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Logging

Shopsys Framework is a Symfony based application that uses Monolog with symfony/monolog-bundle as a logging tool. Currently, this tool is used to manage the log of cron processes, slow responses, unexpected exceptions and application errors.

Logging Using Streams

Based on The Twelve-Factor App principle we decided to use output streams for logging rather than files so debugging and monitoring can be done better and faster.

By default, there are 2 output streams for logging:

  • STDERR should be used only for error logs
  • STDOUT should be used any other info and debug data

In the php-fpm container we used a named pipe as a gateway between the application and stdout. This approach prevents logs from being output to console during console commands.

How to check the logs

To see the logs from all containers including the Postgres database, web server etc. simply run:

docker-compose logs

The output will consist of log messages on separate lines, starting with the container name:

shopsys-framework-redis | 1:M 23 Jul 11:32:57.000 * Ready to accept connections
shopsys-framework-php-fpm | [2018-07-23 11:39:12] security.INFO: Populated the TokenStorage with an anonymous Token. [] []
shopsys-framework-php-fpm | [2018-07-23 11:42:41] slow.NOTICE: 3.14159265359 App\Controller\Front\ProductController::listByCategoryAction /test-category/ [] []

Tip

If you're only interested in some specific messages you can use grep, eg. docker-compose logs | grep slow.NOTICE for slow responses.

Conclusion

Logging into streams is one of the prerequisites for scalable application. With implementation of orchestration tool like Kubernetes we will be able to store logs in a centralized way. This will help us find problems faster and also monitor the production environment. At the moment, we are using a simple workaround for persisting logs to local storage on our CI server that uses Kubernetes.