Add check if server is running by pid

This ensures that it is possible to start new process even when
previous execution was terminated without cleaning files. Also prints
warning if it detects existing file and no running process about forced
process termination.

1 files changed, 24 insertions, 6 deletions

diff --git a/mcwrapper b/mcwrapper
index 565e677..e7802ae 100755
--- a/mcwrapper
+++ b/mcwrapper
@@ -112,11 +112,22 @@ def __server_start__():
         os.mkdir(conf.status)
     except FileExistsError:
         pass
-    if os.path.isfile(inputPipe):
-        if conf.verbose_level >= -1:
-            print("Error: Server input pipe already exists. Is another wrapper running?")
-        sys.exit(4)
-    os.mkfifo(inputPipe, 0o640)
+    try:
+        os.mkfifo(inputPipe, 0o640)
+    except FileExistsError:
+        pass
+    if os.path.isfile(pidfile):
+        with open(pidfile) as f:
+            lpid = int(f.readline())
+        try:
+            os.kill(lpid, 0)
+        except OSError:
+            if conf.verbose_level >= 0:
+                print("Warning: Detected forced termination of previous wrapper instance")
+        else:
+            if conf.verbose_level >= -1:
+                print("Error: Another wrapper is running with given identifier.")
+            sys.exit(4)
     with open(statusFile, 'w') as f:
         f.write(__STATUSSTRINGS__[1] + '\n')
     with open(playersFile, 'w') as f:
@@ -137,6 +148,8 @@ def __server_clean__():
         os.remove(playersFile)
     except FileNotFoundError:
         pass
+    if os.path.isfile(pidfile):
+        os.remove(pidfile)
 
 def __parse_line__(line):
     if ': Done' in line:
@@ -198,7 +211,10 @@ def mcexec():
         print("Start command: " + conf.command)
     os.chdir(os.path.expanduser(conf.directory))
     prc = subprocess.Popen(conf.command, stdin=subprocess.PIPE,
-            stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
+            stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True,
+             start_new_session=False)
+    with open(pidfile, "w") as f:
+        f.write(str(prc.pid))
     inputThread = __InputThread__(prc.stdin)
     inputThread.start()
     inputThread.wake() # Input thread is stuck in waiting for first line
@@ -304,6 +320,8 @@ if __name__ == '__main__':
     statusFile = conf.status + '/status'
     global playersFile
     playersFile = conf.status + '/players'
+    global pidfile
+    pidfile = conf.status + '/server.pid'
     global players
     players = set()