README.md

go-redisson

a Redisson like distributed locking implementation using Redis.

Explanation

中文

Installation

go get github.com/cheerego/go-redisson

Support Lock Category

• Mutex Example

  • Exclusive Lock (X Lock).
  • use it like std package sync.Mutex.
  • not a reentrant lock that can't lock twice in a same goroutine.

• RLock Example

  • Exclusive Reentrant Lock.
  • use it like java redisson.
  • a reentrant lock that can lock many times in a same goroutine.

Features

• tryLock，if waitTime > 0, wait waitTime milliseconds to try to obtain lock by while true and redis pub sub.
• watchdog, if leaseTime = -1, start a time.Ticker(defaultWatchDogTime / 3) to renew lock expiration time.

Options

WatchDogTimeout

g := godisson.NewGodisson(rdb, godisson.WithWatchDogTimeout(30*time.Second))

Examples

Mutex

package main

import (
  "github.com/cheerego/go-redisson"
  "github.com/go-redis/redis/v8"
  "github.com/pkg/errors"
  "log"
  "time"
)

func main() {

  // create redis client
  rdb := redis.NewClient(&redis.Options{
    Addr:     "localhost:6379",
    Password: "", // no password set
    DB:       0,  // use default DB
  })
  defer rdb.Close()

  g := godisson.NewGodisson(rdb, godisson.WithWatchDogTimeout(30*time.Second))

  test1(g)
  test2(g)
}

// can't obtain lock in a same goroutine
func test1(g *godisson.Godisson) {
  m1 := g.NewMutex("godisson")
  m2 := g.NewMutex("godisson")

  err := m1.TryLock(-1, 20000)
  if errors.Is(err, godisson.ErrLockNotObtained) {
    log.Println("can't obtained lock")
  } else if err != nil {
    log.Fatalln(err)
  }
  defer m1.Unlock()

  // because waitTime = -1, waitTime < 0, try once, will return ErrLockNotObtained
  err = m2.TryLock(-1, 20000)
  if errors.Is(err, godisson.ErrLockNotObtained) {
    log.Println("m2 must not obtained lock")
  } else if err != nil {
    log.Fatalln(err)
  }
  time.Sleep(10 * time.Second)
}

func test2(g *godisson.Godisson) {
  m1 := g.NewMutex("godisson")
  m2 := g.NewMutex("godisson")

  go func() {
    err := m1.TryLock(-1, 20000)
    if errors.Is(err, godisson.ErrLockNotObtained) {
      log.Println("can't obtained lock")
    } else if err != nil {
      log.Fatalln(err)
    }
    time.Sleep(10 * time.Second)
    m1.Unlock()
  }()

  // waitTime > 0, after 10 milliseconds will obtain the lock
  go func() {
    time.Sleep(1 * time.Second)

    err := m2.TryLock(15000, 20000)
    if errors.Is(err, godisson.ErrLockNotObtained) {
      log.Println("m2 must not obtained lock")
    } else if err != nil {
      log.Fatalln(err)
    }
    time.Sleep(10 * time.Second)

    m2.Unlock()
  }()
  time.Sleep(20 * time.Second)

}

RLock

package main

import (
  "github.com/cheerego/go-redisson"
  "github.com/go-redis/redis/v8"
  "log"
  "time"
)

func main() {

  // create redis client
  rdb := redis.NewClient(&redis.Options{
    Addr:     "localhost:6379",
    Password: "", // no password set
    DB:       0,  // use default DB
  })
  defer rdb.Close()

  g := godisson.NewGodisson(rdb, godisson.WithWatchDogTimeout(30*time.Second))

  // lock with watchdog without retry
  lock := g.NewRLock("godisson")

  err := lock.Lock()
  if err == godisson.ErrLockNotObtained {
    log.Println("Could not obtain lock")
  } else if err != nil {
    log.Fatalln(err)
  }
  defer lock.Unlock()

  // lock with retry、watchdog
  // leaseTime value is -1, enable watchdog
  lock2 := g.NewRLock("godission-try-watchdog")

  err = lock2.TryLock(20000, -1)
  if err == godisson.ErrLockNotObtained {
    log.Println("Could not obtain lock")
  } else if err != nil {
    log.Fatalln(err)
  }
  time.Sleep(10 * time.Second)
  defer lock.Unlock()
}