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https://issues.apache.org/jira/browse/ZOOKEEPER-5072?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated ZOOKEEPER-5072:
--------------------------------------
Labels: client diagnostics java pull-request-available (was: client
diagnostics java)
> Add opt-in warning for slow ZooKeeper Java client callbacks
> -----------------------------------------------------------
>
> Key: ZOOKEEPER-5072
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-5072
> Project: ZooKeeper
> Issue Type: Improvement
> Components: java client
> Affects Versions: 3.10.0
> Environment: ZooKeeper Java client
> Reporter: DongNyoung Lee
> Priority: Major
> Labels: client, diagnostics, java, pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> h2. Background
> ZooKeeper Java client callbacks are dispatched by a single
> {{{}EventThread{}}}.
> A slow{{{} Watcher{}}}, {{{}AsyncCallback{}}}, or {{LocalCallback}} can
> therefore delay subsequent watcher events, asynchronous callbacks, and
> connection or session state events.
> Operators currently have limited visibility into whether client-side callback
> execution is contributing to observed delays.
> h2. Proposal
> Add an opt-in, threshold-based {{WARN}} log for slow ZooKeeper client
> callback execution.
> Proposed configuration:
>
> {{zookeeper.client.slowCallbackThresholdMs}}
> * Default value: {{0}} — disabled
> * Values less than or equal to {{0}} disable callback duration measurement
> and warning logs.
> * When enabled, the client logs a {{WARN}} when callback execution time
> exceeds the configured threshold.
> * Callback duration should be measured using a monotonic clock.
> The diagnostic logging must preserve the existing {{EventThread}} dispatch
> model. It must not change callback ordering, callback threading, queue
> structures, or exception-handling behavior.
> h2. Non-goals
> * Changing the callback executor
> * Changing callback dispatch behavior
> * Changing callback ordering
> * Measuring queued dispatch delay
> * Modifying queue structures
> * Adding log rate limiting in the initial implementation
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