setting rpc_conn_pool_size to 0 prevents processign of RPCs

[sean mooney]

during the root cause analasyis of downstream bug https://bugzilla.redhat.com/show_bug.cgi?id=1880371 it was observed that setting rpc_conn_pool_size to 0
prevents nova from processing rpc calls.

is defiend here to be any integer defaulting to 30
https://github.com/openstack/oslo.messaging/blob/e44c9883066d9b2d081a594b97aac3d598d491c9/oslo_messaging/_drivers/base.py#L25-L27

it should be defeiend as any positive integer with a min value of 1.

in the rabbit mq driver rpc_conn_pool_size is used to define the max size of the connection pool

https://github.com/openstack/oslo.messaging/blob/8d78ab2339d5798c7d8f5c49eaf6d2ef18859a07/oslo_messaging/_drivers/impl_rabbit.py#L1388

which is then used in put the get methods in the pool class.

https://github.com/openstack/oslo.messaging/blob/4fc9e70aa11f8cb0476a927ee471adbd296bba8f/oslo_messaging/_drivers/pool.py#L88-L105

when rpc_conn_pool_size==0 this loop never exits

to prevent this we shoudl add a min_size=1 to the rpc_conn_pool_size
config option.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/757654

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/757654
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=00d15eaeaba0ded0330cdcec7b19eee3adbfb1e1
Submitter: Zuul
Branch: master

commit 00d15eaeaba0ded0330cdcec7b19eee3adbfb1e1
Author: Sean Mooney <email address hidden>
Date: Mon Oct 12 22:43:31 2020 +0100

    add min of 1 to rpc_conn_pool_size

    This change add a min value of 1 to
    [oslo_messaging_rabbit]/rpc_conn_pool_size
    such that there is always at least 1 connection avaiable.

    This change add a runtime check to ensure that
    [oslo_messaging_rabbit]/rpc_conn_pool_size is greater than
    or equal too [oslo_messaging_rabbit]/conn_pool_min_size

    Change-Id: I2ad4b9f1d012c9f0586a932ac27d96da1bcc4e4c
    Closes-Bug: #1899533

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/victoria
Review: https://review.opendev.org/758414

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/758414
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=8f5847dcbe5144272ff7295fce2b50a9f544e5b0
Submitter: Zuul
Branch: stable/victoria

commit 8f5847dcbe5144272ff7295fce2b50a9f544e5b0
Author: Sean Mooney <email address hidden>
Date: Mon Oct 12 22:43:31 2020 +0100

    add min of 1 to rpc_conn_pool_size

    This change add a min value of 1 to
    [oslo_messaging_rabbit]/rpc_conn_pool_size
    such that there is always at least 1 connection avaiable.

    This change add a runtime check to ensure that
    [oslo_messaging_rabbit]/rpc_conn_pool_size is greater than
    or equal too [oslo_messaging_rabbit]/conn_pool_min_size

    Change-Id: I2ad4b9f1d012c9f0586a932ac27d96da1bcc4e4c
    Closes-Bug: #1899533
    (cherry picked from commit 00d15eaeaba0ded0330cdcec7b19eee3adbfb1e1)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ussuri
Review: https://review.opendev.org/758793

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/758793
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=7c9b070f5bc07692c837f9915eb0d8525065d0f6
Submitter: Zuul
Branch: stable/ussuri

commit 7c9b070f5bc07692c837f9915eb0d8525065d0f6
Author: Sean Mooney <email address hidden>
Date: Mon Oct 12 22:43:31 2020 +0100

    add min of 1 to rpc_conn_pool_size

    This change add a min value of 1 to
    [oslo_messaging_rabbit]/rpc_conn_pool_size
    such that there is always at least 1 connection avaiable.

    This change add a runtime check to ensure that
    [oslo_messaging_rabbit]/rpc_conn_pool_size is greater than
    or equal too [oslo_messaging_rabbit]/conn_pool_min_size

    Change-Id: I2ad4b9f1d012c9f0586a932ac27d96da1bcc4e4c
    Closes-Bug: #1899533
    (cherry picked from commit 00d15eaeaba0ded0330cdcec7b19eee3adbfb1e1)
    (cherry picked from commit 8f5847dcbe5144272ff7295fce2b50a9f544e5b0)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/train
Review: https://review.opendev.org/759410

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/759410
Committed: https://git.openstack.org/cgit/openstack/oslo.messaging/commit/?id=425ef28924f9d4178eaea2c0c0fe9e580b796aaa
Submitter: Zuul
Branch: stable/train

commit 425ef28924f9d4178eaea2c0c0fe9e580b796aaa
Author: Sean Mooney <email address hidden>
Date: Mon Oct 12 22:43:31 2020 +0100

    add min of 1 to rpc_conn_pool_size

    This change add a min value of 1 to
    [oslo_messaging_rabbit]/rpc_conn_pool_size
    such that there is always at least 1 connection avaiable.

    This change add a runtime check to ensure that
    [oslo_messaging_rabbit]/rpc_conn_pool_size is greater than
    or equal too [oslo_messaging_rabbit]/conn_pool_min_size

    Modified:
      oslo_messaging/tests/functional/test_rabbitmq.py

    NOTE(stephenfin): We must set the 'conn_pool_min_size' config option in
    the 'RabbitMQFailoverTests.test_failover_scenario' test to avoid raising
    an error because the minimum is greater than the configured value. This
    wasn't necessary on stable/train due to the presence of change
    I0f86416623a0b718516147f0660b4df2b74cf867 ("Setup backend scenarios for
    functional tests") which changed how our functional tests ran.

    Change-Id: I2ad4b9f1d012c9f0586a932ac27d96da1bcc4e4c
    Closes-Bug: #1899533
    (cherry picked from commit 00d15eaeaba0ded0330cdcec7b19eee3adbfb1e1)
    (cherry picked from commit 8f5847dcbe5144272ff7295fce2b50a9f544e5b0)
    (cherry picked from commit 7c9b070f5bc07692c837f9915eb0d8525065d0f6)