Change default value of "heartbeat_in_pthread" to False

As was reported in the related bug some time ago, setting that
option to True for nova-compute can break it as it's non-wsgi service.
We also noticed same problems with randomly stucked non-wsgi services
like e.g. neutron agents and probably the same issue can happen with
any other non-wsgi service.

To avoid that this patch changes default value of that config option
to be False.
Together with [1] it effectively reverts change done in [2] some time
ago.

[1] https://review.opendev.org/c/openstack/oslo.messaging/+/800621
[2] https://review.opendev.org/c/openstack/oslo.messaging/+/747395

Related-Bug: #1934937
Closes-Bug: #1961402

Change-Id: I85f5b9d1b5d15ad61a9fcd6e25925b7eeb8bf6e7

oslo_messaging/_drivers/impl_rabbit.py

@@ -92,7 +92,7 @@ rabbit_opts = [
                 'executable used does not support OpenSSL FIPS mode, '
                 'an exception will be raised.'),
     cfg.BoolOpt('heartbeat_in_pthread',
-                default=True,
+                default=False,
                 help="Run the health check heartbeat thread "
                      "through a native python thread by default. If this "
                      "option is equal to False then the health check "
@@ -100,7 +100,9 @@ rabbit_opts = [
                      "from the parent process. For "
                      "example if the parent process has monkey patched the "
                      "stdlib by using eventlet/greenlet then the heartbeat "
-                     "will be run through a green thread.",
+                     "will be run through a green thread. "
+                     "This option should be set to True only for the "
+                     "wsgi services.",
                 ),
     cfg.FloatOpt('kombu_reconnect_delay',
                  default=1.0,

releasenotes/notes/do-not-run-heartbeat-in-pthread-by-default-42e1299f59b841f8.yaml

@@ -0,0 +1,9 @@
+---
+upgrade:
+  - |
+    The ``[oslo_messaging_rabbit] heartbeat_in_pthread`` config option
+    defaults to ``False`` again.
+    For wsgi applications it is recommended to set this value to ``True``
+    but enabling it for non-wsgi services may break such service.
+    Please check https://bugs.launchpad.net/oslo.messaging/+bug/1934937
+    for more details.