Pipe Log Output to STDOUT with Docker
Since Docker filesystems are ephemeral, it's important to take into account anything that writes or appends to disk, such as log files. It is standard practice when running Docker containers to pipe log file output to the console, to allow for simple diagnostic and to avoid append-only files from consuming disk space.
In this lesson, we’ll show you how to append output to STDOUT, and how to view log output from your running containers.
I dont't get this lesson. What's the purpose of creating debug.log file if we never write anything to it (at least in Docker environment)?
As noted in the video, this is a non-sensical example. But it demonstrates how you would change an app that normally writes to log files so that they instead pipe to STDOUT, so you can make the app 12-factor friendly.
You don’t need to create a log file if you are already piping things to STDOUT. Note that in this example, we are writing the console.log output directly to the debug.log file.
Ok thanks, I get it. You can also find great explanation here: https://stackoverflow.com/questions/43968560/how-to-log-the-12-factor-application-way/43968637#43968637
it's good tip. Thank you.
I can see the value in keeping the logging agnostic. How would you do this with statsd logging? This often requires a client side package with host name and port number. Would you pass those variables into the docker container? Or can you do a similar thing you do here with standard logging for stats?