Logger

AdonisJS uses pino logger for logging, since it is one of the fastest logging libraries in Node.js ecosystem and also follows the 12factor app guidelines.

How AdonisJS Logger works?

Since, Node.js is a single threaded event-loop, it is very important to keep the main thread free from any extra work required to process or reformat logs.

For this very reason, we opted for pino logger, which does not perform any in-process log formatting and instead encourages you to make use a seperate process for that. In nutshell, this is how the logging works.

1. You can log at different levels using the Logger API, for example: Logger.info('some message').
2. The logs will be send out to stdout.
3. You can redirect the stdout stream to a file or use a seperate process to read and format them.

Logging in Development

Since logs are always written to stdout, there is nothing special required in the development environment. Also, AdonisJS will automatically pretty print the logs when NODE_ENV=development.

Logging in Production

In production, you would want to stream your logs to an external service like Datadog or Papertrail. Following are some of the ways to send logs to an external service.

Using Pino Transports

The simplest way to process the stdout stream is to make use of pino transports. All you need to do is pipe the output to the transport of your choice. For demonstration, let's try to send logs to Datadog.

1. Install the pino-datadog package from npm package registry.

   npm i pino-datadog
   

2. Start the application in production and pipe the stdout output to pino-datadog.

   node build/server.js | ./node_modules/.bin/pino-datadog --key DD_API_KEY
   

Streaming to a File

Another approach is to forward the output of stdout to a physical file on the disk and then configure your logging service to read and rotate the log files.

node build/server.js >> app.log

Now, configure your logging service to read logs from the app.log file