Handle race where process exits immediately in signal()

Author: mnaberez

supervisor/process.py

@@ -512,7 +512,18 @@ def signal(self, sig):
                             ProcessStates.STOPPING)
 
         try:
-            options.kill(self.pid, sig)
+            try:
+                options.kill(self.pid, sig)
+            except OSError as exc:
+                if exc.errno == errno.ESRCH:
+                    msg = ("unable to signal %s (pid %s), it probably just now exited "
+                           "on its own: %s" % (processname, self.pid,
+                           str(exc)))
+                    options.logger.debug(msg)
+                    # we could change the state here but we intentionally do
+                    # not.  we will do it during normal SIGCHLD processing.
+                    return None
+                raise
         except:
             tb = traceback.format_exc()
             msg = 'unknown problem sending sig %s (%s):%s' % (

supervisor/tests/test_process.py

@@ -1004,6 +1004,29 @@ def test_signal_from_running(self):
         self.assertTrue(instance.pid in options.kills)
         self.assertEqual(options.kills[instance.pid], signal.SIGWINCH)
 
+    def test_signal_from_running_error_ESRCH(self):
+        options = DummyOptions()
+        config = DummyPConfig(options, 'test', '/test')
+        options.kill_exception = OSError(errno.ESRCH,
+                                         os.strerror(errno.ESRCH))
+        instance = self._makeOne(config)
+        L = []
+        from supervisor.states import ProcessStates
+        from supervisor import events
+        events.subscribe(events.ProcessStateEvent, lambda x: L.append(x))
+        instance.pid = 11
+        instance.state = ProcessStates.RUNNING
+        instance.signal(signal.SIGWINCH)
+        self.assertEqual(options.logger.data[0],
+            'sending test (pid 11) sig SIGWINCH')
+        self.assertEqual(options.logger.data[1], 'unable to signal test (pid 11), '
+            'it probably just now exited on its own: %s' %
+            str(options.kill_exception))
+        self.assertFalse(instance.killing)
+        self.assertEqual(instance.state, ProcessStates.RUNNING) # unchanged
+        self.assertEqual(instance.pid, 11) # unchanged
+        self.assertEqual(len(L), 0)
+
     def test_signal_from_running_error(self):
         options = DummyOptions()
         config = DummyPConfig(options, 'test', '/test')