JDK 10
JDK 10 introduced some new features. As mentioned earlier, we will concentrate on the most important features related to cloud environments and microservice architecture.
The first one is Docker awareness, which is supported for Linux only. With this feature, you can extract container-specific information about the number of CPUs (automatically) and allocated memory (automatically).
The following new JVM configuration parameters have been introduced:
- -XX:UseContainerSupport: The JVM has been updated in order to be aware that it is running in a Docker container. In this way it will extract container specific configuration information and it will not query the operating system. The more important information that it will be extract is the total memory that have been allocated to the container and the amount of CPUs. The value of CPUs available to the Java process is calculated from any specified CPU shares, CPU quotas or CPU sets.
- -XX:ActiveProcessorCount: This value overrides any other logic of CPU detection implemented automatically by the JVM.
- -XX:InitialRAMPercentage/-XX:MaxRAMPercentage/-XX:MinRAMPercentage: This parameters allows users that run the JVM into Docker containers to have more control over the amount of system memory that will be used for the Java Heap allocation.
A great performance improvement is achieved with the Parallel Full GC for G1, as described in JEP 307 (http://openjdk.java.net/jeps/307). With this feature, full GC occurs on parallel threads with great benefits, such as the following:
- Low latency
- High throughput
- No/fewer stop-of-world (STW) pauses
- Improved G1 worst-case latencies
In order to obtain better performance, it has also introduced the application class-data sharing (CDS) with JEP 310 (http://openjdk.java.net/jeps/310). This feature reduces resource footprint when multiple JVMs are running on the same physical machine, and improves the startup time of applications.
Furthermore, processes and applications can share common class metadata (class data), from a shared archive (the CDS archive); prior to Java SE 10, the use of CDS had been restricted to the bootstrap class loader only.
Another important element in an environment such as the cloud that must be as responsive as possible is the Thread-Local Handshakes feature, defined in JEP 312 (http://openjdk.java.net/jeps/312). It's a new way to execute a callback on threads that reduces the impact of acquiring a stack trace sample, for example, for profiling operations. It makes it possible to cheap-stop individual threads, reduce stops of STW pauses, and give better GC performance. With the Thread-Local Handshakes feature, it is possible to stop single threads and not just all threads or none—in this way, you don't need to make a global JVM safe point, giving a great performance improvement.
Last but not least, JDK 10 makes it possible to perform heap allocation on alternative devices, as described in JEP 316 (http://openjdk.java.net/jeps/316).
This great feature, realized with the contribution of Intel, allows the JVM to allocate the heap needed to store Java objects on a different memory device specified by the user, for example, a Non-Volatile Dual In-line Memory Module (NVDIMM).
This aspect could be extremely important in a multi-JVM environment, where you will instruct the processes with lower priority to use the NVDIMM memory while instructing the higher priority processes to use dynamic random access memory (DRAM).
I have described only a small set of the new features released in JDK 9 and 10 that demonstrate the great effort done to improve the Java language and make it a good choice for microservice implementation in cloud environments.
In September 2018, JDK 11 was released with some new great features, such as Epsilon—a no-op garbage collector.
Do you still have doubts about the use of Java for new microservice architectures?