vgarvardt / go-pg-mutex

Mutex lock based on PostgreSQL advisory locks for Go

go-pg-mutex

Mutex lock based on PostgreSQL advisory locks for Go. Can be used to acquire a lock on a resource exclusively across several running instances of the application.

Install

$ go get -u -v github.com/vgarvardt/go-pg-mutex

PostgreSQL drivers

The store accepts an adapter interface that interacts with the DB. Adapter and implementations are extracted to separate package github.com/vgarvardt/go-pg-adapter for easier maintenance.

Usage example

package main

import (
	"fmt"
	"os"
	"time"

	"github.com/jackc/pgx"
	"github.com/vgarvardt/go-pg-adapter/pgxadapter"
	"github.com/vgarvardt/go-pg-mutex"
)

func main() {
	pgxConnConfig, _ := pgx.ParseURI(os.Getenv("DB_URI"))
	pgxConn, _ := pgx.Connect(pgxConnConfig)
	
	m, _ := pgmutex.New(pgxadapter.NewConn(pgxConn))
	
	useExclusiveResource(m)
	
	if !useExclusiveResourceOrNoOp(m) {
		fmt.Println("Resource is busy, doing nothing")
	}
}

func useExclusiveResource(m *pgmutex.PgMutex) {
	lockName := "my-lock"
	_ := m.Lock(lockName)
	defer m.Unlock(lockName)

	// do something with resource exclusively across several instances
}

func useExclusiveResourceOrNoOp(m *pgmutex.PgMutex) bool {
	lockName := "my-try-lock"
	if success, _ := m.TryLock(lockName); !success {
		return false
	}
	defer m.Unlock(lockName)

	// do something with resource exclusively across several instances
}

How to run tests

You will need running PostgreSQL instance. E.g. the one running in docker and exposing a port to a host system

docker run --rm -p 5432:5432 -it -e POSTGRES_PASSWORD=mutex -e POSTGRES_USER=mutex -e POSTGRES_DB=mutex postgres:10

Now you can run tests using the running PostgreSQL instance using PG_URI environment variable

PG_URI=postgres://mutex:mutex@localhost:5432/mutex?sslmode=disable go test -cover ./...

MIT License

Copyright (c) 2019 Vladimir Garvardt