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Posted to commits@pulsar.apache.org by GitBox <gi...@apache.org> on 2021/09/15 18:01:48 UTC
[GitHub] [pulsar] alexsapps opened a new issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
alexsapps opened a new issue #12053:
URL: https://github.com/apache/pulsar/issues/12053
I find the [Retry letter topic](https://pulsar.apache.org/docs/en/next/concepts-messaging/#retry-letter-topic) docs confusing. Here are some questions:
* Is it really the producer's responsibility to send the message to the retry topic? The docs say "you can configure the producer to send messages to both the business topic and the retry letter topic". If this is accurate, should the producer send to both topics at the same time or only push to retry topic after business topic fails?
* In the code example with `.retryLetterTopic`, does the consumer get both business and retry messages in the same stream? Are retried messages delivered interleaved with business messages based on timestamps, or does the subscription prioritize one topic over the other?
* What is the relationship between retryLetterTopic and enableRetry? (Is retryLetterTopic ignored when enableRetry is false? Is it an error to specify a retryLetterTopic when enableRetry is false?)
* What is "retrial queue" (`reconsumeLater`) ? Is it different than a retry topic?
* Is `reconsumeLater` different from throwing an exception that causes the message to go to the retryLetterTopic?
* What is maxRedeliverCount – is “redeliver” different from “retry”? Is it the number of times it tries to redeliver immediately before putting it in the retry queue, or the number of times it gets put back into the retry queue before going to the dead letter topic?
* The sentence starting "To configure the delay time" does not actually say how or where to specify a delay time. But I assume it is a global setting on the retry topic?
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[GitHub] [pulsar] github-actions[bot] commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-1056055664
The issue had no activity for 30 days, mark with Stale label.
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-986999780
Hi Liudezhi, I'm not sure I understand your comment. What does "scene" mean here? What do you mean handling failed actions "by themselves" - as opposed to what? What can be encapsulated? Thanks!
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-941729849
Hi @Huanli-Meng Let me know if you have advice where to get more information on retry topics :)
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-920253756
If somebody answers the questions here I can try sending a PR.
Really great to have built-in retries. Thank you!
@Huanli-Meng @liudezhi2098 :)
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-951395768
I was able to answer most of the questions myself after reading the original PR that introduced the feature - [6449](https://github.com/apache/pulsar/pull/6449/files).
> Is it really the producer's responsibility to send the message to the retry topic? ...
No. It’s the consumer’s responsibility to call reconsumeLater to effectively move the message to the retry queue upon failing to process a message.
> ... does the consumer get both business and retry messages in the same stream ...
Yes, the consumer implementation automatically subscribes itself to the retry topic as well as the original topic. Still not sure about prioritization or interleaving.
> What is the relationship between retryLetterTopic and enableRetry?
enableRetry must be turned on explicitly to enable retries. retryLetterTopic is only used for customizing the retry topic name; if not set a default retry letter topic name is used. Similarly for dead letter topic name.
> What is "retrial queue" (reconsumeLater) ? Is it different than a retry topic?
Pretty sure it’s the same. Didn’t see any special “retrial queue” in the code.
> Is reconsumeLater different from throwing an exception that causes the message to go to the retryLetterTopic?
Still not sure.
> What is maxRedeliverCount – is “redeliver” different from “retry”? ...
Redeliver and retry seem to be interchangeable here. It’s the number of times it goes into the retry queue before dead letter topic.
> ... configure the delay time ...
reconsumeLater accepts a delay time that can be different each time it’s called.
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[GitHub] [pulsar] liudezhi2098 commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
liudezhi2098 commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-980535585
@alexsapps retry topic scene is mainly to customize different delay intervals for consumers. Of course, you can handle the failed actions by themselves, but in fact, this can be encapsulated and the experience is better.
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[GitHub] [pulsar] liudezhi2098 commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
liudezhi2098 commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-1003326710
I’m sorry I didn’t get here in time.
Retry topic scene is mainly traditional business logic, such as when processing a message fails, the user wants to be able to customize the delay time to process the failed message, such as 1 second, 5 seconds, 10 seconds, it could be any number.
these actions can be implemented in logic, such as having the producer delay sending this message to the current topic or another topic when processing the business logic fails, and then having the consumer process it again. I think this is a common processing mode, so can add it to the client api.
the current approach is to put deferred messages into another Topic of subscriptionName-RETRY, because the business retry message is only relevant to the current subscriber.
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[GitHub] [pulsar] Huanli-Meng commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
Huanli-Meng commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-925436185
@alexsapps thanks for pointing these questions out and I will ping related engineers to see if they can clarify these issues?
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-941729849
Hi @Huanli-Meng Let me know if you have advice where to get more information on retry topics :)
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[GitHub] [pulsar] alexsapps commented on issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
alexsapps commented on issue #12053:
URL: https://github.com/apache/pulsar/issues/12053#issuecomment-926219975
That would be great @Huanli-Meng, thank you!
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[GitHub] [pulsar] Anonymitaet closed issue #12053: Docs clarification needed for concepts-messaging/#retry-letter-topic
Posted by GitBox <gi...@apache.org>.
Anonymitaet closed issue #12053:
URL: https://github.com/apache/pulsar/issues/12053
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