envoyproxy
ext_proc - sampling support
Title: ext_proc - sampling support
Description: We need the ability to sample ext_proc calls. A simple sample_rate field (0.0 to 1.0) within ext_proc filter that activates the filter and makes the external call only when necessary. This becomes especially useful when we finish implementing the async support, allowing users to selectively sample a fraction of traffic for observation.
Once sampled, the stream should be active for the entire request, honoring all the processing modes, etc.
cc @tyxia @htuch
Should the sampling be inside the unified matcher? There's a common need to sample logs statefully and probabilistically, for example in https://github.com/envoyproxy/envoy/issues/30006.
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I am a little bit confused on the comments.
The original issue description is for adding sampling support for ext_proc to makes the external call only when necessary. To implement that, we can simply toss a coin in the ext_proc filter and make the external call based on the coin toss result.
@kyessenov @htuch could you please elaborate the idea to implement it in the unified matcher?
I think @kyessenov is suggesting we just have the coin flip in the matcher, which will be more generic, as there are other legit use cases for sampling.
I think it can be understood as: Performing the sampling at the higher level and centralized place. This will benefit all delegated filters (like ext_proc, ext_authz, etc) as the delegated filters are invoked based on sampling result