How to Deploy a Java Application Using Supervisor and Set Up Log Rotation

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When running a Java application (or any other service) on a linux machine, it's essential to ensure that the application automatically restarts if it crashes and that the log files are managed properly. This guide will show you how to use supervisord to run your service and set up log rotation to manage your logs efficiently.

Prerequisites

• An AWS EC2 instance with access via SSH.

• A Java .jar file or any other service you want to manage. For this example we will use a jar file by name “stock-news” whose functionality is to provide relevant news given a stock symbol.

Step 1: Install Supervisor

Supervisor is a process control system that allows you to monitor and control processes. It’s perfect for ensuring your Java application stays up and running.

For Amazon Linux 2 or CentOS:

sudo amazon-linux-extras install epel -y
sudo yum install supervisor -y
sudo systemctl start supervisord //if not started already
sudo systemctl status supervisord

For Ubuntu:

sudo apt-get update
sudo apt-get install supervisor -y
sudo systemctl start supervisord //if not started already
sudo systemctl status supervisord

Step 2: Create a Supervisor Configuration File for Your Service

Now, let's create a Supervisor configuration file for your Java application. This will ensure the application is automatically restarted if it crashes and runs as a managed service.

1. Create the configuration file:

For Amazon Linux:

sudo vim /etc/supervisord.d/stock-news.ini

For Ubuntu:

sudo vim /etc/supervisor/conf.d/stock-news.ini

[program:stock-news]
command=/usr/bin/java -jar /path/to/your/stock-news-0.1.jar
autostart=true
autorestart=true
stderr_logfile=/var/log/stock-news/stock-news.err.log
stdout_logfile=/var/log/stock-news/stock-news.out.log
stdout_logfile_maxbytes=50MB
stdout_logfile_backups=5
stderr_logfile_maxbytes=50MB
stderr_logfile_backups=5

Replace /path/to/your/stock-news-0.1.jar with the actual path to your .jar file

Step 3: Create the Log Directory

Make sure the directory for the logs exists and is writable:

sudo mkdir -p /var/log/stock-news
sudo chown -R ec2-user:ec2-user /var/log/stock-news
sudo chmod -R 755 /var/log/stock-news

Step 4: Reload and Start Supervisor

After the configuration file is in place, you need to reload Supervisor to pick up the changes and start your service.

1. Reload Supervisor:

sudo supervisorctl reread
sudo supervisorctl update

2. Start the service:

sudo supervisorctl start stock-news

3. Check the status of your service:

sudo supervisorctl status stock-news

Step 5: Set Up Log Rotation

Managing logs effectively is critical for preventing your system from running out of disk space. You can set up log rotation to handle this.

1. Create a log rotation configuration file:

   Open a new log rotation configuration file in /etc/logrotate.d/:

sudo vim /etc/logrotate.d/stock-news

2. Add the following log rotation configuration:

/var/log/stock-news/*.log {
    daily
    rotate 7
    compress
    missingok
    notifempty
    delaycompress
    dateext
    dateformat -%Y-%m-%d-%s
    create 0640 ec2-user ec2-user
    sharedscripts
    postrotate
        /usr/bin/supervisorctl restart stock-news > /dev/null 2>&1 || true
    endscript
}

This configuration:

• Rotates the logs daily (daily).

• Keeps the logs for 7 days (rotate 7).

• Compresses the old log files (compress).

• Adds a date and timestamp to the rotated logs (dateext and dateformat).

• Restarts the service after log rotation (postrotate).

Step 6: Test Log Rotation

To test the log rotation setup, you can run the following commands:

1. Check the rotation configuration:

sudo logrotate -d /etc/logrotate.d/stock-news

2. Force log rotation:

sudo logrotate -f /etc/logrotate.d/stock-news

Check the log directory to verify that logs are rotated and compressed:

ls /var/log/stock-news/

Step 7: Verify Logs and Service

1. Check the logs to ensure they are being written correctly:

tail -f /var/log/stock-news/stock-news.out.log

2. Monitor the service:

sudo supervisorctl status stock-news

This will show the status of the service and any issues that may arise.

Conclusion

Now, your Java application is set up to run as a managed service under Supervisor, and the logs will rotate daily with the date and time of the rotation appended to the filenames. You also have log retention for 7 days, ensuring that your system disk space remains under control.

By following these steps, you can efficiently manage any long-running service on AWS EC2 and ensure stability and log management.