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new a66046adaf6 release notes for the 1.15 release
a66046adaf6 is described below
commit a66046adaf6a96cd09e55ac1a4cf1df63e502708
Author: Joe Moser <j...@ververica.com>
AuthorDate: Tue Apr 26 11:47:16 2022 +0200
release notes for the 1.15 release
---
docs/content/_index.md | 2 +-
docs/content/release-notes/flink-1.15.md | 589 +++++++++++++++++++++++++++++++
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@@ -85,7 +85,7 @@ Release notes cover important changes between Flink versions.
Please read them c
For some reason Hugo will only allow linking to the
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-->
-See the release notes for [Flink 1.14]({{< ref "/release-notes/flink-1.14.md"
>}}), [Flink 1.13]({{< ref "/release-notes/flink-1.13.md" >}}), [Flink
1.12]({{< ref "/release-notes/flink-1.12.md" >}}), [Flink 1.11]({{< ref
"/release-notes/flink-1.11.md" >}}), [Flink 1.10]({{< ref
"/release-notes/flink-1.10.md" >}}), [Flink 1.9]({{< ref
"/release-notes/flink-1.9.md" >}}), [Flink 1.8]({{< ref
"/release-notes/flink-1.8.md" >}}), or [Flink 1.7]({{< ref
"/release-notes/flink-1.7.md" >}}).
+See the release notes for [Flink 1.15]({{< ref "/release-notes/flink-1.15.md"
>}}), [Flink 1.14]({{< ref "/release-notes/flink-1.14.md" >}}), [Flink
1.13]({{< ref "/release-notes/flink-1.13.md" >}}), [Flink 1.12]({{< ref
"/release-notes/flink-1.12.md" >}}), [Flink 1.11]({{< ref
"/release-notes/flink-1.11.md" >}}), [Flink 1.10]({{< ref
"/release-notes/flink-1.10.md" >}}), [Flink 1.9]({{< ref
"/release-notes/flink-1.9.md" >}}), [Flink 1.8]({{< ref
"/release-notes/flink-1.8.md" >}}), or [Fl [...]
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+---
+title: "Release Notes - Flink 1.15"
+---
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# Release notes - Flink 1.15
+
+These release notes discuss important aspects, such as configuration,
behavior,
+or dependencies, that changed between Flink 1.14 and Flink 1.15. Please read
these
+notes carefully if you are planning to upgrade your Flink version to 1.15.
+
+## Summary of changed dependency names
+
+There are Several changes in Flink 1.15 that require updating dependency names
when
+upgrading from earlier versions, mainly including the effort to opting-out
Scala dependencies
+from non-scala modules and reorganize table modules. A quick checklist of the
dependency changes
+is as follows:
+
+* Any dependency to one of the following modules needs to be updated to no
longer include a suffix:
+
+ ```
+ flink-cep
+ flink-clients
+ flink-connector-elasticsearch-base
+ flink-connector-elasticsearch6
+ flink-connector-elasticsearch7
+ flink-connector-gcp-pubsub
+ flink-connector-hbase-1.4
+ flink-connector-hbase-2.2
+ flink-connector-hbase-base
+ flink-connector-jdbc
+ flink-connector-kafka
+ flink-connector-kinesis
+ flink-connector-nifi
+ flink-connector-pulsar
+ flink-connector-rabbitmq
+ flink-container
+ flink-dstl-dfs
+ flink-gelly
+ flink-hadoop-bulk
+ flink-kubernetes
+ flink-runtime-web
+ flink-sql-connector-elasticsearch6
+ flink-sql-connector-elasticsearch7
+ flink-sql-connector-hbase-1.4
+ flink-sql-connector-hbase-2.2
+ flink-sql-connector-kafka
+ flink-sql-connector-kinesis
+ flink-sql-connector-rabbitmq
+ flink-state-processor-api
+ flink-statebackend-rocksdb
+ flink-streaming-java
+ flink-test-utils
+ flink-yarn
+ flink-table-api-java-bridge
+ flink-table-runtime
+ flink-sql-client
+ flink-orc
+ flink-orc-nohive
+ flink-parquet
+ ```
+* For Table / SQL users, the new module `flink-table-planner-loader` replaces
`flink-table-planner_2.12`
+ and avoids the need for a Scala suffix. For backwards compatibility, users
can still
+ swap it with `flink-table-planner_2.12` located in `opt/`.
