Hi Till, Thanks for your feedback.
>>> How will our tests be affected by these changes? Will Flink require more resources and, thus, will it risk destabilizing our testing infrastructure? There are some tests that need to be adjusted, for example, BlockingShuffleITCase. For other tests, theoretically, the influence should be small. I will further run all tests multiple times (like 10 or 20) to ensure that there is no test stability issues before making the change. >>> I would propose to create a FLIP for these changes since you propose to change the default behaviour. It can be a very short one, though. Yes, you are right. I will prepare a simple FLIP soon. Best, Yingjie Till Rohrmann <trohrm...@apache.org> 于2021年12月3日周五 18:39写道： > Thanks for starting this discussion Yingjie, > > How will our tests be affected by these changes? Will Flink require more > resources and, thus, will it risk destabilizing our testing infrastructure? > > I would propose to create a FLIP for these changes since you propose to > change the default behaviour. It can be a very short one, though. > > Cheers, > Till > > On Fri, Dec 3, 2021 at 10:02 AM Yingjie Cao <kevin.ying...@gmail.com> > wrote: > >> Hi dev & users, >> >> We propose to change some default values of blocking shuffle to improve >> the user out-of-box experience (not influence streaming). The default >> values we want to change are as follows: >> >> 1. Data compression >> (taskmanager.network.blocking-shuffle.compression.enabled): Currently, the >> default value is 'false'. Usually, data compression can reduce both disk >> and network IO which is good for performance. At the same time, it can save >> storage space. We propose to change the default value to true. >> >> 2. Default shuffle implementation >> (taskmanager.network.sort-shuffle.min-parallelism): Currently, the default >> value is 'Integer.MAX', which means by default, Flink jobs will always use >> hash-shuffle. In fact, for high parallelism, sort-shuffle is better for >> both stability and performance. So we propose to reduce the default value >> to a proper smaller one, for example, 128. (We tested 128, 256, 512 and >> 1024 with a tpc-ds and 128 is the best one.) >> >> 3. Read buffer of sort-shuffle >> (taskmanager.memory.framework.off-heap.batch-shuffle.size): Currently, the >> default value is '32M'. Previously, when choosing the default value, both >> ‘32M' and '64M' are OK for tests and we chose the smaller one in a cautious >> way. However, recently, it is reported in the mailing list that the default >> value is not enough which caused a buffer request timeout issue. We already >> created a ticket to improve the behavior. At the same time, we propose to >> increase this default value to '64M' which can also help. >> >> 4. Sort buffer size of sort-shuffle >> (taskmanager.network.sort-shuffle.min-buffers): Currently, the default >> value is '64' which means '64' network buffers (32k per buffer by default). >> This default value is quite modest and the performance can be influenced. >> We propose to increase this value to a larger one, for example, 512 (the >> default TM and network buffer configuration can serve more than 10 >> result partitions concurrently). >> >> We already tested these default values together with tpc-ds benchmark in >> a cluster and both the performance and stability improved a lot. These >> changes can help to improve the out-of-box experience of blocking shuffle. >> What do you think about these changes? Is there any concern? If there are >> no objections, I will make these changes soon. >> >> Best, >> Yingjie >> >
