candlerb opened a new issue #5537: Reader method to locate message ID by event time URL: https://github.com/apache/pulsar/issues/5537 **Is your feature request related to a problem? Please describe.** I would like to be able to initialize a reader using an event time. Typical use cases: * I have a long-lived, persistent topic containing system logs, and I want to do an ad-hoc query saying "show me logs starting from 1 hour ago" * I have a reader which is storing its messageID state in a database, and I want to rewind it to a particular point in time * I am developing reader code and I want to test it across a subset of recent messages, not from the very beginning of the topic. Currently when you create a "reader", you can initialize it to start at either the earliest message or the end of the topic - there are special sentinel message IDs for those cases. You can also initialize it to any existing message ID on a topic, but to do that, you must already know a valid message ID. **Describe the solution you'd like** An API call which, given a topic and event time, returns the message ID of the first message after that time. This functionality must already exist internally in Pulsar because the admin API has a `reset-cursor` call for subscriptions. I would like that internal search for event time to be exposed. I suspect this would end up in the REST API rather than the client protocol. Ideally it would be accessible to clients without admin privileges. I found some work to allow subscription-related admin calls to unprivileged consumers when dealing with their own subscriptions - #2964 / #2981 - so I'd like the new call to be covered by this. **Describe alternatives you've considered** For topic X, I could write a separate index topic X1 which emits a messageID and timestamp, say one message for every 10,000 messages in X. Then I can scan X1 looking for the last timestamp before the time of interest, and then read X forward from that messageID. This would have to be duplicated for every topic. I could create a temporary subscription, use reset-cursor on it, and read using a consumer - or read one message, and use it to get the message ID to initialize a reader. It seems overblown to create and destroy a subscription just for that. **Additional context** Provides feature parity to Kafka: `getOffsetsByTimes` / `offsetsForTimes`
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