health

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 Go to latest Published: Nov 18, 2023 License: MIT Imports: 3 Imported by: 39

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Go Health Check

An easy to use, extensible health check library for Go applications.

New package

Use https://github.com/dimiro1/healthz for a basic health check implementation.

Table of Contents

Example

package main

import (
    "net/http"
    "database/sql"
    "time"

    "github.com/dimiro1/health"
    "github.com/dimiro1/health/url"
    "github.com/dimiro1/health/db"
    "github.com/dimiro1/health/redis"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    database, _ := sql.Open("mysql", "/")
	mysql := db.NewMySQLChecker(database)
    timeout := 5 * time.Second
    
    companies := health.NewCompositeChecker()
    companies.AddChecker("Microsoft", url.NewChecker("https://www.microsoft.com/"))
    companies.AddChecker("Oracle", url.NewChecker("https://www.oracle.com/"))
    companies.AddChecker("Google", url.NewChecker("https://www.google.com/"))

    handler := health.NewHandler()
    handler.AddChecker("Go", url.NewCheckerWithTimeout("https://golang.org/", timeout))
    handler.AddChecker("Big Companies", companies)
    handler.AddChecker("MySQL", mysql)
    handler.AddChecker("Redis", redis.NewChecker("tcp", ":6379"))

    http.Handle("/health/", handler)
    http.ListenAndServe(":8080", nil)
}

$ curl localhost:8080/health/

If everything is ok the server must respond with HTTP Status 200 OK and have following json in the body.

{
    "Big Companies": {
        "Google": {
            "code": 200,
            "status": "UP"
        },
        "Microsoft": {
            "code": 200,
            "status": "UP"
        },
        "Oracle": {
            "code": 200,
            "status": "UP"
        },
        "status": "UP"
    },
    "Go": {
        "code": 200,
        "status": "UP"
    },
    "MySQL": {
        "status": "UP",
        "version": "10.1.9-MariaDB"
    },
    "Redis": {
        "status": "UP",
        "version": "3.0.5"
    },
    "status": "UP"
}

The server responds with HTTP Status 503 Service Unavailable if the ckeck is Down and the json response could be something like this.

{
    "Big Companies": {
        "Google": {
            "code": 200,
            "status": "UP"
        },
        "Microsoft": {
            "code": 200,
            "status": "UP"
        },
        "Oracle": {
            "code": 200,
            "status": "UP"
        },
        "status": "UP"
    },
    "Go": {
        "code": 200,
        "status": "UP"
    },
    "MySQL": {
        "status": "DOWN",
        "error": "Error 1044: Access denied for user ''@'localhost' to database 'invalid-database'",
    },
    "Redis": {
        "status": "UP",
        "version": "3.0.5"
    },
    "status": "DOWN"
}

Motivation

It is very important to verify the status of your system, not only the system itself, but all its dependencies, If your system is not Up you can easily know what is the cause of the problem only looking the health check.

Also it serves as a kind of basic integration test between the systems.

Inspiration

I took a lot of ideas from the spring framework.

Installation

This package is a go getable package.

$ go get github.com/dimiro1/health

API

The API is stable and I do not have any plans to break compatibility, but I recommend you to vendor this dependency in your project, as it is a good practice.

Testing

You have to install the test dependencies.

$ go get gopkg.in/DATA-DOG/go-sqlmock.v1
$ go get github.com/rafaeljusto/redigomock

or you can go get this package with the -t flag

go get -t github.com/dimiro1/health

Implementing custom checkers

The key interface is health.Checker, you only have to implement a type that satisfies that interface.

type Checker interface {
	Check() Health
}

Here is an example of Disk Space usage (unix only).

