What?

Cloud Foundry applications are expected to log to stdout and stderr. This is part of Twelve-Factor app design.

A set of Cloud Foundry components (cumulatively named Loggregator) provide a stream of log output from your app and from system components that interact with your app during updates and execution. Logs are gathered and stored in a best-effort manner. If a client is unable to consume log lines quickly enough, logs will be lost. The --recent flag will print the logs that are being buffered.

The log output has a specific format. It’s important to note that when your application logs, the instance number is prepended to the message (i.e. [APP/instance_number]).

System components logs will also appear in relation to your application. Below is a description of a few important ones:

  • The stager STG is responsible for using a Buildpack to create a droplet.
  • The Diego cell CELL is responsible for running your application instance.
  • The Router RTR logs your application has responded to an HTTP request.
  • See more components

How?

cf logs dora --recent

Expected Result

The output will look something like:

20116-12-05T21:37:29.96-0500 [STG/0]     OUT Uploaded build artifacts cache (109B)
2016-12-05T21:37:33.77-0500 [STG/0]      OUT Uploaded droplet (75.7M)
2016-12-05T21:37:33.78-0500 [STG/0]      OUT Uploading complete
2016-12-05T21:37:34.11-0500 [CELL/0]     OUT Creating container
2016-12-05T21:37:35.07-0500 [CELL/0]     OUT Successfully created container
2016-12-05T21:37:39.40-0500 [CELL/0]     OUT Starting health monitoring of container
2016-12-05T21:37:42.08-0500 [APP/0]      OUT 2016-12-06 02:37:42.078  INFO 14 --- [           main] pertySourceApplicationContextInitializer : Adding 'cloud' PropertySource to ApplicationContext
2016-12-05T21:45:25.23-0500 [RTR/0]      OUT dora.pcfdev.io - "GET /favicon.ico HTTP/1.1" 200 0 946 "http://dora.local.pcfdev.io/service" ....

Resources

Logs for CF components Logs for applications