poorbarcode opened a new pull request, #18877:
URL: https://github.com/apache/pulsar/pull/18877
### Motivation
The method `consumer.getLastMessageId` will return the latest message which
can be received.
- If disabled `read compacted`, will return the last confirmed position of
`ManagedLedger`.
- If enabled `read compacted`, will return the latest message id which can
be read from the compacted topic.
If we send a batch message like this:
```java
producer.newMessage().key("k1").value("v0").sendAsync(); // message-id is
[3:1,-1:0]
producer.newMessage().key("k1").value("v1").sendAsync(); // message-id is
[3:1,-1:1]
producer.newMessage().key("k1").value("v2").sendAsync(); // message-id is
[3:1,-1:2]
producer.newMessage().key("k2").value("v0").sendAsync(); // message-id is
[3:1,-1:3]
producer.newMessage().key("k2").value("v1").sendAsync(); // message-id is
[3:1,-1:4]
producer.newMessage().key("k2").value(null).sendAsync(); // message-id is
[3:1,-1:5]
producer.flush();
```
After the compaction task is done, the messages with key `k2` will be
deleted by the compaction task. Then the latest message that can be received
will be `[3:1:-1:2]`.
---
When we call `consumer.getLastMessageId`, the expected result is:
```
[3:1,-1:2]
```
---
But the actual result is:
```
[3:1,-1:5]
```
### Modifications
If enabled `read compacted` and the latest entry of the compacted topic is a
batched message, extract the entry and calculate all internal messages, then
return the latest message which is not marked `compacted out`.
### Documentation
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- [ ] `doc` <!-- Your PR contains doc changes. Please attach the local
preview screenshots (run `sh start.sh` at `pulsar/site2/website`) to your PR
description, or else your PR might not get merged. -->
- [ ] `doc-required` <!-- Your PR changes impact docs and you will update
later -->
- [x] `doc-not-needed` <!-- Your PR changes do not impact docs -->
- [ ] `doc-complete` <!-- Docs have been already added -->
### Matching PR in forked repository
PR in forked repository:
- https://github.com/poorbarcode/pulsar/pull/49
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