core: fix graceful stop (#4866)

core: fix graceful stop (#4865)

* core/grpc: fix graceful stop

* core/http: add graceful stop serve

Co-authored-by: Caleb Doxsey <cdoxsey@pomerium.com>

pkg/httputil/serve.go

@@ -0,0 +1,48 @@
+// Package httputil contains additional functionality for working with http.
+package httputil
+
+import (
+	"context"
+	"errors"
+	"net"
+	"net/http"
+	"time"
+
+	"github.com/pomerium/pomerium/pkg/contextutil"
+)
+
+// ServeWithGracefulStop serves the HTTP listener until ctx.Done(), and then gracefully stops and waits for gracefulTimeout
+// before definitively stopping.
+func ServeWithGracefulStop(ctx context.Context, handler http.Handler, li net.Listener, gracefulTimeout time.Duration) error {
+	// create a context that will be used for the http requests
+	// it will only be cancelled when baseCancel is called but will
+	// preserve the values from ctx
+	baseCtx, baseCancel := context.WithCancelCause(contextutil.OnlyValues(ctx))
+
+	srv := http.Server{
+		Handler: handler,
+		BaseContext: func(l net.Listener) context.Context {
+			return baseCtx
+		},
+	}
+
+	go func() {
+		<-ctx.Done()
+
+		// create a context that will cancel after the graceful timeout
+		timeoutCtx, clearTimeout := context.WithTimeout(context.Background(), gracefulTimeout)
+		defer clearTimeout()
+
+		// shut the http server down
+		_ = srv.Shutdown(timeoutCtx)
+
+		// cancel the base context used for http requests
+		baseCancel(ctx.Err())
+	}()
+
+	err := srv.Serve(li)
+	if errors.Is(err, http.ErrServerClosed) {
+		err = nil
+	}
+	return err
+}