+ `flink-table-uber` has been split into `flink-table-api-java-uber`,
+ `flink-table-planner(-loader)`, and `flink-table-runtime`. Scala users need
to explicitly add a dependency
+ to `flink-table-api-scala` or `flink-table-api-scala-bridge`.
+
+The detail of the involved issues are listed as follows.
+
+#### Add support for opting-out of Scala
+
+##### [FLINK-20845](https://issues.apache.org/jira/browse/FLINK-20845)
+
+The Java DataSet/-Stream APIs are now independent of Scala and no longer
transitively depend on it.
+
+The implications are the following:
+
+* If you only intend to use the Java APIs, with Java types,
+then you can opt-in to a Scala-free Flink by removing the `flink-scala` jar
from the `lib/` directory of the distribution.
+You are then free to use any Scala version and Scala libraries.
+You can either bundle Scala itself in your user-jar; or put into the `lib/`
directory of the distribution.
+
+* If you relied on the Scala APIs, without an explicit dependency on them,
+ then you may experience issues when building your projects. You can solve
this by adding explicit dependencies to
+ the APIs that you are using. This should primarily affect users of the Scala
`DataStream/CEP` APIs.
+
+* A lot of modules have lost their Scala suffix.
+ Further caution is advised when mixing dependencies from different Flink
versions (e.g., an older connector),
+ as you may now end up pulling in multiple versions of a single module (that
would previously be prevented by the name being equal).
+
+#### Reorganize table modules and introduce flink-table-planner-loader
+
+##### [FLINK-25128](https://issues.apache.org/jira/browse/FLINK-25128)
+
+The new module `flink-table-planner-loader` replaces
`flink-table-planner_2.12` and avoids the need for a Scala suffix.
+It is included in the Flink distribution under `lib/`. For backwards
compatibility, users can still swap it with
+`flink-table-planner_2.12` located in `opt/`. As a consequence,
`flink-table-uber` has been split into `flink-table-api-java-uber`,
+`flink-table-planner(-loader)`, and `flink-table-runtime`. `flink-sql-client`
has no Scala suffix anymore.
+
+It is recommended to let new projects depend on `flink-table-planner-loader`
(without Scala suffix) in provided scope.
+
+Note that the distribution does not include the Scala API by default.
+Scala users need to explicitly add a dependency to `flink-table-api-scala` or
`flink-table-api-scala-bridge`.
+
+#### Remove flink-scala dependency from flink-table-runtime
+
+##### [FLINK-25114](https://issues.apache.org/jira/browse/FLINK-25114)
+
+The `flink-table-runtime` has no Scala suffix anymore.
+Make sure to include `flink-scala` if the legacy type system (based on
TypeInformation) with case classes is still used within Table API.
+
+#### flink-table uber jar should not include flink-connector-files dependency
+
+##### [FLINK-24687](https://issues.apache.org/jira/browse/FLINK-24687)
+
+The table file system connector is not part of the `flink-table-uber` JAR
anymore but is a dedicated (but removable)
+`flink-connector-files` JAR in the `/lib` directory of a Flink distribution.
+
+## JDK Upgrade
+
+The support of Java 8 is now deprecated and will be removed in a future
release
+([FLINK-25247](https://issues.apache.org/jira/browse/FLINK-25247)). We
recommend
+all users to migrate to Java 11.
+
+The default Java version in the Flink docker images is now Java 11
+([FLINK-25251](https://issues.apache.org/jira/browse/FLINK-25251)).
+There are images built with Java 8, tagged with “java8”.
