Release Notes - Flink 1.14

Release notes - Flink 1.14 #

These release notes discuss important aspects, such as configuration, behavior, or dependencies, that changed between Flink 1.13 and Flink 1.14. Please read these notes carefully if you are planning to upgrade your Flink version to 1.14.

Known issues #

Memory leak with Pulsar connector on Java 11 #

Netty, which the Pulsar client uses underneath, allocates memory differently on Java 11 and Java 8. On Java 11, it will allocate memory from the pool of Java Direct Memory and is affected by the MaxDirectMemory limit. The current Pulsar client has no configuration options for controlling the memory limits, which can lead to OOM(s).

Users are advised to use the Pulsar connector with Java 8 or overprovision memory for Flink. Read the memory setup guide on how to configure memory for Flink and track the proper solution in FLINK-24302.

Summary of changed dependency names #

There are two changes in Flink 1.14 that require updating dependency names when upgrading from earlier versions.

  • The removal of the Blink planner (FLINK-22879) requires the removal of the blink infix.
  • Due to FLINK-14105, if you have a dependency on flink-runtime, flink-optimizer and/or flink-queryable-state-runtime, the Scala suffix (_2.11/_2.12) needs to be removed from the artifactId.

Table API & SQL #

Use pipeline name consistently across DataStream API and Table API #

The default job name for DataStream API programs in batch mode has changed from "Flink Streaming Job" to "Flink Batch Job". A custom name can be set with the config option pipeline.name.

Propagate unique keys for fromChangelogStream #

Compared to 1.13.2, StreamTableEnvironment.fromChangelogStream might produce a different stream because primary keys were not properly considered before.

Support new type inference for Table#flatMap #

Table.flatMap() supports the new type system now. Users are requested to upgrade their functions.

Add Scala implicit conversions for new API methods #

The Scala implicits that convert between DataStream API and Table API have been updated to the new methods of FLIP-136.

The changes might require an update of pipelines that used toTable or implicit conversions from Table to DataStream[Row].

Remove YAML environment file support in SQL Client #

The sql-client-defaults.yaml file was deprecated in the 1.13 release and is now completely removed. As an alternative, you can use the -i startup option to execute an SQL initialization file to set up the SQL Client session. The SQL initialization file can use Flink DDLs to define available catalogs, table sources and sinks, user-defined functions, and other properties required for execution and deployment.

See more: https://nightlies.apache.org/flink/flink-docs-release-1.14/docs/dev/table/sqlclient/#initialize-session-using-sql-files

Remove the legacy planner code base #

The old Table/SQL planner has been removed. BatchTableEnvironment and DataSet API interoperability with Table API are not supported anymore. Use the unified TableEnvironment for batch and stream processing with the new planner or the DataStream API in batch execution mode.

Users are encouraged to update their pipelines. Otherwise Flink 1.13 is the last version that offers the old functionality.

The following Maven modules have been renamed:

  • flink-table-planner-blink -> flink-table-planner
  • flink-table-runtime-blink -> flink-table-runtime
  • flink-table-uber-blink -> flink-table-uber

It might be required to update job JAR dependencies. Note that flink-table-planner and flink-table-uber used to contain the legacy planner before Flink 1.14 and now they contain the only officially supported planner (i.e. previously known as ‘Blink’ planner).

Due to the removal of BatchTableEnvironment, BatchTableSource and BatchTableSink have been removed as well. Use DynamicTableSource and DynamicTableSink instead. They support the old InputFormat and OutputFormat interfaces as runtime providers if necessary.

Remove TableEnvironment#connect #

The deprecated TableEnvironment.connect() method has been removed. Use the new TableEnvironment.createTemporaryTable(String, TableDescriptor) to create tables programmatically. Please note that this method only supports sources and sinks that comply with FLIP-95. This is also indicated by the new property design 'connector'='kafka' instead of 'connector.type'='kafka'.

Deprecate toAppendStream and toRetractStream #

The outdated variants of StreamTableEnvironment.{fromDataStream|toAppendStream|toRetractStream) have been deprecated. Use the (from|to)(Data|Changelog)Stream alternatives introduced in 1.13.

Remove old connectors and formats stack around descriptors #

The legacy versions of the SQL Kafka connector and SQL Elasticsearch connector have been removed together with their corresponding legacy formats. DDL or descriptors that still use 'connector.type=' or 'format.type=' options need to be updated to the new connector and formats available via the 'connector=' option.

The HBaseTableSource/Sink and related classes including various HBaseInputFormats and HBaseSinkFunction have been removed. It is possible to read via the Table & SQL API and convert the Table to DataStream API (or vice versa) if necessary. The DataSet API is not supported anymore.

The ParquetTableSource and related classes including various ParquetInputFormats have been removed. Use the FileSystem connector with a Parquet format as a replacement. It is possible to read via the Table & SQL API and convert the Table to DataStream API if necessary. The DataSet API is not supported anymore.

