envoyproxy/envoy

wasm: access log extension point is not thread safe

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#41,672 opened on Oct 23, 2025

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area/wasmbughelp wanted

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Description

Access logger instances are shared across all threads, which means log() can be called concurrently. It does not seem that Wasm implementation has proper protection against data races (Wasm runtime assumes single threaded caller I believe).

CC @PiotrSikora @mpwarres

Contributor guide

Research direction
Inspect the Wasm access log extension implementation in Envoy, identify the shared state accessed in the log() method, and add appropriate synchronization (e.g., mutex) to prevent data races across threads.
Tech stack
cpp
Domain
backendinfrastructure
Issue type
Bug
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.
1-3 hours
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++multithreading
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30