+
+## Drop support for Scala 2.11
+
+Support for Scala 2.11 has been removed in
+[FLINK-20845](https://issues.apache.org/jira/browse/FLINK-20845).
+All Flink dependencies that (transitively)
+depend on Scala are suffixed with the Scala version that they are built for,
for
+example `flink-streaming-scala_2.12`. Users should update all Flink
dependecies,
+changing "2.11" to "2.12".
+
+Scala versions (2.11, 2.12, etc.) are not binary compatible with one another.
That
+also means that there's no guarantee that you can restore from a savepoint,
made
+with a Flink Scala 2.11 application, if you're upgrading to a Flink Scala 2.12
+application. This depends on the data types that you have been using in your
+application.
+
+The Scala Shell/REPL has been removed in
+[FLINK-24360](https://issues.apache.org/jira/browse/FLINK-24360).
+
+## Table API & SQL
+
+#### Disable the legacy casting behavior by default
+
+##### [FLINK-26551](https://issues.apache.org/jira/browse/FLINK-26551)
+
+The legacy casting behavior has been disabled by default. This might have
+implications on corner cases (string parsing, numeric overflows, to string
+representation, varchar/binary precisions). Set
+`table.exec.legacy-cast-behaviour=ENABLED` to restore the old behavior.
+
+#### Enforce CHAR/VARCHAR precision when outputting to a Sink
+
+##### [FLINK-24753](https://issues.apache.org/jira/browse/FLINK-24753)
+
+`CHAR`/`VARCHAR` lengths are enforced (trimmed/padded) by default now before
entering
+the table sink.
+
+#### Support the new type inference in Scala Table API table functions
+
+##### [FLINK-26518](https://issues.apache.org/jira/browse/FLINK-26518)
+
+Table functions that are called using Scala implicit conversions have been
updated
+to use the new type system and new type inference. Users are requested to
update
+their UDFs or use the deprecated `TableEnvironment.registerFunction` to
restore
+the old behavior temporarily by calling the function via name.
+
+#### Propagate executor config to TableConfig
+
+##### [FLINK-26421](https://issues.apache.org/jira/browse/FLINK-26421)
+
+`flink-conf.yaml` and other configurations from outer layers (e.g. CLI) are
now
+propagated into `TableConfig`. Even though configuration set directly in
`TableConfig`
+has still precedence, this change can have side effects if table configuration
+was accidentally set in other layers.
+
+#### Remove pre FLIP-84 methods
+
+##### [FLINK-26090](https://issues.apache.org/jira/browse/FLINK-26090)
+
+The previously deprecated methods `TableEnvironment.execute`,
`Table.insertInto`,
+`TableEnvironment.fromTableSource`, `TableEnvironment.sqlUpdate`, and
+`TableEnvironment.explain` have been removed. Please use
+`TableEnvironment.executeSql`, `TableEnvironment.explainSql`,
+`TableEnvironment.createStatementSet`, as well as `Table.executeInsert`,
+`Table.explain` and `Table.execute` and the newly introduces classes
+`TableResult`, `ResultKind`, `StatementSet` and `ExplainDetail`.
+
+#### Fix parser generator warnings
+
+##### [FLINK-26053](https://issues.apache.org/jira/browse/FLINK-26053)
+
+`STATEMENT` is a reserved keyword now. Use backticks to escape tables, fields
and
+other references.
+
+#### Expose uid generator for DataStream/Transformation providers
+
+##### [FLINK-25990](https://issues.apache.org/jira/browse/FLINK-25990)
+
+`DataStreamScanProvider` and `DataStreamSinkProvider` for table connectors
received
+an additional method that might break implementations that used lambdas
before.
+We recommend static classes as a replacement and future robustness.
