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Java RPC Application with ActiveRPC library

activej profile image valerialistratova ・3 min read

What is ActiveRPC?

ActiveRPC is a lightweight and convenient Java library for developing high-load distributed applications and Memcached-like solutions. It introduces a completely alternative approach to microservices implementation and overcomes the overheads of utilizing HTTP protocol with JSON or XML encoding.

ActiveRPC is powered by one of the world's fastest JVM serializer ActiveSerializer, runs on TCP, and has a custom high-performance binary streaming protocol. It features highly optimized flexible server and client implementations along with predefined cloud strategies. With these technologies you can conveniently create even complex scalable solutions like high-performance microservices or Memcached-like servers.

Basic example

public class RpcExample extends Launcher {
    private static final int SERVICE_PORT = 34765;

    private RpcClient client;

    private RpcServer server;

    private Eventloop eventloop;

    Eventloop eventloop() {
        return Eventloop.create();

    RpcServer rpcServer(Eventloop eventloop) {
        return RpcServer.create(eventloop)
                        request -> Promise.of("Hello " + request))

    RpcClient rpcClient(Eventloop eventloop) {
        return RpcClient.create(eventloop)
                .withStrategy(server(new InetSocketAddress(SERVICE_PORT)));

    Initializer<ServiceGraphModuleSettings> configureServiceGraph() {
        // add logical dependency so that service graph starts client only after it started the server
        return settings -> settings.addDependency(Key.of(RpcClient.class), Key.of(RpcServer.class));

    protected Module getModule() {
        return ServiceGraphModule.create();

    protected void run() throws ExecutionException, InterruptedException {
        CompletableFuture<Object> future = eventloop.submit(() ->
                client.sendRequest("World", 1000)
        System.out.printf("%nRPC result: %s %n%n", future.get());

    public static void main(String[] args) throws Exception {
        RpcExample example = new RpcExample();
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RpcExample class extends ActiveJ Launcher to help us manage logging and the whole application lifecycle.

Next, we use dependency injection library ActiveInject to provide RpcServer and RpcClient with relevant configurations and required dependencies. RpcClient sends requests with a String message to the specified server according to the provided RPC strategy (in this case, getting a single RPC-service). For RpcServer we define the type of messages to proceed, a corresponding RpcRequestHandler and a listener port.

Since we extend Launcher, we will also override 2 methods: getModule to provide ServiceGraphModule and run to describe the main logic of the example.

Finally, we define the main method, which will launch our example.

You can find example sources on GitHub.

Combining strategies

In the previous example we've used one of the simplest strategies which simply works with a single provided port. Yet, as it was mentioned above, ActiveRPC includes pre-defined strategies, which you can simply use and combine.

For example, let's combine Round Robin and First Available strategies. First, we create 4 connections without putting connection3 into the pool. Then we start sending 20 requests. As a result, all the requests will be equally distributed between connection1 (as it is always first available) and connection4 (as connection3 isn’t available for the pool):

pool.put(ADDRESS_1, connection1);
pool.put(ADDRESS_2, connection2);
// we don't put connection3
pool.put(ADDRESS_4, connection4);
int iterations = 20;
RpcStrategy strategy = roundRobin(
        firstAvailable(servers(ADDRESS_1, ADDRESS_2)),
        firstAvailable(servers(ADDRESS_3, ADDRESS_4)));

RpcSender sender = strategy.createSender(pool);
for (int i = 0; i < iterations; i++) {
    sender.sendRequest(new Object(), 50, assertNoCalls());
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Let's check out one more example, Type Dispatch Strategy.
This strategy simply distributes requests among shards in accordance to the type of the request. In the example all String requests are sent on the first shard which has First Valid Result strategy for the servers. Requests with all other types are sent to the second shard with First Available Strategy. As a result, connection1 and connection2 will process 35 requests, connection3 - 25 requests, while connection4 and connection5 - 0 requests as connection3 is always First Available:

pool.put(ADDRESS_1, connection1);
pool.put(ADDRESS_2, connection2);
pool.put(ADDRESS_3, connection3);
pool.put(ADDRESS_4, connection4);
pool.put(ADDRESS_5, connection5);
int timeout = 50;
int iterationsPerDataStub = 25;
int iterationsPerDataStubWithKey = 35;
RpcSender sender;
RpcStrategy strategy = typeDispatching()
                firstValidResult(servers(ADDRESS_1, ADDRESS_2)))
                firstAvailable(servers(ADDRESS_3, ADDRESS_4, ADDRESS_5)));

sender = strategy.createSender(pool);
for (int i = 0; i < iterationsPerDataStub; i++) {
    sender.sendRequest(new Object(), timeout, assertNoCalls());
for (int i = 0; i < iterationsPerDataStubWithKey; i++) {
    sender.sendRequest("request", timeout, assertNoCalls());
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In the next tutorial we'll create a Memcached-like solution that can handle up to 10 millions requests per second on a single core using ActiveRPC.

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