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https://github.com/electronicarts/ea-async

EA Async implements async-await methods in the JVM.
https://github.com/electronicarts/ea-async

async async-await asynchronous concurrency ea-async java jvm

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EA Async implements async-await methods in the JVM.

Lists

README 

        
EA Async

============



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EA Async implements Async-Await methods in the JVM.

It allows programmers to write asynchronous code in a sequential fashion.



It is heavily inspired by Async-Await on the .NET CLR, see [Asynchronous Programming with Async and Await](https://msdn.microsoft.com/en-us/library/hh191443.aspx) for more information.



Who should use it?

------



EA Async should be used to write non-blocking asynchronous code that makes heavy use of CompletableFutures or CompletionStage.

It improves scalability by freeing worker threads while your code awaits other processes;

And improves productivity by making asynchronous code simpler and more readable.



Developer & License

======

This project was developed by [Electronic Arts](http://www.ea.com) and is licensed under the [BSD 3-Clause License](LICENSE).



Examples

=======

#### With EA Async



```java

import static com.ea.async.Async.await;

import static java.util.concurrent.CompletableFuture.completedFuture;



public class Store

{

    public CompletableFuture buyItem(String itemTypeId, int cost)

    {

        if(!await(bank.decrement(cost))) {

            return completedFuture(false);

        }

        await(inventory.giveItem(itemTypeId));

        return completedFuture(true);

    }

}

```

In this example `Bank.decrement` returns `CompletableFuture` and `Inventory.giveItem` returns `CompletableFuture`



EA Async rewrites the calls to `Async.await` making your methods non-blocking.



The methods look blocking but are actually transformed into asynchronous methods that use

CompletableFutures to continue the execution as intermediary results arrive.



#### Without EA Async



This is how the first example looks without EA Async. It is a bit less readable.



```java

import static java.util.concurrent.CompletableFuture.completedFuture;



public class Store

{

    public CompletableFuture buyItem(String itemTypeId, int cost)

    {

        return bank.decrement(cost)

            .thenCompose(result -> {

                if(!result) {

                    return completedFuture(false);

                }

                return inventory.giveItem(itemTypeId).thenApply(res -> true);

            });

    }

}

```

This is a small example... A method with a few more CompletableFutures can look very convoluted.



EA Async abstracts away the complexity of the CompletableFutures.



#### With EA Async (2)



So you like CompletableFutures?

Try converting this method to use only CompletableFutures without ever blocking (so no joining):



```java

import static com.ea.async.Async.await;

import static java.util.concurrent.CompletableFuture.completedFuture;



public class Store

{

    public CompletableFuture buyItem(String itemTypeId, int cost)

    {

        if(!await(bank.decrement(cost))) {

            return completedFuture(false);

        }

        try {

            await(inventory.giveItem(itemTypeId));

            return completedFuture(true);

        } catch (Exception ex) {

            await(bank.refund(cost));

            throw new AppException(ex);

        }

    }

}

```



Got it? Send it [to us](https://github.com/electronicarts/ea-async/issues/new). It probably looks ugly...



Getting started

---------------



EA Async currently supports JDK 8-10.



It works with Java and Scala and should work with most JVM languages.

The only requirement to use EA Async is that must be used only inside methods that return `CompletableFuture`, `CompletionStage`, or subclasses of `CompletableFuture`.



### Using with maven



```xml



    com.ea.async

    ea-async

    1.2.3



```



### Gradle



```

'com.ea.async:ea-async:1.2.3'

```



### Instrumenting your code



#### Option 1 - JVM parameter



Start your application with an extra JVM parameter: `-javaagent:ea-async-1.2.3.jar`

```

 java -javaagent:ea-async-1.2.3.jar -cp your_claspath YourMainClass args...

```



It's recommended to add this as a default option to launchers in IntelliJ projects that use ea-async.



#### Option 2 - Runtime

On your main class or as early as possible, call at least once:

```

Async.init();

```

Provided that your JVM has the capability enabled, this will start a runtime instrumentation agent.

If you forget to invoke this function, the first call to `await` will initialize the system (and print a warning).



This is a solution for testing and development, it has the least amount of configuration.

It might interfere with JVM debugging. This alternative is present as a fallback.



#### Option 3 - Run instrumentation tool



The ea-async-1.2.3.jar is a runnable jar that can pre-instrument your files.



Usage:



```bash

java -cp YOUR_PROJECT_CLASSPATH -jar ea-async-1.2.3.jar classDirectory

```



Example:



```bash

java -cp guava.jar;commons-lang.jar  -jar ea-async-1.2.3.jar target/classes

```



After that all the files in target/classes will have been instrumented.

There will be no references to `Async.await` and `Async.init` left in those classes.



#### Option 4 - Build time instrumentation, with Maven - Preferred



Use the [ea-async-maven-plugin](maven-plugin). It will instrument your classes in compile time and

remove all references to `Async.await` and `Async.init()`.



With build time instrumentation your project users won't need to have EA Async in their classpath unless they also choose to use it.

This means that EA Async does not need to be a transitive dependency.



This is the best option for libraries and maven projects.



```xml



    

        

            com.ea.async

            ea-async-maven-plugin

            1.2.3

            

                

                    

                        instrument

                        instrument-test

                    

                

            

        

    



```