BewareMyPower commented on PR #1301:
URL:
https://github.com/apache/pulsar-client-go/pull/1301#issuecomment-2446616656
### The 1st question
What's confusing is the tracking message ID itself. The existing `AckID`
method's semantic is wrong. Let's look at the following example with `AckID`:
```golang
func TestMyAck(t *testing.T) {
client, err := NewClient(ClientOptions{
URL: lookupURL,
})
assert.Nil(t, err)
defer client.Close()
topic := fmt.Sprintf("test-my-ack-%v", time.Now().Nanosecond())
createConsumer := func() Consumer {
consumer, err := client.Subscribe(ConsumerOptions{
Topic: topic,
SubscriptionName: "my-sub",
SubscriptionInitialPosition:
SubscriptionPositionEarliest,
Type: Shared,
AckWithResponse: true,
})
assert.Nil(t, err)
return consumer
}
consumer := createConsumer()
sendMessages(t, client, topic, 0, 2, true) // send 0 and 1 in the same
batch
msgs := receiveMessages(t, consumer, 2)
for i := 0; i < 2; i++ {
fmt.Println("Received message: ", string(msgs[i].Payload()),
msgs[i].ID())
}
if err := consumer.AckID(msgs[0].ID()); err != nil {
fmt.Println("Ack message 0 failed: ", err.Error())
} else {
fmt.Println("Ack message 0 success")
}
consumer.Close()
consumer = createConsumer()
msgs = receiveMessages(t, consumer, 1)
fmt.Println("Received message: ", string(msgs[0].Payload()),
msgs[0].ID())
}
```
Outputs:
```
Received message: msg-0 9:0:0
Received message: msg-1 9:0:0
Ack message 0 success
Received message: msg-0 9:0:0
```
From the perspective from user side:
- "msg-0"'s message ID has been acknowledged successfully
- "msg-0" was delivered again after restarting the consumer
Actually this API implements `AckWithResponse` with correct semantics.
Replacing the `AckID` call with:
```golang
for msgID, err := range consumer.AckIDList([]MessageID{msgs[0].ID()}) {
fmt.Println("Failed to acknowledge ", msgID, err.Error())
}
```
The outputs will be:
```
Received message: msg-0 10:0:0
Received message: msg-1 10:0:0
Failed to acknowledge 10:0:0 incomplete batch
Received message: msg-0 10:0:0
```
P.S. we should fix the `String()` method of message ID.
Users should add the failed message ID to the next message ID list passed to
`AckIDList`. Acknowledging the same message ID
IMO, we should make batch index ACK enabled by default for both client side
and server side. The current default behavior is really confusing.
### The 2nd question
`ackIDCommon` is an abstraction for acknowledgment on a single message ID.
When `AckWithResponse` is true, we cannot reuse this method because we should
avoid sending N requests.
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