Exit daemon if another daemon holds the lock file

Jürgen Knödlseder
1 parent 5269ad65
Showing 1 changed file with 20 additions and 3 deletions
src/support/GDaemon.cpp
@@ -47,6 +47,7 @@
 /* __ Macros _____________________________________________________________ */
 /* __ Coding definitions _________________________________________________ */
+#define G_APPEND_LOG //!< Append output to log file
 /* __ Debug definitions __________________________________________________ */
@@ -175,7 +176,11 @@ GDaemon* GDaemon::clone(void) const
 void GDaemon::start(void)
 {
     // Open logger
+    #if defined(G_APPEND_LOG)
+    m_log.open(gammalib::gamma_filename("daemon.log"), false);
+    #else
     m_log.open(gammalib::gamma_filename("daemon.log"), true);
+    #endif
     m_log.chatter((GChatter)m_chatter);
     m_log.date(true);
@@ -193,6 +198,16 @@ void GDaemon::start(void)
     // Main event handling loop
     while (true) {
+        // If another daemon is running then exit this daemon
+        pid_t pid = lock_pid();
+        if (pid != m_pid) {
+            m_log << "*** Another daemon with PID " << pid;
+            m_log << " is running, while this daemon has PID " << m_pid;
+            m_log << ". Exit this daemon.";
+            m_log << std::endl;
+            break;
+        }
+
         // Put all activities into try-catch block
         try {
@@ -201,7 +216,8 @@ void GDaemon::start(void)
         }
         catch (const std::exception &except) {
-            m_log << "*** Exception catched by daemon:" << std::endl;
+            m_log << "*** Exception catched by daemon with PID " << m_pid;
+            m_log << ":" << std::endl;
             m_log << except.what() << std::endl;
         }
@@ -214,7 +230,8 @@ void GDaemon::start(void)
     } // endwhile: main event loop
     // Log termination of event loop
-    m_log << "Terminated event loop for unknown reason." << std::endl;
+    m_log << "Terminated event loop for daemon with PID " << m_pid;
+    m_log << "." << std::endl;
     // Delete lock file
     delete_lock_file();
@@ -400,7 +417,7 @@ void GDaemon::delete_lock_file(void)
         std::remove(lockfile.url().c_str());
         // Log removal of lock file
-        m_log << "Removal of lock file \"" << lockfile.url();
+        m_log << "Removed lock file \"" << lockfile.url();
         m_log << "\" for PID " << (int)(m_pid) << std::endl;
     }