envoyproxy/envoy

Avoid lossy LRS during cluster updates

Open

#12,823 opened on Aug 26, 2020

View on GitHub
 (0 comments) (0 reactions) (0 assignees)C++ (5,373 forks)batch import
area/load reportingbughelp wanted

Repository metrics

Stars
 (27,997 stars)
PR merge metrics
 (Avg merge 8d) (378 merged PRs in 30d)

Description

From https://github.com/grpc/proposal/pull/200, when a cluster update for X is received and the new cluster is active after warming, the old X cluster may still be draining for an indefinite period if it has active streams. Only the stats for new requests/streams on X will participate in LRS reporting at this point. This seems to be potentially misleading when reporting load only for the new X.

There are two scenarios to consider:

  1. When the EDS service name changes. I think in this case we should generate two LRS reports, one for old cluster X (including the older EDS service name) and another for new cluster X (including the new EDS service name).
  2. When the EDS service name is the same. I think a unified LRS report should be created aggregating old/new cluster X.

Contributor guide

Research direction
Examine the LRS (Load Reporting Service) implementation in Envoy, specifically how cluster updates affect load reporting. Focus on the logic that handles cluster draining and new cluster activation. Look at the code responsible for generating LRS reports during cluster updates and understand how the EDS service name changes are handled. Trace the code path from the CDS update to LRS report generation.
Tech stack
cpp
Domain
networking
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Envoy
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25