This documentation is for an out-of-date version of Apache Flink. We recommend you use the latest stable version.

Release Notes - Flink 1.5

These release notes discuss important aspects, such as configuration, behavior, or dependencies, that changed between Flink 1.4 and Flink 1.5. Please read these notes carefully if you are planning to upgrade your Flink version to 1.5.

Changed syntax of jobmanager.sh script

The jobmanager.sh script was reworked which removed the execution mode parameter (local vs. cluster). Now it has the following syntax: jobmanager.sh ((start|start-foreground) [host] [webui-port])|stop|stop-all.

Consequently, all external scripts need to remove the execution mode parameter when calling jobmanager.sh. Otherwise, the execution mode (local or cluster) will be interpreted as the host name of the started process. This can lead to connectivity problems between Flink’s components.

Update Configuration for Reworked Job Deployment

Flink’s reworked cluster and job deployment component improves the integration with resource managers and enables dynamic resource allocation. One result of these changes is, that you no longer have to specify the number of containers when submitting applications to YARN and Mesos. Flink will automatically determine the number of containers from the parallelism of the application.

Although the deployment logic was completely reworked, we aimed to not unnecessarily change the previous behavior to enable a smooth transition. Nonetheless, there are a few options that you should update in your conf/flink-conf.yaml or know about.

  • The allocation of TaskManagers with multiple slots is not fully supported yet. Therefore, we recommend to configure TaskManagers with a single slot, i.e., set taskmanager.numberOfTaskSlots: 1
  • If you observed any problems with the new deployment mode, you can always switch back to the pre-1.5 behavior by configuring mode: legacy.

Please report any problems or possible improvements that you notice to the Flink community, either by posting to a mailing list or by opening a JIRA issue.

Note: We plan to remove the legacy mode in the next release.

Update Configuration for Reworked Network Stack

The changes on the networking stack for credit-based flow control and improved latency affect the configuration of network buffers. In a nutshell, the networking stack can require more memory to run applications. Hence, you might need to adjust the network configuration of your Flink setup.

There are two ways to address problems of job submissions that fail due to lack of network buffers.

  • Reduce the number of buffers per channel, i.e., taskmanager.network.memory.buffers-per-channel or
  • Increase the amount of TaskManager memory that is used by the network stack, i.e., increase taskmanager.network.memory.fraction and/or taskmanager.network.memory.max.

Please consult the section about network buffer configuration in the Flink documentation for details. In case you experience issues with the new credit-based flow control mode, you can disable flow control by setting taskmanager.network.credit-model: false.

Note: We plan to remove the old model and this configuration in the next release.

Hadoop Classpath Discovery

We removed the automatic Hadoop classpath discovery via the Hadoop binary. If you want Flink to pick up the Hadoop classpath you have to export HADOOP_CLASSPATH. On cloud environments and most Hadoop distributions you would do

export HADOOP_CLASSPATH=`hadoop classpath`.

Problems With Enabling SSL Encryption

Due to a limitation in Netty’s SsLHandler (v4.0.27), it does not work well together with GCM enabled cypher suites. It can cause transmission failures between Flink TaskManager’s which manifest in a LocalTransportException. Therefore, it is highly recommended to either set the security.ssl.algorithms configuration to TLS_RSA_WITH_AES_128_CBC_SHA when enabling SSL encryption or to disable SSL encryption between TaskManagers via taskmanager.data.ssl.enabled: false.

Breaking Changes of the REST API

In an effort to harmonize, extend, and improve the REST API, a few handlers and return values were changed.

  • The jobs overview handler is now registered under /jobs/overview (before /joboverview) and returns a list of job details instead of the pre-grouped view of running, finished, cancelled and failed jobs.
  • The REST API to cancel a job was changed.
  • The REST API to cancel a job with savepoint was changed.

Please check the REST API documentation for details.

Kafka Producer Flushes on Checkpoint by Default

The Flink Kafka Producer now flushes on checkpoints by default. Prior to version 1.5, the behaviour was disabled by default and users had to explicitly call setFlushOnCheckpoints(true) on the producer to enable it.

Updated Kinesis Dependency

The Kinesis dependencies of Flink’s Kinesis connector have been updated to the following versions.

<aws.sdk.version>1.11.319</aws.sdk.version>
<aws.kinesis-kcl.version>1.9.0</aws.kinesis-kcl.version>
<aws.kinesis-kpl.version>0.12.9</aws.kinesis-kcl.version>

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