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retry.go
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retry.go
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// Copyright 2023 The Cockroach Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// SPDX-License-Identifier: Apache-2.0
// Package retry contains utility code for retrying database transactions.
package retry
// This code is taken from the Cacheroach project.
import (
"context"
"fmt"
"github.com/cockroachdb/cdc-sink/internal/types"
"github.com/pkg/errors"
)
// HasInfo contains the Info method.
type HasInfo interface {
Info() *types.PoolInfo
}
// Marker is a settable flag.
type Marker bool
// Mark sets the flag.
func (m *Marker) Mark() { *m = true }
// Marked returns the flag status.
func (m *Marker) Marked() bool { return bool(*m) }
// Execute is a wrapper around Retry that can be used for sql
// queries that don't have any return values.
func Execute[P types.AnyPool](ctx context.Context, db P, query string, args ...any) error {
return Retry(ctx, db, func(ctx context.Context) error {
var err error
switch t := any(db).(type) {
case *types.SourcePool:
_, err = t.ExecContext(ctx, query, args...)
case *types.StagingPool:
_, err = t.Exec(ctx, query, args...)
case *types.TargetPool:
_, err = t.ExecContext(ctx, query, args...)
default:
err = fmt.Errorf("unimplemented %T", t)
}
return err
})
}
// Retry is a convenience wrapper to automatically retry idempotent
// database operations that experience a transaction or a connection
// failure. The provided callback must be entirely idempotent, with
// no observable side-effects during its execution.
func Retry(ctx context.Context, info HasInfo, idempotent func(context.Context) error) error {
return Loop(ctx, info, func(ctx context.Context, _ *Marker) error {
return idempotent(ctx)
})
}
// inLoop is a key used by Loop to detect reentrant behavior.
type inLoop struct{}
// Loop is a convenience wrapper to automatically retry idempotent
// database operations that experience a transaction or a connection
// failure. The provided callback may indicate that it has started
// generating observable effects (e.g. sending result data) by calling
// its second parameter to disable the retry behavior.
//
// If Loop is called in a reentrant fashion, the retry behavior will be
// suppressed within an inner loop, allowing the retryable error to
// percolate into the outer loop.
func Loop(
ctx context.Context, info HasInfo, fn func(ctx context.Context, sideEffect *Marker) error,
) error {
const maxAttempts = 10
if outerMarker, ok := ctx.Value(inLoop{}).(*Marker); ok {
return fn(ctx, outerMarker)
}
var sideEffect Marker
ctx = context.WithValue(ctx, inLoop{}, &sideEffect)
actionsCount.Inc()
attempt := 0
for {
err := fn(ctx, &sideEffect)
if err == nil || sideEffect.Marked() {
return err
}
code, ok := info.Info().ErrCode(err)
if !ok {
code = "unknown"
}
if !info.Info().ShouldRetry(err) {
abortedCount.WithLabelValues(code).Inc()
return err
}
attempt++
retryCount.WithLabelValues(code).Inc()
if attempt >= maxAttempts {
return errors.Wrapf(err, "maximum number of retries (%d) exceeded", maxAttempts)
}
}
}