Be able to give lock to son processes detached by systemctl (#367)

* Give lock to systemctl sons
* Get the 'need_lock' flag from services.yml
* Don't need the lock for enable/disable and other stuff

data/templates/yunohost/services.yml

@@ -47,6 +47,7 @@ yunohost-api:
    log: /var/log/yunohost/yunohost-api.log
 yunohost-firewall:
    status: service
+   need_lock: true
 nslcd:
    status: service
    log: /var/log/syslog

src/yunohost/service.py

@@ -39,10 +39,10 @@
 
 from yunohost.hook import hook_callback
 
-
 BASE_CONF_PATH = '/home/yunohost.conf'
 BACKUP_CONF_DIR = os.path.join(BASE_CONF_PATH, 'backup')
 PENDING_CONF_DIR = os.path.join(BASE_CONF_PATH, 'pending')
+MOULINETTE_LOCK = "/var/run/moulinette_yunohost.lock"
 
 logger = log.getActionLogger('yunohost.service')
 
@@ -493,7 +493,8 @@ def _run_service_command(action, service):
         service -- Service name
 
     """
-    if service not in _get_services().keys():
+    services = _get_services()
+    if service not in services.keys():
         raise MoulinetteError(errno.EINVAL, m18n.n('service_unknown', service=service))
 
     cmd = None
@@ -505,15 +506,65 @@ def _run_service_command(action, service):
     else:
         raise ValueError("Unknown action '%s'" % action)
 
+    need_lock = (services[service].get('need_lock') or False) \
+                and action in ['start', 'stop', 'restart', 'reload']
+
     try:
-        ret = subprocess.check_output(cmd.split(), stderr=subprocess.STDOUT)
+        # Launch the command
+        logger.debug("Running '%s'" % cmd)
+        p = subprocess.Popen(cmd.split(), stderr=subprocess.STDOUT)
+        # If this command needs a lock (because the service uses yunohost
+        # commands inside), find the PID and add a lock for it
+        if need_lock:
+            PID = _give_lock(action, service, p)
+        # Wait for the command to complete
+        p.communicate()
+        # Remove the lock if one was given
+        if need_lock and PID != 0:
+            _remove_lock(PID)
+
     except subprocess.CalledProcessError as e:
         # TODO: Log output?
         logger.warning(m18n.n('service_cmd_exec_failed', command=' '.join(e.cmd)))
         return False
     return True
 
 
+def _give_lock(action, service, p):
+
+    # Depending of the action, systemctl calls the PID differently :/
+    if action == "start" or action == "restart":
+        systemctl_PID_name = "MainPID"
+    else:
+        systemctl_PID_name = "ControlPID"
+
+    cmd_get_son_PID ="systemctl show %s -p %s" % (service, systemctl_PID_name)
+    son_PID = 0
+    # As long as we did not found the PID and that the command is still running
+    while son_PID == 0 and p.poll() == None:
+        # Call systemctl to get the PID
+        # Output of the command is e.g. ControlPID=1234
+        son_PID = subprocess.check_output(cmd_get_son_PID.split()) \
+                            .strip().split("=")[1]
+        son_PID = int(son_PID)
+        time.sleep(1)
+
+    # If we found a PID
+    if son_PID != 0:
+        # Append the PID to the lock file
+        logger.debug("Giving a lock to PID %s for service %s !"
+                     % (str(son_PID), service))
+        filesystem.append_to_file(MOULINETTE_LOCK, "\n%s" % str(son_PID))
+
+    return son_PID
+
+def _remove_lock(PID_to_remove):
+
+    PIDs = filesystem.read_file(MOULINETTE_LOCK).split("\n")
+    PIDs_to_keep = [ PID for PID in PIDs if int(PID) != PID_to_remove ]
+    filesystem.write_to_file(MOULINETTE_LOCK, '\n'.join(PIDs_to_keep))
+
+
 def _get_services():
     """
     Get a dict of managed services with their parameters