Hello again, There has been some interest in this KIP recently. I'm bumping the thread to encourage feedback on the design.
Regards, Sean On Mon, Jul 15, 2019 at 9:01 AM Sean Glover <sean.glo...@lightbend.com> wrote: > To hopefully spark some discussion I've copied the motivation section from > the KIP: > > Consumer lag is a useful metric to monitor how many records are queued to > be processed. We can look at individual lag per partition or we may > aggregate metrics. For example, we may want to monitor what the maximum lag > of any particular partition in our consumer subscription so we can identify > hot partitions, caused by an insufficient producing partitioning strategy. > We may want to monitor a sum of lag across all partitions so we have a > sense as to our total backlog of messages to consume. Lag in offsets is > useful when you have a good understanding of your messages and processing > characteristics, but it doesn’t tell us how far behind *in time* we are. > This is known as wait time in queueing theory, or more informally it’s > referred to as latency. > > The latency of a message can be defined as the difference between when > that message was first produced to when the message is received by a > consumer. The latency of records in a partition correlates with lag, but a > larger lag doesn’t necessarily mean a larger latency. For example, a topic > consumed by two separate application consumer groups A and B may have > similar lag, but different latency per partition. Application A is a > consumer which performs CPU intensive business logic on each message it > receives. It’s distributed across many consumer group members to handle the > load quickly enough, but since its processing time is slower, it takes > longer to process each message per partition. Meanwhile, Application B is > a consumer which performs a simple ETL operation to land streaming data in > another system, such as HDFS. It may have similar lag to Application A, but > because it has a faster processing time its latency per partition is > significantly less. > > If the Kafka Consumer reported a latency metric it would be easier to > build Service Level Agreements (SLAs) based on non-functional requirements > of the streaming system. For example, the system must never have a latency > of greater than 10 minutes. This SLA could be used in monitoring alerts or > as input to automatic scaling solutions. > > On Thu, Jul 11, 2019 at 12:36 PM Sean Glover <sean.glo...@lightbend.com> > wrote: > >> Hi kafka-dev, >> >> I've created KIP-489 as a proposal for adding latency metrics to the >> Kafka Consumer in a similar way as record-lag metrics are implemented. >> >> >> https://cwiki.apache.org/confluence/display/KAFKA/489%3A+Kafka+Consumer+Record+Latency+Metric >> >> Regards, >> Sean >> >> -- >> Principal Engineer, Lightbend, Inc. >> >> <http://lightbend.com> >> >> @seg1o <https://twitter.com/seg1o>, in/seanaglover >> <https://www.linkedin.com/in/seanaglover/> >> > > > -- > Principal Engineer, Lightbend, Inc. > > <http://lightbend.com> > > @seg1o <https://twitter.com/seg1o>, in/seanaglover > <https://www.linkedin.com/in/seanaglover/> >
