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https://issues.apache.org/jira/browse/FLINK-10068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16581068#comment-16581068
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ASF GitHub Bot commented on FLINK-10068:
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alpinegizmo commented on a change in pull request #6504: [FLINK-10068][docs]
Add documentation for RocksDB-based timers and st…
URL: https://github.com/apache/flink/pull/6504#discussion_r210268466
##########
File path: docs/ops/state/large_state_tuning.md
##########
@@ -142,6 +142,17 @@ by default. To enable this feature, users can instantiate
a `RocksDBStateBackend
new RocksDBStateBackend(filebackend, true);
{% endhighlight %}
+**RocksDB Timers**
+
+For RocksDB, user can chose whether timers are stored on the heap (default) or
inside RocksDB. Heap-based timers can have a better performance for smaller
amounts of
+timers, while storing timers inside RocksDB offers higher scalability as the
amount of timers in RocksDB can exceed the available main memory (spilling to
disk).
+
+When using RockDB as state backend, the type of timer storage can be selected
through Flink's configuration via option key
`RocksDBOptions.TIMER_SERVICE_FACTORY`.
+Possible choices are `HEAP` (to store timers on the heap, default) and
`ROCKSDB` (to store timers in RocksDB).
+
+<span class="label label-info">Note</span> *The combination RocksDB state
backend / with incremental checkpoint / with heap-based timers currently does
NOT support asynchronous snapshots for the timers state.
+Other state like keyed state is still snapshotted asynchronously. Please not
that this is no regression from previous versions and will be resolved with
`FLINK-10026`.*
Review comment:
Please note that this is not a regression ...
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> Add documentation for async/RocksDB-based timers
> ------------------------------------------------
>
> Key: FLINK-10068
> URL: https://issues.apache.org/jira/browse/FLINK-10068
> Project: Flink
> Issue Type: Sub-task
> Components: State Backends, Checkpointing
> Reporter: Stefan Richter
> Assignee: Stefan Richter
> Priority: Major
> Labels: pull-request-available
>
> Documentation how to activate RocksDB based timers, and update that
> snapshotting now works async, expect for heap-timers +
> rocks-incremental-snapshot).
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