No two loggers with the same category, why?

[Bertrand Delacretaz <bd...@apache.org>]

Hi,

The code below [1] was introduced in for SLING-525, and prevents
creating two loggers that have one or more log categories in common -
do we really want that?

I'm looking at implementing support for slf4j Markers, which allows
for "orthogonal" log configurations, for example:

a) Send all INFO and higher logs to info.log

b) Send all DEBUG and higher logs which have a FOO marker to foo.log
(useful to keep track of processes spread around several services for
example)

And that gets in the way.

-Bertrand



[1] From
http://svn.apache.org/repos/asf/sling/trunk/bundles/commons/log/src/main/java/org/apache/sling/commons/log/internal/slf4j/LogConfigManager.java

          // verify no other configuration has any of the categories
            for (String cat : categories) {
                SlingLoggerConfig cfg = configByCategory.get(cat);
                if (cfg != null && !pid.equals(cfg.getConfigPid())) {
                    throw new ConfigurationException(LogManager.LOG_LOGGERS,
                        "Category " + cat
                            + " already defined by configuration " + pid);
                }
            }

Re: No two loggers with the same category, why?

[Bertrand Delacretaz <bd...@apache.org>]

On Mon, Nov 19, 2012 at 5:54 PM, Bertrand Delacretaz
<bd...@apache.org> wrote:
> ...The code below [1] was introduced in for SLING-525, and prevents
> creating two loggers that have one or more log categories in common -
> do we really want that?...

I'm revisiting this...just so that the list archives are complete:
this is also needed because loggers are acquired via the
org.slf4j.ILoggerFactory interface:

  /* Return an appropriate Logger instance as specified by the name
parameter. */
  Logger getLogger(String name)

So we need a 1-to-1 mapping of a log category (name) to Logger.

Or something more clever that aggregates Loggers which share
categories, but that's probably going too far.

-Bertrand

Re: No two loggers with the same category, why?

[Felix Meschberger <fm...@adobe.com>]

Hi,

Am 21.11.2012 um 11:35 schrieb Bertrand Delacretaz:

> Hi Felix,
> 
> On Wed, Nov 21, 2012 at 11:18 AM, Felix Meschberger <fm...@adobe.com> wrote:
>> ...Each logger (SlingLogger) is associated with a single configuration
>> (SlingLoggerConfig), which in turn defines the log level and target for that logger.
>> So currently it is not possible to associate a logger with more than one configs....
> 
> Ok, but how about several SlingLoggerConfigs having log categories in common?
> 
> IIUC the current code disallows that, and I don't see why.

Because each logger -- e.g. org.apache.sling.engine.impl -- is backed by a SlingLogger instance which is connect to a single SlingLoggerConfig, which defines which level written to which writer.

So, because the SlingLogger instances don't support it we prevent it.

If you want to improve, I suggest you would probably create SlingLoggerConfig instances for each level/writer combo and have support for SlingLogger instances to be related to more than one SlingLoggerConfig.

Regards
Felix

Re: No two loggers with the same category, why?

[Bertrand Delacretaz <bd...@apache.org>]

Hi Felix,

On Wed, Nov 21, 2012 at 11:18 AM, Felix Meschberger <fm...@adobe.com> wrote:
> ...Each logger (SlingLogger) is associated with a single configuration
> (SlingLoggerConfig), which in turn defines the log level and target for that logger.
> So currently it is not possible to associate a logger with more than one configs....

Ok, but how about several SlingLoggerConfigs having log categories in common?

IIUC the current code disallows that, and I don't see why.

-Bertrand

Re: No two loggers with the same category, why?

[Felix Meschberger <fm...@adobe.com>]

Hi,

Each logger (SlingLogger) is associated with a single configuration (SlingLoggerConfig), which in turn defines the log level and target for that logger. So currently it is not possible to associate a logger with more than one configs.

Of course, we can enhance this and support multiple configurations to which a logger will send messages.

Regards
Felix

Am 19.11.2012 um 17:54 schrieb Bertrand Delacretaz:

> Hi,
> 
> The code below [1] was introduced in for SLING-525, and prevents
> creating two loggers that have one or more log categories in common -
> do we really want that?
> 
> I'm looking at implementing support for slf4j Markers, which allows
> for "orthogonal" log configurations, for example:
> 
> a) Send all INFO and higher logs to info.log
> 
> b) Send all DEBUG and higher logs which have a FOO marker to foo.log
> (useful to keep track of processes spread around several services for
> example)
> 
> And that gets in the way.
> 
> -Bertrand
> 
> 
> 
> [1] From
> http://svn.apache.org/repos/asf/sling/trunk/bundles/commons/log/src/main/java/org/apache/sling/commons/log/internal/slf4j/LogConfigManager.java
> 
>          // verify no other configuration has any of the categories
>            for (String cat : categories) {
>                SlingLoggerConfig cfg = configByCategory.get(cat);
>                if (cfg != null && !pid.equals(cfg.getConfigPid())) {
>                    throw new ConfigurationException(LogManager.LOG_LOGGERS,
>                        "Category " + cat
>                            + " already defined by configuration " + pid);
>                }
>            }