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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: OS-based dynamic configuration file
Date Mon, 19 Sep 2016 23:55:06 GMT
I am OK with ScriptAppenderSelector so I'll change it to that.

Gary

On Mon, Sep 19, 2016 at 3:23 PM, Ralph Goers <ralph.goers@dslextreme.com>
wrote:

> The 3 obvious choices: ScriptSelectorAppender, ScriptAppenderSelector, or
> AppenderScriptSelector. I actually prefer the second as it is an
> AppenderSelector that uses a Script (or rather, a Selector of an Appender
> that uses a Script). The first isn’t too bad as it is an Appender that is a
> ScriptSelector (or an Appender that acts as a Selector using a Script).
> The third choice is just terrible. I suppose with 3 words there are other
> choices as well but they probably suck too.
>
> Ralph
>
>
> On Sep 19, 2016, at 2:42 PM, Gary Gregory <garydgregory@gmail.com> wrote:
>
> ScriptSelectorAppender?
>
> On Sep 19, 2016 2:29 PM, "Ralph Goers" <ralph.goers@dslextreme.com> wrote:
>
>> Actually, I do have one minor issue. It will cause confusion calling it
>> ScriptSelector.  I am imagining the next step will be to create a
>> LayoutSelector that uses Scripts. I can also imagine a Selector for
>> AppenderRefs that uses Scripts. So calling it ScriptSelector is a bit
>> ambiguous, unless it is going to support creating any of these (which would
>> be hard since it extends AbstractAppender).
>>
>> Ralph
>>
>> On Sep 19, 2016, at 12:02 AM, Gary Gregory <garydgregory@gmail.com>
>> wrote:
>>
>> Great, thanks Ralph.
>>
>> Gary
>>
>> On Sun, Sep 18, 2016 at 11:14 PM, Ralph Goers <ralph.goers@dslextreme.com
>> > wrote:
>>
>>> Yup to both. I’ll look at it tomorrow.
>>>
>>> Ralph
>>>
>>> On Sep 18, 2016, at 10:31 PM, Gary Gregory <garydgregory@gmail.com>
>>> wrote:
>>>
>>> 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 <garydgregory@gmail.com>
>>> wrote:
>>>
>>>> Hm, but how? org.apache.logging.log4j.core.appender.AbstractAppender
>>>> .name
>>>> <http://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.goers@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 <garydgregory@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.goers@dslextreme.com> wrote:
>>>>>
>>>>>> See inline
>>>>>>
>>>>>> On Sep 16, 2016, at 10:31 PM, Gary Gregory <garydgregory@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>> On Fri, Sep 16, 2016 at 8:38 PM, Ralph Goers <ralph.goers@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: garydgregory@gmail.com | ggregory@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: garydgregory@gmail.com | ggregory@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: garydgregory@gmail.com | ggregory@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: garydgregory@gmail.com | ggregory@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: garydgregory@gmail.com | ggregory@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

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