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JavaTaskQueue Instructions

Welcome to the JavaTaskQueue repository!

This project implements a robust, distributed-style Task Queue and Job Scheduler built purely with Java 17, without relying on any external frameworks like Spring or Web Application servers. It uses SQLite for lightweight, reliable persistence.

Below you'll find comprehensive instructions on how to use and interact with the project.

Prerequisites

Before running the application, make sure you have:

  • Java 17 (or newer) installed and available in your PATH.
  • Maven (Apache Maven 3.8+ recommended) installed.

1. Building the Application

You need to compile the Java files and package them along with the required dependencies (SQLite JDBC and JSON library) into an executable JAR.

Open your terminal or command prompt in the project root directory and run:

mvn clean package

This command will:

  1. Clean previous build artifacts.
  2. Compile the source code.
  3. Run the automated test suite.
  4. Generate an Uber/Fat JAR inside the target directory: target/JavaTaskQueue-jar-with-dependencies.jar.

Note: If you want to skip tests (not recommended), you can use mvn clean package -DskipTests.

2. Running the Server

The Task Broker acts as the core of the task queue. It orchestrates task scheduling, delegation to worker threads, and saving states to the SQLite database.

In a terminal, start the server using:

java -jar target/JavaTaskQueue-jar-with-dependencies.jar

You should see a banner along with initialization logs confirming that the SQLite repository and TCPServer (on port 9090) have successfully started.

3. Running the Client

The application comes with an interactive command-line interface (CLI) to communicate with the TaskQueue server.

Open a new, separate terminal window and run the client:

java -cp target/JavaTaskQueue-jar-with-dependencies.jar com.taskqueue.client.TaskQueueClient

If your server is running on another machine or port, you can specify them:

java -cp target/JavaTaskQueue-jar-with-dependencies.jar com.taskqueue.client.TaskQueueClient --host 192.168.1.10 --port 9091

Once connected, you will see a jtq> prompt.

4. Using the Client CLI

From the jtq> prompt, you can type several commands.

Submitting Tasks

Submit tasks using JSON strings. The queue currently supports three types of tasks: ECHO, COMPUTE, and SLEEP.

  • Echo Task: 
    SUBMIT {"type":"ECHO","payload":"Hello, JavaTaskQueue!","priority":"HIGH"}
  • Compute Task (Factorial): 
    SUBMIT {"type":"COMPUTE","payload":"FACTORIAL:15","priority":"MEDIUM"}
  • Sleep Task (Delay simulation): 
    SUBMIT {"type":"SLEEP","payload":"3000","priority":"LOW"}

Checking Queue and Task Status

  • Check specific task status: 
    STATUS <task-id-returned-from-submit>
  • List all tasks: 
    LIST

Managing Tasks and Server

  • Cancel a task: 
    CANCEL <task-id>
  • Shutdown Server: 
    SHUTDOWN
  • Exit the Client: 
    exit

5. Running Tests

To just run the tests and verify component integrity (Broker, Workers, Compute Handlers, etc.):

mvn test

Adding New Task Types

If you want to extend the application to support new task logic:

  1. Create a class implementing com.taskqueue.handler.TaskHandler.
  2. Register it in Main.java before starting the server: 
    TaskHandlerRegistry.register("NEW_TYPE", new MyCustomHandler());

Enjoy using JavaTaskQueue!