[jira] [Updated] (KAFKA-14747) FK join should record discarded subscription responses

["Matthias J. Sax (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-14747?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Matthias J. Sax updated KAFKA-14747:
------------------------------------
    Description: 
FK-joins are subject to a race condition: If the left-hand side record is updated, a subscription is sent to the right-hand side (including a hash value of the left-hand side record), and the right-hand side might send back join responses (also including the original hash). The left-hand side only processed the responses if the returned hash matches to current hash of the left-hand side record, because a different hash implies that the lef- hand side record was updated in the mean time (including sending a new subscription to the right hand side), and thus the data is stale and the response should not be processed (joining the response to the new record could lead to incorrect results).

A similar thing can happen on a right-hand side update that triggers a response, that might be dropped if the left-hand side record was updated in parallel.

While the behavior is correct, we don't record if this happens. We should consider to record this using the existing "dropped record" sensor or maybe add a new sensor.

  was:
FK-join are subject to a race condition. If the left-hand side record is updated, a subscription is sent to the right-hand side (including a hash value of the left-hand side record), and the right-hand side might send back join responses (also including the original hash). The left hand side only processed the responses if the hash matches, because a different hash implies that the left hand side row was updated in the mean-time (including sending a new subscription to the right hand side), and thus the data is stale and the response should not be processed.

A similar thing can happen on a right hand side update that triggers a response, that might be dropped if the left hand side row was updated in parallel.

While the behavior is correct, we don't record if this happens. We should consider to record this using the existing "dropped record" sensor or maybe add a new sensor.


> FK join should record discarded subscription responses
> ------------------------------------------------------
>
>                 Key: KAFKA-14747
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14747
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Matthias J. Sax
>            Priority: Minor
>              Labels: beginner, needs-kip, newbie
>
> FK-joins are subject to a race condition: If the left-hand side record is updated, a subscription is sent to the right-hand side (including a hash value of the left-hand side record), and the right-hand side might send back join responses (also including the original hash). The left-hand side only processed the responses if the returned hash matches to current hash of the left-hand side record, because a different hash implies that the lef- hand side record was updated in the mean time (including sending a new subscription to the right hand side), and thus the data is stale and the response should not be processed (joining the response to the new record could lead to incorrect results).
> A similar thing can happen on a right-hand side update that triggers a response, that might be dropped if the left-hand side record was updated in parallel.
> While the behavior is correct, we don't record if this happens. We should consider to record this using the existing "dropped record" sensor or maybe add a new sensor.



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