[openstack-dev] [oslo][performance] Proposing tail-based sampling in OSProfiler

Boris Pavlovic boris at pavlovic.me
Thu Aug 3 19:48:16 UTC 2017


It makes sense! However, maybe it's a bit too late... ;)

Best regards,
Boris Pavlovic

On Thu, Aug 3, 2017 at 12:16 PM, Rajul Kumar <kumar.raju at husky.neu.edu>

> Hello everyone
> I have added a blueprint on having tail-based sampling as a sampling
> option for continuous tracing in OSProfiler. It would be really helpful to
> have some thoughts, ideas, comments on this from the community.
> Continuous tracing provides a good insight on how various transactions
> behave across in a distributed system. Currently, OpenStack doesn't have a
> defined solution for continuous tracing. Though, it has OSProfiler that
> does generates selective traces, it may not capture the occurrence. Even if
> we have OSProfiler running continuously [1], we need to sample the traces
> so as to cut down the data generated and still keep the useful info.
> Head based sampling can be applied that decides initially whether a trace
> should be saved or not. However, it may miss out on some useful traces. I
> propose to have tail-based sampling [2] mechanism that makes the decision
> at the end of the transaction and tends to keep all the useful traces. This
> may require a lot of changes depending on what all type of info is required
> and the solution that we pick to implement it [2]. This may not affect the
> current working of any of the services on OpenStack as it will be off the
> critical path [3].
> Please share your thoughts on this and what solution should be preferred
> in a broader OpenStack's perspective.
> This is a step in the process of having an automated diagnostic solution
> for OpenStack cluster.
> [1] https://blueprints.launchpad.net/osprofiler/+spec/osprofiler-overhead-
> control
> [2] https://blueprints.launchpad.net/osprofiler/+spec/tail-based-coherent-
> sampling
> [3] https://blueprints.launchpad.net/osprofiler/+spec/asynchronous-trace-
> collection
> Thanks
> Rajul Kumar
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