Looks like we already have an outstanding Jira for this: LOG4J2-812 <https://issues.apache.org/jira/browse/LOG4J2-812>. If there are no objections I can take care of this one.
On Sun, Jul 5, 2015 at 9:55 AM, Remko Popma <[email protected]> wrote: > One per logger context would make it easier to clear all ThreadContexts > when a particular logger context is stopped. > > Sent from my iPhone > > On 2015/07/05, at 0:51, Gary Gregory <[email protected]> wrote: > > Would there be one registry or one per logger context? > > Gary > > > -------- Original message -------- > From: Remko Popma <[email protected]> > Date: 07/04/2015 05:41 (GMT-08:00) > To: Log4J Developers List <[email protected]> > Subject: Re: Log4j2 RollingFileAppender deadlock issue > > ThreadLocal is implemented as an internal Map in each Thread instance, so > there is constant lookup time regardless of the number of Threads and the > number of lookups. Contrast this with a lock, where performance will > decrease exponentially with more concurrent threads. > > (See also https://plumbr.eu/blog/java/how-is-threadlocal-implemented ) > > Sent from my iPhone > > On 2015/07/04, at 20:40, Jess Holle <[email protected]> wrote: > > On 7/4/2015 2:51 AM, Gary Gregory wrote: > > On Thu, Jul 2, 2015 at 6:18 AM, Remko Popma <[email protected]> > wrote: > >> Yes, that could still work: We could use a ThreadLocal containing a >> custom class which holds the lastTimestamp, cachedDateString as well as a >> SimpleDateFormat instance. >> >> As Jess pointed out, we would also need a way to clear the ThreadLocal >> when the LoggerContext is stopped (to prevent memory leaks in web apps). >> This may be the third usage of ThreadLocals in log4j2 now, so it may be >> worth creating a reusable mechanism for this. >> One idea would be to have a ThreadLocal registry in the LoggerContext, >> where the LoggerContext is responsible for cleaning up all registered >> ThreadLocals in its stop() method. >> >> Thoughts? >> > > I'm wondering what the performance cost are of doing a ThreadLocal.get() > vs. synchronized(this) on each call to format(). > > Personally I'd be less concerned with optimizing maximum logger > throughput on any given thread than: > > 1. Ensuring that *not* logging takes minimal time > 2. Minimizing potential thread contention > > Logging at maximum efficiency is a priority, but comes after these others. > > -- > Jess Holle > >
