Re: OS-based dynamic configuration file

[Gary Gregory]

Nevermind, I can just overwrite the name in the Node's attribute map...
that works. I'd like a code review before or after merging to master.

Gary

On Sun, Sep 18, 2016 at 9:43 PM, Gary Gregory <garydgreg...@gmail.com>
wrote:

> Hm, but how? org.apache.logging.log4j.core.appender.AbstractAppender.name
> is final and there is no Appender.setName(String). Surely, we should not
> use reflection...
>
> Gary
>
> On Sun, Sep 18, 2016 at 9:34 PM, Ralph Goers <ralph.go...@dslextreme.com>
> wrote:
>
>> I haven’t looked at your code but when you create the “real” appender you
>> need to change its name to match the name of the selector so that
>> AppenderRefs work.
>>
>> Ralph
>>
>> On Sep 18, 2016, at 9:24 PM, Gary Gregory <garydgreg...@gmail.com> wrote:
>>
>> I've implemented a first cut in the branch LOG4J2-1597 but I think I need
>> some help to connect the final dot (or two).
>>
>> When I run the new unit test org.apache.logging.log4j.core.
>> appender.ScriptSelectorAppenderTest, the status logger shows:
>>
>> 2016-09-18 21:19:09,393 main ERROR Unable to locate appender "SelectIt"
>> for logger config "root"
>> 2016-09-18 21:19:09,465 main ERROR Unable to locate appender "SelectIt"
>> for logger config "root"
>> 2016-09-18 21:19:09,485 main ERROR Unable to locate appender "SelectIt"
>> for logger config "root"
>> 2016-09-18 21:19:09,505 main ERROR Unable to locate appender "SelectIt"
>> for logger config "root"
>>
>> Which initially makes sense: the appender created and returned by the
>> builder of "SelectIt" is really an appender named "List2".
>>
>> I tried to add a hack in org.apache.logging.log4j.core.
>> appender.ScriptSelector.Builder.build() to no avail:
>>
>>             // This feels like a hack and it does not work:
>>             configuration.getAppenders().put(name, appender);
>>
>> Any thoughts?
>>
>> Gary
>>
>> On Sat, Sep 17, 2016 at 9:48 AM, Ralph Goers <ralph.go...@dslextreme.com>
>> wrote:
>>
>>> See inline
>>>
>>> On Sep 16, 2016, at 10:31 PM, Gary Gregory <garydgreg...@gmail.com>
>>> wrote:
>>>
>>> On Fri, Sep 16, 2016 at 8:38 PM, Ralph Goers <ralph.go...@dslextreme.com
>>> > wrote:
>>>
>>>> Gary,
>>>>
>>>> I have no problem with components that can be dumbed down to do simple
>>>> things. I do have a problem with components that only do simple things
>>>> because people will constantly asked to have them be enhanced.
>>>>
>>>> As for what you are proposing here, can I just say “No”?
>>>>
>>>
>>> Sure! :-) You can say whatever you want! :-)
>>>
>>>
>>>> Having the Appenders element deferred just smells to me and having an
>>>> arbitrary script there just seems weird to me. Does it even have a contract
>>>> or is it a free-for-all? How does it cause multiple appenders to be
>>>> initialized?
>>>>
>>>> I think the RoutingAppender is a more appropriate solution. However, if
>>>> you want to dumb it down a bit and turn it into an AppenderSelector I’d be
>>>> ok with that. However, it would still be fairly similar to the
>>>> RoutingAppender.
>>>>
>>>
>>> OK, so going back to one of your eariler messages:
>>>
>>> ==copy start==
>>>
>>> This sort of sounds like you want an Appender Selector, which would be
>>> an Appender that uses a Selector to figure out which Appender to delegate
>>> to. This is a bit like the PatternSelector. I would imagine it would make
>>> sense to implement AppenderSelectors and LayoutSelectors.  You probably
>>> would want to dynamically initialize the Appenders much like the
>>> RoutingAppender does.
>>>
>>> Maybe it would look like:
>>>
>>> <Appenders>
>>>   <ScriptSelector name=“" default=“”>
>>>      <Script language=“groovy”><![CDATA[
>>>          if (System.getProperty”os.name”).contains(“OS/390”)) then {
>>>              return “Socket”;
>>>          } else {
>>>              return “File”;
>>>          }
>>>      </Script>
>>>      <Appenders>
>>>          <SocketAppender name=“Socket” …/>
