Hazelcast
Hazelcast is an open-source distributed in-memory data store and computation platform. It provides a wide variety of distributed data structures and concurrency primitives, including:
- a distributed, partitioned and queryable in-memory key-value store implementation, called
IMap - additional data structures and simple messaging constructs such as
Set,MultiMap,Queue,Topic - cluster-wide unique ID generator, called
FlakeIdGenerator - a distributed, CRDT based counter, called
PNCounter - a cardinality estimator based on
HyperLogLog.
Additionally, Hazelcast includes a production-ready Raft implementation which allows implementation of linearizable constructs such as:
- a distributed and reentrant lock implementation, called
FencedLock - primitives for distributed computing such as
AtomicLong,AtomicReferenceandCountDownLatch.
Hazelcast data structures are in-memory, highly optimized and offer very low latencies. For a single get or put operation on an IMap, you can typically expect a round-trip-time of under 100 microseconds.
It's very simple to form a cluster with Hazelcast, you can easily do it on your computer by just starting several instances. The instances will discover each other and form a cluster. There aren't any dependencies on any external systems.
Hazelcast automatically replicates data across the cluster and you are able to seamlessly tolerate failures and add additional capacity to the cluster when needed.
Hazelcast comes with clients in the following programming languages:
Hazelcast also has first-class support for running on different cloud providers such as AWS, GCP and Azure as well as on Kubernetes.
Download
You can download Hazelcast from hazelcast.org. Once you have downloaded, you can start the Hazelcast instance using the script bin/start.sh.
Get Started
Hazelcast allows you to interact with a cluster using a simple API, for example you can use the Hazelcast Java Client to connect to a running cluster and perform operations on it:
HazelcastInstance hz = HazelcastClient.newHazelcastClient();
IMap<String, String> map = hz.getMap("my-distributed-map");
map.put("key", "value");
String current = map.get("key");
map.putIfAbsent("somekey", "somevalue");
map.replace("key", "value", "newvalue");
You only need to add a single JAR as a dependency:
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast</artifactId>
<version>${hazelcast.version}</version>
</dependency>
For more information, see the Getting Started Guide
Documentation
See the reference manual for in-depth documentation about Hazelcast features.
Code Samples
Hazelcast Jet
Hazelcast Jet is a distributed batch and stream processing framework based on Hazelcast. It can be used to import/export data from/to Hazelcast using a very wide variety of data sources including Hadoop, S3, Apache Kafka, Elasticsearch, JDBC and JMS.
Get Help
You can use the following channels for getting help with Hazelcast:
- Hazelcast mailing list
- Slack for chatting with the development team and other Hazelcast users.
- Stack Overflow
Contributing
We encourage Pull Requests and process them promptly.
To contribute:
- see Developing with Git for our Git process
- complete the Hazelcast Contributor Agreement
For an enhancement or larger feature, create a GitHub issue first to discuss.
Using Snapshot Releases
Maven snippet:
<repository>
<id>sonatype-snapshots</id>
<name>Sonatype Snapshot Repository</name>
<url>https://oss.sonatype.org/content/repositories/snapshots</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<dependency>
<groupId>com.hazelcast</groupId>
<artifactId>hazelcast</artifactId>
<version>${hazelcast.version}</version>
</dependency>
Building From Source
Pull latest from repo git pull origin master and use Maven install (or package) to build mvn clean install.
Testing
Hazelcast has 3 testing profiles:
- Default: Type
mvn testto run quick/integration tests (those can be run in parallel without using network). - Slow Tests: Type
mvn test -P slow-testto run tests that are either slow or cannot be run in parallel. - All Tests: Type
mvn test -P all-teststo run all tests serially using network.
Checkstyle and SpotBugs
Hazelcast uses static code analysis tools to check if a Pull Request is ready for merge. Run the following commands locally to check if your contribution is Checkstyle and SpotBugs compatible.
mvn clean validate -P checkstyle
mvn clean compile -P spotbugs
License
Hazelcast is available under the Apache 2 License. Please see the Licensing section for more information.
Acknowledgments
Thanks to YourKit for supporting open source software by providing us a free license for their Java profiler
Copyright
Copyright (c) 2008-2021, Hazelcast, Inc. All Rights Reserved.
Visit www.hazelcast.com for more info.
![Introduce multi partition predicate [HZ-1347]](https://avatars.githubusercontent.com/u/37229146?v=4)
![[operation] Hazelcast 3.7: PollOperation invocation failed to complete due to operation-heartbeat-timeout](https://avatars.githubusercontent.com/u/5618914?v=4)
![Offload non-cooperative ProcessorSupplier.init and ProcessorMetaSupplier.init [HZ-1204]](https://avatars.githubusercontent.com/u/8236272?v=4)
![High latency and steady CPU increase since migration from 3.12.x to 4.x [HZ-871]](https://avatars.githubusercontent.com/u/6304496?v=4)
566 Dec 22, 2022
33 Jan 4, 2023
1k Dec 31, 2022
20.4k Jan 5, 2023
3 Sep 2, 2021
25 Sep 19, 2022
3 Apr 28, 2022
2.1k Jan 4, 2023
1.9k Jan 2, 2023
13.2k Jan 5, 2023
271 Jan 8, 2023
16.6k Jan 4, 2023
9.2k Jan 1, 2023
424 Dec 28, 2022
65 Nov 12, 2022
1.5k Dec 29, 2022