Cron Scheduler Project

Brief Description

This project is a simple cron scheduler in Java, it allows users to schedule job executions periodically. The user defines a job class in Jobs.java file and implements the execution details in the config file. The scheduler is invoked via the Main method from the command line, further details below. There are three example jobs in the Jobs.java file.

In order to allow room for implementation, This project exclusively uses Java Standard Libraries, as well as Maven for building to facilitate unit testing.

Snippets of output are included in the output.log file.

Features

• Periodic Job Scheduling: Users can schedule jobs to run periodically by providing details in a configuration file.
• Flexibility: Jobs are scheduled based on the defined intervals and frequencies, as well as configure the size of the threadpool that will be used for multithreading.
• Out-of-Order Execution: Jobs are independently executed, allowing out-of-order execution. The scheduler does not enforce an order of execution.

Project Structure

project-root/
│
├── src/
│   ├── main/
│   │   ├── java/com/example/cronscheduler/
│   │   │   ├── CronScheduler.java
│   │   │   ├── Jobs.java
│   │   │   └── Main.java
│   │
│   ├── test/
│   │   ├── java/com/example/cronscheduler/
│   │   │   └── CronSchedulerTest.java
│   │
└── config.txt            # Sample configuration file for job scheduling

Getting Started

1. Define Job Class:

   • Define a class for the job in the Jobs.java file. Each job must implement Runnable interface.

2. Configure Jobs:

   • Edit the config.txt file to specify the details of the job's execution.
   • Each line represents one job: <jobClassName> <jobId>, <intervalInMinutes>, <Frequency>

   -Example:

   PrintLineJob jobId1, 2, HOURLY
   

3. Compile Project:

   • Locate the .Java files and from there compile the project using the following command:

      javac -d bin Main.java CronScheduler.java Jobs.java

4. Run Scheduler:

   • Run the scheduler with the desired thread pool size:

     java -cp bin com.example.cronscheduler.Main <poolSize>

     Where <poolSize> is the desired size of the thread pool.

5. View Scheduled Jobs:

   • The scheduler will log information about the scheduled jobs, including job class names, job IDs, and elapsed time and other real-time events.
   • The information will also be logged to a separate file 'output.log'

Sample Configuration File (config.txt)

com.example.Job1 JobId1, 5, MINUTELY
com.example.Job2 JobId2, 10, HOURLY
com.example.Job3 JobId3, 15, DAILY

Assumptions made

• Periodic job execution continues indefinitely until the scheduler is interrupted.
• Interval is the delay before the execution of job.
• Interval must be provided, the user should put 0 if they do not want to set an interval.
• There is no guaranteed order of execution.
• The user will provide all jobs in a single configuration file.

Further Work

This section addresses potential areas of improvements.

• Interactive GUI: Implementing an interactive graphical user interface to enhance user experience.

• Auto-generated JobID: Automate the assignment of JobIDs to avoid potential conflicts when users manually assign JobIDs.

• Enhanced Visibility: Provide detailed logging, real-time updates, and error logs for better user insight.

• Data Storage with Tables: Integrate a database to maintain a history of scheduled jobs for managament, querying, and analysis.

• Job Timeout Option: Implement an option for specifying a timeout for individual jobs.

• Flexible Configuration: Allow users the flexibility to choose not to provide either the "frequency" or "interval" for a job which would allow for one-time jobs.

• Dynamic Job Scheduling: Enable users to dynamically add or remove jobs without stopping the scheduler, this would work especially well with a GUI.

• Error Handling and Notifications: Implement a more robust error-handling mechanism to gracefully handle exceptions during execution.

Dependencies

• Java (JDK 8 or higher)