The OrcTableSource and related classes (including OrcInputFormat) have been removed. Use the FileSystem connector with an ORC format as a replacement. It is possible to read via the Table & SQL API and convert the Table to DataStream API if necessary. The DataSet API is not supported anymore.

Drop usages of BatchTableEnvironment and the old planner in Python #

The Python API does not offer a dedicated BatchTableEnvironment anymore. Instead, users can switch to the unified TableEnvironment for both batch and stream processing. Only the Blink planner (the only remaining planner in 1.14) is supported.

Migrate ModuleFactory to the new factory stack #

The LOAD/UNLOAD MODULE architecture for table modules has been updated to the new factory stack of FLIP-95. Users of this feature should update their ModuleFactory implementations.

Migrate Table API to new KafkaSink #

Table API/SQL now writes to Kafka with the new KafkaSink. When migrating from a query writing to Kafka in exactly-once mode from an earlier Flink version, make sure to terminate the old application with stop-with-savepoint to avoid lingering Kafka transactions. To run in exactly-once processing mode, the sink needs a user-configured and unique transaction prefix, such that transactions of different applications do not interfere with each other.

DataStream API #

Allow @TypeInfo annotation on POJO field declarations #

@TypeInfo annotations can now also be used on POJO fields which, for example, can help to define custom serializers for third-party classes that can otherwise not be annotated themselves.

Clarify SourceFunction#cancel() contract about interruptions #

Contract of the SourceFunction.cancel() method with respect to interruptions has been clarified:

  • source itself should not be interrupting the source thread
  • interrupt should not be expected in the clean cancellation case

Expose a consistent GlobalDataExchangeMode #

The default DataStream API shuffle mode for batch executions has been changed to blocking exchanges for all edges of the stream graph. A new option execution.batch-shuffle-mode allows you to change it to pipelined behavior if necessary.

Python API #

Support loopback mode to allow Python UDF worker and client to reuse the same Python VM #

Instead of launching a separate Python process, the Python UDF worker will reuse the Python process of the client side when running jobs locally. This makes it easier to debug Python UDFs.

Support Python UDF chaining in Python DataStream API #

The job graph of Python DataStream API jobs may be different from before as Python functions will be chained as much as possible to optimize performance. You could disable Python functions chaining by explicitly setting python.operator-chaining.enabled as false.

Connectors #

Expose standardized operator metrics (FLIP-179) #

Connectors using the unified Source and Sink interface will expose certain standardized metrics automatically.

Port KafkaSink to new Unified Sink API (FLIP-143) #

KafkaSink supersedes FlinkKafkaProducer and provides efficient exactly-once and at-least-once writing with the new unified sink interface, supporting both batch and streaming mode of DataStream API. To upgrade, please stop with savepoint. To run in exactly-once processing mode, KafkaSink needs a user-configured and unique transaction prefix, such that transactions of different applications do not interfere with each other.

Deprecate FlinkKafkaConsumer #

FlinkKafkaConsumer has been deprecated in favor of KafkaSource. To upgrade to the new version, please store the offsets in Kafka with setCommitOffsetsOnCheckpoints in the old FlinkKafkaConsumer and then stop with a savepoint. When resuming from the savepoint, please use setStartingOffsets(OffsetsInitializer.committedOffsets()) in the new KafkaSourceBuilder to transfer the offsets to the new source.

InputStatus should not contain END_OF_RECOVERY #

InputStatus.END_OF_RECOVERY was removed. It was an internal flag that should never be returned from SourceReaders. Returning that value in earlier versions might lead to misbehavior.

Connectors do not transitively hold a reference to flink-core anymore. That means that a fat JAR with a connector does not include flink-core with this fix.

Runtime & Coordination #

Increase akka.ask.timeout for tests using the MiniCluster #

The default akka.ask.timeout used by the MiniCluster has been increased to 5 minutes. If you want to use a smaller value, then you have to set it explicitly in the passed configuration.

The change is due to the fact that messages can not get lost in a single-process MiniCluster, so this timeout (which otherwise helps to detect message loss in distributed setups) has no benefit here.

The increased timeout reduces the number of false-positive timeouts, for example, during heavy tests on loaded CI/CD workers or during debugging.

The node IP obtained in NodePort mode is a VIP #

When using kubernetes.rest-service.exposed.type=NodePort, the connection string for the REST gateway is now correctly constructed in the form <nodeIp>:<nodePort> instead of <kubernetesApiServerUrl>:<nodePort>. This may be a breaking change for some users.

This also introduces a new config option kubernetes.rest-service.exposed.node-port-address-type that lets you select <nodeIp> from a desired range.

Timeout heartbeat if the heartbeat target is no longer reachable #

Flink now supports detecting dead TaskManagers via the number of consecutive failed heartbeat RPCs. The threshold until a TaskManager is marked as unreachable can be configured via heartbeat.rpc-failure-threshold. This can speed up the detection of dead TaskManagers significantly.

RPCs fail faster when target is unreachable #

The same way Flink detects unreachable heartbeat targets faster, Flink now also immediately fails RPCs where the target is known by the OS to be unreachable on a network level, instead of waiting for a timeout (akka.ask.timeout).

