go-probe-lib

Go Probe Lib

Go library for writing proper liveness/readiness probes. It's designed for use in a Kubernetes environment, however it is not bound to it.

How it works

This library is simple in design and uses the following flow:

1. Allow the caller to register shutdown functions to gracefully stop the application
2. Wait for an interrupt/terminate signal from the observer (e.g. Kubelet)
3. Mark the /readyz endpoint as failed (so that Kubernetes removes the Pod from service)
4. Call all shutdown functions (http servers are shutdown last)
5. Mark the /livez endpoint as failed (so that Kubernetes kills the Pod)
6. Wait for the observer to send a kill signal or optionally exit after a specified duration

Usage

For a complete example, take a look at the sample app.

go get github.com/djcass44/go-probe-lib

package main

import (
	"context"
	"github.com/djcass44/go-probe-lib/pkg/probe"
	"log"
	"os"
	"time"
)

func main() {
	// set a 30s deadline for killing the application
	// if the kubelet hasn't done it already
	probes := probe.NewHandler(time.Second * 30)
	// register one or more functions
	probes.RegisterShutdownFunc(func() {
		log.Print("I'm a slow shutdown func!!")
		time.Sleep(time.Second * 10)
		log.Print("cya!")
	})
	// don't forget to call this in a goroutine
	// otherwise it will block.
	go func() {
		if err := probes.ListenAndServe(context.TODO(), 8081);
			err != nil {
			os.Exit(1)
		}
	}()
}

Logging

This project uses the go-logr logging facade so that you can provide your own logger. To ensure logs are emitted correctly, make sure that the context.Context you provide contains your LogSink.

package main

func main() {
	// this bit will depend on the logging
	// solution you choose to use
	log := foobar.NewLogger()
    ctx := logr.NewContext(context.TODO(), log)
    // ...
    probes.ListenAndServe(ctx, 8081)
}