Hi Bruno, Just realized that for `addRateSensor` and `addLatencyAndRateSensor` we've actually added the total invocation metric already.
Guozhang On Mon, Aug 19, 2019 at 4:11 PM Guozhang Wang <wangg...@gmail.com> wrote: > Hi Bruno, > > > On Tue, Aug 6, 2019 at 1:51 AM Bruno Cadonna <br...@confluent.io> wrote: > >> Hi Guozhang, >> >> I left my comments inline. >> >> On Thu, Jul 18, 2019 at 8:28 PM Guozhang Wang <wangg...@gmail.com> wrote: >> > >> > Hello Bruno, >> > >> > Thanks for the feedbacks, replied inline. >> > >> > On Mon, Jul 1, 2019 at 7:08 AM Bruno Cadonna <br...@confluent.io> >> wrote: >> > >> > > Hi Guozhang, >> > > >> > > Thank you for the KIP. >> > > >> > > 1) As far as I understand, the StreamsMetrics interface is there for >> > > user-defined processors. Would it make sense to also add a method to >> > > the interface to specify a sensor that records skipped records? >> > > >> > > Not sure I follow.. if users want to add a specific skipped records >> > sensor, she can still do that as a "throughput" sensor via " >> > addThroughputSensor" and then "record" right? >> > >> > As an after-thought, maybe it's better to rename `throughput` to `rate` >> in >> > the public APIs since it is really meant for the latter semantics. I did >> > not change it just to make less API changes / deprecate fewer functions. >> > But if we feel it is important we can change it as well. >> > >> >> I see now that a user can record the rate of skipped records. However, >> I was referring to the total number of skipped records. Maybe my >> question should be more general: should we allow the user to also >> specify sensors for totals or combinations of rate and totals? >> >> Sounds good to me, I will add it to the wiki page as well for > StreamsMetrics. > > > >> Regarding the naming, I like `rate` more than `throughput`, but I >> would not fight for it. >> >> > >> > > 2) What are the semantics of active-task-process and >> standby-task-process >> > > >> > > Ah good catch, I think I made it in the wrong column. Just some >> > explanations here: Within a thread's looped iterations, it will first >> try >> > to process some records from the active tasks, and then see if there are >> > any standby-tasks that can be processed as well (i.e. just reading from >> the >> > restore consumer and apply to the local stores). The ratio metrics are >> for >> > indicating 1) what tasks (active or standby) does this thread own so >> far, >> > and 2) how much time in percentage does it spend on each of them. >> > >> > But this metric should really be a task-level one that includes both the >> > thread-id and task-id, and upon task migrations they will be dynamically >> > deleted / (re)-created. For each task-id it may be owned by multiple >> > threads as one active and others standby, and hence the separation of >> > active / standby seems still necessary. >> > >> >> Makes sense. >> >> >> > >> > >> > > 3) How do dropped-late-records and expired-window-record-drop relate >> > > to each other? I guess the former is for records that fall outside the >> > > grace period and the latter is for records that are processed after >> > > the retention period of the window. Is this correct? >> > > >> > > Yes, that's correct. The names are indeed a bit confusing since they >> are >> > added at different releases historically.. >> > >> > More precisely, the `grace period` is a notion of the operator (hence >> the >> > metric is node-level, though it would only be used for DSL operators) >> while >> > the `retention` is a notion of the store (hence the metric is >> store-level). >> > Usually grace period will be smaller than store retention though. >> > >> > Processor node is aware of `grace period` and when received a record >> that >> > is older than grace deadline, it will be dropped immediately; otherwise >> it >> > will still be processed a maybe a new update is "put" into the store. >> The >> > store is aware of its `retention period` and then upon a "put" call if >> it >> > realized it is older than the retention deadline, that put call would be >> > ignored and metric is recorded. >> > >> > We have to separate them here since the window store can be used in both >> > DSL and PAPI, and for the former case it would likely to be already >> ignored >> > at the processor node level due to the grace period which is usually >> > smaller than retention; but for PAPI there's no grace period and hence >> the >> > processor would likely still process and call "put" on the store. >> > >> >> Alright! Got it! >> >> > >> > > 4) Is there an actual difference between skipped and dropped records? >> > > If not, shall we unify the terminology? >> > > >> > > >> > There is. Dropped records are only due to lateness; where as skipped >> > records can be due to serde errors (and user's error handling indicate >> > "skip and continue"), timestamp errors, etc. >> > >> > I've considered maybe a better (more extensible) way would be defining a >> > single metric name, say skipped-records, but use different tags to >> indicate >> > if its skipping reason (errors, windowing semantics, etc). But there's >> > still a tricky difference: for serde caused skipping for example, they >> will >> > be skipped at the very beginning and there's no effects taken at all. >> For >> > some others e.g. null-key / value at the reduce operator, it is only >> > skipped at the middle of the processing, i.e. some effects may have >> already >> > been taken in up-stream sub-topologies. And that's why for >> skipped-records >> > I've defined it on both task-level and node-level and the aggregate of >> the >> > latter may still be smaller than the former, whereas for >> dropped-records it >> > is only for node-level. >> > >> > So how about an even more significant change then: we enlarge the >> > `dropped-late-records` to `dropped-records` which is node-level only, >> but >> > includes reasons form lateness to semantics (like null-key) as well; and >> > then we have a task-level-only `skipped-records` which only record those >> > dropped at the very beginning and did not make it at all to the >> processing >> > topology. I feel this is a clearer distinguishment but also a bigger >> change >> > to users. >> > >> >> I like the way you dropped-records and skipped-records are now >> defined. My follow-up question is whether we should give names to >> those metrics that better describe their semantics, like: >> >> dropped-records-at-source and dropped-records-at-processor >> >> or >> >> records-dropped-at-source and records-dropped-at-processor >> >> or >> >> source-dropped-records and processor-dropped-records >> >> or alternatively with skipped. However, I would use the same term as >> in expired-window-record-drop >> >> Maybe, we should also consider to rename expired-window-record-drop to >> expired-window-record-dropped to be consistent. >> >> WDYT? >> >> I was not considering "expired-window-record-drop" before since it is a > store-level metric, and I was only considering task-level (skipped-records) > and processor-node-level (dropped-records) metrics, and I'm using different > terms deliberately to hint users that they are different leveled metrics. > > I still feel that using `skip` for task-level metrics indicating that this > record was not processed at all, and using `drop` for processor-level > metrics that this record is only dropped at this stage of the topology is a > better one; but I'm also okay with some finer grained metrics so that we > can align the processor-level with store-level (they are on the same > granularity any ways), like: > > `dropped-records-null-field`: at processor nodes > > `dropped-records-too-late`: at processor nodes > > `dropped-records-expired-window`: at window-stores > > >> > >> > > 5) What happens with removed metrics when the user sets the version of >> > > "built.in.metrics.version" to 2.2- >> > > >> > > I think for those redundant ones like ""forward-rate" and >> "destroy-rate" >> > we can still remove them with 2.2- as well; for other ones that are >> removed >> > / replaced like thread-level skipped-records we should still maintain >> them. >> > >> >> Could you add this comment about removal of redundant metrics to the >> KIP such that is documented somewhere? >> >> Yes, for sure. > > >> >> Best, >> Bruno >> > > I've also decided to remove the rebalance-related metrics from the > instance-level and move it to consumer itself as part of KIP-429. > > > -- > -- Guozhang > -- -- Guozhang
