Re: HC 5.0 scope and design decisions

[Julian Sedding <js...@gmail.com>]

Thank you for these insights, Gary!

So Log4j2 seems fine to me. It is more capable that slf4j, as you say,
yet its API can be used on top of an SLF4j implementation. That ticks
all boxes for me ;)

Regards
Julian


On Fri, Sep 30, 2016 at 11:50 PM, Gary Gregory <ga...@gmail.com> wrote:
> On Fri, Sep 30, 2016 at 1:15 AM, Julian Sedding <js...@apache.org> wrote:
>
>> Hi all
>>
>> I am not familiar with log4j2, but have used slf4j extensively over
>> the last years.
>>
>> As I understand log4j2 clearly separates its API from the
>> implementation. If this is true, are there any major benefits to using
>> the log4j2 API over the slf4j API?
>>
>> If this is not the case, and the benefits of log4j2 are predominantly
>> in the implementation, then it may be sensible to code against the
>> slf4j API and leave the choice of the implementation to the
>> deployment. I.e. it would be possible to use log4j2 as the logging
>> implementation via its slf4j binding[0].
>>
>
> From the Log4j 2 FAQ [
> https://logging.apache.org/log4j/2.x/faq.html#api-tradeoffs]:
>
> The Log4j 2 API and SLF4J have a lot in common. They both share the
> objective of cleanly separating the logging API from the implementation. We
> believe that the Log4j 2 API can help make your application more performant
> while offering more functionality and more flexibility.
>
> There may be a concern that using the Log4j 2 API will tightly couple your
> application to Log4j 2. This is not the case: applications coded to the
> Log4j 2 API always have the option to use any SLF4J-compliant library as
> their logging implementation with the log4j-to-slf4j adapter. See the which
> jars
> <https://logging.apache.org/log4j/2.x/faq.html#which_jars_log4j-to-slf4j> FAQ
> entry for details.
>
> There are several advantages to using the Log4j 2 API:
>
>    - SLF4J forces your application to log Strings. The Log4j 2 API supports
>    logging any CharSequence if you want to log text, but also supports logging
>    any Object as is. It is the responsibility of the logging
>    *implementation* to handle this object, and we consider it a design
>    mistake to limit applications to logging Strings.
>    - The Log4j 2 API offers support for logging Message objects
>    <https://logging.apache.org/log4j/2.x/manual/messages.html>. Messages
>    allow support for interesting and complex constructs to be passed through
>    the logging system and be efficiently manipulated. Users are free to create
>    their own Message types and write custom Layouts, Filters and Lookups to
>    manipulate them.
>    - The Log4j 2 API has support for Java 8 lambda expressions
>    <https://logging.apache.org/log4j/2.x/manual/api.html#LambdaSupport>.
>    - The Log4j 2 API has better support for garbage-free logging
>    <https://logging.apache.org/log4j/2.x/manual/garbagefree.html>: it
>    avoids creating vararg arrays and avoids creating Strings when logging
>    CharSequence objects.
>
> I'm not interested in porting the the HC code from ACL to Slf4j, but I'll
> do the port to Log4j2 ;-)
>
> Gary
>
>>
>> I am sure others, especially Gary, can provide more qualified opinions
>> here.
>>
>> Regards
>> Julian
>>
>> [0] https://logging.apache.org/log4j/2.0/log4j-slf4j-impl/index.html
>>
>>
>> On Thu, Sep 29, 2016 at 10:00 PM, Oleg Kalnichevski <ol...@apache.org>
>> wrote:
>> > On Thu, 2016-09-29 at 09:27 +0530, Asankha C. Perera wrote:
>> >> Hi Oleg
>> >
>> > ...
>> >
>> >> > Should be remain faithful to Commons Logging or shall we finally
>> migrate
>> >> > to SLF4J?
>> >> I agree with Gary that Log4J2 is better than SLF4J too. Since we also
>> >> have Gary's experience and support to move to it, I think that maybe the
>> >> best option.
>> >>
>> >> regards
>> >> asankha
>> >>
>> >
>> > Gary, Asankha
>> >
>> > Being a happy user of Log4J2 myself I would be very much in favor of
>> > using it directly. However we ought not impose a particular choice of
>> > the logging toolkit upon all our users. We should be using a logging
>> > bridge. This essentially leaves with two options: Commons Logging or
>> > SLF4J, both of which can use different backends including Log4J2.
>> >
>> > Oleg
>> >
>> >
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>
>
> --
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