Prototype htex result queue shutdown

Before this PR, this thread stays running forever, until it is terminated
by Python process exit.

After this PR, this thread polls an flag once per second, then properly
closes the ZMQ socket that it is using.

pytest parsl/tests/test_monitoring/ --config local
Before this PR, at end of test: 32 threads, 451 fds open.

After this PR, at end of test: 1 thread, 48 fds open.

Author: benclifford

parsl/executors/high_throughput/executor.py

@@ -331,6 +331,9 @@ def __init__(self,
             interchange_launch_cmd = DEFAULT_INTERCHANGE_LAUNCH_CMD
         self.interchange_launch_cmd = interchange_launch_cmd
 
+        self._result_queue_thread_exit = threading.Event()
+        self._result_queue_thread: Optional[threading.Thread] = None
+
     radio_mode = "htex"
     enable_mpi_mode: bool = False
     mpi_launcher: str = "mpiexec"
@@ -455,9 +458,11 @@ def _result_queue_worker(self):
         """
         logger.debug("Result queue worker starting")
 
-        while not self.bad_state_is_set:
+        while not self.bad_state_is_set and not self._result_queue_thread_exit.is_set():
             try:
-                msgs = self.incoming_q.get()
+                msgs = self.incoming_q.get(timeout_ms=1000)
+                if msgs is None:  # timeout
+                    continue
 
             except IOError as e:
                 logger.exception("Caught broken queue with exception code {}: {}".format(e.errno, e))
@@ -492,7 +497,6 @@ def _result_queue_worker(self):
                         if 'result' in msg:
                             result = deserialize(msg['result'])
                             task_fut.set_result(result)
-
                         elif 'exception' in msg:
                             try:
                                 s = deserialize(msg['exception'])
@@ -515,6 +519,8 @@ def _result_queue_worker(self):
                     else:
                         raise BadMessage("Message received with unknown type {}".format(msg['type']))
 
+        logger.info("Closing result ZMQ pipe")
+        self.incoming_q.close()
         logger.info("Result queue worker finished")
 
     def _start_local_interchange_process(self) -> None:
@@ -817,6 +823,8 @@ def shutdown(self, timeout: float = 10.0):
 
         logger.info("Attempting HighThroughputExecutor shutdown")
 
+        logger.info("Terminating interchange and result queue thread")
+        self._result_queue_thread_exit.set()
         self.interchange_proc.terminate()
         try:
             self.interchange_proc.wait(timeout=timeout)
@@ -841,6 +849,10 @@ def shutdown(self, timeout: float = 10.0):
             logger.info("Closing command client")
             self.command_client.close()
 
+        logger.info("Waiting for result queue thread exit")
+        if self._result_queue_thread:
+            self._result_queue_thread.join()
+
         logger.info("Finished HighThroughputExecutor shutdown attempt")
 
     def get_usage_information(self):

parsl/executors/high_throughput/zmq_pipes.py

@@ -206,12 +206,21 @@ def __init__(self, ip_address, port_range, cert_dir: Optional[str] = None):
         self.port = self.results_receiver.bind_to_random_port(tcp_url(ip_address),
                                                               min_port=port_range[0],
                                                               max_port=port_range[1])
+        self.poller = zmq.Poller()
+        self.poller.register(self.results_receiver, zmq.POLLIN)
 
-    def get(self):
+    def get(self, timeout_ms=None):
+        """Get a message from the queue, returning None if timeout expires
+        without a message. timeout is measured in milliseconds.
+        """
         logger.debug("Waiting for ResultsIncoming message")
-        m = self.results_receiver.recv_multipart()
-        logger.debug("Received ResultsIncoming message")
-        return m
+        socks = dict(self.poller.poll(timeout=timeout_ms))
+        if self.results_receiver in socks and socks[self.results_receiver] == zmq.POLLIN:
+            m = self.results_receiver.recv_multipart()
+            logger.debug("Received ResultsIncoming message")
+            return m
+        else:
+            return None
 
     def close(self):
         self.results_receiver.close()