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 <[email protected]> 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 <[email protected] > <mailto:[email protected]>> 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 <[email protected] <mailto:[email protected]>> >> 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 <[email protected] <mailto:[email protected]> >>>> <mailto:[email protected] <mailto:[email protected]>>> 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 <[email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] <mailto:[email protected]>> >>>>> <mailto:[email protected] <mailto:[email protected]>>> 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 <[email protected] <mailto:[email protected]> >>>>> <mailto:[email protected] <mailto:[email protected]>> <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)" <[email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] <mailto:[email protected]>><javascript:;> >>>>> <mailto:[email protected] <mailto:[email protected]><javascript:;>>> >>>>> >>> *Date:* April 23, 2016 at 4:13:12 AM MST >>>>> >>> *To:*[email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>><javascript:;> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]><javascript:;>> >>>>> >>> *Subject:* *[jira] [Closed] (LOG4J2-1375) Update SLF4J from >>>>> 1.7.13 to >>>>> >>> 1.7.21* >>>>> >>> *Reply-To:* "Log4J Developers List" >>>>> <[email protected] <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>><javascript:;> >>>>> >>> <mailto:[email protected] >>>>> <mailto:[email protected]><javascript:;>>> >>>>> >>> >>>>> >>> >>>>> >>> [ >>>>> >>> >>>>> https://issues.apache.org/jira/browse/LOG4J2-1375?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel >>>>> >>>>> <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 >>>>> <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) >>>>> >>> >>>>> >>> >>>>> --------------------------------------------------------------------- >>>>> >>> To unsubscribe, e-mail: >>>>> [email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>><javascript:;> >>>>> >>> <mailto:[email protected] >>>>> <mailto:[email protected]><javascript:;>> >>>>> >>> For additional commands, e-mail: >>>>> [email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>><javascript:;> >>>>> >>> <mailto:[email protected] >>>>> <mailto:[email protected]><javascript:;>> >>>>> > >>>>> > >>>>> --------------------------------------------------------------------- >>>>> > To unsubscribe, e-mail:[email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>> >>>>> <javascript:;> >>>>> > For additional commands, e-mail: >>>>> [email protected] >>>>> <mailto:[email protected]> >>>>> <mailto:[email protected] >>>>> <mailto:[email protected]>><javascript:;> >>>>> > >>>>> >>>> >>>> --------------------------------------------------------------------- >>>> To unsubscribe, e-mail:[email protected] >>>> <mailto:[email protected]> >>>> <mailto:[email protected] >>>> <mailto:[email protected]>> >>>> For additional commands, e-mail:[email protected] >>>> <mailto:[email protected]> >>>> <mailto:[email protected] >>>> <mailto:[email protected]>> >>> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: [email protected] >> <mailto:[email protected]> >> For additional commands, e-mail: [email protected] >> <mailto:[email protected]> >
