This is a prerelease version.

Release Notes

Hazelcast 5.0 is a major release which unifies the former Hazelcast IMDG and Jet products in a single solution. The changes are summarized below.

For information on upgrading from previous IMDG and Jet releases, see the Upgrading to Hazelcast 5.0 section.

To learn about the changes in previous IMDG and Jet releases, see IMDG release notes and Jet release notes.

New Features

  • SQL Engine: We have added the support of following operators to our SQL engine:

  • Persistence: This allows individual members and whole clusters to recover faster by persisting map entries and JCache data on disk. Members can use persisted data to recover during restarts. See the Persistence section.

  • Compact Serialization Format (Preview Feature): We have introduced a new serialization format (CompactSerializer), which is in its beta stage currently. This format requires much less storage space, provides better latency and throughput, and supports more extensive type sets:

    • It supports schema evolution of a class and does not require any version to be specified explicitly.

    • On common use cases where the field types of an object are natively supported via this compact format, Java DTO classes are automatically serialized without requiring a serializer (CompactSerializer) to be implemented.

    • Your classes do not need to implement an interface like Portable. Once you enable the compact serialization, the classes not matching to any other serialization methods are serialized in this new format.

  • Merkle Tree for ICache: Like Hazelcast maps, now caches (ICache) also support the Delta WAN Synchronization using Merkle trees. #18898

  • Security for Jet Engine Jobs: The Jet engine allows you to upload custom code as well as access data outside of Hazelcast such as files on the device that’s running a member. You can secure your Hazelcast member against malicious uses of the Jet API. See the Job Security section.

Breaking Changes

BETA API Changes

  • Changed the type of YEAR field in the SQL client protocol from short to int. #18984

  • Since the HOST and RACK metadata were deprecated in the previous Hazelcast release, these information are removed from the ZONE_AWARE partition grouping configuration. #18780

  • Since DAG printing was not reflecting the real queue size, the DAG.toDotString(int defaultParallelism) method signature is changed as DAG.toDotString(int defaultLocalParallelism, int defaultQueueSize). You, now, need to supply the queue size that will be shown if it is not overriden on the edge. #18475

Configuration Changes

  • Removed the following properties that were used in the former Jet product, since it is now part of Hazelcast 5.0:

    • jet.home

    • jet.imdg.version.mismatch.check.disabled



  • Hazelcast distribution is now available in two versions: full and slim. While the full one includes Hazelcast and all of its modules along with SQL, Jet engine extensions and Management Center, the slim one only includes the Hazelcast runtime, default configurations and scripts. See here for details. #18990, #18989

  • Consolidated the scripts delivered with the former IMDG and Jet distributions. See the Changes in Distribution Packaging section. #18999

  • The former hazelcast-sql, hazelcast-sql-core and hazelcast-jet-sql Maven modules in the distributions have been merged into a single hazelcast-sql module as a part of the Hazelcast 5.0 distribution. #18584

  • Removed the jackson-core dependency from pom.xml since it was breaking the extensions that depend on jackson. #18665

  • Moved the former Hazelcast Jet code samples into the Hazelcast code samples repository. #475

The Jet and SQL Engine

  • The Jet engine jobs submitted in a Hazelcast cluster are now cancelled when you upgrade your Hazelcast version since the Jet engine doesn’t provide backwards compatibility. #19012

  • Added support of the putIfAbsentAsync() method for maps on the member side; which is required for the usage of INSERT INTO statements in SQL queries. #18946

  • Added support of returning nested fields without having to deserialize them, which enables you to use Portable in client/server deployments without touching the server side; for example, SQL queries can now return columns without having the class on the server-side classpath. #18922

  • Standardized the TIME and TIMESTAMP temporal formats for the SQL engine: You can now use TIME without leading zeroes and TIMESTAMP with space instead of the T symbol. Also added support of leading non-zero characters for the DATE formats. #18881, #18842

  • Added support of OFFSET for SQL queries. #18866

  • Changed the since tags in Jet engine API and its extension modules from @since x.y to @since Jet x.y. #18832

  • Implemented the OnHeapMapScanP class to read the Hazelcast maps directly by the SQL engine. #18685

  • Implemented a basic memory management for the SQL engine so that number of records accumulated by it can be limited to avoid out of memory failures. You can use the max-processor-accumulated-records configuration element for this purpose. #18671

  • Added support of dynamic parameters for the SQL engine and file table functions. #18613, #18522

  • Introduced QueryDataType.MAP and QueryDataTypeFamily.MAP to support map operand checks for file table functions. #18602

  • Added support of EXTRACT(field FROM source) for the SQL engine. The function computes date parts from the source field. The supported types for source argument are as follow:

    • Date

    • Time

    • Timestamp

    • Timestamp With Time Zone

  • Added support of the LIMIT <n> and ORDER BY clauses for the streaming engine. #18479

  • Implemented the following functions for the SQL engine:

  • Added support of plan caching for Jet engine based queries. #18446

  • Added support of plus and minus operations for interval types (date, time, etc.) for the SQL engine. #18390

  • Added support of various new Portable types for the SQL engine. #18115

  • Added support of IN and BETWEEN operators for the SQL queries. #18483, #18422, #18067


  • Added support of default serializers for the following classes which has been necessary for non-Java clients to use these:

    • LocalDate

    • LocalTime

    • LocalDateTime

    • OffsetDatetime


  • Introduced the simple authentication configuration; it allows to have users and their assigned roles stored together with other Hazelcast configurations. See the example:

        enabled: true
          - name: simpleRealm
                  - username: test
                    password: 'a1234'
                      - monitor
                      - hazelcast
                  - username: root
                    password: 'secret'
                      - admin


  • Added a configuration option to enable/disable resource uploading for Jet engine jobs. See here for details.