+
+#### Add new STATEMENT SET syntax
+
+##### [FLINK-25392](https://issues.apache.org/jira/browse/FLINK-25392)
+
+It is recommended to update statement sets to the new SQL syntax:
+
+```SQL
+EXECUTE STATEMENT SET BEGIN ... END;
+EXPLAIN STATEMENT SET BEGIN ... END;
+```
+
+#### Check & possible fix decimal precision and scale for all Aggregate
functions
+
+##### [FLINK-24809](https://issues.apache.org/jira/browse/FLINK-24809)
+
+This changes the result of a decimal `SUM()` with retraction and `AVG()`. Part
of the behavior
+is restored back to be the same with 1.13 so that the behavior as a whole
could be consistent
+with Hive / Spark.
+
+#### Clarify semantics of DecodingFormat and its data type
+
+##### [FLINK-24776](https://issues.apache.org/jira/browse/FLINK-24776)
+
+The `DecodingFormat` interface was used for both projectable and
non-projectable
+formats which led to inconsistent implementations. The `FileSystemTableSource`
+has been updated to distinguish between those two interfaces now. Users that
+implement custom formats for `FileSystemTableSource` might need to verify the
+implementation and make sure to implement `ProjectableDecodingFormat` if
necessary.
+
+#### Push down partitions before filters
+
+##### [FLINK-24717](https://issues.apache.org/jira/browse/FLINK-24717)
+
+This might have an impact on existing table source implementations as push
down
+filters might not contain partition predicates anymore. However, the connector
+implementation for table sources that implement both partition and filter push
+down became easier with this change.
+
+#### Flink SQL `SUM()` causes a precision error
+
+##### [FLINK-24691](https://issues.apache.org/jira/browse/FLINK-24691)
+
+This changes the result of a decimal `SUM()` between 1.14.0 and 1.14.1. It
restores
+the behavior of 1.13 to be consistent with Hive/Spark.
+
+#### Use the new casting rules in TableResult#print
+
+##### [FLINK-24685](https://issues.apache.org/jira/browse/FLINK-24685)
+
+The string representation of `BOOLEAN` columns from DDL results
+(`true/false -> TRUE/FALSE`), and row columns in DQL results
+(`+I[...] -> (...)`) has changed for printing.
+
+#### Casting from a string to a DATE and TIME allows incomplete strings
+
+##### [FLINK-24421](https://issues.apache.org/jira/browse/FLINK-24421)
+
+The defaults for casting incomplete strings like `"12"` to TIME have changed
from `12:01:01` to `12:00:00`.
+
+#### Casting from STRING to TIMESTAMP_LTZ looses fractional seconds
+
+##### [FLINK-24446](https://issues.apache.org/jira/browse/FLINK-24446)
+
+`STRING` to `TIMESTAMP(_LTZ)` casting now considers fractional seconds.
+Previously fractional seconds of any precision were ignored.
+
+#### Sinks built with the unified sink framework do not receive timestamps
when used in Table API
+
+##### [FLINK-24608](https://issues.apache.org/jira/browse/FLINK-Table)
+
+This adds an additional operator to the topology if the new sink interfaces
are used
+(e.g. for Kafka). It could cause issues in 1.14.1 when restoring from a 1.14
savepoint.
+A workaround is to cast the time attribute to a regular timestamp in the SQL
statement
+closely before the sink.
+
+#### SQL functions should return `STRING` instead of `VARCHAR(2000)`
+
+##### [FLINK-24586](https://issues.apache.org/jira/browse/FLINK-24586)
+
+Functions that returned `VARCHAR(2000)` in 1.14, return `VARCHAR` with maximum
+length now. In particular this includes:
+
+```SQL
+SON_VALUE
+CHR
+REVERSE
+SPLIT_INDEX
+REGEXP_EXTRACT
+PARSE_URL
+FROM_UNIXTIME
+DECODE
+DATE_FORMAT
+CONVERT_TZ
+```
+
+#### Support IS JSON for Table API
+
+##### [FLINK-16501](https://issues.apache.org/jira/browse/FLINK-16501)
+
+This issue added IS JSON for Table API. Notes that `IS JSON` does not return
+`NULL` anymore but always `FALSE` (even if the argument is `NULL`).
+
+#### Disable upsert into syntax in Flink SQL
+
+##### [FLINK-22942](https://issues.apache.org/jira/browse/FLINK-22942)
+
+Disabled `UPSERT INTO` statement.
