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From Gary Gregory <garydgreg...@gmail.com>
Subject Re: [jira] [Created] (LOG4J2-1375) Update SLF4J from 1.7.13 to 1.7.21
Date Sun, 24 Apr 2016 23:48:09 GMT
Please make sure you make a Javadoc about what we are not implementing and
why.

Gary
On Apr 23, 2016 11:07 PM, "Remko Popma" <remko.popma@gmail.com> wrote:

> Makes sense to me.
>
> So with the log4j 2.6 release we will compile with SLF4J 1.7.21 but DON'T
> implement the log(org.slf4j.event.LoggingEvent) method yet.
> I've already made this change in master, so if we all agree with the above
> there is no further work necessary for this.
>
> On Sun, Apr 24, 2016 at 2:20 PM, Ralph Goers <ralph.goers@dslextreme.com>
> wrote:
>
>> If we don’t do 3 then we run the risk of losing a few SLF4J events at
>> startup. However, that is the current situation. So given that, I am also
>> in favor of option 2, at least until some time passes and it is likely
>> anyone using SLF4J is using a more current version.
>>
>> Ralph
>>
>> On Apr 23, 2016, at 6:16 PM, Remko Popma <remko.popma@gmail.com> wrote:
>>
>> I agree with Ralph that implementing the new SLF4J method and Log4j
>> startup are separate topics.
>>
>> So let's focus on SLF4J. What are our options? These are the ones I see:
>> 1. We compile our log4j-slf4j-impl and log4j-to-slf4j modules with 1.7.13
>> 2. We compile our log4j-slf4j-impl and log4j-to-slf4j modules with 1.7.21
>> but DON'T implement the log(org.slf4j.event.LoggingEvent) method
>> 3. We compile our log4j-slf4j-impl and log4j-to-slf4j modules
>> with 1.7.21 and DO implement the log(org.slf4j.event.LoggingEvent) method
>>
>> If doing 3 means we break some applications I would favour 2.
>>
>>
>>
>>
>> On Sun, Apr 24, 2016 at 6:33 AM, Ralph Goers <ralph.goers@dslextreme.com>
>> wrote:
>>
>>> I would suggest others review the code in question, but here is what I
>>> see.
>>>
>>> LoggerFactory initializes dynamically. The first caller binds to the
>>> implementation of the LoggerFactory by calling
>>> StaticLoggerBinder.getSingleton(), but only if it is the first caller.
>>> Other callers are given a substitute logger factory until the binding is
>>> complete. Log4j’s implementation creates a Log4jLoggerFactory instance but
>>> performs no initialization at this time, so the amount of time that SLF4J
>>> would be in this state should be very small. Regardless, events could still
>>> be routed to the substitute logger. If we want to ensure that these events
>>> are not discarded then we have to implement the new method.
>>>
>>> Note that due to the way Log4j initializes we don’t have this kind of
>>> race going on anywhere. Ceki seems to imply that the race is in the
>>> underlying logging framework, but it is not. Or perhaps he is just assuming
>>> that all log events are coming through SLF4J, which may or may not actually
>>> be the case.  The race is entirely within SLF4J’s initialization logic.
>>> Anyone using just the Log4j API will not have this problem.
>>>
>>> As I said previously, A Log4j LoggerContext always has a configuration,
>>> at least until it is shut down, and logging an event requires a constructed
>>> LoggerContext. A LoggerContext has a default configuration until the actual
>>> configuration file is processed and the full configuration constructed. The
>>> default configuration logs errors to the console. So any log events that
>>> actually make it to Log4j will have something done with them, but maybe not
>>> what the user wants.  If we wanted to have any events that occur before
>>> configuration is completed subject to that configuration the default
>>> configuration would have to capture them and then republish the events when
>>> the configuration is stopped, which is similar in concept to what SLF4J is
>>> doing. But we can’t rely on SLF4J’s substitute loggers for this as SLF4J
>>> may not even be in the picture.
>>>
>>> So as I see it, the discussion on whether to implement the support for
>>> the new SLF4J method is completely separate from enhancing support of Log4j
>>> logging during startup.
>>>
>>> Ralph
>>>
>>>
>>>
>>>
>>> On Apr 23, 2016, at 11:16 AM, Ceki Gulcu <ceki@qos.ch> wrote:
>>>
>>>
>>> SLF4J will replay the events it captured during the initialization of
>>> the underlying logging framework, log4j2 in this case, assuming log4j2
>>> supports SLF4J replay via the Logger.log(o.s.event.LoggingEvent) method.
