 @@
 package httpc
 
 import (
+	"math/rand/v2"
 	"net"
 	"net/http"
 	"runtime"
@@ -36,6 +37,7 @@ func New(opts ...Option) *Client {
 		},
 		//transport:     transport,
 		retryOpts:     defaultRetryOptions(),
+		randomFloat64: rand.Float64,
 		bufferPool:    newDefaultPool(defaultBufferSize),
 		userAgent:     defaultUserAgent,
 		dumpLog:       nil, // 默认不启用日志

httpc_test.go

@@ -203,3 +203,55 @@ func TestPostJSONSetsContentTypeAndHonorsContext(t *testing.T) {
 		t.Fatal("request context was not propagated")
 	}
 }
+
+func TestCalculateExponentialBackoffWithoutJitter(t *testing.T) {
+	client := New(WithRetryOptions(RetryOptions{
+		BaseDelay: 100 * time.Millisecond,
+		MaxDelay:  700 * time.Millisecond,
+	}))
+
+	tests := []struct {
+		attempt int
+		want    time.Duration
+	}{
+		{attempt: 0, want: 100 * time.Millisecond},
+		{attempt: 1, want: 200 * time.Millisecond},
+		{attempt: 2, want: 400 * time.Millisecond},
+		{attempt: 3, want: 700 * time.Millisecond},
+	}
+
+	for _, tt := range tests {
+		if got := client.calculateExponentialBackoff(tt.attempt, false); got != tt.want {
+			t.Fatalf("attempt %d: backoff = %v, want %v", tt.attempt, got, tt.want)
+		}
+	}
+}
+
+func TestCalculateExponentialBackoffWithJitterUsesRandomFactor(t *testing.T) {
+	client := New(WithRetryOptions(RetryOptions{
+		BaseDelay: 200 * time.Millisecond,
+		MaxDelay:  time.Second,
+		Jitter:    true,
+	}))
+	client.randomFloat64 = func() float64 { return 0.25 }
+
+	got := client.calculateExponentialBackoff(1, true)
+	want := 300 * time.Millisecond
+	if got != want {
+		t.Fatalf("backoff with jitter = %v, want %v", got, want)
+	}
+}
+
+func TestCalculateExponentialBackoffWithJitterStillHonorsMaxDelay(t *testing.T) {
+	client := New(WithRetryOptions(RetryOptions{
+		BaseDelay: 500 * time.Millisecond,
+		MaxDelay:  800 * time.Millisecond,
+		Jitter:    true,
+	}))
+	client.randomFloat64 = func() float64 { return 0.99 }
+
+	got := client.calculateExponentialBackoff(3, true)
+	if got != 800*time.Millisecond {
+		t.Fatalf("backoff with jitter cap = %v, want %v", got, 800*time.Millisecond)
+	}
+}

transport.go

@@ -252,14 +252,19 @@ func parseRetryAfter(retryAfter string) (time.Duration, error) {
 	return 0, errors.New("invalid Retry-After value")
 }
 
-// 指数退避计算 (修改为支持 Jitter)
+// 指数退避计算，启用 jitter 时在 [0.5, 1.5) 区间内随机扰动。
 func (c *Client) calculateExponentialBackoff(attempt int, jitter bool) time.Duration {
 	delay := min(c.retryOpts.BaseDelay*time.Duration(1<<uint(attempt)), c.retryOpts.MaxDelay)
 
 	if jitter {
-		// 添加 Jitter 抖动，防止 thundering herd 问题
-		randomFactor := 0.8 + 0.4*float64(attempt) // 随着重试次数增加，抖动范围略微扩大
+		randomFactor := 0.5 + c.randomFloat64()
 		delay = time.Duration(float64(delay) * randomFactor)
+		if delay > c.retryOpts.MaxDelay {
+			return c.retryOpts.MaxDelay
+		}
+		if delay < 0 {
+			return 0
+		}
 	}
 	return delay
 }

types.go

@@ -58,6 +58,7 @@ type Client struct {
 	client        *http.Client
 	transport     *http.Transport
 	retryOpts     RetryOptions
+	randomFloat64 func() float64
 	bufferPool    BufferPool
 	userAgent     string
 	dumpLog       DumpLogFunc      // 日志记录函数