[openstack-dev] [Ceilometer] Alarming should be outside of Ceilometer as a separate package.

Sandy Walsh sandy.walsh at rackspace.com
Fri Aug 2 16:26:59 UTC 2013

On 08/02/2013 12:27 PM, Eoghan Glynn wrote:
>> On 08/01/2013 07:22 PM, Doug Hellmann wrote:
>>> On Thu, Aug 1, 2013 at 10:31 AM, Sandy Walsh <sandy.walsh at rackspace.com
>>> <mailto:sandy.walsh at rackspace.com>> wrote:
>>>     Hey y'all,
>>>     I've had a little thorn in my claw on this topic for a while and
>>>     thought
>>>     I'd ask the larger group.
>>>     I applaud the efforts of the people working on the alarming additions
>>>     to
>>>     Ceilometer, but I've got concerns that we're packaging things the
>>>     wrong way.
>>>     I fear we're making another Zenoss/Nagios with Ceilometer. It's trying
>>>     to do too much.
>>>     The current trend in the monitoring work (#monitoringlove) is to build
>>>     your own stack from a series of components. These components take in
>>>     inputs, process them and spit out outputs.
>>>     Collectors/Transformers/Publishers. This is the model CM is built on.
>>>     Making an all-singing-all-dancing monolithic monitoring package is the
>>>     old way of building these tools. People want to use best-of-breed
>>>     components for their monitoring stack. I'd like to be able to use
>>>     reimann.io <http://reimann.io> for my stream manager, diamond for my
>>>     collector, logstash for
>>>     my parser, etc. Alarming should just be another consumer.
>>>     CM should do one thing well. Collect data from openstack, store and
>>>     process them, and make them available to other systems via the API or
>>>     publishers. That's all. It should understand these events better than
>>>     any other product out there. It should be able to produce meaningful
>>>     metrics/meters from these events.
>>>     Alarming should be yet another consumer of the data CM produces. Done
>>>     right, the If-This-Then-That nature of the alarming tool could be
>>>     re-used by the orchestration team or perhaps even scheduling.
>>>     Intertwining it with CM is making the whole thing too complex and rigid
>>>     (imho).
>>>     CM should be focused on extending our publishers and input plug-ins.
>>>     I'd like to propose that alarming becomes its own project outside of
>>>     Ceilometer. Or, at the very least, its own package, external of the
>>>     Ceilometer code base. Perhaps it still lives under the CM moniker, but
>>>     packaging-wise, I think it should live as a separate code base.
>>> It is currently implemented as a pair of daemons (one to monitor the
>>> alarm state, another to send the notifications). Both daemons use a
>>> ceilometer client to talk to the REST API to consume the sample data or
>>> get the alarm details, as required. It looks like alarms are triggered
>>> by sending RPC cast message, and that those in turn trigger the webhook
>>> invocation. That seems pretty loosely coupled, as far as the runtime
>>> goes. Granted, it's still in the main ceilometer code tree, but that
>>> doesn't say anything about how the distros will package it.
>>> I'll admit I haven't been closely involved in the development of this
>>> feature, so maybe my quick review of the code missed something that is
>>> bringing on this sentiment?
>> No, you hit the nail on the head. It's nothing with the implementation,
>> it's purely with the packaging and having it co-exist within ceilometer.
>> Since it has its own services, uses Oslo, the CM client and operates via
>> the public API, it should be able to live outside the main CM codebase.
>> My concern is that it has a different mandate than CM (or the CM mandate
>> is too broad).
>> What really brought it on for me was doing code reviews for CM and
>> hitting all this alarm stuff and thinking "this is mental context switch
>> from what CM does, it really doesn't belong here." (though I'm happy to
>> help out with the reviews)
>> -S
> Hi Sandy,
> In terms of distro packaging, the case that I'm most familiar (Fedora & derivatives)
> already splits out the ceilometer packaging in a fairly fine-grained manner (with
> separate RPMs for the various services and agents). I'd envisage a similar packaging
> approach will be followed for the alarming services, so for deployments for which
> alarming is not required, this functionality won't be foisted on anyone.

Thanks for the feedback Eoghan.

I don't imagine that should be a big problem. Packaging in the sense of
the code base is different issue. If, for all intents and purposes,
alarming is a separate system: uses external api's, only uses sanctioned
CM client libraries, is distro packaged separately and optionally
installed/deployed then I don't understand why it has to live in the CM

> Now we could think about splitting it out even further to aid the sort of composability
> you desire, however this functionality is needed by Heat, so it makes sense for it to
> live in one of the integrated projects (as opposed to a newly incubated split-off).

I'm not purposing it becomes a newly incubated project. I think it makes
sense to live under the CM moniker. But code-wise, it should be a
separate repo. This wouldn't pose any problem since -infra already does
this with its many repos.

> In terms of the context switching required for reviewing alarming patches, I don't
> see that as a huge issue for two reasons:
>  - larger projects such as nova already require immensely greater context switching
>    of it's team of core devs
>  - core devs can and do concentrate their reviewing on some functional sub-domains,
>    i.e. everyone doesn't have to the entire spectrum of patches

Having it in a separate repo would lessen the chance of leakage between
dependencies. Are there libraries that alarming needs that CM doesn't
need? Is the db model growing in ways that aren't core to CM? Is there
greater volatility in the project overall because of the increased
number of branches going in? Will new developers have a harder time
onboarding due to more code?

I think the answer is yes across the board.

We're all in agreement that alarming is essentially standalone already
... now it just needs its own repo.

> That being said, the efforts of team members such as yourself who make an obvious
> effort to review a wide range of patches, is of course appreciated! 
> Cheers,
> Eoghan
>>> Doug
>>>     Please, change my view. :)
>>>     -S
>>>     Side note: I might even argue that the statistical features of CM are
>>>     going a little too far. My only counter-argument is that statistics are
>>>     the only way to prevent us from sending large amounts of data over the
>>>     wire for post-processing. But that's a separate discussion.
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