---
id: healthcheck
---

# Health Check

Liveness and readiness probes middleware for [Fiber](https://github.com/gofiber/fiber) that provides two endpoints for checking the liveness and readiness state of HTTP applications.

## Overview

- **Liveness Probe**: Checks if the server is up and running.
  - **Default Endpoint**: `/livez`
  - **Behavior**: By default returns `true` immediately when the server is operational.

- **Readiness Probe**: Assesses if the application is ready to handle requests.
  - **Default Endpoint**: `/readyz`
  - **Behavior**: By default returns `true` immediately when the server is operational.

- **HTTP Status Codes**:
  - `200 OK`: Returned when the checker function evaluates to `true`.
  - `503 Service Unavailable`: Returned when the checker function evaluates to `false`.

## Signatures

```go
func New(config Config) fiber.Handler
```

## Examples

Import the middleware package that is part of the [Fiber](https://github.com/gofiber/fiber) web framework
```go
import (
    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/healthcheck"
)
```

After you initiate your [Fiber](https://github.com/gofiber/fiber) app, you can use the following possibilities:

```go
// Provide a minimal config
app.Use(healthcheck.New())

// Or extend your config for customization
app.Use(healthcheck.New(healthcheck.Config{
    LivenessProbe: func(c fiber.Ctx) bool {
        return true
    },
    LivenessEndpoint: "/live",
    ReadinessProbe: func(c fiber.Ctx) bool {
        return serviceA.Ready() && serviceB.Ready() && ...
    },
    ReadinessEndpoint: "/ready",
}))
```

## Config

```go
type Config struct {
	// Next defines a function to skip this middleware when returned true.
	//
	// Optional. Default: nil
	Next func(fiber.Ctx) bool

	// Function used for checking the liveness of the application. Returns true if the application
	// is running and false if it is not. The liveness probe is typically used to indicate if 
	// the application is in a state where it can handle requests (e.g., the server is up and running).
	//
	// Optional. Default: func(c fiber.Ctx) bool { return true }
	LivenessProbe HealthChecker

	// HTTP endpoint at which the liveness probe will be available.
	//
	// Optional. Default: "/livez"
	LivenessEndpoint string

	// Function used for checking the readiness of the application. Returns true if the application
	// is ready to process requests and false otherwise. The readiness probe typically checks if all necessary
	// services, databases, and other dependencies are available for the application to function correctly.
	//
	// Optional. Default: func(c fiber.Ctx) bool { return true }
	ReadinessProbe HealthChecker

	// HTTP endpoint at which the readiness probe will be available.
	// Optional. Default: "/readyz"
	ReadinessEndpoint string
}
```

## Default Config

The default configuration used by this middleware is defined as follows:
```go
func defaultLivenessProbe(fiber.Ctx) bool { return true }

func defaultReadinessProbe(fiber.Ctx) bool { return true }

var ConfigDefault = Config{
	LivenessProbe:     defaultLivenessProbe,
	ReadinessProbe:    defaultReadinessProbe,
	LivenessEndpoint:  "/livez",
	ReadinessEndpoint: "/readyz",
}
```