QCon Plus Online May 10-20, 2022 Session Project Loom: Revolution in Java Concurrency or Obscure Implementation Detail?

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QCon Plus Online May 10-20, 2022 Session Project Loom: Revolution in Java Concurrency or Obscure Implementation Detail?

Instead, we’re using an instance of a custom, suspiciously looking Loom class to fork code blocks so that they run asynchronously. Although JavaRX is a powerful and potentially high-performance approach to concurrency, it is not without drawbacks. In particular, it is quite different from the existing mental constructs that Java developers have traditionally used. Also, JavaRX can’t match the theoretical performance achievable by managing virtual threads at the virtual machine layer. As mentioned above, work-stealing schedulers like ForkJoinPools are particularly well-suited to scheduling threads that tend to block often and communicate over IO or with other threads.

project loom java

Try hands-on activities in the OpenShift Sandbox Access Red Hat’s products and technologies without setup or configuration, and start developing quicker than ever before with our new, no-cost sandbox environments. Learning paths Customize your learning to align with your needs and make the most of your time by exploring our massive collection of paths and lessons. Learn what are the pros and cons of using Project Loom to see if it’s desirable to incorporate it in a project.


Obfuscation is an important practice to protect source code by making it unintelligible. Obfuscation is often mistaken with encryption, but they are different concepts. In the article we will present a number of techniques and approaches used to obfuscate data in a program. It will be fascinating to watch as Project Loom moves into the main branch and evolves in response to real-world use. As this plays out, and the advantages inherent in the new system are adopted into the infrastructure that developers rely on , we could see a sea change in the Java ecosystem.

You just create treads as if it was a very native, very low footprint abstraction, which is not the case right now. The first takeaway is that this may revolutionize the way you work with concurrent code. On the other hand, we can already see that even though the feature wasn’t yet released, you have to be aware of the shortcomings. And also, there are a few other disadvantages or limitations of Project Loom that you must be aware of. Otherwise, you will just shoot yourself in the foot.

Java’s Project Loom, Virtual Threads and Structured Concurrency with Ron Pressler – InfoQ.com

Java’s Project Loom, Virtual Threads and Structured Concurrency with Ron Pressler.

Posted: Wed, 26 May 2021 07:00:00 GMT [source]

It voluntarily says that it no longer wishes to run because we asked that thread to sleep. Unparking or waking up means basically, that we would like ourselves to be woken up after a certain period of time. Before we put ourselves to sleep, we are scheduling https://globalcloudteam.com/ an alarm clock. It will continue running our thread, it will continue running our continuation after a certain time passes by. In between calling the sleep function and actually being woken up, our virtual thread no longer consumes the CPU.

What the Heck Is Project Loom for Java?

If you’ve already heard of Project Loom a while ago, you might have come across the term fibers. In the first versions of Project Loom, fiber was the name for the virtual thread. It goes back to a previous project of the current Loom project leader Ron Pressler, the Quasar Fibers. However, the name fiber was discarded at the end of 2019, as was the alternative coroutine, and virtual thread prevailed. In the code below, we have a scope that starts three virtual threads, of which the second one throws an exception when it starts. The exception does not propagate to its parent thread, and the other two threads will continue to run.

project loom java

It’s absolutely fine to start 10,000 concurrent connections, because you won’t pay the price of 10,000 carrier or kernel threads, because these virtual threads will be hibernated anyway. Only when the data arrives, the JVM will wake up your virtual thread. However, you just have to be aware of the fact that the kernel threads of your thread pools were actually just natural like limit to concurrency. Just blindly switching from platform threads, the old ones, to virtual threads will change the semantics of your application. This is still work in progress, so everything can change. I’m just giving you a brief overview of how this project looks like.

This new lightweight concurrency model supports high throughput and aims to make it easier for Java coders to write, debug, and maintain concurrent Java applications. With Project Loom, you no longer consume the so-called stack space. The virtual threads that are not running at the moment, which is technically called pinned, so they are not pinned to a carrier thread, but they are suspended.

ZIO vs Loom: the verdict

Kernel threads are created and managed by the kernel. In the very prehistoric days, in the very beginning of the Java platform, there used to be this mechanism called the many-to-one model. The JVM was actually creating user threads, so every time you set newthread.start, a JVM was creating a new user thread. However, these threads, all of them were actually mapped to a single kernel thread, meaning that the JVM was only utilizing a single thread in your operating system. It was doing all the scheduling, so making sure your user threads are effectively using the CPU.

project loom java

Essentially, a continuation is a piece of code that can suspend itself at any moment in time and then it can be resumed later on, typically on a different thread. You can freeze your piece of code, and then you can unlock it, or you can unhibernate it, you can wake it up on a different moment in time, and preferably even on a different thread. This is a software construct that’s built into the JVM, or that will be built into the JVM.