>>>
>>> What Raplh seems to suggest is to duplicate the SLF4J replay
>>> functionality within log4j2. However, given that SLF4J captures events
>>> generated during initialization, log4j2 cannot see them unless it supports
>>> SLF4J replay. For logging frameworks without replay support, i.e. those
>>> which lack the Logger.log(o.s.event.LoggingEvent) method, slf4j will simply
>>> drop the events it captured. Note that log4j1, logback prior to 1.1.4, and
>>> slf4j-jul and slf4j-simple prior to version 1.7.15 all lacked replay
>>> support but continue to work just fine under slf4j-api 1.7.15+.
>>>
>>> Also note that if N is the version of slf4j-api and M is the slf4j-api
>>> version with which a binding is compiled, then slf4j ensures binary
>>> compatibility for all N and M in the 1.6.x and the 1.7.x series. For
>>> example, the slf4j-api-1.6.0.jar/slf4j-simple-1.7.21.jar combination will
>>> work just fine, same goes for the
>>> slf4j-simple-1.7.21.jar/slf4j-api-1.6.0.jar combination.
>>>
>>> Compatibility is broken when the binding voluntarily supports event
>>> replay, as was the case with logback versions 1.1.4+ which require SLF4J
>>> version 1.7.15+. The question is whether log4j2 wants to support event
>>> replay at the cost of dropping compatibility with earlier versions of
>>> slf4j-api.
>>>
>>> I hope this further clarifies the matter,
>>>
>>> --
>>> Ceki
>>>
>>>
>>>
>>> On 4/23/2016 19:00, Ralph Goers wrote:
>>>
>>> I suppose that depends on the definition of “event loss”.  You can’t log
>>> without a LoggerContext and the LoggerContext is initialized with a
>>> default configuration, which means errors will be logged to the console.
>>> We could create a default configuration that buffers the events and logs
>>> then again when stop is called.
>>>
>>> Ralph
>>>
>>> On Apr 23, 2016, at 7:18 AM, Ceki Gulcu <ceki@qos.ch
>>> <mailto:ceki@qos.ch <ceki@qos.ch>>> wrote:
>>>
>>> You are welcome.
>>>
>>> In the principle, the  event loss issue (fixed by event replay
>>> post-initialization) depends on the time it takes for the underlying
>>> implementation to initialize. Unless you can guarantee that log4j2
>>> initializes instantly**, during SLF4J initialization event loss will
>>> occur with log4j2 as well. Note the event loss issue is limited to
>>> applications using slf4j which are multi-threaded early on.
>>>
>>> > Would you mind sharing which applications perform reflection on
>>> > the org.slf4j.Logger implementation (and why)?
>>>
>>> The typical example is Spring which may do reflection on logger
>>> instances. If the org.slg4j.Logger implementation offers the
>>> log(org.slf4j.event.LoggingEvent) method, then the
>>> org.slf4j.event.LoggingEvent interface must exist on the class path.
>>> Otherwise, the Spring initialization will fail. The
>>> org.slf4j.event.LoggingEvent interface was introduced in slf4j-api
>>> version 1.7.15. It follows that if you decide to make use of the slf4j
>>> replay feature, then log42 will de facto depend on slf4j version
>>> 1.7.15 both at compile and runtime.
>>>
>>> --
>>> Ceki
>>>
>>> **I am presuming here that log4j2 initializes when it creates and
>>> returns its first Logger.
>>>
>>> On 4/23/2016 15:54, Remko Popma wrote:
>>>
>>> ...and thank you for the info, Ceki, that is certainly helpful!
>>>
>>> Remko
>>>
>>> On Saturday, 23 April 2016, Remko Popma <remko.popma@gmail.com
>>> <mailto:remko.popma@gmail.com <remko.popma@gmail.com>>
>>> <mailto:remko.popma@gmail.com <remko.popma@gmail.com>>> wrote:
>>>
>>>   Question: does the replay support solve a problem in SLF4J or in
>>>   Logback initialization?
>>>
>>>   If the latter, then perhaps there's no need to implement the new
>>>   method since log4j-slf4j-impl binds to log4j2 anyway, no?
