[openstack-dev] [puppet][Fuel] OpenstackLib Client Provider Better Exception Handling

Matt Fischer matt at mattfischer.com
Thu Oct 15 13:37:09 UTC 2015

On Thu, Oct 15, 2015 at 4:10 AM, Vladimir Kuklin <vkuklin at mirantis.com>

> Gilles,
> 5xx errors like 503 and 502/504 could always be intermittent operational
> issues. E.g. when you access your keystone backends through some proxy and
> there is a connectivity issue between the proxy and backends which
> disappears in 10 seconds, you do not need to rerun the puppet completely -
> just retry the request.
> Regarding "REST interfaces for all Openstack API" - this is very close to
> another topic that I raised ([0]) - using native Ruby application and
> handle the exceptions. Otherwise whenever we have an OpenStack client
> (generic or neutron/glance/etc. one) sending us a message like '[111]
> Connection refused' this message is very much determined by the framework
> that OpenStack is using within this release for clients. It could be
> `requests` or any other type of framework which sends different text
> message depending on its version. So it is very bothersome to write a bunch
> of 'if' clauses or gigantic regexps instead of handling simple Ruby
> exception. So I agree with you here - we need to work with the API
> directly. And, by the way, if you also support switching to native Ruby
> OpenStack API client, please feel free to support movement towards it in
> the thread [0]
> Matt and Gilles,
> Regarding puppet-healthcheck - I do not think that puppet-healtcheck
> handles exactly what I am mentioning here - it is not running exactly at
> the same time as we run the request.
> E.g. 10 seconds ago everything was OK, then we had a temporary
> connectivity issue, then everything is ok again in 10 seconds. Could you
> please describe how puppet-healthcheck can help us solve this problem?

You are right, it probably won't. At that point you are using puppet to
work around some fundamental issues in your OpenStack deployment.

> Or another example - there was an issue with keystone accessing token
> database when you have several keystone instances running, or there was
> some desync between these instances, e.g. you fetched the token at keystone
> #1 and then you verify it again keystone #2. Keystone #2 had some issues
> verifying it not due to the fact that token was bad, but due to the fact
> that that keystone #2 had some issues. We would get 401 error and instead
> of trying to rerun the puppet we would need just to handle this issue
> locally by retrying the request.
> [0] http://permalink.gmane.org/gmane.comp.cloud.openstack.devel/66423

Another one that is a deployment architecture problem. We solved this by
configuring the load balancer to direct keystone traffic to a single db
node, now we solve it with Fernet tokens. If you have this specific issue
above it's going to manifest in all kinds of strange ways and can even
happen to control services like neutron/nova etc as well. Which means even
if we get puppet to pass with a bunch of retries, OpenStack is not healthy
and the users will not be happy about it.

I don't want to give them impression that I am completely opposed to
retries, but on the other hand, when my deployment is broken, I want to
know quickly, not after 10 minutes of retries, so we need to balance that.
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