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https://issues.apache.org/jira/browse/FLINK-39042?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-39042:
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Labels: pull-request-available (was: )
> [webui] Make watermark timestamps timezone-aware and configurable
> -----------------------------------------------------------------
>
> Key: FLINK-39042
> URL: https://issues.apache.org/jira/browse/FLINK-39042
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Web Frontend
> Reporter: featzhang
> Priority: Major
> Labels: pull-request-available
>
> h4. Summary
> The Flink Web UI Watermarks page already supports displaying *formatted
> datetime strings* for watermark timestamps.
> However, the {*}timezone is neither explicitly indicated nor configurable{*},
> which can easily lead to ambiguity and operational confusion in multi-region
> environments.
> This issue proposes to *explicitly label the timezone* used for formatted
> timestamps and *add a timezone switching capability* to the UI.
> ----
> h4. Current Behavior
> * The Watermarks page displays:
> ** Raw timestamp (milliseconds since epoch)
> ** A formatted datetime string (e.g. {{{}2026-02-05 09:58:50{}}})
> * {*}Problems with the current behavior{*}:
> ## The formatted time {*}does not clearly indicate which timezone it belongs
> to{*}.
> ## Users cannot switch the timezone (e.g. UTC vs local time).
> ## Operators must _infer_ the timezone based on browser or deployment
> context, which is error-prone.
> Example (current UI):
>
> {{1770256730000 → 2026-02-05 09:58:50}}
> From this display alone, it is unclear whether the time is UTC, browser local
> time, or another timezone.
> ----
> h4. Proposed Improvements
> h5. 1. Explicit Timezone Labeling
> * Always display the timezone together with the formatted timestamp.
> * Suggested format:
>
> {{Timestamp (YYYY-MM-DD HH:mm:ss Z)}}
> Example:
>
> {{1770256730000 (2026-02-05 09:58:50 UTC+8)}}
> This removes ambiguity and makes the time semantics explicit.
> ----
> h5. 2. Timezone Switching Support
> * Add a timezone selector (e.g. dropdown or toggle group) above the
> Watermarks table.
> * Supported options could include:
> ** UTC
> ** Browser Local Time
> ** Fixed offsets (e.g. UTC+8)
> Example UI concept:
>
> {{[ Timezone: UTC | Local | UTC+8 ]}}
> Changing the selection updates all formatted timestamps on the page
> accordingly.
> ----
> h5. 3. Consistency & Reusability
> * The same timezone formatting and switching logic should be reusable for:
> ** Checkpoints
> ** Backpressure
> ** Other Web UI pages displaying time-based metrics
> ----
> h4. Motivation & Use Cases
> * *Debugging*
> Quickly determine whether a subtask watermark is lagging behind wall-clock
> time without guessing the timezone.
> * *Monitoring & Operations*
> Teams operating clusters across regions can view timestamps in a consistent,
> explicit timezone.
> * *User Experience*
> Avoid confusion caused by implicit timezone assumptions.
> ----
> h4. Non-Goals
> * This issue does *not* change watermark semantics or calculation logic.
> * This issue focuses purely on {*}UI presentation and usability
> improvements{*}.
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