envoyproxy/envoy

The cache demo returns 503 when the cached response is no longer valid

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#29,105 opened on Aug 17, 2023

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Description

Title: The cache demo returns 503 when the cached response is no longer valid

Description: The demo works fine as long as the response is either not cached or the cached response is still valid. Once the cached answer times out or requires validation, Envoy replies with 503.

Repro steps: Follow the instructions from the documentation:

$ cd examples/cache
$ docker compose pull
$ docker compose up --build -d

The no-cache example is a good demonstrator of this behaviour:

$ curl -i localhost:8000/service/1/no-cache
HTTP/1.1 200 OK
content-type: text/plain; charset=utf-8
cache-control: max-age=0, no-cache
etag: "1621f3c428db2d63d351830b17508da8bfabfca0"
content-length: 125
date: Thu, 17 Aug 2023 14:13:24 GMT
server: envoy
x-envoy-upstream-service-time: 1

This response can be cached, but it has to be validated on each request
Response generated at: Thu, 17 Aug 2023 14:13:24 GMT

$ curl -i localhost:8000/service/1/no-cache
HTTP/1.1 503 Service Unavailable
content-length: 95
content-type: text/plain
date: Thu, 17 Aug 2023 14:13:24 GMT
server: envoy

upstream connect error or disconnect/reset before headers. reset reason: connection termination%

Contributor guide

Research direction
Examine the cache filter implementation in Envoy, focusing on the handling of revalidation requests (e.g., no cache with ETag). Look at how the filter handles cache validation responses and why it might fail with a 503. Check if there is a missing upstream connection during revalidation.
Tech stack
cpp
Domain
backendnetworking
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Dockercurl
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65