Logging

Logging macros which delegate to a specific logging implementation, selected at runtime when the clojure.tools.logging namespace is first loaded.

Installation

Lastest stable release is 0.5.0

Leiningen:

[org.clojure/tools.logging "0.5.0"]

Maven:

<dependency>
  <groupId>org.clojure</groupId>
  <artifactId>tools.logging</artifactId>
  <version>0.5.0</version>
</dependency>

Gradle:

compile "org.clojure:tools.logging:0.5.0"

Usage

Latest API Documentation

Logging occurs with the log macro, or the level-specific convenience macros (e.g., debug, debugf). Only when the specified logging level is enabled will the message arguments be evaluated and the underlying logging implementation be invoked. By default that invocation will occur via an agent when inside a running STM transaction.

Namespacing of log entries

Unless otherwise specified, the current namespace (as identified by *ns*) will be used as the log-ns. This value can be emitted in the log entry, and used by most logging implementations when using namespace-specific logging levels.

Note: You should configure your logging implementation to display the name that was passed to it. If it instead performs stack-inspection you'll see some ugly and unhelpful text in your logs.

Redirecting output to logs

You can redirect all java writes of System.out and System.err to the log system by calling log-capture!. To bind *out* and *err* to the log system invoke with-logs. In both cases a log-ns value must be specified in order to namespace the output.

Configuration

NOTE: Logging configuration (e.g., setting of logging levels, formatting) is specific to the underlying logging implementation, and is out of scope for this library.

Selecting a logging implementation

To control which logging implementation is used, set the clojure.tools.logging.factory system property to the fully-qualified name of a no-arg function that returns an instance of clojure.tools.logging.impl/LoggerFactory. There are a number of factory functions provided in the clojure.tools.logging.impl namespace.

Leiningen example:

:jvm-opts ["-Dclojure.tools.logging.factory=clojure.tools.logging.impl/slf4j-factory"]

If the system property is unset, an implementation will be automatically chosen based on whichever of the following implementations is successfully loaded first:

1. SLF4J
2. Apache Commons Logging
3. Log4J 2
4. Log4J
5. java.util.logging

The above approach is problematic given that applications often inadvertently pull in multiple logging implementations as transitive dependencies. As such, it is strongly advised that you set the system property.

Thanks

• Chris Dean
• Phil Hagelberg
• Richard Newman
• Sean Corfield
• Timothy Pratley

License

Copyright © 2009 Alex Taggart

Licensed under the EPL. (See the file epl.html.)