rkhachatryan commented on a change in pull request #18431:
URL: https://github.com/apache/flink/pull/18431#discussion_r793495141
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File path: docs/content/docs/ops/state/state_backends.md
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@@ -325,6 +325,129 @@ public class MyOptionsFactory implements
ConfigurableRocksDBOptionsFactory {
{{< top >}}
+## Enabling Changelog
+
+// todo: Chinese version of all changed docs
+
+// todo: mention in [large state tuning]({{< ref
"docs/ops/state/large_state_tuning" >}})? or 1.16?
+
+{{< hint warning >}} This feature is in experimental status. {{< /hint >}}
+
+{{< hint warning >}} Enabling Changelog may have a negative performance impact
on your application (see below). {{< /hint >}}
+
+### Introduction
+
+Changelog is a feature that aims to decrease checkpointing time and,
therefore, end-to-end latency in exactly-once mode.
+
+Most commonly, checkpoint duration is affected by:
+
+1. Barrier travel time and alignment, addressed by
+ [Unaligned checkpoints]({{< ref
"docs/ops/state/checkpointing_under_backpressure#unaligned-checkpoints" >}})
+ and [Buffer debloating]({{< ref
"docs/ops/state/checkpointing_under_backpressure#buffer-debloating" >}})
+2. Snapshot creation time (so-called synchronous phase), addressed by
asynchronous snapshots
Review comment:
> What are asynchronous snapshots? and how it is different from
asynchronous phase
synchronous phase = create a snapshot
asynchronous phase = upload a snapshot
Implemented naively, sync phase would duplicate **all** the state (copying
all in-memory tables and/or on-disk files). So that async phase and processing
can proceed concurrently.
With Asynchronous snapshots (probably a misnormer), sync phase only flushes
or modifies small portions of data, as I explained
[above](https://github.com/apache/flink/pull/18431#discussion_r790783796).
> Do you mean the materialization is separated and independent with the
checkpointing/snapshotting?
No. As I said
[above](https://github.com/apache/flink/pull/18431#discussion_r791455950),
asynchronous snapshots are not related to Changelog.
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