[openstack-dev] [nova] Deprecating CONF.block_device_allocate_retries_interval

Nikola Đipanov ndipanov at redhat.com
Fri Aug 8 12:42:53 UTC 2014

On 08/06/2014 07:54 PM, Jay Pipes wrote:
> I bring this up on the mailing list because I think Liyi's patch offers
> an interesting future direction to the way that we think about our retry
> approach in Nova. Instead of having hard-coded or configurable interval
> times, I think Liyi's approach of calculating the interval length based
> on some input values is a good direction to take.

This indeed is a problem that we've seen bite us a number of times, and
I tried to solve it by proposing [1] but didn't get to work on it
further yet.

Having said that - after thinking about it more, I was not sure I like
my own approach in [1] on the grounds of it being too generic (and
overly elaborate) for the particular problem it is solving.

I was then thinking of something similar to what is proposed here, where
we would have a waiting time that is a function of a value that we could
query Cinder on. Allocation rate proposed here seems to fit this nicely,
but in my mind we would have a way to query cinder about it instead of
hardcoding it, however this can be done later and in cooperation with
the Cinder team.

> 2) We should deprecate the CONF.block_device_allocate_retries_interval
> option only, and keep the CONF.block_device_allocate_retries
> configuration option as-is, changing the help text to read something
> like "Max number of retries. We calculate the interval of the retry
> based on the size of the volume."

I'd go with this as the number of retries can still be useful as a tool
for easy workaround and troubleshooting, but I'd put a big disclaimer
that it is mostly meant for debugging/workaround purposes.


[1] https://review.openstack.org/#/c/87546/

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