operator: make an infinity retry for connecting to store (#52177)

close pingcap/tidb#52175

br/pkg/backup/prepare_snap/env.go

@@ -180,9 +180,8 @@ type RetryAndSplitRequestEnv struct {
 }
 
 func (r RetryAndSplitRequestEnv) ConnectToStore(ctx context.Context, storeID uint64) (PrepareClient, error) {
-	// Retry for about 2 minutes.
-	rs := utils.InitialRetryState(12, 10*time.Second, 10*time.Second)
-	bo := utils.Backoffer(&rs)
+	rs := utils.ConstantBackoff(10 * time.Second)
+	bo := utils.Backoffer(rs)
 	if r.GetBackoffer != nil {
 		bo = r.GetBackoffer()
 	}

br/pkg/utils/BUILD.bazel

@@ -77,7 +77,7 @@ go_test(
     ],
     embed = [":utils"],
     flaky = True,
-    shard_count = 32,
+    shard_count = 33,
     deps = [
         "//br/pkg/errors",
         "//pkg/kv",

br/pkg/utils/backoff.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"database/sql"
 	"io"
+	"math"
 	"strings"
 	"time"
 
@@ -62,6 +63,20 @@ func isGRPCCancel(err error) bool {
 	return false
 }
 
+// ConstantBackoff is a backoffer that retry forever until success.
+type ConstantBackoff time.Duration
+
+// NextBackoff returns a duration to wait before retrying again
+func (c ConstantBackoff) NextBackoff(err error) time.Duration {
+	return time.Duration(c)
+}
+
+// Attempt returns the remain attempt times
+func (c ConstantBackoff) Attempt() int {
+	// A large enough value. Also still safe for arithmetic operations (won't easily overflow).
+	return math.MaxInt16
+}
+
 // RetryState is the mutable state needed for retrying.
 // It likes the `utils.Backoffer`, but more fundamental:
 // this only control the backoff time and knows nothing about what error happens.

br/pkg/utils/backoff_test.go

@@ -4,7 +4,9 @@ package utils_test
 
 import (
 	"context"
+	"fmt"
 	"io"
+	"math"
 	"testing"
 	"time"
 
@@ -213,3 +215,43 @@ func TestNewBackupSSTBackofferWithCancel(t *testing.T) {
 		context.Canceled,
 	}, multierr.Errors(err))
 }
+
+func TestConstantBackoff(t *testing.T) {
+	backedOff := func(t *testing.T) {
+		backoffer := utils.ConstantBackoff(10 * time.Millisecond)
+		ctx, cancel := context.WithCancel(context.Background())
+		i := 0
+		ch := make(chan error)
+
+		go func() {
+			_, err := utils.WithRetryV2(ctx, backoffer, func(ctx context.Context) (struct{}, error) {
+				i += 1
+				return struct{}{}, fmt.Errorf("%d times, no meaning", i)
+			})
+			ch <- err
+		}()
+		time.Sleep(100 * time.Millisecond)
+		cancel()
+		require.Error(t, <-ch)
+		// Make sure we have backed off.
+		require.Less(t, i, 20)
+	}
+
+	infRetry := func(t *testing.T) {
+		backoffer := utils.ConstantBackoff(0)
+		ctx := context.Background()
+		i := math.MaxInt16
+
+		_, err := utils.WithRetryV2(ctx, backoffer, func(ctx context.Context) (struct{}, error) {
+			i -= 1
+			if i == 0 {
+				return struct{}{}, nil
+			}
+			return struct{}{}, fmt.Errorf("try %d more times", i)
+		})
+		require.NoError(t, err)
+	}
+
+	t.Run("backedOff", backedOff)
+	t.Run("infRetry", infRetry)
+}

br/pkg/utils/retry.go

@@ -238,6 +238,7 @@ func WithRetryV2[T any](
 		allErrors = multierr.Append(allErrors, err)
 		select {
 		case <-ctx.Done():
+			// allErrors must not be `nil` here, so ignore the context error.
 			return *new(T), allErrors
 		case <-time.After(backoffer.NextBackoff(err)):
 		}