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: >> Ensuring that not logging takes minimal time >> Minimizing potential thread contention >> Logging at maximum efficiency is a priority, but comes after these others. >> -- >> Jess Holle >>