+`UPSERT INTO` syntax was exposed by mistake in previous releases without
detailed discussed.
+From this release every `UPSERT INTO` is going to throw an exception.
+Users of `UPSERT INTO` should use the documented `INSERT INTO` statement
instead.
+
+#### RuntimeException: while resolving method 'booleanValue' in class class
java.math.BigDecimal
+
+##### [FLINK-23271](https://issues.apache.org/jira/browse/FLINK-23271)
+
+Casting to `BOOLEAN` is not allowed from decimal numeric types anymore.
+
+#### Upsert materializer is not inserted for all sink providers
+
+##### [FLINK-23895](https://issues.apache.org/jira/browse/FLINK-23895)
+
+This issue aims to fix various primary key issues that effectively made it
impossible to use this feature.
+The change might affect savepoint backwards compatibility for those incorrect
pipelines.
+Also the resulting changelog stream might be different after these changes.
+Pipelines that were correct before should be restorable from a savepoint.
+
+#### Propagate unique keys for fromChangelogStream
+
+##### [FLINK-24033](https://issues.apache.org/jira/browse/FLINK-24033)
+
+`StreamTableEnvironment.fromChangelogStream` might produce a different stream
because
+primary keys were not properly considered before.
+
+#### TableResult#print() should use internal data types
+
+##### [FLINK-24461](https://issues.apache.org/jira/browse/FLINK-24461)
+
+The results of `Table#print` have changed to be closer to actual SQL data
types.
+E.g. decimal is printing correctly with leading/trailing zeros.
+
+## Connectors
+
+#### Remove MapR filesystem
+
+##### [FLINK-25553](https://issues.apache.org/jira/browse/FLINK-25553)
+
+Support for the MapR FileSystem has been dropped.
+
+#### Merge flink-connector-testing into flink-connector-test-utils
+
+##### [FLINK-25712](https://issues.apache.org/jira/browse/FLINK-25712)
+
+The `flink-connector-testing` module has been removed and users should use
+`flink-connector-test-utils` module instead.
+
+#### Support partition keys through metadata (for FileSystem connector)
+
+##### [FLINK-24617](https://issues.apache.org/jira/browse/FLINK-24617)
+
+Now the formats implementing `BulkWriterFormatFactory` don't need to implement
+partition keys reading anymore, as it's managed internally by
`FileSystemTableSource`.
+
+#### Port ElasticSearch Sink to new Unified Sink API (FLIP-143)
+
+##### [FLINK-24323](https://issues.apache.org/jira/browse/FLINK-24323)
+
+`ElasticsearchXSinkBuilder` supersedes `ElasticsearchSink.Builder` and
provides at-least-once writing with the
+new unified sink interface supporting both batch and streaming mode of
DataStream API.
+
+For Elasticsearch 7 users that use the old ElasticsearchSink interface
+(`org.apache.flink.streaming.connectors.elasticsearch7.ElasticsearchSink`)
+and depend on their own elasticsearch-rest-high-level-client version,
+updating the client dependency to a version >= 7.14.0 is required due to
internal changes.
+
+#### Reduce legacy in Table API connectors
+
+##### [FLINK-24397](https://issues.apache.org/jira/browse/FLINK-24397)
+
+The old JDBC connector (indicated by `connector.type=jdbc` in DDL) has been
removed.
+If not done already, users need to upgrade to the newer stack (indicated by
`connector=jdbc` in DDL).
+
+## Runtime & Coordination
+
+#### Integrate retry strategy for cleanup stage
+
+##### [FLINK-25433](https://issues.apache.org/jira/browse/FLINK-25433)
+
+Adds retry logic to the cleanup steps of a finished job. This feature changes
the
+way Flink jobs are cleaned up. Instead of trying once to clean up the job, this
+step will be repeated until it succeeds. Users are meant to fix the issue that
+prevents Flink from finalizing the job cleanup. The retry functionality can be
+configured and disabled. More details can be found
+[in the
documentation](https://nightlies.apache.org/flink/flink-docs-release-1.15/docs/deployment/config/#retryable-cleanup).
