From 5b7d51f210e956ef2b356bd64dba6c0f02de453c Mon Sep 17 00:00:00 2001
From: Erik Brakkee <erik@brakkee.org>
Date: Sat, 10 Aug 2024 17:27:50 +0200
Subject: [PATCH] Code is more robust and should now never try to send a
notification to a web client that can block, using a context with
cancellation.
---
cmd/converge/converge.go | 6 ++++--
pkg/server/converge/websessions.go | 15 ++++++++++++---
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/cmd/converge/converge.go b/cmd/converge/converge.go
index 8a592a4..9000096 100644
--- a/cmd/converge/converge.go
+++ b/cmd/converge/converge.go
@@ -1,6 +1,7 @@
package main
import (
+ "context"
"converge/pkg/server/converge"
"converge/pkg/support/websocketutil"
"fmt"
@@ -134,13 +135,14 @@ func main() {
// for the web browser getting live status updates.
sessionService := websocketutil.WebSocketService{
Handler: func(w http.ResponseWriter, r *http.Request, conn net.Conn) {
- websession := websessions.NewSession(conn)
+ ctx, cancel := context.WithCancel(context.Background())
+ websession := websessions.NewSession(conn, ctx)
defer websessions.SessionClosed(websession)
location, err := converge.GetUserLocation(r)
if err != nil {
panic(err)
}
- websession.WriteNotifications(location)
+ websession.WriteNotifications(location, cancel)
},
Text: true,
}
diff --git a/pkg/server/converge/websessions.go b/pkg/server/converge/websessions.go
index a868204..504bafb 100644
--- a/pkg/server/converge/websessions.go
+++ b/pkg/server/converge/websessions.go
@@ -20,6 +20,7 @@ type WebSessions struct {
type WebSession struct {
notifications chan *models.State
conn net.Conn
+ ctx context.Context
}
func NewWebSessions(notifications chan *models.State) *WebSessions {
@@ -41,16 +42,22 @@ func (sessions *WebSessions) notifyWebSessions(notification *models.State) {
defer sessions.mutex.Unlock()
sessions.lastNotification = notification
for session, _ := range sessions.sessions {
- session.notifications <- notification
+ select {
+ case <-session.ctx.Done():
+ // session is closed, will be removed at higher level when session is done.
+ case session.notifications <- notification:
+ // Sent notification
+ }
}
}
-func (sessions *WebSessions) NewSession(wsConnection net.Conn) *WebSession {
+func (sessions *WebSessions) NewSession(wsConnection net.Conn, ctx context.Context) *WebSession {
sessions.mutex.Lock()
defer sessions.mutex.Unlock()
session := &WebSession{
notifications: make(chan *models.State, 10),
conn: wsConnection,
+ ctx: ctx,
}
sessions.sessions[session] = true
sessions.logSessions()
@@ -70,9 +77,11 @@ func GetUserLocation(r *http.Request) (*time.Location, error) {
return time.LoadLocation(tzName)
}
-func (session *WebSession) WriteNotifications(location *time.Location) {
+func (session *WebSession) WriteNotifications(location *time.Location, cancel context.CancelFunc) {
timer := time.NewTicker(10 * time.Second)
defer timer.Stop()
+ // if for some reason we cannot send notifications to the web client then the context is canceled.
+ defer cancel()
for {
select {
case notification, ok := <-session.notifications: