Hi, Patrick -- I gave that a go locally, and it works as desired.
Best. -- Paul — p...@mult.ifario.us | Multifarious, Inc. | http://mult.ifario.us/ On Fri, Feb 7, 2014 at 6:10 PM, Patrick Wendell <pwend...@gmail.com> wrote: > Ah okay sounds good. This is what I meant earlier by "You have > some other application that directly calls log4j."... i.e. you have > for historical reasons installed the log4j-over-slf4j. > > Would you mind trying out this fix and seeing if it works? This is > designed to be a hotfix for 0.9, not a general solution where we rip > out log4j from our published dependencies: > > https://github.com/apache/incubator-spark/pull/560/files > > - Patrick > > On Fri, Feb 7, 2014 at 5:57 PM, Paul Brown <p...@mult.ifario.us> wrote: > > Hi, Patrick -- > > > > I forget which other component is responsible, but we're using the > > log4j-over-slf4j as part of an overall requirement to centralize logging, > > i.e., *someone* else is logging over log4j and we're pulling that in. > > (There's also some jul logging from Jersey, etc.) > > > > Goals: > > > > - Fully control/capture all possible logging. (God forbid we have to > grab > > System.out/err, but we'd do it if needed.) > > - Use the backend we like best at the moment. (Happens to be logback.) > > > > Possible cases: > > > > - If Spark used Log4j at all, we would pull in that logging via > > log4j-over-slf4j. > > - If Spark used only slf4j and referenced no backend, we would use it > as-is > > although we'd still have the log4j-over-slf4j because of other libraries. > > - If Spark used only slf4j and referenced the slf4j-log4j12 backend, we > > would exclude that one dependency (via our POM). > > > > Best. > > -- Paul > > > > > > -- > > p...@mult.ifario.us | Multifarious, Inc. | http://mult.ifario.us/ > > > > > > On Fri, Feb 7, 2014 at 5:38 PM, Patrick Wendell <pwend...@gmail.com> > wrote: > > > >> Hey Paul, > >> > >> So if your goal is ultimately to output to logback. Then why don't you > >> just use slf4j and logback-classic.jar as described here [1]. Why > >> involve log4j-over-slf4j at all? > >> > >> Let's say we refactored the spark build so it didn't advertise > >> slf4j-log4j12 as a dependency. Would you still be using > >> log4j-over-slf4j... or is this just a "fix" to deal with the fact that > >> Spark is somewhat log4j dependent at this point. > >> > >> [1] http://www.slf4j.org/manual.html > >> > >> - Patrick > >> > >> On Fri, Feb 7, 2014 at 5:14 PM, Paul Brown <p...@mult.ifario.us> wrote: > >> > Hi, Patrick -- > >> > > >> > That's close but not quite it. > >> > > >> > The issue that occurs is not the delegation loop mentioned in slf4j > >> > documentation. The stack overflow is entirely within the code in the > >> Spark > >> > trait: > >> > > >> > at org.apache.spark.Logging$class.initializeLogging(Logging.scala:112) > >> > at > org.apache.spark.Logging$class.initializeIfNecessary(Logging.scala:97) > >> > at org.apache.spark.Logging$class.log(Logging.scala:36) > >> > at org.apache.spark.SparkEnv$.log(SparkEnv.scala:94) > >> > > >> > > >> > And then that repeats. > >> > > >> > As for our situation, we exclude the slf4j-log4j12 dependency when we > >> > import the Spark library (because we don't want to use log4j) and have > >> > log4j-over-slf4j already in place to ensure that all of the logging in > >> the > >> > overall application runs through slf4j and then out through logback. > (We > >> > also, as another poster already mentioned, also force jcl and jul > through > >> > slf4j.) > >> > > >> > The zen of slf4j for libraries is that the library uses the slf4j API > and > >> > then the enclosing application can route logging as it sees fit. > Spark > >> > master CLI would log via slf4j and include the slf4j-log4j12 backend; > >> same > >> > for Spark worker CLI. Spark as a library (versus as a container) > would > >> not > >> > include any backend to the slf4j API and leave this up to the > >> application. > >> > (FWIW, this would also avoid your log4j warning message.) > >> > > >> > But as I was saying before, I'd be happy with a situation where I can > >> avoid > >> > log4j being enabled or configured, and I think you'll find an existing > >> > choice of logging framework to be a common scenario for those > embedding > >> > Spark in other systems. > >> > > >> > Best. > >> > -- Paul > >> > > >> > -- > >> > p...@mult.ifario.us | Multifarious, Inc. | http://mult.ifario.us/ > >> > > >> > > >> > On Fri, Feb 7, 2014 at 3:01 PM, Patrick Wendell <pwend...@gmail.com> > >> wrote: > >> > > >> >> Paul, > >> >> > >> >> Looking back at your problem. I think it's the one here: > >> >> http://www.slf4j.org/codes.html#log4jDelegationLoop > >> >> > >> >> So let me just be clear what you are doing so I understand. You have > >> >> some other application that directly calls log4j. So you have to > >> >> include log4j-over-slf4j to route those logs through slf4j to > logback. > >> >> > >> >> At the same time you embed Spark in this application. In the past it > >> >> was fine, but now that Spark programmatic ally initializes log4j, it > >> >> screws up your application because log4j-over-slf4j doesn't work with > >> >> applications that do this explicilty as discussed here: > >> >> http://www.slf4j.org/legacy.html > >> >> > >> >> Correct? > >> >> > >> >> - Patrick > >> >> > >> >> On Fri, Feb 7, 2014 at 2:02 PM, Koert Kuipers <ko...@tresata.com> > >> wrote: > >> >> > got it. that sounds reasonable > >> >> > > >> >> > > >> >> > On Fri, Feb 7, 2014 at 2:31 PM, Patrick Wendell < > pwend...@gmail.com> > >> >> wrote: > >> >> > > >> >> >> Koert - my suggestion was this. We let users use any slf4j backend > >> >> >> they want. If we detect that they are using the log4j backend and > >> >> >> *also* they didn't configure any log4j appenders, we set up some > nice > >> >> >> defaults for them. If they are using another backend, Spark > doesn't > >> >> >> try to modify the configuration at all. > >> >> >> > >> >> >> On Fri, Feb 7, 2014 at 11:14 AM, Koert Kuipers <ko...@tresata.com > > > >> >> wrote: > >> >> >> > well "static binding" is probably the wrong terminology but you > get > >> >> the > >> >> >> > idea. multiple backends are not allowed and cause an even uglier > >> >> >> warning... > >> >> >> > > >> >> >> > see also here: > >> >> >> > https://github.com/twitter/scalding/pull/636 > >> >> >> > and here: > >> >> >> > > https://groups.google.com/forum/#!topic/cascading-user/vYvnnN_15ls > >> >> >> > all me being annoying and complaining about slf4j-log4j12 > >> dependencies > >> >> >> > (which did get removed). > >> >> >> > > >> >> >> > > >> >> >> > On Fri, Feb 7, 2014 at 2:09 PM, Koert Kuipers < > ko...@tresata.com> > >> >> wrote: > >> >> >> > > >> >> >> >> the issue is that slf4j uses static binding. you can put only > one > >> >> slf4j > >> >> >> >> backend on the classpath, and that's what it uses. more than > one > >> is > >> >> not > >> >> >> >> allowed. > >> >> >> >> > >> >> >> >> so you either keep the slf4j-log4j12 dependency for spark, and > >> then > >> >> you > >> >> >> >> took away people's choice of slf4j backend which is considered > bad > >> >> form > >> >> >> for > >> >> >> >> a library, or you do not include it and then people will always > >> get > >> >> the > >> >> >> big > >> >> >> >> fat ugly warning and slf4j logging will not flow to log4j. > >> >> >> >> > >> >> >> >> including log4j itself is not necessary a problem i think? > >> >> >> >> > >> >> >> >> > >> >> >> >> On Fri, Feb 7, 2014 at 1:11 PM, Patrick Wendell < > >> pwend...