[openstack-dev] [Ceilometer] Looking for some help understanding default meters

Thomas Maddox thomas.maddox at RACKSPACE.COM
Tue Aug 6 15:56:38 UTC 2013

On 8/5/13 4:02 PM, "Monsyne Dragon" <mdragon at RACKSPACE.COM> wrote:

>On 8/5/13 8:40 AM, "Julien Danjou" <julien at danjou.info> wrote:
>>On Mon, Aug 05 2013, Thomas Maddox wrote:
>>> Thinking about it, the latter option seems to describe a very real
>>> going forward that didn't occur to me when I was wandering around the
>>> code. Specifically regarding option 2a, if message 2 arrives at CM
>>> message 1 because it ended up on a faster route, then message 1 will
>>> overwrite the metadata from message 2 and we record an incorrect state.
>>> Isn't the nature of network comms for messages at the application layer
>>> potentially be out of order and in the case of UDP, even lost? What is
>>> leftover purpose of resource-show when we can't trust its output to
>>> represent the actual state of whatever resource is in question? It
>>> that timestamps could be used to prevent overwriting of the latest
>>> by checking that the incoming notification doesn't have a timestamp
>>> than the already recorded one. I hope I'm not seeing a problem that
>>> doesn't exist here or misunderstanding something. If so, please correct
>>No you're absolutely right. Checking the timestamp before we override
>>resource metadata would be a great idea. Would you mind reporting a bug
>>first, so we can schedule to fix it?
>It's probably good to keep in mind that AMQP does not guarantee order of
>At any point in the future, if we need to rely on ordering, we will need
>to check timestamps too.

Definitely. Thanks for the help, Dragon!

>>Julien Danjou
>>;; Free Software hacker ; freelance consultant
>>;; http://julien.danjou.info

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