go-probe-lib

README

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 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.

// 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)