Goro

Goro performs asynchronous operations in a queue. You may ask Goro to perform some task with schedule method invocation:

Goro goro = Goro.create();
goro.schedule(myOperations);

Tasks are instances of Callable.

All the operations you ask Goro to perform are put in a queue and executed one by one. Goro allows you to organize multiple queues. You can specify what queue a task should be sent to with the second argument of schedule method:

goro.schedule("firstQueue", myOperations1);
goro.schedule("secondQueue", myOperations2);
goro.schedule("firstQueue", myOperations3);
goro.schedule("secondQueue", myOperations4);

Queue is defined with a name. Goro does not limit number of your queues and lazily creates a new queue when a new name is passed. Controlling number of queues (actually number of different strings you pass to Goro) is your responsibility.

While operations scheduled for the same queue are guaranteed to be executed sequentially, operations in different queues may be executed in parallel.

After scheduling your task to be performed, Goro returns a Future instance that may be used to cancel your task or wait for its finishing synchronously.

Future<?> taskFuture = goro.schedule(task);
taskFuture.cancel(true);

Future returned by Goro has an extended interface ObservableFuture, which allows you to asynchronously listen to task execution results:

// executed in the task thread
goro.schedule(task).subscribe(new FutureObserver() {
  public void onSuccess(Result value) {
    Log.i(TAG, "Task result: " + value);
  }
  public void onError(Throwable error) {
    Log.e(TAG, "Task error: " + error);
  }
});
// customize how observer is executed
goro.schedule(task).subscribe(uiThreadExecutor, observer);

You may also get an Executor instance for a particular queue to integrate Goro with other libraries:

// --- RxJava ---
// Perform actions in "actions queue"
Observable.from([1, 2, 3])
    .subscribeOn(Schedulers.executor(goro.getExecutor("actions queue")))
// Subscribe to scheduled task result
Observable.from(goro.schedule(myTask)).subscribe(...);

// --- Bolts ---
// Fetch something and post database write operation to a dedicated queue
fetchAsync(object).continueWith(new Continuation<ParseObject, Long>() {
  public Long then(ParseObject object) throws Exception {
    return database.storeUser(object.get("name"), object.get("age"));
  }
}, goro.getExecutor("database"));

Goro Motivation

Developing Android apps you'll find out that it's a good practice to ensure sequential order of some of your asynchronous operations, like remote backend interactions or writing to the local database. Actually this is perhaps one of the main reasons why Android AsyncTask executes its tasks one by one. However often you want to go beyond one global queue: e. g. you want to have separate series of networking and local database operations. And here Goro helps.

Service

Usually we run Goro within a Service context to tell Android system that there are ongoing tasks and ensure that our process is not the first candidate for termination. Such a service is GoroService. If you use aar package of this library in a Gradle build based project, the service will be added to your app automatically. Otherwise you'll need to insert the following line into your AndroidManifest.xml:

<service android:name="com.stanfy.enroscar.goro.GoroService" />

The service creates a Goro instance when it's created. To interact with this instance you'll need to bind to the service. Use BoundGoro for this:

public class MyApplciation extends Applciation {

  @Override
  public void onCreate() {
    super.onCreate();
    Goro goro = Goro.create();
    GoroService.setup(this, goro);
  }

}

public class MyActivity extends Activity {

  // Goro instance
  private BoundGoro goro;

  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // The factory method is supplied with a Context used to execute bindService method.
    goro = Goro.bindWith(this);

    findViewById(R.id.submitButton).setOnClickListener(new OnClickListener() {
      public void onClick(View view) {
        goro.schedule(submissionTask);
      }
    });
  }

  protected void onStart() {
    super.onStart();
    goro.bind();
  }

  protected void onStop() {
    super.onStop();
    goro.unbind();
  }

}

We may also ask GoroService to perform some task sending an intent containing our Callable instance. Yet this instance must also implement Parcelable to be able to be packaged into Intent extras. This way we won't need any service binding.

  context.startService(GoroService.taskIntent(context, myTask));
  context.startService(GoroService.taskIntent(context, "notDefaultQueue", myTask2));

