Changelog and documentation for new daemon discovery files

CHANGELOG

@@ -12,6 +12,7 @@ nsmd now follows the XDG Base Directory Specifications:
  Lockfiles fixed (see issue #gh-31)
  Lockfiles are now in $XDG_RUNTIME_DIR/nsm/
  Lockfiles now each contain the session path, the osc NSM_URL and the nsmd PID
+ One daemon file for each currently running nsmd is created in $XDG_RUNTIME_DIR/nsm/d/ containing the osc url. This enables discovery of running daemons.
  New section in the API documentation for the above.
 Fixes and guards against trying to load non-existing sessions and creating new sessions under existing names
 

docs/api/index.html

@@ -467,6 +467,7 @@ body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-b
 <ul class="sectlevel4">
 <li><a href="#_subdirectories_hierarchical_structure">1.2.3.1. Subdirectories / Hierarchical Structure</a></li>
 <li><a href="#_lockfiles">1.2.3.2. Lockfiles</a></li>
+<li><a href="#_daemon_discovery">1.2.3.3. Daemon Discovery</a></li>
 </ul>
 </li>
 </ul>
@@ -796,6 +797,19 @@ osc.udp://myuser.localdomain:11287/
 </div>
 </div>
 </div>
+<div class="sect4">
+<h5 id="_daemon_discovery">1.2.3.3. Daemon Discovery</h5>
+<div class="paragraph">
+<p>Each running <code>nsmd</code>, per user, creates a state file under <code>$XDG_RUNTIME_DIR/nsm/d/</code> (usually
+<code>/run/user/XXXX/nsm/d/</code>) that can be used to look up running daemons, even if no session is loaded.
+The files contains the daemons osc.udp URL that is compatible with the --nsm-url parameter of the GUI.</p>
+</div>
+<div class="paragraph">
+<p>This enables you to e.g. start nsmd at boot with a random free port. Server-control programs such
+as GUIs can then use this to look for running servers without requiring the user to look up and
+input an osc URL manually as command line parameter.</p>
+</div>
+</div>
 </div>
 </div>
 </div>
@@ -1871,7 +1885,7 @@ behaviour more strictly as well, removing false session entries in 3rd party cli
 <li>
 <p>nsmd now follows the XDG Base Directory Specifications for it&#8217;s session root and lock files. This
 if of no consequence to clients but required documentation nevertheless, which was described as
-"background information" in the new section.</p>
+"background information" in the chapters for lock files and daemon disovery.</p>
 </li>
 </ul>
 </div>
@@ -1882,7 +1896,7 @@ if of no consequence to clients but required documentation nevertheless, which w
 <div id="footer">
 <div id="footer-text">
 Version API 1.1.2<br>
-Last updated 2022-03-05 12:34:04 +0100
+Last updated 2022-03-15 18:44:44 +0100
 </div>
 </div>
 </body>

docs/index.html

@@ -557,7 +557,7 @@ Documentation and tutorials for software-developers will be added at a later dat
 <div id="footer">
 <div id="footer-text">
 Version 1.6.0<br>
-Last updated 2022-03-05 12:34:04 +0100
+Last updated 2022-03-15 18:44:44 +0100
 </div>
 </div>
 </body>

