From e37e27036ee34792a0db6c7553d341e70d9b6f9e Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Sat, 12 Sep 2020 12:42:48 +0200
Subject: [PATCH] Implement graceful server shutdown.

This gives the user a friendly message when the server shuts down.
---
 client.go    |  4 ++++
 group.go     | 12 +++++++++++-
 sfu.go       |  3 ++-
 webclient.go | 10 +++++++---
 webserver.go | 19 +++++++++++++++++--
 5 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/client.go b/client.go
index 32954cd..9873306 100644
--- a/client.go
+++ b/client.go
@@ -12,3 +12,7 @@ type client interface {
 	pushConn(id string, conn upConnection, tracks []upTrack, label string) error
 	pushClient(id, username string, add bool) error
 }
+
+type kickable interface {
+	kick(message string) error
+}
diff --git a/group.go b/group.go
index a45bce9..a980ee7 100644
--- a/group.go
+++ b/group.go
@@ -64,7 +64,7 @@ type connectionFailedAction struct {
 
 type permissionsChangedAction struct{}
 
-type kickAction struct{
+type kickAction struct {
 	message string
 }
 
@@ -288,6 +288,16 @@ func (g *group) Range(f func(c client) bool) {
 	}
 }
 
+func (g *group) shutdown(message string) {
+	g.Range(func(c client) bool {
+		cc, ok := c.(kickable)
+		if ok {
+			cc.kick(message)
+		}
+		return true
+	})
+}
+
 const maxChatHistory = 20
 
 func (g *group) clearChatHistory() {
diff --git a/sfu.go b/sfu.go
index 8f817d7..5368249 100644
--- a/sfu.go
+++ b/sfu.go
@@ -87,6 +87,7 @@ func main() {
 	webserver()
 
 	terminate := make(chan os.Signal, 1)
-	signal.Notify(terminate, syscall.SIGINT)
+	signal.Notify(terminate, syscall.SIGINT, syscall.SIGTERM)
 	<-terminate
+	shutdown()
 }
diff --git a/webclient.go b/webclient.go
index 4a5beaa..e20e0db 100644
--- a/webclient.go
+++ b/webclient.go
@@ -943,6 +943,10 @@ func setPermissions(g *group, id string, perm string) error {
 	return c.action(permissionsChangedAction{})
 }
 
+func (c *webClient) kick(message string) error {
+	return c.action(kickAction{message})
+}
+
 func kickClient(g *group, id string, message string) error {
 	g.mu.Lock()
 	defer g.mu.Unlock()
@@ -952,12 +956,12 @@ func kickClient(g *group, id string, message string) error {
 		return userError("no such user")
 	}
 
-	c, ok := client.(*webClient)
+	c, ok := client.(kickable)
 	if !ok {
-		return userError("this is not a real user")
+		return userError("this client is not kickable")
 	}
 
-	return c.action(kickAction{message})
+	return c.kick(message)
 }
 
 func handleClientMessage(c *webClient, m clientMessage) error {
diff --git a/webserver.go b/webserver.go
index a512f93..007bd9d 100644
--- a/webserver.go
+++ b/webserver.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -19,6 +20,8 @@ import (
 	"github.com/gorilla/websocket"
 )
 
+var server *http.Server
+
 func webserver() {
 	http.Handle("/", mungeHandler{http.FileServer(http.Dir(staticRoot))})
 	http.HandleFunc("/group/", groupHandler)
@@ -39,17 +42,24 @@ func webserver() {
 	http.HandleFunc("/stats", statsHandler)
 
 	go func() {
-		server := &http.Server{
+		server = &http.Server{
 			Addr:              httpAddr,
 			ReadHeaderTimeout: 60 * time.Second,
 			IdleTimeout:       120 * time.Second,
 		}
+		server.RegisterOnShutdown(func() {
+			groups.mu.Lock()
+			defer groups.mu.Unlock()
+			for _, g := range groups.groups {
+				go g.shutdown("server is shutting down")
+			}
+		})
 		var err error
 		err = server.ListenAndServeTLS(
 			filepath.Join(dataDir, "cert.pem"),
 			filepath.Join(dataDir, "key.pem"),
 		)
-		if err != nil {
+		if err != nil && err != http.ErrServerClosed {
 			log.Printf("ListenAndServeTLS: %v", err)
 		}
 	}()
@@ -457,3 +467,8 @@ func serveGroupRecordings(w http.ResponseWriter, r *http.Request, f *os.File, gr
 	fmt.Fprintf(w, "</table>\n")
 	fmt.Fprintf(w, "</body></html>\n")
 }
+
+func shutdown() {
+	ctx, _ := context.WithTimeout(context.Background(), 2*time.Second)
+	server.Shutdown(ctx)
+}