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Examples

note

To run the examples in an IDE, you need to clone ActiveJ project:

git clone https://github.com/activej/activej

And import it as a Maven project. Check out branch v4.3. Before running the example, build the project (Ctrl + F9 for IntelliJ IDEA).

Server Setup#

Let's have a closer look at Server Setup Example. To make setup and launching as simple as possible, there is a special SimpleTcpServerLauncher, an ActiveJ Launcher implementation (abstracted implementation of main methods). It allows to simply set up applications, so all you need to set up an FS server is to override several Launcher methods:

  • onInit - runs prior to application start
  • getOverrideModule - overrides Launcher's default internal module definitions
  • run - Launcher's main method, represents business logic

Then launch the Launcher

public class ServerSetupExample extends SimpleTcpServerLauncher {
private Path storage;
@Override
protected void onInit(Injector injector) throws Exception {
storage = Files.createTempDirectory("server_storage");
}
@Override
protected Config createConfig() {
return super.createConfig()
.with("activefs.path", storage.toString())
.with("activefs.listenAddresses", "6732");
}
@Override
protected void run() throws Exception {
awaitShutdown();
}
public static void main(String[] args) throws Exception {
Launcher launcher = new ServerSetupExample();
launcher.launch(args);
}
}

See full example on GitHub

File Upload#

FileUploadExample also extends Launcher and thus implements the aforementioned Launcher methods.

In this example we will use a ActiveFs instance which depends on asynchronous ActiveJ Eventloop To simplify working with dependencies we will use ActiveJ Inject DI library. It is lightning-fast, efficient and perfectly compatible with Launcher. So we simply @Inject two instances and @Provides factory methods. Just like in the previous example, we will also overwrite Launcher methods onInit, getOverrideModule, and run.

Also, this example utilizes ActiveJ CSP component, particularly ChannelFileReader class. It allows to asynchronously read binary data from files.

You can see full example sources on GitHub, here we will consider only the upload process that is defined in the overwritten method run.

@Override
protected void run() throws Exception {
ExecutorService executor = newSingleThreadExecutor();
CompletableFuture<Void> future = eventloop.submit(() ->
// consumer result here is a marker of it being successfully uploaded
ChannelFileReader.open(executor, clientFile)
.then(cfr -> cfr.streamTo(client.upload(FILE_NAME, EXAMPLE_TEXT.length())))
.whenResult(() -> System.out.printf("%nFile '%s' successfully uploaded%n%n", FILE_NAME))
);
try {
future.get();
} finally {
executor.shutdown();
}
}

See full example on GitHub

File Download#

FileDownloadExample has an implementation that is similar to the File Upload example. Here we will consider only the download process that is defined in the overwritten method run.

@Override
protected void run() throws Exception {
ExecutorService executor = newSingleThreadExecutor();
CompletableFuture<Void> future = eventloop.submit(() ->
ChannelSupplier.ofPromise(client.download(REQUIRED_FILE))
.streamTo(ChannelFileWriter.open(executor, clientStorage.resolve(DOWNLOADED_FILE)))
.whenResult(() -> System.out.printf("%nFile '%s' successfully downloaded to '%s'%n%n",
REQUIRED_FILE, clientStorage))
);
try {
future.get();
} finally {
executor.shutdown();
}
}

See full example on GitHub

ActiveFs Decorator#

Sometimes you may need to override/expand the default behavior of ActiveFs implementation. To do so, you may utilize a Decorator pattern.

DecoratedActiveFsExample demonstrates how to do just that. It decorates `ActiveFs` implementation by adding additional logging for file uploads and downloads.

DecoratedActiveFsExample extends ServerSetupExample so it inherits its DI bindings. First, we need to override the binding for ActiveFsServer to pass decorated ActiveFs instead of the original one. To do so, we will override Launcher#getOverrideModule method and provide a new binding for AsyncFsServer that uses decorated ActiveFs.

@Override
protected Module getOverrideModule() {
return new AbstractModule() {
@Eager
@Provides
ActiveFsServer activeFsServer(Eventloop eventloop, @Named("decorated") ActiveFs decoratedFs, Config config) {
return ActiveFsServer.create(eventloop, decoratedFs)
.withInitializer(ofActiveFsServer(config.getChild("activefs")));
}
@Provides
@Named("decorated")
ActiveFs decoratedActiveFs(ActiveFs fs) {
return new LoggingActiveFs(fs);
}
};
}

As you can see in decoratedActiveFs(ActiveFs fs) method, we request original ActiveFs and return the decorated one (wrapped in LoggingActiveFs).

private static final class LoggingActiveFs extends ForwardingActiveFs {
private static final Logger logger = LoggerFactory.getLogger(LoggingActiveFs.class);
public LoggingActiveFs(ActiveFs peer) {
super(peer);
}
@Override
public Promise<ChannelConsumer<ByteBuf>> upload(@NotNull String name, long size) {
return super.upload(name)
.map(consumer -> {
logger.info("Starting upload of file: {}. File size is {} bytes", name, size);
return consumer
.withAcknowledgement(ack -> ack
.whenResult(() -> logger.info("Upload of file {} finished", name)));
});
}
@Override
public Promise<ChannelSupplier<ByteBuf>> download(@NotNull String name, long offset, long limit) {
return super.download(name, offset, limit)
.map(supplier -> {
logger.info("Starting downloading file: {}", name);
return supplier
.withEndOfStream(eos -> eos
.whenResult(() -> logger.info("Download of file {} finished", name)));
});
}
}

LoggingActiveFs extends ForwardingActiveFs which simply delegates all of the ActiveFs method calls to some underlying ActiveFs instance. We override methods we want to decorate (download, upload) and add custom logging messages when upload/download starts and finishes.

