如何实现Play Framework因异常崩溃时自动重启？

Great question! Even though Play Framework is built to be rock-solid and avoid crashes by design, we all know unexpected issues—like unhandled exceptions, resource leaks, or external service outages—can take an app down. Here are the most practical, battle-tested ways to set up automatic restarts for your Play app:

1. Systemd (Linux Production Standard) #

Systemd is the go-to init system on nearly all modern Linux distros, and it’s perfect for ensuring your Play app stays running.

• First, create a systemd service file (e.g., /etc/systemd/system/play-app.service):

  [Unit]
  Description=My Play Framework Application
  After=network.target
  
  [Service]
  User=your-app-user
  Group=your-app-group
  WorkingDirectory=/path/to/your/app
  ExecStart=/usr/bin/java -jar your-play-app.jar
  Restart=always
  RestartSec=5
  Environment="PLAY_CONF_FILE=/path/to/application.conf"
  
  [Install]
  WantedBy=multi-user.target
  

• Key details to note:
  • Restart=always: Tells systemd to restart the service no matter why it exited—including crashes.
  • RestartSec=5: Waits 5 seconds before restarting to avoid thrashing if the app crashes immediately on startup.
• Then set up and start the service:

  sudo systemctl daemon-reload
  sudo systemctl enable play-app.service
  sudo systemctl start play-app.service
  

• Check status or live logs anytime with:

  sudo systemctl status play-app.service
  journalctl -u play-app.service -f
  

2. Supervisor (Lightweight Cross-Platform Option) #

Supervisor is a simple process control system that works great for Play apps, especially if you’re on a Linux distro without systemd or prefer a more flexible tool.

• Install Supervisor first (e.g., on Debian/Ubuntu: sudo apt-get install supervisor).
• Create a config file in /etc/supervisor/conf.d/play-app.conf:

  [program:play-app]
  command=/usr/bin/java -jar /path/to/your-app/your-play-app.jar
  directory=/path/to/your-app
  user=your-app-user
  autorestart=true
  startretries=3
  redirect_stderr=true
  stdout_logfile=/var/log/play-app.log
  

• Critical config options:
  • autorestart=true: Automatically restarts the process if it crashes.
  • startretries=3: Gives up after 3 consecutive failed starts (adjust this number based on your needs).
• Update Supervisor and launch your app:

  sudo supervisorctl reread
  sudo supervisorctl update
  sudo supervisorctl start play-app
  

• Check the app’s status with sudo supervisorctl status play-app.

3. Play’s Built-in Dev Mode (For Local Development Only) #

If you’re working locally, Play’s dev mode already handles automatic restarts—both for code changes and unexpected crashes. Just run:

sbt run

Or if you’re using Activator:

activator run

Heads up: This mode is not meant for production. Stick to the process managers above for live environments.

4. Docker Restart Policies (Modern Containerized Deployments) #

If you’re deploying your Play app with Docker, you can use Docker’s built-in restart policies to keep it alive.

• When running your container directly, use the --restart flag:

  docker run -d --restart always -p 9000:9000 your-play-app-image
  

• Available --restart options:
  • always: Restarts the container no matter why it exits.
  • on-failure:3: Restarts only if the container exits with a non-zero code, up to 3 times.
• For Docker Compose, add the restart policy to your service definition:

  services:
    play-app:
      image: your-play-app-image
      ports:
        - "9000:9000"
      restart: always
  

Quick Pro Tips #

• Graceful Shutdown: Make sure your app handles shutdown properly! Use Play’s ApplicationLifecycle hooks to clean up connections or save state—this prevents data corruption when restarts happen.
• Don’t Ignore Crashes: Automatic restarts are a safety net, not a fix. Always monitor your logs to track down why crashes are occurring in the first place.

内容的提问来源于stack exchange，提问作者vaj oja