cinder/releasenotes/notes/rpc_compatibility-375be8ac3158981d.yaml
Michał Dulko c9a55d852e Add SIGHUP handlers to reset RPC version pins
Adding SIGHUP handlers (by implementing reset from oslo.service) to
cinder-scheduler, cinder-backup and cinder-volume that reset cached RPC
version pins. This is to avoid the need to restart all the services when
upgrade of the deployment is completed.

Some changes go a little deep into the stack, because to reload all the
pins we need to recreate <service>.rpcapi.<service>API objects that are
stored in the memory.

Please note that SIGHUP signal is handled by oslo.service only when
service runs in daemon mode (without tty attached). To test this commit
in DevStack you need to add "&" to the end of the command that starts
the service.

Situation is more complicated with the API service, so we're leaving it
with restart required for now. In the deployments with HA cinder-api is
typically behind a load balancer, so restarting individual nodes
one-by-one should be easy.

DocImpact: Add information on rolling upgrades procedures to the docs.
Implements: blueprint rpc-object-compatibility

Change-Id: I03ed74e17dc9a4b9aa2ddcfbeb36a106a0f035f8
2016-02-19 10:30:17 +01:00

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YAML

---
features:
- Added RPC backward compatibility layer similar to the
one implemented in Nova. This means that Cinder
services can be upgraded one-by-one without breakage.
After all the services are upgraded SIGHUP signals
should be issued to all the services to signal them
to reload cached minimum RPC versions. Alternative
is of course restart of them. Please note that
cinder-api service doesn't support SIGHUP yet.
Please also take into account that all the rolling
upgrades capabilities are considered tech preview,
as we don't have a CI testing it yet.
upgrade:
- Starting from Mitaka release Cinder is having a tech
preview of rolling upgrades support.