+
+#### Introduce explicit shutdown signaling between `TaskManager` and
`JobManager`
+
+##### [FLINK-25277](https://issues.apache.org/jira/browse/FLINK-25277)
+
+`TaskManagers` now explicitly send a signal to the `JobManager` when shutting
down. This reduces the down-scaling delay in reactive mode (which was
previously bound to the heartbeat timeout).
+
+#### Release `TaskManagerJobMetricGroup` with the last slot rather than task
+
+##### [FLINK-24864](https://issues.apache.org/jira/browse/FLINK-24864)
+
+Job metrics on the TaskManager are now removed when the last slot is released,
rather than the last task.
+This means they may be reported for a longer time than before and when no
tasks are running on the TaskManager.
+
+#### Make errors happened during JobMaster initialization accessible through
the exception history
+
+##### [FLINK-25096](https://issues.apache.org/jira/browse/FLINK-25096)
+
+Fixes issue where the failover is not listed in the exception history but as a
root
+cause. That could have happened if the failure occurred during `JobMaster`
+initialization.
+
+
+#### DispatcherResourceManagerComponent fails to deregister application if no
leading ResourceManager
+
+##### [FLINK-24038](https://issues.apache.org/jira/browse/FLINK-24038)
+
+A new multiple component leader election service was implemented that only
runs a single leader election per Flink process.
+If this should cause any problems, then you can set
`high-availability.use-old-ha-services: true` in the `flink-conf.yaml`
+to use the old high availability services.
+
+#### Allow idempotent job cancellation
+
+##### [FLINK-24275](https://issues.apache.org/jira/browse/FLINK-24275)
+
+Attempting to cancel a `FINISHED/FAILED` job now returns 409 Conflict instead
of 404 Not Found.
+
+#### Move async savepoint operation cache into Dispatcher
+
+#### [FLINK-18312](https://issues.apache.org/jira/browse/FLINK-18312)
+
+All `JobManagers` can now be queried for the status of a savepoint operation,
irrespective of which `JobManager` received the initial request.
+
+#### Standby per job mode Dispatchers don't know job's JobSchedulingStatus
+
+##### [FLINK-11813](https://issues.apache.org/jira/browse/FLINK-11813)
+
+The issue of re-submitting a job in Application Mode when the job finished but
failed during
+cleanup is fixed through the introduction of the new component JobResultStore
which enables
+Flink to persist the cleanup state of a job to the file system. (see
[FLINK-25431](https://issues.apache.org/jira/browse/FLINK-25431))
+
+
+#### Change some default config values of blocking shuffle for better usability
+
+##### [FLINK-25636](https://issues.apache.org/jira/browse/FLINK-25636)
+
+Since 1.15, sort-shuffle has become the default blocking shuffle
implementation and shuffle data
+compression is enabled by default. These changes influence batch jobs only,
for more information,
+please refer to the [official
document](https://nightlies.apache.org/flink/flink-docs-release-1.15).
+
+
+## Checkpoints
+
+#### FLIP-193: Snapshots ownership
+
+##### [FLINK-25154](https://issues.apache.org/jira/browse/FLINK-25154)
+
+When restoring from a savepoint or retained externalized checkpoint you can
choose
+the mode in which you want to perform the operation. You can choose from
`CLAIM`,
+`NO_CLAIM`, `LEGACY` (the old behavior).
+
+In `CLAIM` mode Flink takes ownership of the snapshot and will potentially try
to
+remove the snapshot at a certain point in time. On the other hand the
`NO_CLAIM`
+mode will make sure Flink does not depend on the existence of any files
belonging
+to the initial snapshot.
+
+For a more thorough description see [the
documentation](https://nightlies.apache.org/flink/flink-docs-release-1.15/docs/ops/state/savepoints/#restore-mode).
