haxe-concurrent - cross-platform concurrency support

1. What is it?
2. hx.concurrent.atomic package
3. hx.concurrent.collection package
4. hx.concurrent.executor package
5. hx.concurrent.event package
6. hx.concurrent.lock package
7. hx.concurrent.thread package
8. Installation
9. Using the latest code
10. License
11. Alternatives

What is it?

A haxelib that provides some basic platform agnostic concurrency support.

All classes are located in the package hx.concurrent or below.

The library has been extensively unit tested (over 400 individual test cases) on the targets C++, C#, Eval, Flash, HashLink, Java, JavaScript (Node.js and PhantomJS), Lua, Neko, PHP 7 and Python 3.

Note:

• When targeting Flash the option -swf-version 11.5 (or higher) must be specified, otherwise you will get Class flash.concurrent::Condition could not be found.
• When targeting C# the option -D net-ver=45 must be specified, otherwise you may get error CS0234: The type or namespace name 'Volatile' does not exist in the namespace 'System.Threading'. Are you missing an assembly reference?
• Multi-threading/locking support in Eval is broken, see some of the unresolved issues:
  • https://github.com/HaxeFoundation/haxe/issues/8524
  • https://github.com/HaxeFoundation/haxe/issues/8525

Haxe compatibility

The hx.concurrent.atomic package

The hx.concurrent.atomic package contains mutable value holder classes that allow for thread.safe manipulation:

• AtomicBool
• AtomicInt
• AtomicValue

The hx.concurrent.collection package

The hx.concurrent.collection package contains thread-safe implementations of different types of collections:

• CopyOnWriteArray
• Queue
• SynchronizedArray
• SynchronizedLinkedList
• SynchronizedMap

The hx.concurrent.executor package

The hx.concurrent.executor package contains Executor implementations that allow to execute functions concurrently and to schedule tasks for later/repeated execution.

On platform with the thread support (C++, C#, Eval, HashLink, Neko, Python, Java) threads are used to realize true concurrent execution, on other platforms haxe.Timer is used to at least realize async execution.

import hx.concurrent.executor.Schedule;
import hx.concurrent.executor.Executor;

class Test {

   static function main() {
      var executor = Executor.create(3);  // <- 3 means to use a thread pool of 3 threads on platforms that support threads
      // depending on the platform either a thread-based or timer-based implementation is returned

      // define a function to be executed concurrently/async/scheduled (return type can also be Void)
      var myTask = function():Date {
         trace("Executing...");
         return Date.now();
      }

      // submit 10 tasks each to be executed once asynchronously/concurrently as soon as possible
      for (i in 0...10) {
         executor.submit(myTask);
      }

      executor.submit(myTask, ONCE(2000));            // async one-time execution with a delay of 2 seconds
      executor.submit(myTask, FIXED_RATE(200));       // repeated async execution every 200ms
      executor.submit(myTask, FIXED_DELAY(200));      // repeated async execution 200ms after the last execution
      executor.submit(myTask, HOURLY(30));            // async execution 30min after each full hour
      executor.submit(myTask, DAILY(3, 30));          // async execution daily at 3:30
      executor.submit(myTask, WEEKLY(SUNDAY, 3, 30)); // async execution Sundays at 3:30

      // submit a task and keep a reference to it
      var future = executor.submit(myTask, FIXED_RATE(200));

      // check if a result is already available
      switch (future.result) {
         case VALUE(value, time, _): trace('Successfully execution at ${Date.fromTime(time)} with result: $value');
         case FAILURE(ex, time, _):  trace('Execution failed at ${Date.fromTime(time)} with exception: $ex');
         case PENDING(_):            trace("No result yet...");
      }

      // check if the task is scheduled to be executed (again) in the future
      if (!future.isStopped) {
         trace('The task is scheduled for further executions with schedule: ${future.schedule}');
      }

      // cancel any future execution of the task
      future.cancel();
   }
}

The hx.concurrent.event package

The hx.current.event package contains classes for type-safe event dispatching.

import hx.concurrent.event.AsyncEventDispatcher;
import hx.concurrent.event.SyncEventDispatcher;
import hx.concurrent.Future;
import hx.concurrent.executor.Executor;

class Test {

   static function main() {
      /**
       * create a dispatcher that notifies listeners/callbacks synchronously in the current thread
       */
      var syncDispatcher = new SyncEventDispatcher<String>(); // events are of type string

