Hello World RPC!

Hopefully you have looked at and understood the Hello World tutorial. This tutorial builds on the previous concepts and introduces calling an RPC.

This is what this tutorial will run in a single VM:

Running this code will output the following to the console:

Hello world!

The code

EndPointAddress registryAddress = new EndPointAddress(TcpChannelUtils.LOCALHOST_IP, 22222);

PlatformRegistry registry = new PlatformRegistry("Hello World Platform", registryAddress);

PlatformRegistryAgent agent = new PlatformRegistryAgent("Agent1", registryAddress);

agent.createPlatformServiceInstance("Foo", "Bar1", TcpChannelUtils.LOCALHOST_IP, WireProtocolEnum.STRING,
    RedundancyModeEnum.FAULT_TOLERANT);

IPlatformServiceInstance serviceInstance = agent.getPlatformServiceInstance("Foo", "Bar1");

//
// Now construct the RPC.
// The RPC is analogous to: String helloWorld_RPC(String echoBack) { return echoBack; }
//
IRpcExecutionHandler handler = new IRpcExecutionHandler()
{
    @Override
    public IValue execute(IValue... args) throws TimeOutException, ExecutionException
    {
        //
        // Here is where the logic for the RPC goes
        // For this example, we simply echo back the argument
        //
        return args[0];
    }
};
TypeEnum returnType = TypeEnum.TEXT;
String rpcName = "helloWorld_RPC";
String[] argNames = new String[] {"echoBack"};
TypeEnum argTypes = TypeEnum.TEXT;
IRpcInstance rpc = new RpcInstance(handler, returnType, rpcName, argNames, argTypes);

//
// Now publish the RPC - after this it is available for execution by clients (proxies)
//
serviceInstance.publishRPC(rpc);

//
// Now we get a "client" to be able to invoke the RPC
//
agent.waitForPlatformService("Foo");

IPlatformServiceProxy proxy = agent.getPlatformServiceProxy("Foo");

//
// The timeout defines how long the execution will wait for discovering the RPC if it is not
// available when the code is executed. In a distributed environment you are not guaranteeed
// that all distributed resources are available so we provide this facility to allow for the
// RPC to become available.
//
long discoveryTimeoutMillis = 5000;
final IValue result = proxy.executeRpc(discoveryTimeoutMillis, "helloWorld_RPC", TextValue.valueOf("Hello world!"));

System.out.println(result.textValue());

Distributed Example

As with the previous helloworld example, we can run the RPC helloworld example in a distributed manner, separating the client and server components into distinct runtimes. Again, its the same code but simply split to run in different runtimes.

Note again: the registry is run in the server VM only for convenience of this example. In reality it should run in its own, separate and dedicated VM.

The code for server runtime

EndPointAddress registryAddress = new EndPointAddress(TcpChannelUtils.LOCALHOST_IP, 22222);

PlatformRegistry registry = new PlatformRegistry("Hello World Platform", registryAddress);

PlatformRegistryAgent agent = new PlatformRegistryAgent("Server-helloworld", registryAddress);

agent.createPlatformServiceInstance("Foo", "Bar1", TcpChannelUtils.LOCALHOST_IP, WireProtocolEnum.STRING,
    RedundancyModeEnum.FAULT_TOLERANT);

IPlatformServiceInstance serviceInstance = agent.getPlatformServiceInstance("Foo", "Bar1");

IRpcInstance rpc = new RpcInstance(new IRpcExecutionHandler()
{
    @Override
    public IValue execute(IValue... args) throws TimeOutException, ExecutionException
    {
        return args[0];
    }
}, TypeEnum.TEXT, "helloWorld_RPC", new String[] {"echoBack"}, TypeEnum.TEXT);

serviceInstance.publishRPC(rpc);

//wait forever as this is the "server" VM
synchronized("")
{
 "".wait();
}

The code for the client runtime

EndPointAddress registryAddress = new EndPointAddress(TcpChannelUtils.LOCALHOST_IP, 22222);

PlatformRegistryAgent agent = new PlatformRegistryAgent("Client-helloworld", registryAddress);

agent.waitForPlatformService("Foo");

IPlatformServiceProxy proxy = agent.getPlatformServiceProxy("Foo");

long discoveryTimeoutMillis = 5000;
final IValue result = proxy.executeRpc(discoveryTimeoutMillis, "helloWorld_RPC", TextValue.valueOf("Hello world!"));

System.out.println(result.textValue());