> On May 1, 2018, 9:25 a.m., Zhitao Li wrote: > > 3rdparty/libprocess/include/process/metrics/push_gauge.hpp > > Lines 70-75 (patched) > > <https://reviews.apache.org/r/66828/diff/1/?file=2013207#file2013207line70> > > > > Hmm, is there a possible race condition here? > > > > Consider two threads calling this with `v=2` and `v=3`, and initial > > value as `0`, and the order would be: > > > > T1: `fetch_add(2)`, `prev` in T1 == 0; > > T2: `fetch_add(3)`, `prev` in T2 == 2; > > T2: `push(2 + 3)`, metric value is 5; > > T1: `push(0 + 2)`, metric value is 2. > > > > Metric value and cached value in gauge would be out of sync due to the > > race condition?
My bad, realized that `push()` is only used as history. Actual sampling happens through `value()` function. Please ignore my comment. - Zhitao ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviews.apache.org/r/66828/#review202194 ----------------------------------------------------------- On April 26, 2018, 2:54 p.m., Benjamin Mahler wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviews.apache.org/r/66828/ > ----------------------------------------------------------- > > (Updated April 26, 2018, 2:54 p.m.) > > > Review request for mesos, Gaston Kleiman, Gilbert Song, Greg Mann, James > Peach, and Vinod Kone. > > > Bugs: MESOS-8851 > https://issues.apache.org/jira/browse/MESOS-8851 > > > Repository: mesos > > > Description > ------- > > A push-based gauge differs from a pull-based gauge in that the > client is responsible for pushing the latest value into the gauge > whenever it changes. This can be challenging in some cases as it > requires the client to have a good handle on when the gauge value > changes (rather than just computing the current value when asked). > > It is highly recommended to use push-based gauges if possible as > they provide significant performance benefits over pull-based > gauges. Pull-based gauge suffer from delays getting processed on > the event queue of a `Process`, as well as incur computation cost > on the `Process` each time the metrics are collected. Push-based > gauges, on the other hand, incur no cost to the owning `Process` > when metrics are collected, and instead incur a trivial cost when > the `Process` pushes new values in. > > > Diffs > ----- > > 3rdparty/libprocess/include/Makefile.am > cd2c3bc62df8de5b50ec2fa830b3e2634ba11e28 > 3rdparty/libprocess/include/process/metrics/push_gauge.hpp PRE-CREATION > > > Diff: https://reviews.apache.org/r/66828/diff/1/ > > > Testing > ------- > > Test added in the subsequent patch. > > > Thanks, > > Benjamin Mahler > >
