[logback-dev] if-then-else support in Joran.

[Ceki Gülcü]

Hello Ralph,

I actually agree with you and would expect some mockery. XML does NOT
provide a good basis for a programming language. I don't intend to go
beyond if-then-else, i.e. there won't be 'for' or 'while'
loops. However, having parts of the config file conditioned on the
host seems useful. It is more convenient to deal with a single file
with some conditional parts than shuffling around 2 or 3 files 90%
identical.

A groovy or scala DSL for logback configuration would make sense and
would be much cooler then what I am trying to accomplish in XML. We
should have a page proposing tasks for volunteers and hope that one of
the readers writes a DSL.

As for adding support for Messages, it is on my todo list. However, to
be honest, there are other items which come beforehand.

Cheers,

On 30/03/2010 7:27 AM, Ralph Goers wrote:
> This just feels overly complicated.  I have a feeling you are going to get pushback from all the folks who have learned over the years that XML is a good configuration language but sucks as a programming language. Wouldn't it make more sense to just use a real scripting language if you want this?
>
> I find it odd that you find this more important than adding support for Messages.
>
> Ralph
>
> On Mar 29, 2010, at 2:07 PM, Ceki Gülcü wrote:
>
>>
>> Just committed new code so that the following configuration file is
>> interpreted correctly.
>>
>> <configuration>
>>
>>   <appender name="FILE" class="ch.qos.logback.core.FileAppender">
>>     <file>${randomOutputDir}/conditional.log</file>
>>     <encoder>
>>       <pattern>%d %-5level %logger{35} - %msg %n</pattern>
>>    </encoder>
>>   </appender>
>>
>>   <root level="ERROR">
>>      <appender-ref ref="FILE" />
>>   </root>
>>
>>
>>   <if condition='property("HOSTNAME").contains("${aHost}")'>
>>     <then>
>>       <appender name="CON" class="ch.qos.logback.core.ConsoleAppender">
>>         <encoder>
>>           <pattern>%d %-5level %logger{35} - %msg %n</pattern>
>>         </encoder>
>>       </appender>
>>       <root>
>>         <appender-ref ref="CON" />
>>       </root>
>>     </then>
>>   </if>
>>
>> </configuration>
>>
>> where "aHost" is set to be the name of the current host. Note that
>> HOSTNAME always contains the name of the current host so that the
>> condition property("HOSTNAME").contains("${aHost}") evaluates to true.
>>
>> In my previous message, the config file get set the incremental
>> attribute of the root element to true. No such attribute
>> exists. Logger declaration in logback configuration files are
>> incremental by design. I mistakenly thought that it was like in log4j
>> where each logger declaration removes all attached appenders.
>>
>> I hope that you'll find the XML-conditional syntax not too
>> horrible. Your comments are welcome,
>>
>> --
>> Ceki
>>
>>
>> On 29/03/2010 9:50 PM, Ceki Gülcü wrote:
>>>
>>> Hello all,
>>>
>>> I began implementing if-then-else support in Joran. If you wish to
>>> enable part of a config file in one environment and disable it
>>> another, now you can.
>>>
>>> Here is an example,
>>>
>>> <configuration>
>>>
>>> <appender name="FILE" class="ch.qos.logback.core.FileAppender">
>>> <encoder>
>>> <pattern>%d %-5level %logger{35} - %msg %n</pattern>
>>> </encoder>
>>> </appender>
>>>
>>> <root level="DEBUG">
>>> <appender-ref ref="FILE" />
>>> </root>
>>>
>>>
>>> <if condition='property("HOSTNAME").contains("mydevHost")'>
>>> <then>
>>> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
>>> <encoder>
>>> <pattern>%d %-5level %logger{35} - %msg %n</pattern>
>>> </encoder>
>>> </appender>
>>> <root incremental="true">
>>> <appender-ref ref="STDOUT" />
>>> </root>
>>> </then>
>>> </if>
>>>
>>> </configuration>
>>>
>>> Thus, the ConsoleAppender will be attached to the root logger only on
>>> "mydevHost" but not on other hosts.
>>>
>>> This feature is still experimental. Your feedback is welcome.
>>>
>>> --
>>> Ceki
>>>