logging.md

Logging

The Buildpack logs to both <app dir>/.buildpack-diagnostics/buildpack.log and standard error. Logs are filtered according to the configured log level.

If the buildpack fails with an exception, the exception message is logged with a log level of ERROR whereas the exception stack trace is logged with a log level of DEBUG to prevent users from seeing stack traces by default.

Sensitive Information in Logs

The Buildpack logs sensitive information, such as environment variables which may contain security credentials.

Note: Be careful not to expose the sensitive information, for example by posting standard error stream contents or the contents of <app dir>/.buildpack-diagnostics/buildpack.log to a public discussion list.

Logger Usage

The LoggerFactory class in the LibertyBuildpack::Diagnostics module manages a single instance of a subclass of the standard Ruby Logger. The Buildpack class creates a logger which is shared by all other classes and which is retrieved from the LoggerFactory as necessary:

logger = LoggerFactory.get_logger

This logger is used in the same ways as the standard Ruby logger and supports both parameter and block forms:

logger.info('success')
logger.debug { "#{costly_method}" }

Configuration

For general information on configuring the Buildpack, refer to Configuration and Extension.

You can set the $JBP_LOG_LEVEL environment variable to configure the log level. There are five logs levels:

DEBUG | INFO | WARN | ERROR | FATAL

For example:

cf set-env <app name> JBP_LOG_LEVEL DEBUG

If JBP_LOG_LEVEL is not set, the default log level is read from the configuration in config/logging.yml.

You can use any mixture of upper and lower case letters to specify the logging levels in the JBP_LOG_LEVEL environment variable and the config/logging.yml file.

If you do not set the JBP_LOG_LEVEL environment variable, the Ruby verbose and debug modes override the default log level and change it to DEBUG.