gin_healthcheck

Gin Healthcheck

This module will create a simple endpoint for Gin framework, which can be used to determine the healthiness of Gin application.

Installation

Install package:

go get github.com/tavsec/gin-healthcheck

Usage

package main

import (
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
)

func main() {
    r := gin.Default()

    healthcheck.New(r, config.DefaultConfig(), []checks.Check{})
	
    r.Run()
}

This will add the healthcheck endpoint to the default path, which is /healthz. The path can be customized using config.Config structure. In the example above, no specific checks will be included, only API availability.

Health checks

SQL

Currently, gin-healthcheck comes with SQL check, which will send ping request to SQL.

package main

import (
    "database/sql"
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
)

func main() {
    r := gin.Default()
	
    db, _ := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/hello")
    sqlCheck := checks.SqlCheck{Sql: db}
    healthcheck.New(r, config.DefaultConfig(), []checks.Check{sqlCheck})

    r.Run()
}

Ping

In case you want to ensure that your application can reach a separate service, you can utilize PingCheck.

package main

import (
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
)

func main() {
    r := gin.Default()

    pingCheck := checks.NewPingCheck("https://www.google.com", "GET", 1000, nil, nil)
    healthcheck.New(r, config.DefaultConfig(), []checks.Check{pingCheck})

    r.Run()

Redis check

You can perform Redis ping check using RedisCheck checker:

package main

import (
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
    "github.com/redis/go-redis/v9"
)

func main() {
    r := gin.Default()

    rdb := redis.NewClient(&redis.Options{
        Addr:     "localhost:6379",
        Password: "",
        DB:       0,
    })
    redisCheck := checks.NewRedisCheck(rdb)
    healthcheck.New(r, config.DefaultConfig(), []checks.Check{redisCheck})

    r.Run()

Environmental variables check

You can check if an environmental variable is set using EnvCheck:

package main

import (
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
)

func main(){
    r := gin.Default()

    dbHostCheck := checks.NewEnvCheck("DB_HOST")
	
    // You can also validate env format using regex
    dbUserCheck := checks.NewEnvCheck("DB_HOST")
    dbUserCheck.SetRegexValidator("^USER_")
	
    healthcheck.New(r, config.DefaultConfig(), []checks.Check{dbHostCheck, dbUserCheck})

    r.Run()
}

context.Context check

You can check if a context has not been canceled, by using a ContextCheck:

package main

import (
    "context"
    "net/http"
    "os/signal"
    "syscall"

    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
    "github.com/tavsec/gin-healthcheck/config"
)

func main(){
    r := gin.Default()

    ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
    defer stop()

    signalsCheck := checks.NewContextCheck(ctx, "signals")
    healthcheck.New(r, config.DefaultConfig(), []checks.Check{signalsCheck})

    r.Run()
}

Custom checks

Besides built-in health checks, you can extend the functionality and create your own check, utilizing the Check interface:

package checks

type Check interface {
    Pass() bool
    Name() string
}

Notification of health check failure

It is possible to get notified when the health check failed a certain threshold of call. This would match for example the failureThreshold of Kubernetes and allow us to take action in that case.

package main

import (
    "github.com/gin-gonic/gin"
    healthcheck "github.com/tavsec/gin-healthcheck"
    "github.com/tavsec/gin-healthcheck/checks"
)

func main() {
    r := gin.Default()

    conf := healthcheck.DefaultConfig()

    conf.FailureNotification.Chan = make(chan error, 1)
	defer close(conf.FailureNotification.Chan)
	conf.FailureNotification.Threshold = 3

    go func() {
        <-conf.FailureNotification.Chan
        os.Exit(1)
    }

    ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
    defer stop()

    signalsCheck := checks.NewContextCheck(ctx, "signals")
    healthcheck.New(r, conf, []checks.Check{signalsCheck})
	
    r.Run()
}

Note that the following example is not doing a graceful shutdown. If Kubernetes is set up with a failureThreshold of 3, it will mark the pod as failing after that third call, but there is no guarantee that you have processed and answered all HTTP requests before the call to os.Exit(1). It is necessary to use something like https://github.com/gin-contrib/graceful at that point to have a graceful shutdown.