package main

import (
    "syscall"
    "os"
)

type DiskSpaceChecker struct {
	Dir       string
	Threshold uint64
}

func NewDiskSpaceChecker(dir string, threshold uint64) DiskSpaceChecker {
	return DiskSpaceChecker{Dir: dir, Threshold: threshold}
}

func (d DiskSpaceChecker) Check() health.Health {
	health := health.NewHealth()

	var stat syscall.Statfs_t

	wd, err := os.Getwd()

	if err != nil {
        health.Down().AddInfo("error", err.Error()) // Why the check is Down
        return health
	}

	syscall.Statfs(wd, &stat)

	diskFreeInBytes := stat.Bavail * uint64(stat.Bsize)

	if diskFreeInBytes < d.Threshold {
		health.Down()
	} else {
        health.Up()
    }

    health.
        AddInfo("free", diskFreeInBytes).
        AddInfo("threshold", d.Threshold)

	return health
}

Important

The status key in the json has priority over a status key added by a Checker, so if some checker adds a status key to the json, it will not be rendered

Implemented health check indicators

Health Description Package
url.Checker Check the connection with some URL https://github.com/dimiro1/health/tree/master/url
db.Checker Check the connection with the database https://github.com/dimiro1/health/tree/master/db
redis.Checker Check the connection with the redis https://github.com/dimiro1/health/tree/master/redis

LICENSE

The MIT License (MIT)

Copyright (c) 2016 Claudemiro

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Documentation

Overview

Package health is a easy to use, extensible health check library.

Example 

package main

import (
    "net/http"
    "database/sql"

    "github.com/dimiro1/health"
    "github.com/dimiro1/health/url"
    "github.com/dimiro1/health/db"
    "github.com/dimiro1/health/redis"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    database, _ := sql.Open("mysql", "/")
    mysql := db.NewMySQLChecker(database)

    companies := health.NewCompositeChecker()
    companies.AddChecker("Microsoft", url.NewChecker("https://www.microsoft.com/"))
    companies.AddChecker("Oracle", url.NewChecker("https://www.oracle.com/"))
    companies.AddChecker("Google", url.NewChecker("https://www.google.com/"))

    handler := health.NewHandler()
    handler.AddChecker("Go", url.NewChecker("https://golang.org/"))
    handler.AddChecker("Big Companies", companies)
    handler.AddChecker("MySQL", mysql)
    handler.AddChecker("Redis", redis.NewChecker("tcp", ":6379"))

    http.Handle("/health/", handler)
    http.ListenAndServe(":8080", nil)
}

Executing a curl 

$ curl localhost:8080/health/

If everything is ok the server must respond with HTTP Status 200 OK and have following json in the body. 

{
    "Big Companies": {
        "Google": {
            "code": 200,
            "status": "UP"
        },
        "Microsoft": {
            "code": 200,
            "status": "UP"
        },
        "Oracle": {
            "code": 200,
            "status": "UP"
        },
        "status": "UP"
    },
    "Go": {
        "code": 200,
        "status": "UP"
    },
    "MySQL": {
        "status": "UP",
        "version": "10.1.9-MariaDB"
    },
    "Redis": {
        "status": "UP",
        "version": "3.0.5"
    },
    "status": "UP"
}

The server responds with HTTP Status 503 Service Unavailable if the ckeck is Down and the json response could be something like this. 

{
    "Big Companies": {
        "Google": {
            "code": 200,
            "status": "UP"
        },
        "Microsoft": {
            "code": 200,
            "status": "UP"
        },
        "Oracle": {
            "code": 200,
            "status": "UP"
        },
        "status": "UP"
    },
    "Go": {
        "code": 200,
        "status": "UP"
    },
    "MySQL": {
        "status": "DOWN",
        "error": "Error 1044: Access denied for user ''@'localhost' to database 'invalid-database'",
    },
    "status": "DOWN"
}

Motivation

It is very important to verify the status of your system, not only the system itself, but all its dependencies, If your system is not Up you can easily know what is the cause of the problem only looking the health check.

Also it serves as a kind of basic itegration test between the systems.

Inspiration

I took a lot of ideas from the spring framework (http://spring.io/).

Installation

This package is a go getable packake. 

$ go get github.com/dimiro1/health

API

The API is stable and I do not have any plans to break compatibility, but I recommend you to vendor this dependency in your project, as it is a good practice.

Testing

You have to install the test dependencies. 

