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https://issues.apache.org/jira/browse/KAFKA-9800?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jun Rao resolved KAFKA-9800.
----------------------------
Fix Version/s: 3.7.0
Resolution: Fixed
Merged [https://github.com/apache/kafka/pull/14111] to trunk.
> [KIP-580] Client Exponential Backoff Implementation
> ---------------------------------------------------
>
> Key: KAFKA-9800
> URL: https://issues.apache.org/jira/browse/KAFKA-9800
> Project: Kafka
> Issue Type: New Feature
> Reporter: Cheng Tan
> Assignee: Andrew Schofield
> Priority: Major
> Labels: KIP-580, client
> Fix For: 3.7.0
>
>
> Design:
> The main idea is to bookkeep the failed attempt. Currently, the retry backoff
> has two main usage patterns:
> # Synchronous retires and blocking loop. The thread will sleep in each
> iteration for retry backoff ms.
> # Async retries. In each polling, the retries do not meet the backoff will
> be filtered. The data class often maintains a 1:1 mapping to a set of
> requests which are logically associated. (i.e. a set contains only one
> initial request and only its retries.)
> For type 1, we can utilize a local failure counter of a Java generic data
> type.
> For case 2, I already wrapped the exponential backoff/timeout util class in
> my KIP-601
> [implementation|https://github.com/apache/kafka/pull/8683/files#diff-9ca2b1294653dfa914b9277de62b52e3R28]
> which takes the number of attempts and returns the backoff/timeout value at
> the corresponding level. Thus, we can add a new class property to those
> classes containing retriable data in order to record the number of failed
> attempts.
>
> Changes:
> KafkaProducer:
> # Produce request (ApiKeys.PRODUCE). Currently, the backoff applies to each
> ProducerBatch in Accumulator, which already has an attribute attempts
> recording the number of failed attempts. So we can let the Accumulator
> calculate the new retry backoff for each bach when it enqueues them, to avoid
> instantiate the util class multiple times.
> # Transaction request (ApiKeys..*TXN). TxnRequestHandler will have a new
> class property of type `Long` to record the number of attempts.
> KafkaConsumer:
> # Some synchronous retry use cases. Record the failed attempts in the
> blocking loop.
> # Partition request (ApiKeys.OFFSET_FOR_LEADER_EPOCH, ApiKeys.LIST_OFFSETS).
> Though the actual requests are packed for each node, the current
> implementation is applying backoff to each topic partition, where the backoff
> value is kept by TopicPartitionState. Thus, TopicPartitionState will have the
> new property recording the number of attempts.
> Metadata:
> # Metadata lives as a singleton in many clients. Add a new property
> recording the number of attempts
> AdminClient:
> # AdminClient has its own request abstraction Call. The failed attempts are
> already kept by the abstraction. So probably clean the Call class logic a bit.
> Existing tests:
> # If the tests are testing the retry backoff, add a delta to the assertion,
> considering the existence of the jitter.
> # If the tests are testing other functionality, we can specify the same
> value for both `retry.backoff.ms` and `retry.backoff.max.ms` in order to make
> the retry backoff static. We can use this trick to make the existing tests
> compatible with the changes.
> There're other common usages look like client.poll(timeout), where the
> timeout passed in is the retry backoff value. We won't change these usages
> since its underlying logic is nioSelector.select(timeout) and
> nioSelector.selectNow(), which means if no interested op exists, the client
> will block retry backoff milliseconds. This is an optimization when there's
> no request that needs to be sent but the client is waiting for responses.
> Specifically, if the client fails the inflight requests before the retry
> backoff milliseconds passed, it still needs to wait until that amount of time
> passed, unless there's a new request need to be sent.
>
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