jetty/jetty.project

Review RolloverFileOutputStream locking

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#5092 opened on Jul 29, 2020

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Description

Spawned by #5083.

Jetty version 9.4.x

Description RolloverFileOutputStream locking should be improved/removed.

Currently it locks on a class lock for no reasons, since __rollover is only ever written in the constructor (and thus could be final).

There should be some synchronization between the writes and the scheduled task (so that the file can be swapped without losing log lines), but the class locks seem unnecessary.

Contributor guide

Tech stack
java
Domain
backendperformance
Issue type
refactor
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
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Java concurrency basicsUnderstanding of synchronized blocks
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Start by examining the `RolloverFileOutputStream` class, likely in `org.eclipse.jetty.util.log` package. Focus on the ` rollover` field and how it is used in the constructor and the scheduled rollover task. The goal is to remove the unnecessary class level lock and introduce minimal synchronization between writes and the rollover task to prevent log line loss. Look at how the file is opened and rotated, and consider using a private lock object or atomic operations. Check the linked issue #5083 for more context.