Proposal: Envoy Admission Control calculation to use latency statistics

[marcusoyang]

tl:dr

Add latency statistics into the Admission Control filter success rate calculation

Context

To make the Admission Control capability more effective in the context of slow dependency response times, the proposal is to add to the Admission Control filter envoy/source/extensions/filters/http/admission_control at main · envoyproxy/envoy and add response latency statistics in its successRateThreshold calculation.

Currently, success rate is derived only from the HTTP response status codes of a dependency. This heuristic is effective when response latency is relatively fast, however in the situation when a dependency’s response latency is degraded, this would be useful.

[kyessenov]

CC @tonya11en

[tonya11en]

@marcusoyang I'm happy to explore this with you. Have you taken a look at Adaptive Concurrency
Control? That mechanism uses sampled latencies to make adjustments to the concurrency limit (essentially circuit breaking) thresholds.

I'm curious whether that meets your requirements and if not, why.

[tonya11en]

/assign @tonya11en

[tonya11en]

It may also help to get more context around what "slow dependency response times" means.