$ go get gopkg.in/DATA-DOG/go-sqlmock.v1

or you can go get this package with the -t flag 

$ go get -t github.com/dimiro1/health

Implementing custom checkers

The key interface is health.Checker, you only have to implement a type that satisfies that interface. 

type Checker interface {
    Check() Health
}

Here an example of Disk Space usage (unix only). 

package main

import (
    "syscall"
    "os"
)

type DiskSpaceChecker struct {
    Dir       string
    Threshold uint64
}

func NewDiskSpaceChecker(dir string, threshold uint64) DiskSpaceChecker {
    return DiskSpaceChecker{Dir: dir, Threshold: threshold}
}

func (d DiskSpaceChecker) Check() health.Health {
    health := health.NewHealth()

    var stat syscall.Statfs_t

    wd, err := os.Getwd()

    if err != nil {
        health.Down().AddInfo("error", err.Error()) // Why the check is Down
        return health
    }

    syscall.Statfs(wd, &stat)

    diskFreeInBytes := stat.Bavail * uint64(stat.Bsize)

    if diskFreeInBytes < d.Threshold {
        health.Down()
    } else {
        health.Up()
    }

    health.
        AddInfo("free", diskFreeInBytes).
        AddInfo("threshold", d.Threshold)

    return health
}

Important

The **status** key in the json have priority over a "status" key added by a Checker, so if some checker add a "status" key to the json, it will not be rendered

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Checker 

type Checker interface {
	Check() Health
}

Checker is a interface used to provide an indication of application health.

type CheckerFunc 

type CheckerFunc func() Health

CheckerFunc is an adapter to allow the use of ordinary go functions as Checkers.

func (CheckerFunc) Check 

func (f CheckerFunc) Check() Health

type CompositeChecker 

type CompositeChecker struct {
	// contains filtered or unexported fields
}

CompositeChecker aggregate a list of Checkers

func NewCompositeChecker 

func NewCompositeChecker() CompositeChecker

NewCompositeChecker creates a new CompositeChecker

func (*CompositeChecker) AddChecker 

func (c *CompositeChecker) AddChecker(name string, checker Checker)

AddChecker add a Checker to the aggregator

func (*CompositeChecker) AddInfo 

func (c *CompositeChecker) AddInfo(key string, value interface{}) *CompositeChecker

AddInfo adds a info value to the Info map

func (CompositeChecker) Check 

func (c CompositeChecker) Check() Health

Check returns the combination of all checkers added if some check is not up, the combined is marked as down

type Handler 

type Handler struct {
	CompositeChecker
}

Handler is a HTTP Server Handler implementation

func NewHandler 

func NewHandler() Handler

NewHandler returns a new Handler

func (Handler) ServeHTTP 

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request)

ServeHTTP returns a json encoded Health set the status to http.StatusServiceUnavailable if the check is down

type Health 

type Health struct {
	// contains filtered or unexported fields
}

Health is a health status struct

func NewHealth 

func NewHealth() Health

NewHealth return a new Health with status Down

func (*Health) AddInfo 

func (h *Health) AddInfo(key string, value interface{}) *Health

AddInfo adds a info value to the Info map

func (*Health) Down 

func (h *Health) Down() *Health

Down set the status to Down

func (Health) GetInfo 

func (h Health) GetInfo(key string) interface{}

GetInfo returns a value from the info map

func (Health) IsDown 

func (h Health) IsDown() bool

IsDown returns true if Status is Down

func (Health) IsOutOfService 

func (h Health) IsOutOfService() bool

IsOutOfService returns true if Status is IsOutOfService

func (Health) IsUnknown 

func (h Health) IsUnknown() bool

IsUnknown returns true if Status is Unknown

func (Health) IsUp 

func (h Health) IsUp() bool

IsUp returns true if Status is Up

func (Health) MarshalJSON 

func (h Health) MarshalJSON() ([]byte, error)

MarshalJSON is a custom JSON marshaller

func (*Health) OutOfService 

func (h *Health) OutOfService() *Health

OutOfService set the status to OutOfService

func (*Health) Unknown 

func (h *Health) Unknown() *Health

Unknown set the status to Unknown

func (*Health) Up 

func (h *Health) Up() *Health

Up set the status to Up

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