envoyproxy/envoy

Access log status code filter not working for response code 0

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#17,482 opened on Jul 26, 2021

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Description

Description: Unable to use status code filters to log requests with a 0 response code.

Repro steps: We are running Istio 1.6.13 which uses Envoy 1.15.4. We want to only output access logs for HTTP requests with responses >= 400 or == 0.

This is the filter being applied:

filter:
  or_filter:
    filters:
    - status_code_filter:
        comparison:
          op: GE
          value:
            default_value: "400"
            runtime_key: "400"
    - status_code_filter:
        comparison:
          op: EQ
          value:
            default_value: "0"
            runtime_key: "0"

All 4xx/5xx requests are being logged, and 1xx/2xx/3xx requests are not logged, as expected. However, any requests with response code 0 are also not being logged.

Has this been resolved in a newer version of Envoy/Istio?

If not:

  1. Is this the intended behaviour because the status code filter only gets applied to valid HTTP response codes?
  2. Is there a different filter that can be applied to make sure all 0 responses get logged?

Contributor guide

Research direction
Inspect the status code filter implementation in Envoy to understand why it does not match response code 0. It likely treats 0 as an invalid HTTP status code and skips it. Consider modifying the filter to allow matching status code 0.
Tech stack
cpp
Domain
backend
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.
Half day
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
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65