GoroService can be run in the foreground (to support background execution in android 8 https://developer.android.com/about/versions/oreo/android-8.0-changes.html#back-all):

  Intent intent = GoroService.foregroundTaskIntent(context, myTask, notificationId, notification);
  ContextCompat.startForegroundService(intent);
  Intent intent2 = GoroService.foregroundTaskIntent(context, "notDefaultQueue", myTask2, notificationId, notification);
  ContextCompat.startForegroundService(intent2);

Intent constructed with GoroService.taskIntent can also be used to obtain a PendingIntent and schedule task execution with AlarmManager or Notification:

  Intent taskIntent = GoroService.taskIntent(context, myTask);
  PendingIntent pending = PendingIntent.getService(context, 0, taskIntent, 0);

  AlarmManager alarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
  alarmManager.set(AlarmManager.ELAPSED_REALTIME, scheduleTime, pending);

  new Notification.Builder(context).setContentIntent(pending);

Goro listeners

You may add listeners that will be notified when each task starts, finishes, fails, or is canceled.

  goro.addTaskListener(myListener);

All the listener callbacks are invoked in the main thread. Listener can be added or removed in the main thread only too.

Errors Handling

Goro schedule method returns you an ObservableFuture instance. Hence you can handle an error thrown by a scheduled Callable in try-catch block that wraps future's get method invocation.

Future<Result> f = goro.schedule(task);
// ...
try {
  Result result = f.get();
} catch (ExecutionException e) {
  Exception thrownException = e.getCause();
}

Also the thrown exception will be passed to all observers that are subscribed to the Future instance:

goro.schedule(task).subscribe(new FutureObserver() {
  public void onSuccess(Result value) { }

  public void onError(Throwable error) {
    // handle you error here
  }
});

This is your responsibility to handle an error. If the returned Future instance is not interacted in any way, the thrown error will be never handled by anyone. Although your app won't crash, you'll never know about the error.

When you schedule your task with an Intent sent to GoroService (either directly with context.startService(GoroService.taskIntent(task)) or with execution of PendingIntent), you do not have these means to track an error though. Hence, GoroService sets its own observer, and if an exception is thrown by a Callable in such conditions, service will throw GoroException wrapping the cause, which will crash the app. This policy can be soften, if you set EXTRA_IGNORE_ERROR to true on the Intent passed to the service. However we discourage you from doing this. And if you do, ensure that you have set up a global GoroListener that can handle the error.

Usage

Maven Central

Goro is an Android library packaged as AAR and available in Maven Central. Add this dependency to your Android project in build.gradle:

dependencies {
  compile 'com.stanfy.enroscar:enroscar-goro:2.0.0@aar'
}

Using this library with Android Gradle plugin will automatically add GoroService to your application components, so that you won't need to add anything to you AndroidManifest file.

If you do not plan to use GoroService as it is provided, change your dependency specification to fetch a JAR instead of AAR:

dependencies {
  compile 'com.stanfy.enroscar:enroscar-goro:2.0.0'
}

You may also simply grab a JAR or an AAR from Maven Central. Or use it with Maven:

  <dependency>
    <groupId>com.stanfy.enroscar</groupId>
    <artifactId>enroscar-goro</artifactId>
    <version>$latestVersion</version>
  </dependency>

Queues are not threads

There is no mapping between queues and actual threads scheduled operations are executed in. By default, to perform tasks Goro uses the same thread pool that AsyncTask operate with. On older Android versions, where this thread pool is not available in public API, Goro creates its own pool manually with configuration similar to what is used in AsyncTask.

You may also specify different actual executor for Goro either with GoroService.setDelegateExecutor(myThreadPool) or with new Goro(myThreadPool) depending on how you use Goro.

Sample

In this repository you'll also find a sample demonstrating what Goro does.

RxJava Integration

As long as you have RxJava jar in your classpath, you can use class RxGoro, which can wrap a Goro instance and provide schedule methods that return rx.Observable instead of Future.

License

 Copyright 2012-2015 Stanfy Corp.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
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