>>>          <FileAppender name=“File” …/>
>>>      </Appenders>
>>>   </ScriptSelector>
>>> </Appenders>
>>>
>>> The thing is that this script would run every time the Selector was
>>> accessed while it sounds like you would only want the script to run when
>>> the Selector is initialized. We could do that too but the script would need
>>> to be declared in a property that would only be used when the selector is
>>> initialized. I would want to support being able to do both.
>>>
>>> ==copy end==
>>>
>>> This is indeed like the RoutingAppender _except_ that the whole point is
>>> to do the script selection on start up. When you say that you'd want it
>>> both ways, on start up and on each log event; what would the configuration
>>> difference look like?
>>>
>>> But.. "Appender that uses a Selector to figure out which Appender to
>>> delegate to" ... that is _so_ much like a RoutingAppender as to be
>>> redundant, no?
>>>
>>>
>>> The difference is that a AppenderSelector can just implement the Builder
>>> or Factory and invoke the script at that time to figure out which Appender
>>> to create. It then returns that Appender. So while the AppenderSelector is
>>> technically an Appender, it really is just an AppenderBuilder.  The
>>> RoutingAppender is a real Appender.
>>>
>>>
>>> What I want is for the script to determine which appender to use (once),
>>> and instantiate that appender (once). There is no need for one appender to
>>> delegate to another appender.
>>>
>>>
>>> And that is what I just described.
>>>
>>>
>>> The more general case is for the script to determine which appenders
>>> (plural) to use (once), and instantiate those appenders (plural) (once).
>>> There is no need for one appender to delegate to another appender list. I
>>> do not have a use case for this today, but I do for the one appender case.
>>>
>>>
>>> An AppenderSelector could only instantiate a single Appender, not a
>>> group. If you wanted multiple appenders dynamically created this way you
>>> would using multiple selectors. I’m not sure I see that as a drawback.
>>>
>>>
>>>
>>> My goal would be explained to a user like this: "This feature helps you
>>> build your configuration dynamically, all from the configuration file, to
>>> determine which appender(s) to configure. This is different from using a
>>> RoutingAppender which creates a level of indirection and decides what to do
>>> for each log event _at runtime_" Yes, this is a simpler explanation than
>>> also explaining the new role of scripts in the RoutingAppender but you get
>>> the idea.
>>>
>>> I am open different solutions that meet the goal of building the
>>> configuration dynamically, as if you'd done it in XML explicitly (or JSON)
>>> but does not end up with one appender delegating to another.
>>>
>>> Thoughts?
>>>
>>> Gary
>>>
>>>
>>
>>
>> --
>> E-Mail: garydgreg...@gmail.com | ggreg...@apache.org
>> Java Persistence with Hibernate, Second Edition
>> <http://www.manning.com/bauer3/>
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>> Spring Batch in Action <http://www.manning.com/templier/>
>> Blog: http://garygregory.wordpress.com
>> Home: http://garygregory.com/
>> Tweet! http://twitter.com/GaryGregory
>>
>>
>>
>
>
> --
> E-Mail: garydgreg...@gmail.com | ggreg...@apache.org
> Java Persistence with Hibernate, Second Edition
> <http://www.manning.com/bauer3/>
> JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
> Spring Batch in Action <http://www.manning.com/templier/>
> Blog: http://garygregory.wordpress.com
> Home: http://garygregory.com/
> Tweet! http://twitter.com/GaryGregory
>



-- 
E-Mail: garydgreg...@gmail.com | ggreg...@apache.org
Java Persistence with Hibernate, Second Edition
<http://www.manning.com/bauer3/>
JUnit in Action, Second Edition <http://www.manning.com/tahchiev/>
Spring Batch in Action <http://www.manning.com/templier/>
Blog: http://garygregory.wordpress.com
Home: http://garygregory.com/
Tweet! http://twitter.com/GaryGregory