healthcheck

[[TOC]]

Goal

This library aims to make easy to set up healthchecks with prometheus metrics. There are some ready-to-use checks.

Liveness vs Readiness

There are 2 probes in Kubernetes: liveness and readiness.

• Liveness - need to check whether pod is stuck and needs to be restarted. Most common way to do it - just respond 200 OK on main port always without any subchecks. In most of our services GRPC is the main port so GRPC handler should be used.
• Readiness - need to check whether pod is ready to accept traffic. There is no need to place in on main port so we use debug port for it.

How to use

1. Create new HealthChecker with all required subchecks. You can also specify its name (for metrics) and enable metrics
2. Use it either as http.Handler (HealthChecker implements it) or call GRPCRegisterService method for GRPC handler

How to add new checks

In this library

1. Add new file with Subcheck implementation in internal/pkg/healthcheck
2. Add new file with HealthCheckerOption implementation in root directory

Outside library

Implement Subcheck interface and add it via AddSubcheck method on HealthChecker.

package main

import (
	"context"

	"gitlab.com/picnic-app/backend/libs/golang/healthcheck"
)

type BlablaSubcheck struct {}

func (*BlablaSubcheck) name() string { return "blabla" }
func (*BlablaSubcheck) run(_ context.Context) error { return nil }
func (*BlablaSubcheck) isWarning() bool { return false }

func main() {
	hc := healthcheck.New()
	hc.AddSubcheck(&BlablaSubcheck{})
}