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

I'm not familiar with the Equinox ExtendedLogService, so I don't want to have any opinion about it before I take a look at it. :) Where should I look? :)

That being said... If I understand correctly the second paragraph in your message, the Equinox ExtendedLogService acts as an implementation for slf4j.  That doesn't make a lot of sense to me because slf4j is already a facade for almost all the other major logging frameworks out there.  I don't see any advantage in pluging in something in between slf4j and the final logging framework (logback, log4j, etc).  Having a layer in between can cause major performance problems (please note that slf4j and logback were developed for near zero performance impact).

As I said in the reply to Igor, I don't see the use case for having multiple logging frameworks plugged in slf4j concurrently, but I'm opened to hearing about such use cases.

About log listeners... they can be both good and evil. :) Depending on what they do and how they are implemented, of course. :)  But it's not easy at all to implement good log listeners.  On the other hand it's trivial to plugin log listeners in logback and log4j using log appenders.  Most probably other logging frameworks have similar features.  The big advantages in using appenders are:
- they can be plugged in and configured via logback/log4j config files.
- the logging framework is responsible for dealing with "bad" appenders - and in my experience, both logback and log4j are good at that :)

I wasn't aware of  The discussion points out something that really bothers me: the proliferation of slf4j/logging solutions in eclipse.  Especially conflicting solutions.  For example, somebody said that they "have a framework hook which routes all Eclipse logging into SLF4J".  Well, m2eclipse has an appender that routes slf4j logging to eclipse log.  That will obviously cause circular logging if installed and activated together.


On 3/17/2011 3:12 PM, Thomas Watson wrote:

We have been having a similar discussion in Equinox in the p2 bug

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.


Inactive hide details for Vlad Tatavu ---03/17/2011
          11:52:23 AM---Hi all,Vlad Tatavu ---03/17/2011 11:52:23 AM---Hi all,


Vlad Tatavu <vtatavu@xxxxxxxxxxxx>




03/17/2011 11:52 AM


[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].

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.

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.


Best regards,
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