>>>
>>>   Remko
>>>
>>>   Sent from my iPhone
>>>
>>>    > On 2016/04/23, at 22:12, Ceki Gulcu <ceki@qos.ch
>>> <mailto:ceki@qos.ch <ceki@qos.ch>> <javascript:;>>
>>>   wrote:
>>>    >
>>>    > Hello,
>>>    >
>>>    > For your information, slf4j-api version 1.7.21 will work with
>>>   current versions of log4j2 just fine albeit without replay support.
>>>   For replay support, log4j2's implementation of org.slf4j.Logger
>>>   interface needs to have a method with the signature
>>>   log(org.slf4j.event.LoggingEvent) in which case events generated
>>>   during SLF4J initialization will be replayed. Note that if log4j2's
>>>   Logger implementation chooses to implement the aforementioned log
>>>   method, log42 will de facto depend on SLF4J version 1.7.15 and later
>>>   both at compile and *runtime*.
>>>    >
>>>    > The runtime dependency might seem surprising but some
>>>   applications perform reflection on the org.slf4j.Logger
>>>   implementation which will fail without slf4j-api 1.7.15 or later
>>>   being present on the classpath.
>>>    >
>>>    > I hope this helps,
>>>    >
>>>    > --
>>>    > Ceki
>>>    >
>>>    >> On 4/23/2016 14:47, Ralph Goers wrote:
>>>    >> We are not fully compatible with this version of SLF4J.  It
>>> had some
>>>    >> initialization race conditions so Substitute Loggers were
>>> invented.
>>>    >> Anyway, there is a new interface we need to implement.
>>>    >>
>>>    >> Ralph
>>>    >>
>>>    >> Begin forwarded message:
>>>    >>
>>>    >>> *From:* "Remko Popma (JIRA)" <jira@apache.org
>>> <mailto:jira@apache.org <jira@apache.org>><javascript:;>
>>>   <mailto:jira@apache.org <jira@apache.org><javascript:;>>>
>>>    >>> *Date:* April 23, 2016 at 4:13:12 AM MST
>>>    >>> *To:*log4j-dev@logging.apache.org
>>> <mailto:log4j-dev@logging.apache.org <log4j-dev@logging.apache.org>
>>> ><javascript:;>
>>>   <mailto:log4j-dev@logging.apache.org <log4j-dev@logging.apache.org>
>>> <javascript:;>>
>>>    >>> *Subject:* *[jira] [Closed] (LOG4J2-1375) Update SLF4J from
>>>   1.7.13 to
>>>    >>> 1.7.21*
>>>    >>> *Reply-To:* "Log4J Developers List"
>>>   <log4j-dev@logging.apache.org
>>> <mailto:log4j-dev@logging.apache.org <log4j-dev@logging.apache.org>
>>> ><javascript:;>
>>>    >>> <mailto:log4j-dev@logging.apache.org
>>> <log4j-dev@logging.apache.org><javascript:;>>>
>>>    >>>
>>>    >>>
>>>    >>>    [
>>>    >>>
>>>
>>> https://issues.apache.org/jira/browse/LOG4J2-1375?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
>>>    >>> ]
>>>    >>>
>>>    >>> Remko Popma closed LOG4J2-1375.
>>>    >>> -------------------------------
>>>    >>>   Resolution: Fixed
>>>    >>>
>>>    >>>> Update SLF4J from 1.7.13 to 1.7.21
>>>    >>>> ----------------------------------
>>>    >>>>
>>>    >>>>               Key: LOG4J2-1375
>>>    >>>>               URL:
>>> https://issues.apache.org/jira/browse/LOG4J2-1375
>>>    >>>>           Project: Log4j 2
>>>    >>>>        Issue Type: Improvement
>>>    >>>>        Components: SLF4J Bridge
>>>    >>>>  Affects Versions: 2.5
>>>    >>>>          Reporter: Remko Popma
>>>    >>>>          Assignee: Remko Popma
>>>    >>>>           Fix For: 2.6
>>>    >>>>
>>>    >>>>
>>>    >>>> Update SLF4J from 1.7.13 to 1.7.21
>>>    >>>
>>>    >>>
>>>    >>>
>>>    >>> --
>>>    >>> This message was sent by Atlassian JIRA
>>>    >>> (v6.3.4#6332)
>>>    >>>
>>>    >>>
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