Open Stack

On Tue, 2014-04-22 at 15:54 -0700, Devananda van der Veen wrote:
> Hi!
> 
> When a project is using oslo.messaging, how can we change our default
> rpc_thread_pool_size?
> 
> -----------------------
> Background
> 
> Ironic has hit a bug where a flood of API requests can deplete the RPC
> worker pool on the other end and cause things to break in very bad ways.
> Apparently, nova-conductor hit something similar a while back too. There've
> been a few long discussions on IRC about it, tracked partially here:
>   https://bugs.launchpad.net/ironic/+bug/1308680
> 
> tldr; a way we can fix this is to set the rpc_thread_pool_size very small
> (eg, 4) and keep our conductor.worker_pool size near its current value (eg,
> 64). I'd like these to be the default option values, rather than require
> every user to change the rpc_thread_pool_size in their local ironic.conf
> file.
> 
> We're also about to switch from the RPC module in oslo-incubator to using
> the oslo.messaging library.
> 
> Why are these related? Because it looks impossible for us to change the
> default for this option from within Ironic, because the option is
> registered when EventletExecutor is instantaited (rather than loaded).
> 
> https://github.com/openstack/oslo.messaging/blob/master/oslo/messaging/_executors/impl_eventlet.py#L76

It may have been possible for Ironic to set its own default before
oslo.messaging, but it wouldn't have been recommended because there's no
explicit API for doing so.

With oslo.messaging, we have a set_transport_defaults() which shows how
we'd approach adding this capability.

The question comes down to whether this really is a situation where we
need per-application defaults or just that the current defaults are
screwed up. If the latter, I'd much rather just change the defaults.

Mark.