BewareMyPower commented on code in PR #19031:
URL: https://github.com/apache/pulsar/pull/19031#discussion_r1059642489
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pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java:
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@@ -204,6 +208,10 @@
private final AtomicReference<ClientCnx>
clientCnxUsedForConsumerRegistration = new AtomicReference<>();
private final List<Throwable> previousExceptions = new
CopyOnWriteArrayList<Throwable>();
+ // Key is the ledger id and the entry id, entry is the acker that
represents which single messages are acknowledged
+ private final ConcurrentNavigableMap<Pair<Long, Long>, BatchMessageAcker>
batchMessageToAcker =
Review Comment:
> Users should not continue to process/ack the messages before the seek
operation.
This implicit rule is never documented and even it's documented, it could be
a burden to users.
Assuming there are a message ID set, given the following steps:
1. Acnowledge some message IDs
2. Perform some operations, e.g. `seek`.
3. Acknowledge other message IDs.
```java
consumer.acknowledge(msgId1);
consumer.doSomething(); // pseudo code
consumer.acknowledge(msgId2);
```
The rule means, the steps above could have the different result with
acknowledging the whole message ID set:
```java
consumer.acknowledge(msgId1);
consumer.acknowledge(msgId2);
```
A more confusing thing is that with this rule, consumer can acknowledge
another message ID that has the same position with `msgId1` to have the same
result. i.e.
```java
// CODE 1
consumer.acknowledge(msgId1);
consumer.doSomething();
consumer.acknowledge(msgId2);
consumer.acknowledge(msgId3);
// msgId3.getLedgerId() == msgId1.getLedgerId()
// msgId3.getEntryId() == msgId1.getEntryId()
// msgId3.getBatchIndex() == msgId1.getBatchIndex()
```
is equivalent with
```java
// CODE 2
consumer.acknowledge(msgId1);
consumer.acknowledge(msgId2);
```
What's more confusing is, `msgId1.equals(msgId3)` is true and if we replace
`consumer.acknowledge(msgId3)` with `consumer.acknowledge(msgId1)` in `CODE 1`,
`CODE 1` won't be equivalent with `CODE 2`.
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