I have an API written in Go that has been Dockerised and runs in a Kubernetes cluster on GKE.
At the moment my API server does not handle any shutdown scenarios such as a Pod dying or being purposefully brought down.
What set of UNIX signals should I expect to trap to gracefully shutdown the server and what circumstances would trigger them? For example, crashes, K8s shutdowns etc.
Kubernetes sends a SIGTERM signal. So the graceful shutdown may look like this:
package main
import (
"context"
"log"
"net/http"
"os"
"os/signal"
"syscall"
)
func main() {
var srv http.Server
idleConnsClosed := make(chan struct{})
go func() {
sigint := make(chan os.Signal, 1)
// interrupt signal sent from terminal
signal.Notify(sigint, os.Interrupt)
// sigterm signal sent from kubernetes
signal.Notify(sigint, syscall.SIGTERM)
<-sigint
// We received an interrupt signal, shut down.
if err := srv.Shutdown(context.Background()); err != nil {
// Error from closing listeners, or context timeout:
log.Printf("HTTP server Shutdown: %v", err)
}
close(idleConnsClosed)
}()
if err := srv.ListenAndServe(); err != http.ErrServerClosed {
// Error starting or closing listener:
log.Printf("HTTP server ListenAndServe: %v", err)
}
<-idleConnsClosed
}
Also you should add Liveness and Readiness probes to your pods:
livenessProbe:
httpGet:
path: /health
port: 80
readinessProbe:
httpGet:
path: /health
port: 80