add sigterm sigint handling

Author: spompea-cfa

middleware/consumer.py

@@ -1,5 +1,6 @@
 import json
 import os
+import signal
 import time
 import sys
 import boto3
@@ -135,6 +136,26 @@ def go():
     log.info('Spinning up messages generator')
     msgs = get_msgs(sqs, Q_URL)
 
+    receipt_handle = None
+
+    # Orderly clean-up logic if process is suddenly shut down.
+    def clean_up(signum, frm):
+        '''Attempt to cleanly reset the visiblity of the current in-flight
+        message before exiting. (It's possible we are exiting after
+        a message was deleted but the next has not yet been retrieved; that's ok'''
+        nonlocal sqs
+        nonlocal receipt_handle
+        log.info('***************************')
+        log.info('SIGINT or SIGTERM received.')
+        log.info('***************************')
+        try:
+            make_msg_visible(sqs, Q_URL, receipt_handle)
+        except Exception as ex:
+            log.error(ex)
+        sys.exit(0)
+    signal.signal(signal.SIGINT, clean_up)
+    signal.signal(signal.SIGTERM, clean_up)
+
     # Senzing init tasks.
     sz_eng = None
     try: