Make AMQP based RPC consumer threads more robust

This is a backport from oslo-incubator,
commit 22ec8ff616a799085239e3e529daeeefea6366c4:

bug 1189711 Should RPC consume_in_thread() be more fault tolerant?

There are unprotected holes in the thread kicked off by RPC
consume_in_thread such that an exception will kill the thread.
This exists for both the service (TopicConsumer) and the new
reply proxy (DirectConsumer) consumers. This patch plugs
those holes as close to the base of the consumer thread as
possible by catching all non-caught exceptions and retrying
with sleeps between retries and some pacing of the log
output to prevent log flooding.

Change-Id: Ic7b286933a51d070e73eae452b93f8a011eb05c0

heat/openstack/common/excutils.py

@@ -22,6 +22,7 @@ Exception related utilities.
 import contextlib
 import logging
 import sys
+import time
 import traceback
 
 from heat.openstack.common.gettextutils import _
@@ -49,3 +50,33 @@ def save_and_reraise_exception():
                       traceback.format_exception(type_, value, tb))
         raise
     raise type_, value, tb
+
+
+def forever_retry_uncaught_exceptions(infunc):
+    def inner_func(*args, **kwargs):
+        last_log_time = 0
+        last_exc_message = None
+        exc_count = 0
+        while True:
+            try:
+                return infunc(*args, **kwargs)
+            except Exception as exc:
+                if exc.message == last_exc_message:
+                    exc_count += 1
+                else:
+                    exc_count = 1
+                # Do not log any more frequently than once a minute unless
+                # the exception message changes
+                cur_time = int(time.time())
+                if (cur_time - last_log_time > 60 or
+                        exc.message != last_exc_message):
+                    logging.exception(
+                        _('Unexpected exception occurred %d time(s)... '
+                          'retrying.') % exc_count)
+                    last_log_time = cur_time
+                    last_exc_message = exc.message
+                    exc_count = 0
+                # This should be a very rare event. In case it isn't, do
+                # a sleep.
+                time.sleep(1)
+    return inner_func

heat/openstack/common/rpc/impl_kombu.py

@@ -30,6 +30,7 @@ import kombu.entity
 import kombu.messaging
 from oslo.config import cfg
 
+from heat.openstack.common import excutils
 from heat.openstack.common.gettextutils import _
 from heat.openstack.common import network_utils
 from heat.openstack.common.rpc import amqp as rpc_amqp
@@ -723,6 +724,7 @@ class Connection(object):
 
     def consume_in_thread(self):
         """Consumer from all queues/consumers in a greenthread"""
+        @excutils.forever_retry_uncaught_exceptions
         def _consumer_thread():
             try:
                 self.consume()

heat/openstack/common/rpc/impl_qpid.py

@@ -24,6 +24,7 @@ import eventlet
 import greenlet
 from oslo.config import cfg
 
+from heat.openstack.common import excutils
 from heat.openstack.common.gettextutils import _
 from heat.openstack.common import importutils
 from heat.openstack.common import jsonutils
@@ -541,6 +542,7 @@ class Connection(object):
 
     def consume_in_thread(self):
         """Consumer from all queues/consumers in a greenthread"""
+        @excutils.forever_retry_uncaught_exceptions
         def _consumer_thread():
             try:
                 self.consume()