Thanks for the review Guozhang! responding to your feedback inline: > 1) I agree that the current ratio metrics is just "snapshot in point", and more flexible metrics that would allow reporters to calculate based on window intervals are better. However, the current mechanism of the proposed metrics assumes the thread->clients mapping as of today, where each thread would own exclusively one main consumer, restore consumer, producer and an admin client. But this mapping may be subject to change in the future. Have you thought about how this metric can be extended when, e.g. the embedded clients and stream threads are de-coupled?
Of course this depends on how exactly we refactor the runtime - assuming that we plan to factor out consumers into an "I/O" layer that is responsible for receiving records and enqueuing them to be processed by processing threads, then I think it should be reasonable to count the time we spend blocked on this internal queue(s) as blocked. The main concern there to me is that the I/O layer would be doing something expensive like decompression that shouldn't be counted as "blocked". But if that really is so expensive that it starts to throw off our ratios then it's probably indicative of a larger problem that the "i/o layer" is a bottleneck and it would be worth refactoring so that decompression (or insert other expensive thing here) can also be done on the processing threads. > 2) [This and all below are minor comments] The "flush-time-total" may better be a producer client metric, as "flush-wait-time-total", than a streams metric, though the streams-level "total-blocked" can still leverage it. Similarly, I think "txn-commit-time-total" and "offset-commit-time-total" may better be inside producer and consumer clients respectively. Good call - I'll update the KIP > 3) The doc was not very clear on how "thread-start-time" would be needed when calculating streams utilization along with total-blocked time, could you elaborate a bit more in the KIP? Yes, will do. > For "txn-commit-time-total" specifically, besides producer.commitTxn. other txn-related calls may also be blocking, including producer.beginTxn/abortTxn, I saw you mentioned "txn-begin-time-total" later in the doc, but did not include it as a separate metric, and similarly, should we have a `txn-abort-time-total` as well? If yes, could you update the KIP page accordingly. Ack. On Mon, Jul 12, 2021 at 11:29 PM Rohan Desai <desai.p.ro...@gmail.com> wrote: > Hello All, > > I'd like to start a discussion on the KIP linked above which proposes some > metrics that we would find useful to help measure whether a Kafka Streams > application is saturated. The motivation section in the KIP goes into some > more detail on why we think this is a useful addition to the metrics > already implemented. Thanks in advance for your feedback! > > Best Regards, > > Rohan > > On Mon, Jul 12, 2021 at 12:00 PM Rohan Desai <desai.p.ro...@gmail.com> > wrote: > >> >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-761%3A+Add+Total+Blocked+Time+Metric+to+Streams >> >
