Hussein Messi
août 25, 2021

Using Java’s Project Loom To Build More Reliable Distributed Systems

As a comparative tool, the results speak for themselves. In the early days, many fanciful claims made by database companies bit the dust, and more recently contracting Kyle Kingsbury to stress your database has become something of a rite of passage. This article discusses the problems in Java’s current concurrency model and how the Java project Loom aims to change them.

project loom

It is not helpful that the interrupted status can be reset, or that InterruptedException is a checked exception. Sure, each the call to readPage blocks, but with fibers, we don’t care. At the time of writing this readme, the latest jdk version was jdk-17.

The project Loon makes use of software algorithms to determine the position of the balloons and where it needs to go so that it is always in the right direction. Because The Balloons always stay above ground level it was necessary that they use a renewable kind of energy. They use solar cells and wind energy for power themselves. The Loon design comprises three parts which are the envelope, solar panels, and equipment. In the year 2013 in New Zealand Google sent 30 balloons in the air with internet capability with the help of the Civil Aviation Authority .

What Does This Mean To Java Library Developers?

Java does not make it easy to control the threads , and so influencing the interleaving of execution is very difficult except for in very isolated cases. As the author of the database, we have much more access to the database if we so desire, as shown by FoundationDB. The cost to the company would be high after hiring skilled workers and other human resource teams for the workers. When not playing guitar, Matt explores the backcountry and the philosophical hinterlands. Already, Java and its primary server-side competitor Node.js are neck and neck in performance. An order of magnitude boost to Java performance in typical web app use cases could alter the landscape for years to come.

project loom

I have no clear comparison point, but on my computer with reasonable-looking latency configurations I was able to simulate about 40k Raft rounds per second on a single core, and 500k when running multiple simulations in parallel. This represents simulating hundreds of thousands of individual RPCs per second, and represents 2.5M Loom context switches per second on a single core. Run tests continuously, using a server farm to accelerate the rate of test execution, different runs starting on different seeds; flag failures for diagnosis.

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Each balloon’s electronics were powered by an array of solar panels that sat between the envelope and the hardware. In full sun, the panels produced 100 watts of power, which was sufficient to keep the unit running while also charging a battery for use at night. A parachute, called Raven Aerostar Payload Recovery Parachute, was attached to the top of the envelope to allow for a controlled descent, landing and payload recovery when a balloon was ready to be taken out of service.

Java’s Project Loom makes fine grained control over execution easier than ever before, enabling a hybridized approach to be cheaply invested in. I believe that there’s a competitive advantage to be had for a development team that uses simulation to guide their development, and usage of Loom should allow a team to dip in and out where the approach is and isn’t beneficial. Historically this approach was viable, but a gamble, since it led to large compromises elsewhere in the stack.

  • Project Loom allows us to write highly scalable code with the one lightweight thread per task.
  • A carrier thread can support a thousand fibers if each of them is parked much of the time.
  • Yes – since deterministic, all failures replayable Java’s Project Loom considerably shakes up this tradeoff.
  • Note that the part that changed is only the thread scheduling part; the logic inside the thread remains the same.
  • The balloons consist of four crucial parts – the flight capsule, the solar panels, transceivers, and the parachute.
  • Deterministic scheduling entirely removes noise, ensuring that improvements over a wide spectrum can be more easily measured.
  • Google has also had to figure out how to make the balloons sturdier, so they can spend more time in the stratosphere.

Later that year, from the months of May to June, Google ran tests in Piaui, Brazil, on the loon balloons providing internet access, and had their first LTE experiments as well as the launch near the equator. Project Loom allows us to write highly scalable code with the one lightweight thread per task. This simplifies development, as you do not need to use reactive programming to write scalable code. Another benefit is that lots of legacy code can use this optimization without much change in the code base. I would say Project Loom brings similar capability as goroutines and allows Java programmers to write internet scale applications without reactive programming.

Implement the ability to insert delays, errors in the results as necessary. One could implement a simulation of core I/O primitives like Socket, or a much higher level primitive like a gRPC unary RPC4. FoundationDB’s usage of this model required them to build their own programming language, Flow, which is transpiled to C++.

This approach provides better usage and much less context switching. Consider an application in which all the threads are waiting for a database to respond. Although the application computer is waiting for the database, many resources are being used on the application computer. With the rise of web-scale applications, this threading model can become the major bottleneck for the application.

Let’s look at the two most common use cases for concurrency and the drawbacks of the current Java concurrency model in these cases. Deterministic scheduling entirely removes noise, ensuring that improvements over a wide spectrum can be more easily measured. Even when the improvements are algorithmic and so not represented in the time simulation, the fact that the whole cluster runs in a single core will naturally lead to reduced noise over something that uses a networking stack. The determinism made it straightforward to understand the throughput of the system.