You can run FileUploadExample followed by FileDownloadExample After this you should see logging output:

INFO Starting upload of file: example.txt. File size is 12 bytes
INFO Upload of file example.txt finished
INFO Starting downloading file: example.txt
INFO Download of file example.txt finished

See full example on GitHub

Cluster File Storage#

With ActiveJ FS you can simply create distributed cluster file storage with high fault tolerance. We will use Docker to launch three virtual servers and one client. The storage will support file uploads with automatic repartitioning according to the provided rule and replication count.

The first thing we need to do is to create a launcher class ClusterTcpServerLauncher for our server. Extend SimpleTcpServerLauncher to get all the required instances: ActiveFsServer, local ActiveFS, AsyncHttpServer for GUI that will simplify working with your storage, and other helper instances. In the ClusterTcpServerLauncher we'll only need to set up utils for repartitioning management like task schedulers, ClusterRepartitionController, and FsPartitions for tracking alive partitions and their statuses. The partitions will communicate via TCP protocol, while GUI server will use HTTP.

@Provides
@Eager
@Named("repartition")
EventloopTaskScheduler repartitionScheduler(Config config, ClusterRepartitionController controller) {
return EventloopTaskScheduler.create(controller.getEventloop(), controller::repartition)
.withInitializer(ofEventloopTaskScheduler(config.getChild("activefs.repartition")));
}
@Provides
@Eager
@Named("clusterDeadCheck")
EventloopTaskScheduler deadCheckScheduler(Config config, FsPartitions partitions) {
return EventloopTaskScheduler.create(partitions.getEventloop(), partitions::checkDeadPartitions)
.withInitializer(ofEventloopTaskScheduler(config.getChild("activefs.repartition.deadCheck")));
}
@Provides
ClusterRepartitionController repartitionController(Config config, ActiveFsServer localServer, FsPartitions partitions) {
String localPartitionId = first(partitions.getAllPartitions());
assert localPartitionId != null;
return ClusterRepartitionController.create(localPartitionId, partitions)
.withInitializer(ofClusterRepartitionController(config.getChild("activefs.repartition")));
}
@Provides
FsPartitions fsPartitions(Config config, Eventloop eventloop, @Optional ServerSelector serverSelector, ActiveFs fs) {
Map<Object, ActiveFs> partitions = new LinkedHashMap<>();
partitions.put(config.get("activefs.repartition.localPartitionId"), fs);
return FsPartitions.create(eventloop, partitions)
.withServerSelector(nullToDefault(serverSelector, RENDEZVOUS_HASH_SHARDER))
.withInitializer(ofFsPartitions(config.getChild("activefs.cluster")));
}

Now we can move on to creating a client launcher ClusterTcpClientLauncher. We need to provide ClusterRepartitionController and a task scheduler to detect dead partitions. Similarly to the server launcher, we need to provide an AsyncHttpServer for GUI and FsPartitions for managing partitions. We also need an instance of ClusterActiveFs class, an ActiveFs implementation that operates on other partitions as a cluster and contains some redundancy and fail-safety capabilities.

@Provides
@Eager
@Named("clusterDeadCheck")
EventloopTaskScheduler deadCheckScheduler(Config config, FsPartitions partitions) {
return EventloopTaskScheduler.create(partitions.getEventloop(), partitions::checkDeadPartitions)
.withInitializer(ofEventloopTaskScheduler(config.getChild("activefs.repartition.deadCheck")));
}
@Provides
@Eager
AsyncHttpServer guiServer(Eventloop eventloop, AsyncServlet servlet, Config config) {
return AsyncHttpServer.create(eventloop, servlet)
.withInitializer(ofHttpServer(config.getChild("activefs.http.gui")));
}
@Provides
AsyncServlet guiServlet(ActiveFs activeFs) {
return ActiveFsGuiServlet.create(activeFs, "Cluster FS Client");
}
@Provides
ActiveFs remoteActiveFs(Eventloop eventloop, FsPartitions partitions, Config config) {
return ClusterActiveFs.create(partitions)
.withInitializer(ofClusterActiveFs(config.getChild("activefs.cluster")));
}
@Provides
FsPartitions fsPartitions(Eventloop eventloop, Config config) {
return FsPartitions.create(eventloop)
.withInitializer(ofFsPartitions(config.getChild("activefs.cluster")));
}

Here's the architecture of our distributed P2P storage:

Distributed P2P storageDistributed P2P storage

You can create as many partitions as you wish.

To launch the example, run the following scripts to create Docker images and build containers (run all the scripts under activej/launchers/fs directory):

# building two images for server and client
docker build -t cluster-server -f ClusterServerDockerfile .
docker build -t cluster-client -f ClusterClientDockerfile .
# launching all the servers and client instances in background
docker-compose up -d

The containers will be built with the following configurations:

  • Server1: TCP-connection port 9001, HTTP GUI port 8081
  • Server2: TCP-connection port 9002, HTTP GUI port 8082
  • Server3: TCP-connection port 9003, HTTP GUI port 8083
  • Client: HTTP GUI port 8080

Use this script to manage containers:

# to stop a single container:
docker-compose stop server1
# to stop all the containers:
docker-compose down
# check containers status:
docker-compose ps

See full example on GitHub