      // create event listener
      var onEvent = function(event:String):Void {
         trace('Received event: $event');
      }

      syncDispatcher.subscribe(onEvent);

      // notify all registered listeners synchronously,
      // meaning this method call blocks until all listeners are finished executing
      syncDispatcher.fire("Hey there");

      /**
       * create a dispatcher that notifies listeners asynchronously using an executor
       */
      var executor = Executor.create(5); // thread-pool with 5 threads
      var asyncDispatcher = new AsyncEventDispatcher<String>(executor);

      // create event listener
      var onAsyncEvent = function(event:String):Void {
         trace('Received event: $event');
      }

      // notify all registered listeners asynchronously,
      // meaning this method call returns immediately
      asyncDispatcher.fire("Hey there");

      // fire another event and get notified when all listeners where notified
      var future = asyncDispatcher.fire("Boom");

      asyncDispatcher.subscribe(onAsyncEvent);

      future.onCompletion(result -> {
         switch(result) {
            case VALUE(count, _): trace('$count listeners were successfully notified');
            case FAILURE(ex, _):  trace('Event could not be delivered because of: $ex');
            case PENDING(_):      trace("Nothing is happening");
          }
      });
   }
}

The hx.concurrent.lock package

The hx.concurrent.lock package contains lock implementations for different purposes:

• RLock - a reentrant lock
• RWLock - an upgradeable read-write lock
• Semaphore

The hx.concurrent.thread package

The hx.concurrent.thread package contains classes for platforms supporting threads:

• ThreadPool - basic thread-pool implementation supporting C++, C#, HashLink, Neko, Java and Python. For advanced concurrency or cross-platform requirements use Executor instead.

  import hx.concurrent.thread.*;
  
  class Test {
  
     static function main() {
        var pool = new ThreadPool(4); // 4 concurrent threads
  
        pool.submit(function(ctx:ThreadContext) {
           // do some work here
        });
  
        pool.awaitCompletion(30 * 1000); // wait 30 seconds for all submitted tasks to be processed
  
        pool.cancelPendingTasks(); // cancels execution of all currently queued tasks
  
        // initiate graceful stop of all running threads, i.e. they finish the current tasks they process
        // execution of all other queued tasks is cancelled
        pool.stop();
     }
  }

• Threads

Installation

1. install the library via haxelib using the command:

   haxelib install haxe-concurrent

2. use in your Haxe project

   • for OpenFL/Lime projects add <haxelib name="haxe-concurrent" /> to your project.xml
   • for free-style projects add -lib haxe-concurrent to your *.hxml file or as command line option when running the Haxe compiler

Using the latest code

Using haxelib git

haxelib git haxe-concurrent https://github.com/vegardit/haxe-concurrent main D:\haxe-projects\haxe-concurrent

Using Git

1. check-out the main branch

   git clone https://github.com/vegardit/haxe-concurrent --branch main --single-branch D:\haxe-projects\haxe-concurrent

2. register the development release with Haxe

   haxelib dev haxe-concurrent D:\haxe-projects\haxe-concurrent

License

All files are released under the Apache License 2.0.

Individual files contain the following tag instead of the full license text:

SPDX-License-Identifier: Apache-2.0

This enables machine processing of license information based on the SPDX License Identifiers that are available here: https://spdx.org/licenses/.

Alternatives

Other libraries addressing concurrency/parallelism:

• https://github.com/botsman/hxasync - async/await implementation for Python and JavaScript
• https://github.com/haxetink/tink_concurrent - abstraction layer over the target-specific concurrency APIs
• https://github.com/thomasuster/haxe-threadpool (2017) thread pool implementation for C++, Neko, Java, C# and Python
• https://github.com/Rezmason/Golems (2017)
• https://github.com/kevinresol/filelock (2016)
• https://github.com/Blank101/haxe-concurrency (2015)
• https://github.com/TiVo/activity (2015)
• https://gist.github.com/hamaluik/80fb81f84ecedbe2a6af (2014) - cross platform API but only uses real threads on C++ and Neko, otherwise single threaded blocking execution
• https://github.com/zjnue/hxworker (2014)