[jira] [Created] (KAFKA-16780) Txn consumer exerts pressure on remote storage when reading non-txn topic

["Kamal Chandraprakash (Jira)" <ji...@apache.org>]

Kamal Chandraprakash created KAFKA-16780:
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             Summary: Txn consumer exerts pressure on remote storage when reading non-txn topic
                 Key: KAFKA-16780
                 URL: https://issues.apache.org/jira/browse/KAFKA-16780
             Project: Kafka
          Issue Type: Task
            Reporter: Kamal Chandraprakash


h3. Logic to read aborted txns:
 # When the consumer enables isolation_level as {{READ_COMMITTED}} and reads a non-txn topic, then the broker has to [traverse|https://github.com/apache/kafka/blob/trunk/core/src/main/scala/kafka/log/LocalLog.scala#L394] all the local log segments to collect the aborted transactions since there won't be any entry in the transaction index.
 # The same [logic|https://github.com/apache/kafka/blob/trunk/core/src/main/java/kafka/log/remote/RemoteLogManager.java#L1436] is applied while reading from remote storage. In this case, when the FETCH request is reading data from the first remote log segment, then it has to fetch the transaction indexes of all the remaining remote-log segments, and then the call lands to the local-log segments before responding to the FETCH request which increases the time taken to serve the requests.

The [EoS Abort Index|https://docs.google.com/document/d/1Rlqizmk7QCDe8qAnVW5e5X8rGvn6m2DCR3JR2yqwVjc] design doc explains how the transaction index file filters out the aborted transaction records.

The issue is when consumers are enabled with the {{READ_COMMITTED}} isolation level but read the normal topics. If the topic is enabled with the transaction, then we expect the transaction to either commit/rollback within 15 minutes (default transaction.max.timeout.ms = 15 mins), possibly we may have to search only for one (or) two remote log segments.



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