Hey Vijay! On Mon, Mar 7, 2016 at 8:42 PM, Vijay Srinivasaraghavan <vijikar...@yahoo.com> wrote: > 3) How can I simulate and verify backpressure? I have introduced some delay > (Thread Sleep) in the job before the sink but the "backpressure" tab from UI > does not show any indication of whether backpressure is working or not.
If a task is slow, it is back pressuring upstream tasks, e.g. if your transformations have the sleep, the sources should be back pressured. It can happen that even with the sleep the tasks still produce their data as fast as they can and hence no back pressure is indicated in the web interface. You can increase the sleep to check this. The mechanism used to determine back pressure is based on sampling the stack traces of running tasks. You can increase the number of samples and/or decrease the delay between samples via config parameters shown in [1]. It can happen that the samples miss the back pressure indicators, but usually the defaults work fine. [1] https://ci.apache.org/projects/flink/flink-docs-master/setup/config.html#jobmanager-web-frontend
