hozumi opened a new issue #12291:
URL: https://github.com/apache/pulsar/issues/12291
**Describe the bug**
Pulsar and java client version: 2.8.1
When a reader that listens multiple topics is configured
`.startMessageId(MessageId.earliest)` , it seems that initial position is
actually `latest` .
Also `reader.hasMessageAvailable()` causes NPE.
```
Exception in thread "main" java.lang.NullPointerException
at
org.apache.pulsar.client.impl.ConsumerImpl.hasMessageAvailableAsync(ConsumerImpl.java:1880)
at
org.apache.pulsar.client.impl.MultiTopicsConsumerImpl.hasMessageAvailableAsync(MultiTopicsConsumerImpl.java:751)
at
org.apache.pulsar.client.impl.MultiTopicsConsumerImpl.hasMessageAvailable(MultiTopicsConsumerImpl.java:741)
at
org.apache.pulsar.client.impl.MultiTopicsReaderImpl.hasMessageAvailable(MultiTopicsReaderImpl.java:144)
at example.foo.Main.main(Main.java:20)
```
It seems that the java client support MultiTopicsReaderImpl since 2.8.0.
https://github.com/apache/pulsar/pull/9995
**To Reproduce**
Steps to reproduce the behavior:
1. Setup standalone pulsar
```
docker run -it -p 6650:6650 -p 8080:8080 --name pulsar_broker
apachepulsar/pulsar:2.8.1 bin/pulsar standalone
```
2. Configure a namespace
```
docker exec -it pulsar_broker bin/pulsar-admin namespaces create sample/mytes
docker exec -it pulsar_broker bin/pulsar-admin namespaces set-retention
sample/mytest --size 10M --time -1
```
3. Store some messages into two topics.
```
docker exec -it pulsar_broker bin/pulsar-client produce
"persistent://sample/mytest/mytopic1" --messages "hello1"
docker exec -it pulsar_broker bin/pulsar-client produce
"persistent://sample/mytest/mytopic1" --messages "hello2"
docker exec -it pulsar_broker bin/pulsar-client produce
"persistent://sample/mytest/mytopic2" --messages "world1"
docker exec -it pulsar_broker bin/pulsar-client produce
"persistent://sample/mytest/mytopic2" --messages "world2"
```
4. Run multi-topic reader
```java
package example.foo;
import org.apache.pulsar.client.api.Message;
import org.apache.pulsar.client.api.MessageId;
import org.apache.pulsar.client.api.PulsarClient;
import org.apache.pulsar.client.api.PulsarClientException;
import org.apache.pulsar.client.api.Reader;
import java.util.Arrays;
public class Main {
public static void main(String[] args) throws PulsarClientException {
PulsarClient pClient =
PulsarClient.builder().serviceUrl("pulsar://localhost:6650").build();
Reader<byte[]> reader = pClient.newReader()
.readerName("myreader1")
.topics(Arrays.asList("persistent://sample/mytest/mytopic1",
"persistent://sample/mytest/mytopic2"))
.startMessageId(MessageId.earliest)
.create();
// reader.hasMessageAvailable(); // causes NPE
while(true) {
Message<byte[]> m = reader.readNext();
System.out.println(m.getTopicName() + " value:" + new
String(m.getData(), java.nio.charset.StandardCharsets.UTF_8));
}
}
}
```
**Expected behavior**
Multi-topic reader should follow`startMessageId` configuration.
**Additional context**
I am not sure how this issue is related
https://github.com/apache/pulsar/issues/9301 .
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