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

Rajul Kumar kumar.raju at husky.neu.edu
Thu Aug 3 19:56:43 UTC 2017

Hi Boris

Good to hear from you.
May I ask why you think so?

We do see some potential with OSProfiler for this and further objectives.


On Thu, Aug 3, 2017 at 3:48 PM, Boris Pavlovic <boris at pavlovic.me> wrote:

> Rajul,
> 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>
> wrote:
>> 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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