Virtual Threads – Example

Instead of shared, mutable state, they rely on immutable messages that are written to a channel and received from there by the receiver. Whether channels will become part of Project Loom, however, is still open. Then again, it may not be necessary for Project Loom to solve all problems – any gaps will certainly be filled by new third-party libraries that provide solutions at a higher level of abstraction using virtual threads as a basis. For example, the experimental “Fibry” is an actor library for Loom. Things become interesting when all these virtual threads only use the CPU for a short time.

  • First of all, each Saft Node is run on a dedicated thread.
  • Similarly, the Executors.newVirtualThreadPerTaskExecutor() method has also been added, which can be used to create an ExecutorService that uses virtual threads.
  • Since then and still with the release of Java 19, a limitation was prevalent, leading to Platform Thread pinning, effectively reducing concurrency when using synchronized.
  • Then on line 16, something really exciting and interesting happens.
  • Another relatively major design decision concerns thread locals.
  • Structured concurrency aims to simplify multi-threaded and parallel programming.
  • If a thread goes to wait state (e.g., waiting for a database call to respond), the thread will be marked as paused and a separate thread is allocated to the CPU resource.

When these features are production ready, it will be a big deal for libraries and frameworks that use threads or parallelism. Library authors will see huge performance and scalability improvements while simplifying the codebase and making it more maintainable. Most Java projects using thread pools and platform threads will benefit from switching to virtual threads.

JVM and Kubernetes walk into a bar

Like any ambitious new project, Loom is not without its challenges. Dealing with sophisticated interleaving of threads is always going to be a complex challenge, and we’ll have to wait to see exactly what library support and design patterns emerge to deal with these situations. Code running inside a continuation is not expected to have a reference to the continuation, and the scopes normally have some fixed names . However, the yield point provides a mechanism to pass information from the code to the continuation instance and back.

It runs the first line, and then goes to bar method, it goes to bar function, it continues running. Then on line 16, something really exciting and interesting happens. The function bar voluntarily says it would like to suspend itself. The code says that it no longer project loom java wishes to run for some bizarre reason, it no longer wishes to use the CPU, the carrier thread. What happens now is that we jump directly back to line four, as if it was an exception of some kind. Then we move on, and in line five, we run the continuation once again.

Different Ways to Use Function as Values in Go

A virtual thread is very lightweight, it’s cheap, and it’s a user thread. By lightweight, I mean you can really allocate millions of them without using too much memory. A carrier thread is the real one, it’s the kernel one that’s actually running your virtual threads.

This is your typical Spring Boot application, or any other framework like Quarkus, or whatever, if you put a lot of different technologies like adding security, aspect oriented programming, your stack trace will be very deep. With platform threads, the size of the stack trace is actually fixed. In real life, what you will get normally is actually, for example, a very deep stack with a lot of data.

Project Loom features a lightweight concurrency construct for Java. There are some prototypes already introduced in the form of Java libraries. The project is currently in the final stages of development and is planned to be released as a preview feature with JDK19. Project Loom is certainly a game-changing feature from Java so far.

Will your application benefit from Virtual Threads?

Past years indicated a trend towards applications that communicate over the network with each other. Many applications make use of data stores, message brokers, and remote services. I/O-intensive applications are the primary ones that benefit from Virtual Threads if they were built to use blocking I/O facilities such as InputStream and synchronous HTTP, database, and message broker clients. Running such workloads on Virtual Threads helps reduce the memory footprint compared to Platform Threads and in certain situations, Virtual Threads can increase concurrency.

In essence, the primary goal of Project Loom is to support a high-throughput, lightweight concurrency model in Java. So now we can start a million threads at the same time. This may be a nice effect to show off, but is probably of little value for the programs we need to write. A native thread in a 64-bit JVM with default settings reserves one megabyte alone for the call stack (the “thread stack size”, which can also be set explicitly with the -Xss option). And if the memory isn’t the limit, the operating system will stop at a few thousand. Spent half of his life on programming, for the last decade professionally in Java land.

Project Loom’s virtual threads are merged and ship with JDK 19 – here’s to prepare for them. Also, news on Project Lilliput, proposal for record patterns in pattern matching, some astonishing numbers from Sonatype on Maven Central, and the move of OpenJDK to openjdk.org. A point to be noted is this suspension or resuming occurs in the application runtime instead of the OS.

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