@gmail.com > >> >> >> >wrote: > >> >> >> >> > >> >> >> >>> This also seems relevant - but not my area of expertise > (whether > >> >> this > >> >> >> >>> is a valid way to check this). > >> >> >> >>> > >> >> >> >>> > >> >> >> >>> > >> >> >> > >> >> > >> > http://stackoverflow.com/questions/10505418/how-to-find-which-library-slf4j-has-bound-itself-to > >> >> >> >>> > >> >> >> >>> On Fri, Feb 7, 2014 at 10:08 AM, Patrick Wendell < > >> >> pwend...@gmail.com> > >> >> >> >>> wrote: > >> >> >> >>> > Hey Guys, > >> >> >> >>> > > >> >> >> >>> > Thanks for explainning. Ya this is a problem - we didn't > really > >> >> know > >> >> >> >>> > that people are using other slf4j backends, slf4j is in > there > >> for > >> >> >> >>> > historical reasons but I think we may assume in a few places > >> that > >> >> >> >>> > log4j is being used and we should minimize those. > >> >> >> >>> > > >> >> >> >>> > We should patch this and get a fix into 0.9.1. So some > >> solutions I > >> >> >> see > >> >> >> >>> are: > >> >> >> >>> > > >> >> >> >>> > (a) Add SparkConf option to disable this. I'm fine with this > >> one. > >> >> >> >>> > > >> >> >> >>> > (b) Ask slf4j which backend is active and only try to > enforce > >> this > >> >> >> >>> > default if we know slf4j is using log4j. Do either of you > know > >> if > >> >> >> this > >> >> >> >>> > is possible? Not sure if slf4j exposes this. > >> >> >> >>> > > >> >> >> >>> > (c) Just remove this default stuff. We'd rather not do this. > >> The > >> >> goal > >> >> >> >>> > of this thing is to provide good usability for people who > have > >> >> linked > >> >> >> >>> > against Spark and haven't done anything to configure > logging. > >> For > >> >> >> >>> > beginners we try to minimize the assumptions about what else > >> they > >> >> >> know > >> >> >> >>> > about, and I've found log4j configuration is a huge mental > >> barrier > >> >> >> for > >> >> >> >>> > people who are getting started. > >> >> >> >>> > > >> >> >> >>> > Paul if you submit a patch doing (a) we can merge it in. If > you > >> >> have > >> >> >> >>> > any idea if (b) is possible I prefer that one, but it may > not > >> be > >> >> >> >>> > possible or might be brittle. > >> >> >> >>> > > >> >> >> >>> > - Patrick > >> >> >> >>> > > >> >> >> >>> > On Fri, Feb 7, 2014 at 6:36 AM, Koert Kuipers < > >> ko...@tresata.com> > >> >> >> >>> wrote: > >> >> >> >>> >> Totally agree with Paul: a library should not pick the > slf4j > >> >> >> backend. > >> >> >> >>> It > >> >> >> >>> >> defeats the purpose of slf4j. That big ugly warning is > there > >> to > >> >> >> alert > >> >> >> >>> >> people that its their responsibility to pick the back > end... > >> >> >> >>> >> On Feb 7, 2014 3:55 AM, "Paul Brown" <p...@mult.ifario.us> > >> wrote: > >> >> >> >>> >> > >> >> >> >>> >>> Hi, Patrick -- > >> >> >> >>> >>> > >> >> >> >>> >>> From slf4j, you can either backend it into log4j (which is > >> the > >> >> way > >> >> >> >>> that > >> >> >> >>> >>> Spark is shipped) or you can route log4j through slf4j and > >> then > >> >> on > >> >> >> to > >> >> >> >>> a > >> >> >> >>> >>> different backend (e.g., logback). We're doing the latter > >> and > >> >> >> >>> manipulating > >> >> >> >>> >>> the dependencies in the build because that's the way the > >> >> enclosing > >> >> >> >>> >>> application is set up. > >> >> >> >>> >>> > >> >> >> >>> >>> The issue with the current situation is that there's no > way > >> for > >> >> an > >> >> >> >>> end user > >> >> >> >>> >>> to choose to *not* use the log4j backend. (My short-term > >> >> solution > >> >> >> >>> was to > >> >> >> >>> >>> use the Maven shade plugin to swap in a version of the > >> Logging > >> >> >> trait > >> >> >> >>> with > >> >> >> >>> >>> the body of that method commented out.) In addition to > the > >> >> >> situation > >> >> >> >>> with > >> >> >> >>> >>> log4j-over-slf4j and the empty enumeration of ROOT > appenders, > >> >> you > >> >> >> >>> might > >> >> >> >>> >>> also run afoul of someone who intentionally configured > log4j > >> >> with > >> >> >> an > >> >> >> >>> empty > >> >> >> >>> >>> set of appenders at the time that Spark is initializing. > >> >> >> >>> >>> > >> >> >> >>> >>> I'd be happy with any implementation that lets me choose > my > >> >> logging > >> >> >> >>> >>> backend: override default behavior via system property, > >> plug-in > >> >> >> >>> >>> architecture, etc. I do think it's reasonable to expect > >> someone > >> >> >> >>> digesting > >> >> >> >>> >>> a substantial JDK-based system like Spark to understand > how > >> to > >> >> >> >>> initialize > >> >> >> >>> >>> logging -- surely they're using logging of some kind > >> elsewhere > >> >> in > >> >> >> >>> their > >> >> >> >>> >>> application -- but if you want the default behavior there > as > >> a > >> >> >> >>> courtesy, it > >> >> >> >>> >>> might be worth putting an INFO (versus a the glaring log4j > >> WARN) > >> >> >> >>> message on > >> >> >> >>> >>> the output that says something like "Initialized default > >> logging > >> >> >> via > >> >> >> >>> Log4J; > >> >> >> >>> >>> pass -Dspark.logging.loadDefaultLogger=false to disable > this > >> >> >> >>> behavior." so > >> >> >> >>> >>> that it's both convenient and explicit. > >> >> >> >>> >>> > >> >> >> >>> >>> Cheers. > >> >> >> >>> >>> -- Paul > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> -- > >> >> >> >>> >>> p...@mult.ifario.us | Multifarious, Inc. | > >> >> http://mult.ifario.us/ > >> >> >> >>> >>> > >> >> >> >>> >>> > >> >> >> >>> >>> On Fri, Feb 7, 2014 at 12:05 AM, Patrick Wendell < > >> >> >> pwend...@gmail.com> > >> >> >> >>> >>> wrote: > >> >> >> >>> >>> > >> >> >> >>> >>> > A config option e.g. could just be to add: > >> >> >> >>> >>> > > >> >> >> >>> >>> > spark.logging.loadDefaultLogger (default true) > >> >> >> >>> >>> > If set to true, Spark will try to initialize a log4j > >> logger if > >> >> >> none > >> >> >> >>> is > >> >> >> >>> >>> > detected. Otherwise Spark will not modify logging > behavior. > >> >> >> >>> >>> > > >> >> >> >>> >>> > Then users could just set this to false if they have a > >> logging > >> >> >> >>> set-up > >> >> >> >>> >>> > that conflicts with this. > >> >> >> >>> >>> > > >> >> >> >>> >>> > Maybe there is a nicer fix... > >> >> >> >>> >>> > > >> >> >> >>> >>> > On Fri, Feb 7, 2014 at 12:03 AM, Patrick Wendell < > >> >> >> >>> pwend...@gmail.com> > >> >> >> >>> >>> > wrote: > >> >> >> >>> >>> > > Hey Paul, > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > Thanks for digging this up. I worked on this feature > and > >> the > >> >> >> >>> intent > >> >> >> >>> >>> > > was to give users good default behavior if they didn't > >> >> include > >> >> >> any > >> >> >> >>> >>> > > logging configuration on the classpath. > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > The problem with assuming that CL tooling is going to > fix > >> >> the > >> >> >> job > >> >> >> >>> is > >> >> >> >>> >>> > > that many people link against spark as a library and > run > >> >> their > >> >> >> >>> >>> > > application using their own scripts. In this case the > >> first > >> >> >> thing > >> >> >> >>> >>> > > people see when they run an application that links > >> against > >> >> >> Spark > >> >> >> >>> was a > >> >> >> >>> >>> > > big ugly logging warning. > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > I'm not super familiar with log4j-over-slf4j, but this > >> >> >> behavior of > >> >> >> >>> >>> > > returning null for the appenders seems a little weird. > >> What > >> >> is > >> >> >> >>> the use > >> >> >> >>> >>> > > case for using this and not just directly use > >> slf4j-log4j12 > >> >> >> like > >> >> >> >>> Spark > >> >> >> >>> >>> > > itself does? > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > Did you have a more general fix for this in mind? Or > was > >> >> your > >> >> >> >>> plan to > >> >> >> >>> >>> > > just revert the existing behavior... We might be able > to > >> >> add a > >> >> >> >>> >>> > > configuration option to disable this logging default > >> stuff. > >> >> Or > >> >> >> we > >> >> >> >>> >>> > > could just rip it out - but I'd like to avoid that if > >> >> possible. > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > - Patrick > >> >> >> >>> >>> > > > >> >> >> >>> >>> > > On Thu, Feb 6, 2014 at 11:41 PM, Paul Brown < > >> >> >> p...@mult.ifario.us> > >> >> >> >>> >>> wrote: > >> >> >> >>> >>> > >> We have a few applications that embed Spark, and in > >> 0.8.0 > >> >> and > >> >> >> >>> 0.8.1, > >> >> >> >>> >>> we > >> >> >> >>> >>> > >> were able to use slf4j, but 0.9.0 broke that and > >> >> >> unintentionally > >> >> >> >>> >>> forces > >> >> >> >>> >>> > >> direct use of log4j as the logging backend. > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> The issue is here in the org.apache.spark.Logging > trait: > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > > >> >> >> >>> >>> > >> >> >> >>> > >> >> >> > >> >> > >> > https://github.com/apache/incubator-spark/blame/master/core/src/main/scala/org/apache/spark/Logging.scala#L107 > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> log4j-over-slf4j *always* returns an empty > enumeration > >> for > >> >> >> >>> appenders > >> >> >> >>> >>> to > >> >> >> >>> >>> > the > >> >> >> >>> >>> > >> ROOT logger: > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > > >> >> >> >>> >>> > >> >> >> >>> > >> >> >> > >> >> > >> > https://github.com/qos-ch/slf4j/blob/master/log4j-over-slf4j/src/main/java/org/apache/log4j/Category.java?source=c#L81 > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> And this causes an infinite loop and an eventual > stack > >> >> >> overflow. > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> I'm happy to submit a Jira and a patch, but it would > be > >> >> >> >>> significant > >> >> >> >>> >>> > enough > >> >> >> >>> >>> > >> reversal of recent changes that it's probably worth > >> >> discussing > >> >> >> >>> before > >> >> >> >>> >>> I > >> >> >> >>> >>> > >> sink a half hour into it. My suggestion would be > that > >> >> >> >>> initialization > >> >> >> >>> >>> > (or > >> >> >> >>> >>> > >> not) should be left to the user with reasonable > default > >> >> >> behavior > >> >> >> >>> >>> > supplied > >> >> >> >>> >>> > >> by the spark commandline tooling and not forced on > >> >> >> applications > >> >> >> >>> that > >> >> >> >>> >>> > >> incorporate Spark. > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> Thoughts/opinions? > >> >> >> >>> >>> > >> > >> >> >> >>> >>> > >> -- Paul > >> >> >> >>> >>> > >> -- > >> >> >> >>> >>> > >> p...@mult.ifario.us | Multifarious, Inc. | > >> >> >> http://mult.ifario.us/ > >> >> >> >>> >>> > > >> >> >> >>> >>> > >> >> >> >>> > >> >> >> >> > >> >> >> >> > >> >> >> > >> >> > >> >
