Terminating systems with multiple components, in style.
guillotine is a package for shutting down complex, multi-component systems.
It defines a Finalizer, which is a function that should be run during program
termination.
type Finalizer func() errorFinalizers should be added to the Guillotine in your main function, after
resources are initialized. After all Finalizers are added, you should start
long-running processes like HTTP servers on separate goroutines; call
guillotine.Trigger after these processes exit, in case they exit early due
to a startup failure.
package main
import (
"context"
"fmt"
"io"
"net/http"
"os"
"github.com/cockroachdb/errors"
"go.stevenxie.me/guillotine"
)
func main() {
// Create a guillotine, configure it to trigger when receiving a termination
// signal from the OS.
guillo := guillotine.New()
guillo.TriggerOnTerminate()
// Execute the guillotine before main finishes.
defer func() {
if ok, errs := guillo.Execute(); !ok {
for _, err := range errs {
fmt.Fprintf(os.Stderr, "A finalizer failed: %v\n", err)
}
os.Exit(1)
}
}()
// Initialize resources, like files or databases.
file, err := os.Open("resource.txt")
if err != nil {
panic(err)
}
guillo.AddCloser(file, guillotine.WithPrefix("closing file"))
// Start long-running processes, like servers.
//
// We add the server itself as a finalizer so it can be shut down in response
// to some other shutdown signal, like an interrupt / termination signal.
const port = 8080
srv := &http.Server{
Addr: fmt.Sprintf(":%d", port),
Handler: http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
if _, err := io.Copy(w, file); err != nil {
panic(err)
}
}),
}
guillo.AddFinalizer(
func() error { return srv.Shutdown(context.Background()) },
guillotine.WithPrefix("shutting down server"),
)
// Blocks thread while server runs; stops either when the Guillotine
// shuts down the server, or the server fails to start up.
fmt.Printf("Listening on port %d...\n", port)
if err = srv.ListenAndServe(); err != nil {
if !errors.Is(err, http.ErrServerClosed) {
fmt.Fprintf(os.Stderr, "Error while starting server: %v\n", err)
guillo.Execute()
os.Exit(2)
}
}
}See the full example for more details.