+
+#### Support native savepoints (w/o modifying the statebackend specific
snapshot strategies)
+
+##### [FLINK-25744](https://issues.apache.org/jira/browse/FLINK-25744)
+
+When taking a savepoint you can specify the binary format. You can choose from
native
+(specific to a particular state backend) or canonical (unified across all
state backends).
+
+#### Prevent JM from discarding state on checkpoint abortion
+
+##### [FLINK-24611](https://issues.apache.org/jira/browse/FLINK-24611)
+
+Shared state tracking changed to use checkpoint ID instead of reference
counts.
+Shared state is not cleaned up on abortion anymore (but rather on subsumption
or
+job termination).
+
+This might result in delays in discarding the state of aborted checkpoints.
+
+#### Introduce incremental/full checkpoint size stats
+
+##### [FLINK-25557](https://issues.apache.org/jira/browse/FLINK-25557)
+
+Introduce metrics of persistent bytes within each checkpoint (via REST API and
UI),
+which could help users to know how much data size had been persisted during
the
+incremental or change-log based checkpoint.
+
+#### Enables final checkpoint by default
+
+##### [FLINK-25105](https://issues.apache.org/jira/browse/FLINK-25105)
+
+In 1.15 we enabled the support of checkpoints after part of tasks finished by
default,
+and made tasks waiting for the final checkpoint before exit to ensure all data
got
+committed.
+
+However, it's worth noting that this change forces tasks to wait for one more
+checkpoint before exiting. In other words, this change will block the tasks
until
+the next checkpoint get triggered and completed. If the checkpoint interval is
long,
+the tasks' execution time would also be extended largely. In the worst case if
the
+checkpoint interval is `Long.MAX_VALUE`, the tasks would be in fact blocked
forever.
+
+More information about this feature and how to disable it could be found in
+[the
documentation](https://nightlies.apache.org/flink/flink-docs-master/docs/dev/datastream/fault-tolerance/checkpointing/#checkpointing-with-parts-of-the-graph-finished-beta).
+
+#### Migrate state processor API to DataStream API
+
+##### [FLINK-24912](https://issues.apache.org/jira/browse/FLINK-24912)
+
+The State Processor API has been migrated from Flinks legacy DataSet API to
now
+run over DataStreams run under `BATCH` execution.
+
+#### Relocate RocksDB's log under flink log directory by default
+
+##### [FLINK-24785](https://issues.apache.org/jira/browse/FLINK-24785)
+
+The internal log of RocksDB would stay under flink's log directory by default.
+
+## Dependency upgrades
+
+#### Upgrade the minimal supported hadoop version to 2.8.5
+
+##### [FLINK-25224](https://issues.apache.org/jira/browse/FLINK-25224)
+
+Minimal supported Hadoop client version is now 2.8.5 (version of the Flink
runtime
+dependency). The client can still talk to older server versions as the binary
protocol
+should be backward compatible.
+
+#### Update Elasticsearch Sinks to latest minor versions
+
+##### [FLINK-25189](https://issues.apache.org/jira/browse/FLINK-25189)
+
+Elasticsearch libraries used by the connector are bumped to 7.15.2 and 6.8.20
+respectively.
+
+For Elasticsearch 7 users that use the old ElasticsearchSink interface
+(`org.apache.flink.streaming.connectors.elasticsearch7.ElasticsearchSink`) and
+depend on their own `elasticsearch-rest-high-level-client` version, will need
+to update the client dependency to a version >= 7.14.0 due to internal changes.
+
+
+#### Drop support for Zookeeper 3.4
+
+##### [FLINK-25146](https://issues.apache.org/jira/browse/FLINK-25146)
+
+Support for using Zookeeper 3.4 for HA has been dropped.
+Users relying on Zookeeper need to upgrade to 3.5/3.6.
+By default Flink now uses a Zookeeper 3.5 client.
+
+#### Upgrade Kafka dependency
+
+##### [FLINK-24765](https://issues.apache.org/jira/browse/FLINK-24765)
+
+Kafka connector uses Kafka client 2.8.1 by default now.
