fiber/docs/middleware/healthcheck.md

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---
id: healthcheck
---
# Health Check
Liveness, readiness and startup probes middleware for [Fiber](https://github.com/gofiber/fiber) that provides three endpoints for checking the liveness, readiness, and startup 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.
- **Startup Probe**: Checks if the application has completed its startup sequence and is ready to proceed with initialization and readiness checks.
- **Default Endpoint**: `/startupz`
- **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 NewHealthChecker(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 for liveness check
app.Get(healthcheck.DefaultLivenessEndpoint, healthcheck.NewHealthChecker())
// Provide a minimal config for readiness check
app.Get(healthcheck.DefaultReadinessEndpoint, healthcheck.NewHealthChecker())
// Provide a minimal config for startup check
app.Get(healthcheck.DefaultStartupEndpoint, healthcheck.NewHealthChecker())
// Provide a minimal config for check with custom endpoint
app.Get("/live", healthcheck.NewHealthChecker())
// Or extend your config for customization
app.Get(healthcheck.DefaultLivenessEndpoint, healthcheck.NewHealthChecker(healthcheck.Config{
Probe: func(c fiber.Ctx) bool {
return true
},
}))
// And it works the same for readiness, just change the route
app.Get(healthcheck.DefaultReadinessEndpoint, healthcheck.NewHealthChecker(healthcheck.Config{
Probe: func(c fiber.Ctx) bool {
return true
},
}))
// And it works the same for startup, just change the route
app.Get(healthcheck.DefaultStartupEndpoint, healthcheck.NewHealthChecker(healthcheck.Config{
Probe: func(c fiber.Ctx) bool {
return true
},
}))
// With a custom route and custom probe
app.Get("/live", healthcheck.NewHealthChecker(healthcheck.Config{
Probe: func(c fiber.Ctx) bool {
return true
},
}))
// It can also be used with app.All, although it will only respond to requests with the GET method
// in case of calling the route with any method which isn't GET, the return will be 404 Not Found when app.All is used
// and 405 Method Not Allowed when app.Get is used
app.All(healthcheck.DefaultReadinessEndpoint, healthcheck.NewHealthChecker(healthcheck.Config{
Probe: func(c fiber.Ctx) bool {
return true
},
}))
```
## Config
```go
type Config struct {
// Next defines a function to skip this middleware when returned true. If this function returns true
// and no other handlers are defined for the route, Fiber will return a status 404 Not Found, since
// no other handlers were defined to return a different status.
//
// 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).
// The readiness probe is typically used to indicate if the application is ready to start accepting traffic (e.g., all necessary components
// are initialized and dependent services are available) and the startup probe typically used to
// indicate if the application has completed its startup sequence and is ready to proceed with
// initialization and readiness checks
//
// Optional. Default: func(c fiber.Ctx) bool { return true }
Probe HealthChecker
}
```
## Default Config
The default configuration used by this middleware is defined as follows:
```go
func defaultProbe(fiber.Ctx) bool { return true }
var ConfigDefault = Config{
Probe: defaultProbe,
}
```