Hi Martin, More information about the bridge can be found in https://www.slf4j.org/legacy.html#log4j-over-slf4j
Terence On Thu, Feb 9, 2017 at 11:19 AM, Terence Yim <cht...@gmail.com> wrote: > Hi Martin, > > Twill has a logback Appender implementation for capturing logs emitted via > slf4j api from runnable and publish them to the embedded Kafka running > inside the AM process. If you are using log4j as the API for emitting logs, > what you can do is to use the log4j-over-slf4j bridge to have logs emitted > via the log4j API get bridged to slf4j. > > I suspect why you are seeing the class missing error is most likely > because you have the slf4j to log4j bridge (the reverse of the one I > mentioned above, look for a jar with name containing "slf4j-log4j12" in the > client classpath) that comes earlier in the classpath then the logback jars. > > Terence > > On Thu, Feb 9, 2017 at 10:47 AM, Martin Serrano <mar...@attivio.com> > wrote: > >> Henry, >> >> I see this behavior deploying with YARN 2.7.1, HDP 2.3. But I'm not sure >> you understood my issue. >> >> * The logback jar dependency is only picked up if it is on the classpath >> when the bundle is created. >> * With logback in my twill client classpath, the appmaster starts fine. >> However without logback in my client classpath the appmaster will get a >> ClassNotFoundException. >> * We use log4j and with logback in my client classpath, it takes over the >> slf4j bindings and I lose control of the client logging. >> >> So my question was about whether this is expected or if there is a >> well-known procedure for working around it. It seems there should be a way >> to tell the twill system to where to find the appmaster dependencies >> without having them in the classpath of the twill client. >> >> Thanks! >> -Martin >> >> >> On 02/08/2017 08:09 PM, Henry Saputra wrote: >> >>> But the logback dependency should be included in the jar packaging that >>> YARN client sends for Twill ApplicationMaster. >>> >>> Are you seeing this behavior in deploying Twill app in latest YARN? >>> >>> - Henry >>> >>> On Wed, Feb 8, 2017 at 12:30 PM, Martin Serrano <mar...@attivio.com> >>> wrote: >>> >>> Hey Devs, >>>> >>>> It seems like the twill project goes through some pain to try to >>>> insulate >>>> itself logging frameworks. I see use of the slf4j API. However, the >>>> appmaster code has a dependency on logback via the >>>> org.apache.twill.internal.logging.Loggings class. The appmaster will >>>> not start up without this dependency present. With the dependency code >>>> as >>>> it is now, there is no way to include the logback jar in the generated >>>> bundle without it being on the current classpath. I've created a ticket >>>> (TWILL-215) to make a missing dependency trigger an exception at bundle >>>> generation time rather than appmaster execution time. >>>> >>>> When the logback jar is on my classpath, my client code picks up logback >>>> instead of our current logger (log4j). Is this what is expected? Is >>>> there >>>> any known workaround? It seems like there may be a case for specifying >>>> dependencies of the appmaster that are located outside of the current >>>> jvm >>>> classpath. >>>> >>>> Thanks, >>>> Martin >>>> >>>> >>>> >> >
