envoyproxy/envoy

Add additional health status to Endpoints

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#22,120 opened on Jul 12, 2022

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area/load balancinghelp wanted

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Description

When a controlplane has to send "Unready" k8s endpoints to Envoy, when Envoy runs in to panic mode, Envoy sends traffic to "Unready" endpoints. This breaks the Kubernetes contract that "Unready" endpoints should never receive traffic.

In Istio, we send "Unready" endpoints with "Unhealthy" status. So the panic threshold algorithm can not distinguish between "Unready" vs. "Unhealthy".

Please refer to https://github.com/istio/istio/issues/18367 for why we send "Unready" endpoints. This also needed for warmup duration (slow start mode) so that intermittent readiness failures (after the service is ready for the first time) does not cause spurious warmups.

The feature request is to add additional status for "UNREADY" endpoints, that load balancer can exclude while considering hosts during panic threshold scenarios.

Contributor guide

Research direction
Investigate Envoy's load balancing algorithms, specifically the panic threshold behavior, and understand how health statuses are mapped from Kubernetes endpoints. Then implement a new status for 'UNREADY' endpoints and modify the panic threshold logic to exclude them.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Load BalancingHealth Checking
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25