aloyszhang opened a new issue #11612:
URL: https://github.com/apache/pulsar/issues/11612
**Describe the bug**
In our product environment, sometimes set `startMessageId` for a
reader(created by flink source) has no effect.
After troubleshoot, we found the root cause is the reader re-use the same
subscriptionName exist before, and reader misuse the Durable Subscription
object, so reader will read message from the Durable Subscription's
`readPosition` instead of the `startMessageId`.
**To Reproduce**
Steps to reproduce the behavior:
1. build a topic and setup producer/consumer
```java
String topicName = "t/ns/topic";
Producer<String> producer =
pulsarClient.newProducer(Schema.STRING).topic(topicName)
.create();
Consumer<String> consumer =
pulsarClient.newConsumer(Schema.STRING).topic(topicName)
.readCompacted(true)
.subscriptionMode(SubscriptionMode.Durable)
.subscriptionType(SubscriptionType.Exclusive)
.subscriptionName("mix-subscription")
.subscriptionInitialPosition(SubscriptionInitialPosition.Earliest)
.subscribe();
```
2. send message
```java
int messageNum = 10;
for (int i = 0; i < messageNum; i++) {
producer.send("message" + i);
```
3. receive the first 5 messages by this consumer and close
```java
for (int i = 0; i < 5; i++) {
Message<String> message = consumer.receive();
assertNotNull(message);
Assert.assertEquals(message.getValue(), "message" + i);
consumer.acknowledge(message);
}
consumer.close();
```
4. Setup a reader with the same subscription name and start from earliest
```java
Reader<String> reader =
pulsarClient.newReader(Schema.STRING).topic(topicName)
.subscriptionName("mix-subscription")
.startMessageId(MessageId.earliest)
.create();
```
5. reader message by this reader and only five message can be read
```java
Message<String> message;
int readCount = 0;
while((message = reader.readNext(3, TimeUnit.SECONDS)) != null) {
log.info("###Message id : {}", message.getMessageId());
readCount ++;
}
Assert.assertEquals(readCount, 5);
```
**Expected behavior**
reader using the same subsciprioinName shoud be forbidden
**Screenshots**
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**Desktop (please complete the following information):**
- OS: [e.g. iOS]
**Additional context**
Add any other context about the problem here.
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