docs/src/api/index.adoc

@@ -230,6 +230,18 @@ osc.udp://myuser.localdomain:11287/
 3022
 ```
 
+===== Daemon Discovery
+
+Each running `nsmd`, per user, creates a state file under `$XDG_RUNTIME_DIR/nsm/d/` (usually
+`/run/user/XXXX/nsm/d/`) that can be used to look up running daemons, even if no session is loaded.
+The files contains the daemons osc.udp URL that is compatible with the --nsm-url parameter of the GUI.
+
+
+This enables you to e.g. start nsmd at boot with a random free port. Server-control programs such
+as GUIs can then use this to look for running servers without requiring the user to look up and
+input an osc URL manually as command line parameter.
+
+
 == NSM OSC Protocol
 
 All message parameters are REQUIRED. All messages MUST be sent from the same socket as the `announce`
@@ -908,4 +920,4 @@ behaviour more strictly as well, removing false session entries in 3rd party cli
 
 * nsmd now follows the XDG Base Directory Specifications for it's session root and lock files. This
 if of no consequence to clients but required documentation nevertheless, which was described as
-"background information" in the new section.
+"background information" in the chapters for lock files and daemon disovery.

src/nsmd.cpp

@@ -64,6 +64,7 @@ static int signal_fd;
 
 static char *session_root;
 static char *lockfile_directory;
+static char *daemon_file;
 
 #define NSM_API_VERSION_MAJOR 1
 #define NSM_API_VERSION_MINOR 1
@@ -2584,6 +2585,10 @@ handle_signal_clean_exit ( int signal )
     close_session();
     free( session_root );
     free( lockfile_directory );
+    unlink( daemon_file );
+    MESSAGE( "Deleted daemon file %s", daemon_file );
+    free( daemon_file );
+
     exit(0);
 }
 
@@ -2717,9 +2722,24 @@ int main(int argc, char *argv[])
             }
         }
         MESSAGE( "Using %s for lock-files.", lockfile_directory );
-    }
-
 
+        //Now create another subdir for daemons .../nsm/d/ where each daemon has a port number file
+        char * daemon_directory;
+        asprintf( &daemon_directory, "%s/d", lockfile_directory);
+        struct stat st_daemonfile_dir_mkdir;
+        if ( stat( daemon_directory, &st_daemonfile_dir_mkdir ) )
+        {
+            if ( mkdir( daemon_directory, 0771 ) )
+            {
+                FATAL( "Failed to create daemon file directory %s with error: %s", daemon_directory, strerror( errno ) );
+            }
+        }
+        //daemon_file is a global var
+        asprintf( &daemon_file, "%s/%d", daemon_directory, getpid());
+        free ( daemon_directory );
+        MESSAGE( "Using %s as daemon file.", daemon_file );
+        //The actual daemon file will be written below after announcing the session url.
+    }
 
     if ( !session_root ) {
         /* The user gave no specific session directory. We use the default.
@@ -2736,6 +2756,7 @@ int main(int argc, char *argv[])
         */
         struct stat st_session_root;
 
+        //TODO: Valgrind shows a memory leak for the next line. Why?
         asprintf( &session_root, "%s/%s", getenv( "HOME" ), "NSM Sessions" );
         if ( stat( session_root, &st_session_root ) == 0 && S_ISDIR(st_session_root.st_mode)) {
             WARNING ( "An old session directory was detected in %s. You can continue to use it but it is recommended to move your sessions to $XDG_DATA_HOME/nsm-sessions/. If you don't know where that is simply rename your current session-directory and start nsmd, which will tell you the new directory.", session_root);
@@ -2775,7 +2796,20 @@ int main(int argc, char *argv[])
         FATAL( "Failed to create OSC server." );
     }
 
-    printf( "NSM_URL=%s\n", osc_server->url() );
+    char * url = osc_server->url();
+
+    printf( "NSM_URL=%s\n", url );
+
+    //Write the URL into the daemon_file that is named after our PID
+    FILE *fpdaemon = fopen( daemon_file, "w" );
+    if ( !fpdaemon )  {
+        FATAL( "Failed to write daemon file to %s with error: %s", daemon_file, strerror( errno ) );
+    }
+    fprintf( fpdaemon, "%s\n", url );
+    MESSAGE( "Created daemon file %s", daemon_file );
+    fclose( fpdaemon );
+
+    free( url );
 
     if ( gui_url )
     {
@@ -2847,24 +2881,20 @@ int main(int argc, char *argv[])
     }
 
     /* listen for sigchld signals and process OSC messages forever */
-    int start_pid = getppid(); //get parent pid
+    int start_ppid = getppid(); //get parent pid
     for ( ;; )
     {
         wait( 1000 ); //1000 ms
         //This still has some corner cases, like a race condition on startup that never gets the real PID, but
         //we cover the majority of cases at least:
-        if ( start_pid != getppid() ) {
-            WARNING ( "Our parent PID changed from %d to %d, which indicates a possible GUI crash. The user has no control over the session anymore. Trying to shut down cleanly.", start_pid, getppid());
+        if ( start_ppid != getppid() ) {
+            WARNING ( "Our parent PID changed from %d to %d, which indicates a possible GUI crash. The user has no control over the session anymore. Trying to shut down cleanly.", start_ppid, getppid());
             handle_signal_clean_exit ( 0 );
         }
     }
 
     //Code after here will not be executed if nsmd is stopped with any abort-signal like SIGINT.
     //Without a signal handler clients will remain active ("zombies") without nsmd as parent.
-    //MESSAGE ( "End of Program");
-
-    //free(session_root);// This was not executed if nsmd received a stop signal. It is now handled by handle_signal_clean_exit()
-    //osc_server->run();
-
+    //Therefore exit is handled by handle_signal_clean_exit()
     return 0;
 }