fix: handle race condition when logging to removed logger (fixes #318224)

[vs-code-engineering]

Summary

The error Create the logger before logging is thrown in LoggerChannel.log() when a renderer process sends an IPC log message for a logger that has already been removed from the loggers map. This is a race condition introduced by commit 1fc96f74 which added eager logger cleanup on deregistration — IPC messages already in the pipeline arrive after the logger entry is deleted.

Hits: ~113k across 1600+ users on 1.122.0-insider builds since 2026-05-22.

Fixes #318224
Recommended reviewer: @SimonSiefke

Culprit Commit

1fc96f74 — "fix: memory leak in LoggerChannel (#315875)" by @SimonSiefke (2026-05-21)

This commit added an onDidChangeLoggers listener that deletes loggers from the ResourceMap when they are deregistered. The error first appeared the next day (2026-05-22), confirming causality.

Code Flow

sequenceDiagram
    participant Renderer
    participant IPC as IPC Pipeline
    participant LC as LoggerChannel
    participant LS as LoggerMainService

    Renderer->>IPC: log(file, messages)
    LS->>LC: onDidChangeLoggers({removed: [file]})
    LC->>LC: loggers.delete(file)
    IPC->>LC: call('log', [file, messages])
    LC->>LC: loggers.get(file) → undefined
    LC->>LC: throw Error('Create the logger before logging')

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Affected Files

File	Role
src/vs/platform/log/electron-main/logIpc.ts	Error construction site; log() method throws when logger not found

Repro Steps

1. Open VS Code Insiders (1.122.0+)
2. A window/extension host deregisters a logger (e.g., during extension deactivation or window close)
3. Log messages that were already queued in the IPC pipeline arrive at the main process
4. LoggerChannel.log() throws because the logger was already removed from the map

This is a timing-dependent race that occurs on all platforms (Windows, Mac, Linux).

How the Fix Works

Chosen approach (src/vs/platform/log/electron-main/logIpc.ts:74):

Replaced the throw new Error('Create the logger before logging') with a guard clause that returns early when the logger is not found. This is the correct fix because the error is produced at this exact site — it is the error construction code, not a downstream crash site. The invalid state (missing logger) is produced by the onDidChangeLoggers cleanup handler in the same class (line 20-23) racing with in-flight IPC messages. Since we cannot prevent the renderer from sending messages that are already in the IPC pipeline, the appropriate fix is to gracefully discard stale log messages rather than throw.

After this change, logIpc.ts:74 cannot produce the error because when loggers.get(file) returns undefined, execution returns immediately instead of reaching the throw statement.

Alternatives considered:

• Buffering messages and replaying after logger creation — overly complex for stale messages that should simply be dropped.
• Reverting the memory leak fix — reintroduces the original memory leak from fix: memory leak in LoggerChannel #315875.

Recommended Owner

@SimonSiefke — authored the culprit commit 1fc96f74 that introduced the race condition.

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