Hazelcast Jet 4.4 is Released!

Marko Topolnik | Feb 3, 2021

Today we’re releasing Hazelcast Jet 4.4 and we have some exciting new features!


Hazelcast Jet 4.4 brings you the first beta version of our SQL interface. You can now log into Jet from the command line and issue queries against the data sources you specify. They can be both data at rest (batch sources) and live feeds (streaming sources).

If you have Docker at hand, here’s something you can try out right now! (For examples that don’t require Docker, go to the docs.)

docker pull hazelcast/hazelcast-jet
docker network create jet-network
docker run --name jet --network jet-network -v "$(pwd)":/csv-dir --rm hazelcast/hazelcast-jet

Wait for a message like this in the output:

2021-01-15 17:50:18,645 [ INFO] [main] [c.h.c.LifecycleService]: []:5701 is STARTED

Now start another terminal window and enter the SQL shell:

$ docker run --network jet-network -it --rm hazelcast/hazelcast-jet jet --targets jet sql
Connected to Hazelcast Jet 4.4 at []:5701 (+0 more)
Type 'help' for instructions

You are now ready to write some SQL. Try these:

sql〉SELECT * FROM TABLE(generate_series(1,3));
|           v|
|           1|
|           2|
|           3|
3 row(s) selected
sql〉SELECT key, sum(key) as total FROM (
          SELECT v/2 as key FROM TABLE(generate_series(0, 7))
      ) GROUP BY key;
|                 key|               total|
|                   0|                   0|
|                   1|                   2|
|                   2|                   4|
|                   3|                   6|
4 row(s) selected

Here are two more examples with streaming SQL. Streaming queries never complete, so use Ctrl+C to cancel them after a while:

sql〉SELECT * FROM TABLE(generate_stream(10));
|                   v|
|                   0|
|                   1|
|                   2|
Query cancelled.
sql〉SELECT * FROM TABLE(generate_stream(100)) WHERE v / 10 * 10 = v;
|                   v|
|                   0|
|                  10|
|                  20|
Query cancelled.

For more examples with CSV files, Kafka and IMap, go to the docs.

We’re currently very focused on bringing more features to our SQL, so stay tuned!

File Connector

The Unified File Connector API gives you a simple way to read files, unified across different storage systems. Using the same API you can read files from the local filesystem, Hadoop FS, Amazon S3, Google Cloud Storage, and Azure Blob Storage. At the same time, the connector supports a variety of encoding formats: text files, CSV, JSON, Avro, etc., equally for all storage systems.

Here’s how the Java syntax looks:

BatchSource<String> source = FileSources

You specify the storage system type with the URI schema, for example to access S3:

BatchSource<String> source = FileSources

And this is how you tell it to use the Avro encoding:

BatchSource<User> source = FileSources

Read more in the Programming Guide.

Enforce Strict Event Order

Hazelcast Jet’s primary focus is to leverage all opportunities to improve the throughput and latency of its computation. One example is using logic that isn’t sensitive to the exact event order. Jet can use this freedom to optimally load-balance the data across parallel tasks. This works great for stateless transforms like map and filter as well as aggregate operations specifically written in terms of commutative and associative functions. However, Jet also supports transforms such as mapStateful, where reordering any two events is likely to result in different output.

In version 4.4 we provide a new option, pipeline.setPreserveOrder(true), which tells Jet to disable the dataflow optimizations that result in reordered events. One consequence of enabling it is that the level of parallelism in the source stage determines the parallelism of all the subsequent stages because the data flows in parallel lanes through the pipeline. So if you have a source that isn’t paralellized, your whole pipeline won’t be parallelized either (at least until a stage that explicitly changes the order, such as rebalance or groupingKey). This feature works best when you have a partitioned source and you only require strict order among events with the same key. Then you get both the ordering you need and decent parallelization.

Improved Packaging

We used to offer Jet packaged with some hand-picked extensions while you could add others by downloading them separately. As of 4.4 we offer two kinds: a full package with all the extensions, and a slim one with none. Normally you want to use the full package, but if you want to optimize the download size or disk usage, use the slim package.

Along the same lines, we now provide a slim Docker image, hazelcast/hazelcast-jet:4.4-slim, to serve as the base image in your Dockerfile that combines it with the extensions, like this:

FROM hazelcast-jet:4.4-slim
ARG JET_HOME=/opt/hazelcast-jet
ARG REPO_URL=https://repo1.maven.org/maven2/com/hazelcast/jet
ADD $REPO_URL/hazelcast-jet-kafka/4.4/hazelcast-jet-kafka-4.4-jar-with-dependencies.jar $JET_HOME/lib/
# ... more ADD statements ...

See the instructions in our docs for more details.

Full Release Notes

Hazelcast Jet 4.4 is based on IMDG version 4.1.1. Check out its Release Notes here and, for the Enterprise Edition, here.

Members of the open source community that appear in these release notes:

  • @TomaszGaweda
  • @hhromic

Thank you for your valuable contributions!

New Features

  • [sql] SQL Beta: submit jobs to Jet from the command-line SQL shell. (#2595, #2636, #2648, #2654, #2665, #2729, #2763, #2788)
  • [file-api] [017] Unified API to create sources and sinks from file-like resources: local filesystem, Amazon S3, Azure Blob Storage and Data Lake Storage, Google Cloud Storage (#2518)
  • [kinesis] [018] Amazon Kinesis connector (#2656)
  • [pipeline-api] [016] Prevent event reordering: by default Jet reorders data for performance, now you can disable this to get strict event order where you need it.


  • [connectors] @hhromic improved the naming of source and sink stages across different connectors, bringing them all in line with the same convention xSource / xSink (#2685)
  • [pipeline-api] @TomaszGaweda added the pipeline.isEmpty() method that tells whether it contains any stage (#2659)
  • [core] @TomaszGaweda added the jet.imdg.version.mismatch.check.disabled config property that disables the enforcement of the exact IMDG dependency version. This allows adding IMDG quick fixes to the existing Jet release. (#2610)
  • [core] New packaging: download either the full package with all the extensions enabled, or the minimal package and separately download the extensions you want. (#2796)
  • [cli] Improved the behavior of jet submit: now it waits for the job to start and prints a message about it. (#2699)
  • [python] Improved the error message when using a Python function but Python is not installed. (#2672)
  • [kafka] Improved the performance of the Kafka source by fine-tuning some timeouts. (#2732)


  • [core] Fixed a problem where Jet would close System.out during JVM shutdown, preventing shutdown hooks from printing to stdout. (#2649)
  • [file-connector] Fixed the blocking File connector declaring its processors as cooperative, resulting in performance loss. (#2628)
  • [file-connector] Several bug fixes in the File connector. (#2772)
  • [core] Fixed a leak caused by Jet’s ephemeral loggers created for each job. They didn’t get released from internal maps in the logging framework. (#2737)
  • [core] Fixed two problems with the peek transform. (#2740, #2765)
  • [hadoop] Fixed a problem when using Hadoop for local files, it behaved as if the files were shared. (#2764)

Breaking Changes


If you enjoyed reading this post, check out Jet at GitHub and give us a star!

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About the Author

Marko Topolnik

Senior Software Engineer, Hazelcast

Marko Topolnik, PhD, has been a Java professional since 2001. His current position is in the core team of Hazelcast Jet, where he co-wrote the core execution engine based on coroutine-like suspendable code that runs many concurrent tasks on a fixed thread pool. Marko is also an active contributor on Stack Overflow on the kotlin-coroutines tag.