rueidislock

rueidislock

A Redis Distributed Lock Pattern enhanced by Client Side Caching.

package main

import (
	"context"
	"github.com/rueian/rueidis"
	"github.com/rueian/rueidis/rueidislock"
)

func main() {
	locker, err := rueidislock.NewLocker(rueidislock.LockerOption{
		ClientOption: rueidis.ClientOption{InitAddress: []string{"node1:6379", "node2:6380", "node3:6379"}},
		KeyMajority:  2,
	})
	if err != nil {
		panic(err)
	}
	defer locker.Close()

	// acquire the lock "my_lock"
	ctx, cancel, err := locker.WithContext(context.Background(), "my_lock")
	if err != nil {
		panic(err)
	}

	// "my_lock" is acquired. use the ctx as normal.
	doSomething(ctx)

	// invoke cancel() to release the lock.
	cancel()
}

Features backed by the Redis Client Side Caching

• The returned ctx will be canceled automatically if the KeyMajority is not held anymore.
• The waiting Locker.WithContext will retry again if the lock is released by someone.

How it works

When the locker.WithContext is invoked, it will:

1. Try acquiring 3 keys (given that KeyMajority is 2), which are rueidislock:0:my_lock, rueidislock:1:my_lock and rueidislock:2:my_lock, by sending redis command SET NX PXAT.
2. If the KeyMajority is satisfied within the KeyValidity duration, the invocation is successful and a ctx is returned.
3. If the invocation is not successful, it will wait for client-side caching notification to retry again.
4. If the invocation is successful, the Locker will extend the ctx validity periodically and also watch client-side caching notification for canceling the ctx if the KeyMajority is not held anymore.