This creates faster task failovers because cancelling tasks on a dead TaskExecutor no longer gets delayed by the RPC timeout.

If this faster failover is a problem in certain setups (which might rely on the fact that external systems hit timeouts), we recommend configuring the application’s restart strategy with a restart delay.

Changes in accounting of IOExceptions when triggering checkpoints on JobManager #

In previous versions, IOExceptions thrown from the JobManager would not fail the entire Job. We changed the way we track those exceptions and now they do increase the number of checkpoint failures.

The number of tolerable checkpoint failures can be adjusted or disabled via: org.apache.flink.streaming.api.environment.CheckpointConfig#setTolerableCheckpointFailureNumber (which is set to 0 by default).

Refine ShuffleMaster lifecycle management for pluggable shuffle service framework #

We improved the ShuffleMaster interface by adding some lifecycle methods, including open, close, registerJob and unregisterJob. Besides, the ShuffleMaster now becomes a cluster level service which can be shared by multiple jobs. This is a breaking change to the pluggable shuffle service framework and the customized shuffle plugin needs to adapt to the new interface accordingly.

Group job specific ZooKeeper HA services under common jobs/ zNode #

The ZooKeeper job-specific HA services are now grouped under a zNode with the respective JobID. Moreover, the config options high-availability.zookeeper.path.latch, high-availability.zookeeper.path.leader, high-availability.zookeeper.path.checkpoints, and high-availability.zookeeper.path.checkpoint-counter have been removed and, thus, no longer have an effect.

Fallback value for taskmanager.slot.timeout #

The config option taskmanager.slot.timeout now falls back to akka.ask.timeout if no value has been configured. Previously, the default value for taskmanager.slot.timeout was 10 s.

DuplicateJobSubmissionException after JobManager failover #

The fix for this problem only works if the ApplicationMode is used with a single job submission and if the user code does not access the JobExecutionResult. If any of these conditions is violated, then Flink cannot guarantee that the whole Flink application is executed.

Additionally, it is still required that the user cleans up the corresponding HA entries for the running jobs registry because these entries won’t be reliably cleaned up when encountering the situation described by FLINK-21928.

Zookeeper node under leader and leaderlatch is not deleted after job finished #

The HighAvailabilityServices interface has received a new method cleanupJobData which can be implemented in order to clean up job-related HA data after a given job has terminated.

Optimize scheduler performance for large-scale jobs #

The performance of the scheduler has been improved to reduce the time of execution graph creation, task deployment, and task failover. This improvement is significant to large scale jobs which currently may spend minutes on the processes mentioned above. This improvement also helps to avoid cases when the job manager main thread gets blocked for too long and leads to heartbeat timeout.

Checkpoints #

The semantic of alignmentTimeout configuration has changed meaning #

The semantic of alignmentTimeout configuration has changed meaning and now it is measured as the time between the start of a checkpoint (on the checkpoint coordinator) and the time when the checkpoint barrier is received by a task.

Disable unaligned checkpoints for BROADCAST exchanges #

Broadcast partitioning can not work with unaligned checkpointing. There are no guarantees that records are consumed at the same rate in all channels. This can result in some tasks applying state changes corresponding to a certain broadcasted event while others do not. Upon restore, it may lead to an inconsistent state.

DefaultCompletedCheckpointStore drops unrecoverable checkpoints silently #

On recovery, if a failure occurs during retrieval of a checkpoint, the job is restarted (instead of skipping the checkpoint in some circumstances). This prevents potential consistency violations.

Remove the CompletedCheckpointRecover#recover() method. #

Flink no longer reloads checkpoint metadata from the external storage before restoring the task state after failover (except when the JobManager fails over / changes leadership). This results in less external I/O and faster failover.

Please note that this changes public interfaces around CompletedCheckpointStore, that we allow overriding by providing custom implementation of HA Services.

Remove the deprecated CheckpointConfig#setPreferCheckpointForRecovery method. #

The deprecated method CheckpointConfig#setPreferCheckpointForRecovery was removed, because preferring older checkpoints over newer savepoints for recovery can lead to data loss.

Dependency upgrades #

Bump up RocksDb version to 6.20.3 #

RocksDB has been upgraded to 6.20.3. The new version contains lots of bug fixes, ARM platform support, musl library support, and more attractive features. However, the new version can entail at most 8% performance regression according to our tests.

See the corresponding ticket for more information.

Support configuration of the RocksDB info logging via configuration #

With RocksDB upgraded to 6.20.3 (FLINK-14482), you can now also configure a rolling info logging strategy by configuring it accordingly via the newly added state.backend.rocksdb.log.* settings. This can be helpful for debugging RocksDB (performance) issues in containerized environments where the local data directory is volatile but the logs should be retained on a separate volume mount.

Flink’s Akka dependency is now loaded with a separate classloader and no longer accessible from the outside.

As a result, various modules (most prominently, flink-runtime) no longer have a scala suffix in their artifactId.

Drop Mesos support #

The support for Apache Mesos has been removed.