Apache Druid is a high-performance, real-time analytics database designed for fast ingest and querying of large-scale datasets. One of the powerful features of Druid is its ability to implement distributed remote method invocation (RMI) using Java.

In this blog post, we will guide you through the process of implementing Java RMI with Apache Druid, allowing you to leverage the distributed computing capabilities of Druid in your Java applications.

Prerequisites

To follow along with this tutorial, you should have a basic understanding of:

• Java programming language
• Apache Druid
• Remote Method Invocation (RMI) concept

If needed, you can refer to the official documentation of Apache Druid and Java RMI to get up to speed.

Step 1: Set up the Druid cluster

Before we can start implementing Java RMI with Apache Druid, we need to set up a Druid cluster. Follow these steps to set up a basic Druid cluster:

1. Download the latest version of Apache Druid from the official website.
2. Extract the downloaded archive to a directory of your choice.
3. Configure the necessary environment variables like JAVA_HOME, DRUID_HOME, and PATH to point to the correct directories.
4. Start a Druid coordinator, broker, and historical process by running their respective scripts.

Step 2: Define the RMI interface

In Java RMI, the first step is to define the remote interface that will be used for RMI communication. Below is an example RMI interface that we will use:

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface RemoteDruidService extends Remote {
    int queryData(String query) throws RemoteException;
}

In this example, we have a single method queryData that takes a query string as input and returns an integer result.

Step 3: Implement the RMI server

Next, we need to implement the RMI server class that will provide the functionality to clients through remote method invocation. Here’s an example of how the server implementation may look like:

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;

public class RemoteDruidServiceImpl extends UnicastRemoteObject implements RemoteDruidService {
    protected RemoteDruidServiceImpl() throws RemoteException {
        super();
    }

    @Override
    public int queryData(String query) throws RemoteException {
        // Implement your logic to query data from Druid cluster
        return 0;
    }
}

In this example, RemoteDruidServiceImpl extends the UnicastRemoteObject class, which provides a default implementation of the Remote interface. We override the queryData method to implement the logic to query data from the Druid cluster.

Step 4: Start the RMI registry

To enable remote method invocation, we need to start the RMI registry. Open a terminal and navigate to the directory where your server class is located. Then, run the following command:

rmiregistry

The RMI registry should start and bind to the default port 1099.

Step 5: Register the RMI server

To register our RMI server with the RMI registry, we need to modify our server class. Add the following code at the end of the class:

public static void main(String[] args) {
    try {
        RemoteDruidService remoteDruidService = new RemoteDruidServiceImpl();
        Naming.rebind("//localhost/RemoteDruidService", remoteDruidService);
        System.out.println("RMI Server is running...");
    } catch (Exception e) {
        System.err.println("RMI Server Error: " + e.getMessage());
        e.printStackTrace();
    }
}

In this code, we create an instance of our server class, bind it to the RMI registry using the Naming.rebind method, and print a confirmation message if successful.

Step 6: Implement the RMI client

Finally, we need to implement the RMI client that will invoke the methods exposed by the RMI server. Here’s an example of how the client implementation may look like:

import java.rmi.Naming;

public class RemoteDruidClient {
    public static void main(String[] args) {
        try {
            RemoteDruidService remoteDruidService = (RemoteDruidService) Naming.lookup("//localhost/RemoteDruidService");
            int result = remoteDruidService.queryData("SELECT COUNT(*) FROM events");
            System.out.println("Query Result: " + result);
        } catch (Exception e) {
            System.err.println("RMI Client Error: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

In this example, we use the Naming.lookup method to get a reference to the remote object registered with the RMI registry. We then invoke the queryData method and print the result.

Conclusion

Congratulations! You have successfully implemented Java RMI with Apache Druid. You can now leverage the distributed computing capabilities of Druid in your Java applications by invoking remote methods exposed by the Druid cluster.

By combining the power of Apache Druid’s real-time analytics with Java RMI, you can build scalable and efficient data applications that process and analyze large-scale datasets in real-time.

#java #rmi #apachedruid