  • Even when the factory configuration is missing on the member but the map is configured to have the the in-memory format as OBJECT, Hazelcast now can store portables as PortableGenericRecord and still query them without needing to convert them to Object/Data. #18891

  • Introduced the following properties:

    • hazelcast.partition.rebalance.mode: It determines whether cluster membership change triggers partition rebalancing automatically (auto) or explicit action is required for rebalancing to occur (manual). Its default is auto.

    • hazelcast.partition.rebalance.delay.seconds: it specifies the time in seconds to wait before triggering automatic partition rebalancing after a member leaves the cluster unexpectedly. Unexpectedly in this context means that a member leaves the cluster by programmatic termination, a process crash or network partition. Its default is 0, which means rebalancing is triggered immediately.

Other Enhancements

  • Added the client console entry point to the Hazelcast command line interface; you can now use the hazelcast console command to start the client console application. #18857

  • Enhanced the getPartitionGroupStrategy() method to have cluster members as arguments so that useful partitioning strategies can be implemented by accessing the members using this method. #18794

  • The log message for infinite cluster connection timeout is clearer now. Previously, it was represented as the value of Long.MAX_VALUE. #18642

  • Introduced a new mechanism in the background expiration tasks; now a thread local array controls the allocations for these tasks otherwise which may cause increased garbage collection pressure and CPU usage spikes when you use aggressive expiration configurations, e.g., low time-to-live values. #18633

  • The license key is, now, not shown while starting a member on Docker with overriding configurations. #18568

  • Limited the number of parallel partition reads (to a fixed value of five) for maps and caches to prevent out of memory failures. #18663, #18499

  • Added a comprehensive documentation for metrics produced by Hazelcast. See here for the full list of metrics with their descriptions. #17880

  • Improved the speed of connection by a member when it joins the cluster, by removing the unnecessary sleep statements in the code. #17428


  • SQL expressions now does not fail when used with trailing semicolons. 18976

  • Fixed an issue where the health monitor was incorrectly showing the value for free metadata memory. #18951

  • Some merge policies like LatestUpdateMergePolicy for the map and WAN replication configurations require the per-entry statistics to be enabled. Previously, this configuration inconsistency was causing the related member to fail at runtime. Now, the Hazelcast member fails to start, i.e., fast fails, in such a case. #18928

  • Fixed an issue where the maximum size policy for a map was being ignored when the policy is PER_NODE and the cluster is scaled down (due to losing or killing a member). #18927

  • The LRU eviction policy now takes last access time value into account to prevent premature removal of the lately added but not yet accessed map entries. #18909

  • Fixed an issue where the map’s Near Cache was setting its maximum size as 10.000 even if the configured eviction policy is NONE. #18835

  • Fixed a regression issue where a job using map reader/writer could not be completed when the target map has a configured Near Cache. #18696

  • Fixed an issue where the updates made to a persistent map store might be lost when the write coalescing is enabled. #18686

  • Fixed a reconnection flood when members are separated by a proxy: When a member is disconnected from the cluster, the alive cluster members still try to reconnect to it if the dying member connection is not closed explicitly. In the cases where the connection is explicitly closed with a cause (such as Connection reset by peer or Remote socket closed!), a new connection was being established if the member is placed behind a proxy. This scenario was end causing opening and closing connections continuously. This issue has been fixed. #18673

  • Fixed an issue where the multicast discovery was not working between the members when the loopback mode is enabled. #18669

  • The HazelcastInstance.shutdown() method now gracefully terminate Jet engine jobs, too. After the merge of IMDG and Jet, it was failing. #18625

  • Replicated Map does not fail to publish events anymore, from an entry listener with a predicate which has an attribute path. #18623

  • Fixed a possible performance regression by not starting the cooperative threads until a job is submitted; otherwise the Jet engine was consuming system resources. #18574

  • Fixed an issue where running SQL statements was fetching results incorrectly (from an unexpected mapping) when there are different user-provided schemas for data structures and mappings. #18428

  • Fixed an issue where there might be continuous reconnection attempts by the cluster members to a failed member, even its connection is explicitly closed and when Hazelcast is placed behind a proxy. #18320

  • Hazelcast now properly works on hosts with multiple NICs. #17834

Removed/Deprecated Features

  • Former Jet, JetInstance and JetCacheManager classes have been deprecated. See here for details. Accordingly JetInstance has been removed from Hazelcast’s command line interface (CLI) and Jet engine tests (also the name of CLI has been changed to HazelcastCommandLine). #18829, #18775, #18667

  • Former Hazelcast Jet’s bootstrappedInstance() has been deprecated. Instead, you can use Hazelcast.bootstrappedInstance(). See here for details.

  • The support of NULLS FIRST and NULLS LAST has been removed from the SQL engine; the indices treat NULL as the smallest value in ordering, therefore we needed to disable temporarily these constructs. #19031

  • The configuration element hot-restart-persistence has been deprecated. You can use persistence instead, which is the successor of hot-restart-persistence. If both are enabled, Hazelcast uses the persistence configuration. The hot-restart-persistence element will be removed in a future release. #19004

  • The hazelcast-all module has been removed from the Hazelcast distribution after the merge of former IMDG and Jet products.


We would like to thank the contributors from our open source community who worked on this release: