Re: [cross-project-issues-dev] slf4j logging configuration in eclipse

[Thomas Watson <tjwatson@xxxxxxxxxx>]

We have been having a similar discussion in Equinox in the p2 bug https://bugs.eclipse.org/bugs/show_bug.cgi?id=338232

One thing we could consider doing is to provide an Equinox ExtendedLogService binding for SLF4J. Currently bindings to the org.slf4j.api orbit bundle are "configured" as fragments of the org.slf4j.api bundle and provide the org.slf4j.impl package. This allows the slf4j api to get bound to the implementation and load the implementation classes. The problem with this approach (as you point out) is that it only allows a single binding (one fragment wins in providing the host with the org.slf4.impl package).

The advantage of providing an Equinox ExtendedLogService binding for slf4j is that it opens up the ability to have multiple backends (e.g. logback, eclipse log etc.) configured with the system by implementing OSGi LogService LogListeners that intercept the log entries and do what ever is needed with them on the back end.

Tom



Vlad Tatavu ---03/17/2011 11:52:23 AM---Hi all,

From:	Vlad Tatavu <vtatavu@xxxxxxxxxxxx>
To:	cross-project-issues-dev@xxxxxxxxxxx
Date:	03/17/2011 11:52 AM
Subject:	[cross-project-issues-dev] slf4j logging configuration in eclipse

---

Hi all,

I want to open a discussion about slf4j logging configuration in eclipse. :)

For those not familiar with slf4j, see [1].

Background/problem:
Currently, several eclipse packages/components use slf4j for logging.
Since slf4j is just a logging facade, if there isn't any logging 
framework supported by slf4j "available", the logging defaults to noop.
There are several logging frameworks supported by slf4j (all major 
ones), but only one should be available/used in a JVM.  Depending on the 
available logging framework and how that framework is configured, the 
logging behavior can be quite different.  If more than one logging 
framework is available, slf4j picks one (pretty much randomly).  That 
can cause problems and it almost forces each eclipse component to load 
and configure a specific logging framework.  Which can be quite bad... 
conflicting logging frameworks, configurations, etc.
As the number of components that use slf4j increases, the problems will 
just multiply and it may become a nightmare to handle and configure 
slf4j logging.

Proposal:
Add generic support for slf4j logging at platform level.  That requires 
two things:
- Choose a logging framework to be used by default - I propose logback - 
for those not familiar with logback, see [2]
- Provide default configuration for the chosen logging framework
Currently, the m2eclipse component provides an optional bundle that 
loads and configures logback for slf4j in eclipse.  The bundle is pretty 
generic and it provides the following functionality:
- Loads logback as logging framework for slf4j
- Default logback configuration if logback configuration was not 
provided already through one of the standard logback configuration 
mechanisms - see [3]
The default configuration:
- Provides a log file destination
- Pipes the logging into the console if -consoleLog is specified
- Pipes the WARN and ERROR logging into the eclipse log
- Pipes the logging into MavenConsole - this part is a little bit 
specific to m2eclipse.  On the other hand, the MavenConsole acts more 
like a console viewer and it could be easily re-factored to not be maven 
or m2eclipse specific.


[1] http://www.slf4j.org/
[2] http://logback.qos.ch/
[3] http://logback.qos.ch/manual/configuration.html

Best regards,
Vlad
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