Hello John, Thanks for the KIP. Some comments:
1. Could you list all the possible values of the "reason" tag? In the JIRA ticket I left some potential reasons but I'm not clear if you're going to categorize each of them as a separate reason, or is there any additional ones you have in mind. Also I'm wondering if we should add another metric that do not have the reason tag but aggregates among all possible reasons? This is for users to easily set their alerting notifications (otherwise they have to write on notification rule per reason) in their monitoring systems. 2. Note that the processor-node metrics is actually "per-thread, per-task, per-processor-node", and today we only set the per-thread metrics as INFO while leaving the lower two layers as DEBUG. I agree with your argument that we are missing the per-client roll-up metrics today, but I'm convinced that the right way to approach it would be "just-providing-the-lowest-level metrics only". Note the recoding implementation of these three levels are different internally today: we did not just do the rolling up to generate the higher-level metrics from the lower level ones, but we just record them separately, which means that, if we turn on multiple levels of metrics, we maybe duplicate collecting some metrics. One can argue that is not the best way to represent multi-level metrics collecting and reporting, but by only enabling thread-level metrics as INFO today, that implementation could be more efficient than only collecting the metrics at the lowest level, and then do the roll-up calculations outside of the metrics classes. Plus, today not all processor-nodes may possibly skip records, AFAIK we will only skip records at the source, sink, window and aggregation processor nodes, so adding a metric per processor looks like an overkill to me as well. On the other hand, from user's perspective the "reason" tag may be sufficient for them to narrow down where inside the topology is causing records to be dropped on the floor. So I think the "per-thread, per-task" level metrics should be sufficient for them in trouble shoot in DEBUG mode, and we can add another "per-thread" level metrics as INFO which is turned on by default. So under normal execution users still only need INFO level metrics for alerting (e.g. set alerts on all skipped-records metrics as non-zero), and then upon trouble shooting they can turn on DEBUG metrics to look into which task is actually causing the skipped records. Guozhang On Thu, Mar 29, 2018 at 2:03 PM, Matthias J. Sax <matth...@confluent.io> wrote: > Thanks for the KIP John. > > Reading the material on the related Jiras, I am wondering what `reason` > tags you want to introduce? Can you elaborate? The KIP should list those > IMHO. > > About the fine grained metrics vs the roll-up: you say that > > > the coarse metric aggregates across two dimensions simultaneously > > Can you elaborate why this is an issue? I am not convinced atm that we > should put the fine grained metrics into INFO level and remove the > roll-up at thread level. > > > Given that they have to do this sum to get a usable top-level view > > This is a fair concern, but I don't share the conclusion. Offering a > built-in `KafkaStreams` "client" roll-up out of the box might be a > better solution. In the past we did not offer this due to performance > concerns, but we could allow an "opt-in" mechanism. If you disagree, can > you provide some reasoning and add them to the "Rejected alternatives" > section. > > To rephrase: I understand the issue about missing top-level view, but > instead of going more fine grained, we should consider to add this > top-level view and add/keep the fine grained metrics at DEBUG level only > > I am +1 to add TopologyTestDriver#metrics() and to remove old metrics > directly as you suggested. > > > -Matthias > > > > On 3/28/18 6:42 PM, Ted Yu wrote: > > Looks good to me. > > > > On Wed, Mar 28, 2018 at 3:11 PM, John Roesler <j...@confluent.io> wrote: > > > >> Hello all, > >> > >> I am proposing KIP-274 to improve the metrics around skipped records in > >> Streams. > >> > >> Please find the details here: > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP- > >> 274%3A+Kafka+Streams+Skipped+Records+Metrics > >> > >> Please let me know what you think! > >> > >> Thanks, > >> -John > >> > > > > -- -- Guozhang
