envoyproxy/envoy

Send retry reason to upstream

Open

#6,001 opened on Feb 19, 2019

View on GitHub
 (4 comments) (0 reactions) (0 assignees)C++ (5,373 forks)batch import
enhancementhelp wanted

Repository metrics

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

Description

We're interested in passing information to the upstream about why the request was retried.

The idea is to avoid retrying in the upstream if the request was retried due to an application issue, to prevent an explosion of retries. Currently we can infer whether a retry happened with the x-envoy-attempt-count header, but this doesn't differentiate between different retry reasons. We're interested in being able to adjust retry behavior in the upstream only on certain kinds of retry reasons.

I'm imaging this being implemented by setting a header with a comma separated list of retry reasons, something like x-envoy-retry-reason: 5xx,connect-failure. This way the upstream can determine that we're currently retrying a 5xx that saw a connect failure when attempting the first retry.

This would be guarded by a config flag on the Route, similar to the attempt count header.

Contributor guide

Research direction
Study the existing implementation of the `x envoy attempt count` header in the Envoy codebase, then extend it to support a new header for retry reasons. Look at the route configuration to add a boolean flag. Understand the retry logic to gather the reasons.
Tech stack
None
Domain
backendinfrastructure
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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
GitC++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65