[openstack-dev] [Congress] Austin recap

Eric K ekcs.openstack at gmail.com
Fri May 6 03:08:28 UTC 2016

Thanks for the summary, Tim. Very productive summit!

I¹ve added more notes and a diagram to the HA ether pad. Is that the best
way to continue the discussion?

From:  Tim Hinrichs <tim at styra.com>
Reply-To:  "OpenStack Development Mailing List (not for usage questions)"
<openstack-dev at lists.openstack.org>
Date:  Tuesday, May 3, 2016 at 11:37 AM
To:  "OpenStack Development Mailing List (not for usage questions)"
<openstack-dev at lists.openstack.org>
Subject:  [openstack-dev] [Congress] Austin recap

> Hi all,
> Here¹s a quick summary of the Congress activities in Austin.  Everyone should
> feel free to chime in with corrections and things I missed.
> 1. Talks
> Masahito gave a talk on applying Congress for fault recovery in the context of
> NFV.
> https://www.openstack.org/summit/austin-2016/summit-schedule/events/7199
> <https://www.openstack.org/summit/austin-2016/summit-schedule/events/7199>
> Fabio gave a talk on applying Congress + Monasca to enforce application-level
> SLAs.
> https://www.openstack.org/summit/austin-2016/summit-schedule/events/7363
> <https://www.openstack.org/summit/austin-2016/summit-schedule/events/7363>
> 2. Integrations
> We had discussions, both within the Congress Integrations fishbowl session,
> and outside of that session on potential integrations with other OpenStack
> projects.  Here's a quick overview.
> - Monasca (fabiog). The proposed integration: Monasca pushes data to Congress
> using the push driver to let Congress know about the alarms Monasca
> configured.  Can use multiple alarms using a single table.  Eventually we
> talked about having Congress analyze the policy to configure the alarms that
> Monasca uses, completing the loop.
> - Watcher (acabot). Watcher aims to optimize the placement of VMs by pulling
> data from Ceilometer/Monasca and Nova (including affinity/anti-affinity info),
> computing necessary migrations for whichever strategy is configured, and
> migrates the VMs.  Want to use Congress as a source of policies that they take
> into account when computing the necessary migrations.
> - Nova scheduler.  There¹s interest in policy-enabling the Nova scheduler, and
> then integrating that with Congress in the context of delegation, both to give
> Congress the ability to pull in the scheduling policy and to push the
> scheduling policy.
> - Mistral.  The use case for this integration is to help people create an HA
> solution for VMs.  So have Congress monitor VMs, identify when they have
> failed, and kick off a Mistral workflow to resurrect them.
> - Vintrage.  Vintrage does root-cause-analysis.  It provides a graph-based
> model for the structure of the datacenter (switches attached to hypervisors,
> servers attached to hypervisors, etc.) and a templating language for defining
> how to create new alarms from existing alarms.  The action item that we left
> is that the Vintrage team will initiate a mailing list thread where we discuss
> which Vintrage data might be valuable for Congress policies.
> 3. Working sessions
> - The new distributed architecture is nearing completion.  There seems to be 1
> blocker for having the basic functionality ready to test: at boot, Congress
> doesn¹t properly spin up datasources that have already been configured in the
> database.  As an experiment to see how close we were to completion, we started
> up the Congress server with just the API and policy engine and saw the basics
> actually working!  When we added the datasources, we found a bug where the API
> was assuming the datasources could be referenced by UUID, when in fact they
> can only be referenced by Name on the message-bus.   So while there¹s still
> quite a bit to do, we¹re getting close to having all the basics working.
> - We made progress on the high-availability and high-throughput design.  This
> is still very much open to design and discussion, so continuing the design on
> the mailing list would be great.  Here are the highlights.
>     o  Policy engine: split into (i) active-active for queries to deal with
> high-throughput (ii) active-passive for action-execution (requiring
> leader-election, etc.).  Policy CRUD modifies DB; undecided whether API also
> informs all policy-engines, or whether they all sync from the DB.
>     o  Pull datasources: no obvious need for replication, since they restart
> really fast and will just re-pull the latest data anyhow
>     o  Push datasources: Need HA for ensuring the pusher can always push, e.g.
> the pusher drops the message onto oslo-messaging.  Still up for debate is
> whether we also need HA for storing the data since there is no way to ask for
> it after a restart; one suggestion is that every datasource must allow us to
> ask for the state.  HT does not require replication, since syncing the state
> between several instances would be required and would be less performant than
> a single instance.
>     o  API (didn¹t really discuss this, so here¹s my take).  No obvious need
> for replication for HT, since if the API is a bottleneck, the backend will be
> an even bigger bottleneck.  For HA, could do active-active since the API is
> just a front-end to the message bus + database, though we would need to look
> into locking now that there is no GIL.
> It was great seeing everyone in Austin!
> Tim
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