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What's new in version 0.44.0

The following new features and notable changes since version 0.43.0 are included in this release:

Features and changes

Binaries and supported environments

Eclipse OpenJ9™ release 0.44.0 supports OpenJDK 8, 11, 17, and 21.

To learn more about support for OpenJ9 releases, including OpenJDK levels and platform support, see Supported environments.

Change in behavior of the system property for OpenJDK version 8

From OpenJDK version 18 onwards, if you enable the SecurityManager at runtime by calling the System.setSecurityManager() API, you must set the option. To disable the SecurityManager, you must specify the option. If an application is designed to run on multiple OpenJDK versions, the same command line might be used across multiple versions. Because of this use of the same command line across multiple versions, in OpenJDK versions before version 18, the runtime attempts to load a SecurityManager with the class name allow or disallow resulted in an error and the application was not starting.

To resolve this issue, OpenJDK version 17 ignores these options and from 0.41.0 release onwards, OpenJDK version 11 also ignores these options. With this release, OpenJDK version 8 too ignores the allow and disallow keywords, if specified.

Start of content that applies to Java 21 (LTS) and later Display of multiple warnings on loading the same agent restricted on AIX systems

Earlier, on AIX systems, warnings were issued each time the agents were loaded dynamically into a running VM after startup without specifying the -XX:+EnableDynamicAgentLoading option, even if the same agents were loaded before.

Now, from 0.44.0 release onwards, AIX systems, like other OpenJ9 supported operating systems, can detect whether an agent was previously loaded or not. Therefore, like other platforms, on AIX systems also, the warnings are issued only once for the same agent when the -XX:+EnableDynamicAgentLoading option is not specified.

For more information, see -XX:[+|-]EnableDynamicAgentLoading. End of content that applies to Java 21 (LTS) and later

XL C++ Runtime or later required for AIX OpenJ9 builds on OpenJDK 8

AIX OpenJ9 builds now require version or later of the IBM XL C++ Runtime on OpenJDK 8 as well.

Start of content that applies to Java 21 (LTS) New -XX:[+|-]ShowUnmountedThreadStacks option added

Java™ core file lists stacks of only those threads that are mapped to platform threads. An unmounted virtual thread is not mapped to any platform thread. Therefore, the stack of any unmounted virtual thread is not included in the Java core file and thus, the virtual thread information remains incomplete.

You can use the -XX:+ShowUnmountedThreadStacks option to include all the thread data that a VM is aware of, both regular Java threads and the unmounted virtual threads, in a Java core file.

For more information, see -XX:[+|-]ShowUnmountedThreadStacks. End of content that applies to Java 21 (LTS)

VMID query in the jcmd tool enhanced

Earlier in OpenJ9, when sending a jcmd command to a VM, you had to run jcmd -l to retrieve all the pids for all the VMs found on the machine. Then, you had to use jcmd [vmid] [command] to send the command to the specific VM.

For OpenJDK compatibility, OpenJ9 now supports direct use of the Java process name, full or partial, as the ID to send the jcmd command.

The jcmd tool also now supports specifying 0 as a VMID to target all VMs.

For more information, see Java diagnostic command (jcmd) tool.

DDR field names in J9BuildFlags changed

The Direct Dump Reader (DDR) code enables reading system dump data by using the OpenJ9 Diagnostic Tool Framework for Java (DTFJ) API or the jdmpview tool. DDR code uses fields of J9BuildFlags to access build flags in the system dump data. The names of J9BuildFlags fields changed over time and therefore, supporting system dumps with different build flags became a challenge.

Earlier, field names in J9BuildFlags were based on names defined in j9.flags. Now, when the J9BuildFlags is generated for each build, the flag names are those names that are specified in j9cfg.h (derived from j9cfg.h.ftl or instead of the names that are defined in j9.flags. For example, env_data64 is now referred to as J9VM_ENV_DATA64.

You can extend the DDR code, adding your own commands, by writing plug-ins. If the user plug-in code contains references to fields of J9BuildFlags to read the build flags in the system dump data, you must change references to use the names as specified in j9cfg.h.

New system property added to prevent the deletion of the Attach API control files within the /tmp/ folder

You can use the system property to prevent Linux® systemd-tmpfiles from deleting the Attach API control files within the /tmp/ folder. By updating the Attach API control file access times to avoid deletion by systemd-tmpfiles, the long-running Attach API can continue to use the control files to operate. This system property enables Attach API to update the control file access times at specific intervals.

For more information, see

Known problems and full release information

To see known problems and a complete list of changes between Eclipse OpenJ9 v0.43.0 and v0.44.0 releases, see the Release notes.