[jira] [Resolved] (CAMEL-24265) DefaultTracer.traceCounter should use AtomicLong instead of plain long

["Guillaume Nodet (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CAMEL-24265?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Guillaume Nodet resolved CAMEL-24265.
-------------------------------------
    Resolution: Fixed

> DefaultTracer.traceCounter should use AtomicLong instead of plain long
> ----------------------------------------------------------------------
>
>                 Key: CAMEL-24265
>                 URL: https://issues.apache.org/jira/browse/CAMEL-24265
>             Project: Camel
>          Issue Type: Improvement
>          Components: camel-core
>            Reporter: Guillaume Nodet
>            Assignee: Guillaume Nodet
>            Priority: Major
>              Labels: good-first-issue
>             Fix For: 4.22.0
>
>
> Found during review of PR #24985 (CAMEL-24227: volatile sweep for JMX-writable fields).
> This is the reverse direction from CAMEL-24227 — routing threads *write* traceCounter++ while JMX *reads* it via ManagedTracer.getTraceCounter() / resetTraceCounter().
> h3. Problem
> {{DefaultTracer.traceCounter}} is a plain {{long}} that is:
> * *Incremented* non-atomically ({{traceCounter++}}) on routing threads in the tracing hot path
> * *Read and reset* via JMX through {{ManagedTracer}}
> This has two JMM issues:
> # *Visibility* — JMX reads may see stale values
> # *Atomicity* — {{++}} is a non-atomic read-modify-write; on 32-bit JVMs even the read of a {{long}} is non-atomic (JLS 17.7)
> {{BacklogTracer}} already uses {{AtomicLong}} for the same purpose — {{DefaultTracer}} should be aligned.
> h3. Suggested fix
> Replace {{private long traceCounter}} with {{private final AtomicLong traceCounter = new AtomicLong()}} and update {{getTraceCounter()}} / {{resetTraceCounter()}} accordingly.
> h3. References
> * PR [#24985|https://github.com/apache/camel/pull/24985] review comment by oscerd
> * {{core/camel-base-engine/src/main/java/org/apache/camel/impl/engine/DefaultTracer.java}} line 62



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