graceful server shutdown in go

Graceful shutdowns are needed for proper cleanup of resources before the server goes down.

This includes waiting for existing/inflight connections to be released and other dependent resources such as db transactions, producing/consuming from a queue, etc. (Most of the time these are async, so you can handle it via context.)

Go provides server.Shutdown which prevents the server from accepting any new connections and waits indefinitely untill all existing connections have been closed OR untill the supplied context is cancelled.

On the contrary, server.Close immediately closes all active connections.

Here’s a sample snippet on how you could handle graceful shutdowns based on some signals such as :

Manual/Automated (ex: via k8s sending signal events to the pod app) intervention such as SIGINT, SIGKILL, etc.
Fatal server errors or panics.

main.go

// When this context is canceled, we will gracefully stop the server.
ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
defer stop()
 
// When the server is stopped *not by that context*, but by any
// other server errors/issues, return it via an error chan.
serr := make(chan error, 1)
 
// Start the server
go func() { serr <- server.ListenAndServe() }()
 
// Wait for either the server to fail, or the context to end.
var err error
select {
    case err = <-serr:
 
    case <-ctx.Done():
 
}  
 
// Make a best effort to shut down the server cleanly
// Parent context passed here shouldn't be the signal ctx cause
// it will cancel all the in-flight requests once ctx.Done() chan is closed
// on signal receival, resulting in immediate shutdown of the server.
sdctx, sdcancel := context.WithTimeout(context.Background(), 30*time.Second)
defer sdcancel()
 
err := server.Shutdown(sdctx)
if err!=nil{
    log.Fatal("Unclean shutdown", err)
}
 
log.Info("Graceful shutdown completed!")

There are multiple ways in which you can do graceful shutdowns. But just make sure, context propagation
is handled appropriately.

dbmusings

graceful server shutdown in go