YARN containers launched by a CDAP application use a default container logback file—logback-container.xml—packaged with CDAP and installed in the CDAP configuration directory. This logback does log rotation once every day at midnight and deletes logs older than 14 days. Depending on the use case, the default configuration may be sufficient. As long as the container is running, these policies will apply. (As the lifetime of many containers is often less than 14 days, these limits may never be reached.)
Note: In the case of the CDAP Sandbox, the logback file used is logback.xml, located in the <CDAP-HOME>/conf directory.
You can specify a custom logback.xml for a CDAP application by packaging it with the application in the application's src/main/resources directory. The packaged logback.xml is then used for each container launched by the application.
To write a custom logback.xml, refer to the Logback manual for information.
Note: When a custom logback.xml is specified for an application, the custom logback.xml will be used in place of the logback-container.xml. A custom logback.xml needs to be configured for log rotation (rollingPolicy) and log clean-up (maxHistory) to ensure that long-running containers don't fill up the disk.