Don't respawn procs when the watcher is stopping.

Fix #529

circus/watcher.py

@@ -182,6 +182,7 @@ def __init__(self, name, cmd, args=None, numprocesses=1, warmup_delay=0.,
         self.args = args
         self._process_counter = 0
         self.stopped = stopped
+        self._stopping = False
         self.graceful_timeout = float(graceful_timeout)
         self.prereload_fn = prereload_fn
         self.executable = None
@@ -434,7 +435,8 @@ def manage_processes(self):
                     self.kill_process(process)
 
         # adding fresh processes
-        if self.respawn and len(self.processes) < self.numprocesses:
+        if (self.respawn and len(self.processes) < self.numprocesses
+                and not self._stopping):
             self.spawn_processes()
 
         # removing extra processes
@@ -561,7 +563,6 @@ def kill_process(self, process, sig=signal.SIGTERM):
             self.send_signal(process.pid, sig)
             self.notify_event("kill", {"process_pid": process.pid,
                                        "time": time.time()})
-
         except NoSuchProcess:
             # already dead !
             return
@@ -645,6 +646,8 @@ def stop(self, async=True, restarting=False):
         for process in self.get_active_processes():
             self.send_signal(process.pid, signal.SIGTERM)
 
+        self._stopping = True
+
         # delayed SIGKILL if async is True
         limit = time.time() + self.graceful_timeout
 
@@ -691,6 +694,7 @@ def _final_stop(self, limit=None, restarting=False, async=True):
             self.notify_event("stop", {"time": time.time()})
 
         self.stopped = True
+        self._stopping = False
 
         # We ignore the hook result
         self.call_hook('after_stop')