Logger

Contents of This File

• Introduction
• Installation
• Instrumentation

Introduction

Current maintainer: whitehouse

The Logger module provides event logging facilities that are decoupled from any particular storage backend. It is useful for module developers who want to instrument their code for monitoring and alerting without forcing their users to use a particular backend technology, like StatsD. The module doesn't provide any visible functionality out-of-the-box. You only need it if you're a module developer looking to instrument your code or if a module you're using depends on it.

Installation

Logger itself is installed in the usual way. See Installing contributed modules. An implementation of hook_logger_event() is required to connect to a logging backend so as to actually do something with event data. See [logger.api.php] (logger.api.php). This implementation may be supplied in custom code or by a contributed module like StatsD.

Instrumentation

Instrumentation is the process of adding "probes" to your application code to fire events for Logger to log. If you're installing Logger as a dependency of another module, presumably that module is already instrumented. To instrument your own code, simply invoke logger_event(), much as you would [watchdog()] (https://api.drupal.org/api/drupal/includes!bootstrap.inc/function/watchdog/7). See logger.module.

If you're instrumenting a contributed module, you must declare a dependency on Logger in your .info file. Alternatively, you can create a "soft", or optional, dependency on Logger by using a wrapping function instead of calling logger_event() directly, like this:

function example_logger_event($name, $type = 'count', $value = 1) {
  if (function_exists('logger_event')) {
    logger_event($name, $type, $value);
  }
}

Event names should be Graphite-compatible, i.e., paths delimited by dots (.). See [Getting Your Data Into Graphite: Step 1] (http://graphite.readthedocs.org/en/latest/feeding-carbon.html#step-1-plan-a-naming-hierarchy) for some helpful advice.

Note: Logger has a debug mode that logs events to watchdog, which can be helpful during development. It can be enabled at admin/config/development/logging or by setting the logger_debug variable directly, e.g.:

# Enable debugging.
drush variable-set --exact logger_debug 1
# Disable debugging.
drush variable-delete --exact logger_debug