Upgrading KSQL

Upgrade one KSQL server at a time (i.e. rolling restart). The remaining KSQL servers should have sufficient spare capacity to take over temporarily for unavailable, restarting servers.

Upgrading from KSQL 5.2 to KSQL 5.3

Notable changes in 5.3:

  • KSQL Server

    • Avro schema compatibility

      • This version of KSQL fixes a bug where the schemas returned by UDF and UDAFs might not be marked as nullable. This can cause serialization issues in the presence of null values, as might be encountered if the UDF fails.

        With the bug fix all fields are now optional.

        This is a forward compatible change in Avro, i.e. after upgrading, KSQL will be able to read old values using the new schema. However, it is important to ensure downstream consumers of the data are using the updated schema before upgrading KSQL, as otherwise deserialization may fail. The updated schema is best obtained from running the query in another KSQL cluster, running version 5.3.

        See Github issue #2769 for more info.

  • Configuration:

    • ksql.sink.partitions and ksql.sink.replicas are deprecated. All new queries will use the source topic partition count and replica count for the sink topic instead unless partitions and replicas are set in the WITH clause.
    • A new config variable, ksql.internal.topic.replicas, was introduced to set the replica count for the internal topics created by KSQL Server. The internal topics include command topic or config topic.

Upgrading from KSQL 5.1 to KSQL 5.2

Notable changes in 5.2:
  • KSQL Server

    • Interactive mode:

      • The use of the RUN SCRIPT statement via the REST API is now deprecated and will be removed in the next major release. (Github issue 2179). The feature circumnavigates certain correctness checks and is unnecessary, given the script content can be supplied in the main body of the request. If you are using the RUN SCRIPT functionality from the KSQL CLI you will not be affected, as this will continue to be supported. If you are using the RUN SCRIPT functionality directly against the REST API your requests will work with the 5.2 server, but will be rejected after the next major version release. Instead, include the contents of the script in the main body of your request.
  • Configuration:

    • When upgrading your headless (non-interactive) mode application from version 5.0.0 and below, you must include the configs specified in the 5.1 upgrade instructions.
    • When upgrading your headless (non-interactive) mode application, you must include the following properties in your properties file:
ksql.windowed.session.key.legacy=true
ksql.named.internal.topics=off
ksql.streams.topology.optimization=none

Upgrading from KSQL 5.0.0 and below to KSQL 5.1

  • KSQL server:

    • The KSQL engine metrics are now prefixed with the ksql.service.id. If you have been using any metric monitoring tool you need to update your metric names. For instance, assuming ksql.service.id is set to default_, messages-produced-per-sec will be changed to _confluent-ksql-default_messages-consumed-per-sec.
  • Configuration:

    • When upgrading your headless (non-interactive) mode application, you must either update your queries to use the new SUBSTRING indexing semantics, or set ksql.functions.substring.legacy.args to true. If possible, we recommend that you update your queries accordingly, instead of enabling this configuration setting. Refer to the SUBSTRING documentation in the function guide for details on how to do so. Note that this is NOT required for interactive mode KSQL.

Upgrading from KSQL 0.x (Developer Preview) to KSQL 4.1

KSQL 4.1 is not backward-compatible with the previous KSQL 0.x developer preview releases. In particular, you must manually migrate queries running in the older preview releases of KSQL to the 4.1 version by issuing statements like CREATE STREAM and CREATE TABLE again.

Notable changes in 4.1:

  • KSQL CLI:

    • The ksql-cli command was renamed to ksql.
    • The CLI no longer supports what was formerly called “standalone” or “local” mode, where ksql-cli would run both the CLI and also a KSQL server process inside the same JVM. In 4.1, ksql will only run the CLI. For local development and testing, you can now run confluent start (which will also launch a KSQL server), followed by ksql to start the CLI. This setup is used for the Confluent Platform quickstart. Alternatively, you can start the KSQL server directly as described in Starting the KSQL Server, followed by ksql to start the CLI.
  • KSQL server:

    • The default listeners address was changed to http://localhost:8088 (KSQL 0.x used http://localhost:8080).
    • Assigning KSQL servers to a specific KSQL cluster has been simplified and is now done with the ksql.service.id setting. See Configuring KSQL Server for details.
  • Executing .sql files: To run pre-defined KSQL queries stored in a .sql file, see Non-interactive (Headless) KSQL Usage.

  • Configuration: Advanced KSQL users can configure the Kafka Streams and Kafka producer/consumer client settings used by KSQL. This is achieved by using prefixes for the respective configuration settings. See KSQL Configuration Parameter Reference as well as Configuring KSQL Server and Configuring KSQL CLI for details.