Add SIGTERM handling to segment gatherer

pytroll_collectors/segments.py

@@ -37,10 +37,11 @@
 
 import datetime as dt
 import logging.handlers
+import os
+import signal
 from abc import ABCMeta, abstractmethod
 from collections import OrderedDict
 from enum import Enum
-import os
 
 import trollsift
 from posttroll import message as pmessage
@@ -610,6 +611,7 @@ def __init__(self, config):
         self._group_by_minutes = self._config.get('group_by_minutes', None)
 
         self._loop = False
+        self._sigterm_caught = False
         self._providing_server = self._config.get('providing_server')
         self._is_first_message_after_start = True
 
@@ -711,9 +713,13 @@ def _collect_publisher_config(self):
     def run(self):
         """Run SegmentGatherer."""
         self._setup_messaging()
+        signal.signal(signal.SIGTERM, self._handle_sigterm)
 
         self._loop = True
         while self._loop:
+            if self._sigterm_caught and not self.slots:
+                self.stop()
+
             self.triage_slots()
 
             # Check listener for new messages
@@ -734,6 +740,10 @@ def run(self):
                 logger.info("New message received: %s", str(msg))
                 self.process(msg)
 
+    def _handle_sigterm(self, signum, frame):
+        logging.info("Caught SIGTERM, shutting down when all collections are finished.")
+        self._sigterm_caught = True
+
     def triage_slots(self):
         """Check if there are slots ready for publication."""
         slots = self.slots.copy()

pytroll_collectors/tests/test_segments.py

@@ -747,6 +747,57 @@ def test_listener_use_first_nameserver(self):
             self.msg0deg._setup_listener()
         assert_messaging(None, None, None, 'localhost', None, ListenerContainer)
 
+    def test_sigterm(self):
+        """Test that SIGTERM signal is handled."""
+        import os
+        import signal
+        import time
+        from multiprocessing import Process
+
+        with patch('pytroll_collectors.segments.ListenerContainer'):
+            col = SegmentGatherer(CONFIG_SINGLE)
+            proc = Process(target=col.run)
+            proc.start()
+            time.sleep(1)
+            os.kill(proc.pid, signal.SIGTERM)
+            proc.join()
+
+        assert proc.exitcode == 0
+
+    def test_sigterm_nonempty_slots(self):
+        """Test that SIGTERM signal is handled properly when there are active slots present."""
+        import os
+        import signal
+        import time
+        from multiprocessing import Process
+
+        with patch('pytroll_collectors.segments.ListenerContainer'):
+            with patch('pytroll_collectors.segments.SegmentGatherer.triage_slots',
+                       new=_fake_triage_slots):
+                col = SegmentGatherer(CONFIG_SINGLE)
+                proc = Process(target=col.run)
+                proc.start()
+                time.sleep(1)
+                tic = time.time()
+                os.kill(proc.pid, signal.SIGTERM)
+                proc.join()
+
+        assert proc.exitcode == 0
+        # Triage after the kill signal takes 1 s
+        assert time.time() - tic > 1.
+
+
+def _fake_triage_slots(self):
+    """Fake the triage_slots() method.
+
+    The fake triage adds a new slot if SIGTERM has not been caught, and removes it when the signal comes.
+    """
+    import time
+    self.slots["foo"] = "bar"
+    if self._sigterm_caught:
+        del self.slots["foo"]
+        time.sleep(1)
+
 
 def _get_message_from_metadata_and_patterns(mda, patterns):
     fake_message = FakeMessage(mda)