[jira] [Commented] (KAFKA-6830) Add new metrics for consumer/replication fetch requests

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-6830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16454561#comment-16454561 ] 

ASF GitHub Bot commented on KAFKA-6830:
---------------------------------------

adamkotwasinski opened a new pull request #4936: KAFKA-6830 Add consumer/replication fetch request metrics for topics
URL: https://github.com/apache/kafka/pull/4936
 
 
   Description:
   Introduce two new metrics (ConsumerFetchRequestsPerSec/ReplicationFetchRequestsPerSec) for each topic. They are used to differentiate whether the fetch requests received by broker instance originated from clients or from replicas.
   
   Testing strategy:
   We want to verify that correct metric is growing depending on whether the partitions hosted by given broker instance are being read from (by clients), and by 
   
   Have a cluster with 2+ nodes (needed for replication).
   
   a1) Create a topic with replication factor = 1.
   a2) Observe that `ConsumerFetchRequestsPerSec` & `ReplicationFetchRequestsPerSec` do not change value.
   a3) Start a consumer reading from that topic. Observe that `ConsumerFetchRequestsPerSec` grows, while `ReplicationFetchRequestsPerSec` does not.
   a4) Stop the consumer. Observe that `ConsumerFetchRequestsPerSec` is no longer growing.
   
   b1) Create a topic with replication factor >= 2.
   b2) Observe that `ConsumerFetchRequestsPerSec` is not changing value. Observe that `ReplicationFetchRequestsPerSec` is growing.
   b3) Start a consumer reading from that topic. Observe that `ConsumerFetchRequestsPerSec` grows.
   b4) Stop the consumer. Observe that `ConsumerFetchRequestsPerSec` is no longer growing.
   
   ### Committer Checklist (excluded from commit message)
   - [ ] Verify design and implementation 
   - [ ] Verify test coverage and CI build status
   - [ ] Verify documentation (including upgrade notes)
   

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> Add new metrics for consumer/replication fetch requests
> -------------------------------------------------------
>
>                 Key: KAFKA-6830
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6830
>             Project: Kafka
>          Issue Type: Improvement
>          Components: core
>            Reporter: Adam Kotwasinski
>            Priority: Major
>
> Currently, we have only one fetch request-related metric for a topic.
> As fetch requests are used by both client consumers and replicating brokers, it is impossible to tell if the particular partition (with replication factor > 1) is being actively read from client by consumers.
> Rationale for this improvement: as owner of kafka installation, but not the owner of clients, I want to know which topics still have active (real) consumers.



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