Do you know why they did this rather than just enabling GC logging by default? Why re-invent the wheel?
I seem to remember seeing a push do enable GC logging by default a few years ago. In particular around the time when the JVM added GC log rolling as a feature. Here's an example: https://batmat.net/2016/10/17/always-enable-gc-logs-and-how-to-enable-logs-rotation-with-hotspot/ My understanding is that the overhead is so low that it's feasible to do this. Good improvement though regardless which way we go. Regards, Patrick On Wed, May 9, 2018 at 9:36 AM, Andor Molnar <[email protected]> wrote: > +1 cool! > > > On Wed, May 9, 2018 at 7:59 AM, Norbert Kalmar <[email protected]> > wrote: > > > Okay, thanks Ed, I created the Jira, will look into it soon :) > > https://issues.apache.org/jira/browse/ZOOKEEPER-3037 > > > > Regards, > > Norbert > > > > On Wed, May 9, 2018 at 4:44 PM Edward Ribeiro <[email protected]> > > wrote: > > > > > +1. Sounds really nice to have feature. Let's open a ticket and open a > > PR. > > > :) > > > > > > Ed > > > > > > Em qua, 9 de mai de 2018 11:15, Norbert Kalmar <[email protected]> > > > escreveu: > > > > > > > Hi, > > > > > > > > I just got a tip that we could improve on the logging in ZooKeeper. > > > After a > > > > ZK crash, or client timeout sometimes it's hard to determine from the > > > logs > > > > what happened. Knowing if ZK was responsive at the time would help a > > lot. > > > > For example, ZK might spend a lot of time waiting on GC (there is > still > > > > some misconception that ZK is a storage). > > > > > > > > To help detect this, HADOOP already has a great tool called JVM Pause > > > > Monitor. (As the name suggest, it can be also used for monitoring, > but > > it > > > > also helps post-mortem in a lot of cases). Basically it has a daemon > > that > > > > sleeps for one second, and if the sleep time exceeds the 1s by more > > than > > > > the threshold (1s: INFO, 10s: WARN by default - this can be > > configurable > > > in > > > > our case, see below), it will alert/make a log entry. It can also > > monitor > > > > the time GC took. > > > > > > > > Now, this class is in the HADOOP-common. I wouldn't want to depend on > > > > Hadoop-common because of this one feature/class (it is actually a > > single > > > > class). Since this is a straightforward implementation, and in the > past > > > > five years the few commits it had is nothing really serious, I think > we > > > > could just copy this class in ZooKeeper, and introduce it as a > > > configurable > > > > feature, by default it can be off. > > > > > > > > The class: > > > > > > > > > > > https://github.com/apache/hadoop/blob/trunk/hadoop- > > common-project/hadoop-common/src/main/java/org/apache/ > > hadoop/util/JvmPauseMonitor.java > > > > > > > > What do You think? > > > > > > > > Regards, > > > > Norbert > > > > > > > > > >
