The reasoning to have debug.log enabled by default after CASSANDRA-10241 is to have a "safety log" that you can use when you want to troubleshoot issues after the fact, that is verbose enough that you can reconstruct events that may have caused a problem, but should have negligible performance impact. The way we found to implement this was the following: - INFO: Human-readable operator log. - DEBUG: Safety-log to be used for troubleshooting and bug reporting. - TRACE: C* Programmer Debugging.
If debug.log is causing performance problems we should definitely fix it, but this has been very useful to troubleshoot complex production issues since it has been added. 2018-03-17 16:35 GMT-03:00 Michael Kjellman <kjell...@apple.com>: > ive never understood this change. and it’s been explained to me multiple > times. > > DEBUG shouldn’t run by default in prod. and it certainly shouldn’t be enabled > by default for users. > > but hey, what do i know! just my 2 cents. > >> On Mar 17, 2018, at 10:55 AM, J. D. Jordan <jeremiah.jor...@gmail.com> wrote: >> >> We went through an exercise of setting things up so that DEBUG logging was >> asynchronous would give people a “production” debug log. >> https://issues.apache.org/jira/browse/CASSANDRA-10241 >> If there are some things going out at DEBUG that cause performance issues >> then most likely those should be moved to TRACE so that debug logging can >> stay enabled for all the useful information found there. >> >> -Jeremiah >> >>> On Mar 17, 2018, at 1:49 PM, Alexander Dejanovski <a...@thelastpickle.com> >>> wrote: >>> >>> Hi folks, >>> >>> we've been upgrading clusters from 2.0 to 2.2 recently and we've noticed >>> that debug logging was causing serious performance issues in some cases, >>> specifically because of its use in the query pager. >>> >>> I've opened a ticket with some benchmarks and flame graphs : >>> https://issues.apache.org/jira/browse/CASSANDRA-14318 >>> >>> The problem should be less serious in the read path with Cassandra 3.0 and >>> above as the query pager code has been reworked and doesn't log at debug >>> level. >>> I think that debug logging shouldn't be turned on by default though, since >>> we see it doesn't come for free and that it lowers read performance in 2.2. >>> >>> Was there any specific reason why it was enabled by default in 2.2 ? >>> >>> Is anyone opposed to disabling debug logging by default in all branches ? >>> >>> -- >>> ----------------- >>> Alexander Dejanovski >>> France >>> @alexanderdeja >>> >>> Consultant >>> Apache Cassandra Consulting >>> http://www.thelastpickle.com > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > For additional commands, e-mail: dev-h...@cassandra.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org For additional commands, e-mail: dev-h...@cassandra.apache.org