Loon Working

Some of the technology and methods developed by Loon LLC live on as telecommunications infrastructure in Africa. Project Taara, which started its pan-African rollout in Kenya, continues to provide reliable high-speed internet to the unconnected and under-connected. It is also serving as of 2021 to bridge a « particularly stubborn connectivity gap » of 3.0 miles (4.8 km) between Brazzaville, Republic of the Congo and Kinshasa, Democratic Republic of Congo, across the Congo River. It was wryly noted that while there are many, many areas worldwide with clear climates which could be served by this technology that foggy San Francisco, California would not ideally be one of them.

Each thread has a separate flow of execution, and multiple threads are used to execute different parts of a task simultaneously. Usually, it is the operating system’s job to schedule and manage threads depending on the performance of the CPU. As mentioned, the new Fiber class represents a virtual thread.

project loom

It can be used to provide internet connectivity even during natural calamity. One balloon approximately covers 40 km and it would need thousands of balloons to connect the entire globe. In May-June 2014, Google experimented with its internet-based balloons. This was recorded as the first LTE experiment performed near the equator. At a high level, a continuation is a representation in code of the execution flow.

Loon LLC was an Alphabet Inc. subsidiary working on providing Internet access to rural and remote areas. The company used high-altitude balloons in the stratosphere at an altitude of 18 km to 25 km to create an aerial wireless network with up to 1 Mbit/s speeds. A reference to the balloons used, Project Loon began as a research and development project by X in 2011, but later spun out into Java Loom a separate company in July 2018. In January 2021, it was announced that the company would be shut down due to lack of profitability. This is far more performant than using platform threads with thread pools. Of course, these are simple use cases; both thread pools and virtual thread implementations can be further optimized for better performance, but that’s not the point of this post.

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For example, there are many potential failure modes for RPCs that must be considered; network failures, retries, timeouts, slowdowns etc; we can encode logic that accounts for a realistic model of this. If the ExecutorService involved is backed by multiple operating system threads, then the task will not be executed in a deterministic fashion because the operating system task scheduler is not pluggable. If instead it is backed by a single operating system thread, it will deadlock.

Sufficiently high level tests would be run against the real system as well, with any unobserved behaviours or failures that cannot be replicated in the simulation the start of a refining feedback loop. A point to be noted is this suspension or resuming occurs in the application runtime instead of the OS. As a result, it prevents the expensive context switch between kernel threads. The only difference in asynchronous mode is that the current working threads steal the task from the head of another deque. ForkJoinPool adds a task scheduled by another running task to the local queue. The project Loon would provide humanitarian support to places where there is no access to common communication networks due to restrictions on the free flow of information.

project loom

The good news for early adopters and Java enthusiasts is that Java virtual threads libraries are already included in the latest early access builds of JDK 19. The sole purpose of this addition is to acquire constructive feedback from Java developers so that JDK developers can adapt and improve the implementation in future versions. The company uses hot air balloons that are placed in the stratosphere at an altitude ranging between 18 km to 25 km. These balloons create a wireless network up in the air which has a speed of up to 4G- LTE.

Perform Inference Using Intel Openvino Model Server On Openshift

Another stated goal of Loom is Tail-call elimination (also called tail-call optimization). This is a fairly esoteric element of the proposed system. The core idea is that the system will be able to avoid allocating new stacks for continuations wherever possible. Loon 4G balloons are essentially flying cell phone towers but they are much lighter and more durable. They have the ability to withstand temperatures below -90°C and to remain steady amid violent winds. A section of the runtime stack needs to be replaced each time.

Loon Llc

The handleOrder() task will be blocked on inventory.get() even though updateOrder() threw an error. Ideally, we would like the handleOrder() task to cancel updateInventory() when a failure occurs in updateOrder() so that we are not wasting time. If a server has applied a log entry at a given index to its state machine, no other server will ever apply a different log entry for the same index. This test is highly limited as compared to a tool like jcstress, since any issues related to compiler reordering of reads or writes will be untestable. There are however two key advantages of testing using this style.

In this eMag on “Modern Data Architectures, Pipelines and Streams”, you’ll find up-to-date case studies and real-world data architectures from technology SME’s and leading data practitioners in the industry. On August 9, 2017, a Loon Balloon crashed in a reedbed in Olmos, Lambayeque, Peru. On August 26, 2016, a Loon balloon landed northwest of Madison, South Dakota. On April 22, 2016, a Loon balloon crashed in a field in the Ñeembucú Department, Paraguay.


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