From 1e550b518fd49f954b6c422174f4a1a50f5268dc Mon Sep 17 00:00:00 2001
From: Christian Mollekopf <chrigi_1@fastmail.fm>
Date: Tue, 28 Apr 2015 09:47:28 +0200
Subject: Listener: Use a lockfile to enforce that only a single instance is
 running.

I tried using flock on a socket, but without success.
---
 synchronizer/listener.cpp | 9 +++++++++
 synchronizer/listener.h   | 3 +++
 2 files changed, 12 insertions(+)

(limited to 'synchronizer')

diff --git a/synchronizer/listener.cpp b/synchronizer/listener.cpp
index e930a02..e9e6188 100644
--- a/synchronizer/listener.cpp
+++ b/synchronizer/listener.cpp
@@ -33,6 +33,7 @@
 
 #include <QLocalSocket>
 #include <QTimer>
+#include <QLockFile>
 
 Listener::Listener(const QByteArray &resourceName, QObject *parent)
     : QObject(parent),
@@ -48,6 +49,14 @@ Listener::Listener(const QByteArray &resourceName, QObject *parent)
     connect(m_server, &QLocalServer::newConnection,
              this, &Listener::acceptConnection);
     Trace() << "Trying to open " << m_resourceName;
+
+    m_lockfile = new QLockFile(resourceName + ".lock");
+    m_lockfile->setStaleLockTime(0);
+    if (!m_lockfile->tryLock(0)) {
+        Warning() << "Failed to acquire exclusive lock on socket.";
+        exit(-1);
+    }
+
     if (!m_server->listen(QString::fromLatin1(resourceName))) {
         // FIXME: multiple starts need to be handled here
         m_server->removeServer(resourceName);
diff --git a/synchronizer/listener.h b/synchronizer/listener.h
index d2ef0fc..b3929e7 100644
--- a/synchronizer/listener.h
+++ b/synchronizer/listener.h
@@ -53,6 +53,8 @@ public:
     QByteArray commandBuffer;
 };
 
+class QLockFile;
+
 class Listener : public QObject
 {
     Q_OBJECT
@@ -93,4 +95,5 @@ private:
     QTimer *m_clientBufferProcessesTimer;
     QTimer *m_checkConnectionsTimer;
     int m_messageId;
+    QLockFile *m_lockfile;
 };
-- 
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