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https://issues.apache.org/jira/browse/KAFKA-3905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15351906#comment-15351906
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James Cheng commented on KAFKA-3905:
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I think it's better to throw an error, instead of silently removing them. The
user may be unaware they are passing in bad data, and would be confused why the
consumer is not acting as they expected.
The NullPointerException is definitely ugly though. Maybe some sort of
Exception (not sure which type) which says "can't subscribe to topic (null)"?
> remove null from subscribed topics in KafkaConsumer#subscribe
> --------------------------------------------------------------
>
> Key: KAFKA-3905
> URL: https://issues.apache.org/jira/browse/KAFKA-3905
> Project: Kafka
> Issue Type: Wish
> Components: clients
> Affects Versions: 0.10.0.0
> Reporter: Xing Huang
> Assignee: Rekha Joshi
> Priority: Minor
>
> Currently, KafkaConsumer's subscribe methods accept Collection<String> as
> topics to be subscribed, but a Collection may have null as its element. For
> example
> {code}
> String topic = null;
> Collection<String> topics = Arrays.asList(topic);
> consumer.subscribe(topics)
> {code}
> When this happens, consumer will throw a puzzling NullPointerException:
> {code}
> at org.apache.kafka.common.utils.Utils.utf8Length(Utils.java:245)
> at org.apache.kafka.common.protocol.types.Type$6.sizeOf(Type.java:248)
> at
> org.apache.kafka.common.protocol.types.ArrayOf.sizeOf(ArrayOf.java:85)
> at org.apache.kafka.common.protocol.types.Schema.sizeOf(Schema.java:89)
> at org.apache.kafka.common.protocol.types.Struct.sizeOf(Struct.java:244)
> at
> org.apache.kafka.common.requests.RequestSend.serialize(RequestSend.java:35)
> at
> org.apache.kafka.common.requests.RequestSend.<init>(RequestSend.java:29)
> at
> org.apache.kafka.clients.NetworkClient$DefaultMetadataUpdater.request(NetworkClient.java:616)
> at
> org.apache.kafka.clients.NetworkClient$DefaultMetadataUpdater.maybeUpdate(NetworkClient.java:639)
> at
> org.apache.kafka.clients.NetworkClient$DefaultMetadataUpdater.maybeUpdate(NetworkClient.java:552)
> at org.apache.kafka.clients.NetworkClient.poll(NetworkClient.java:258)
> at
> org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.clientPoll(ConsumerNetworkClient.java:360)
> at
> org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:224)
> at
> org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:192)
> at
> org.apache.kafka.clients.consumer.internals.ConsumerNetworkClient.poll(ConsumerNetworkClient.java:163)
> at
> org.apache.kafka.clients.consumer.internals.AbstractCoordinator.ensureCoordinatorReady(AbstractCoordinator.java:179)
> at
> org.apache.kafka.clients.consumer.KafkaConsumer.pollOnce(KafkaConsumer.java:970)
> at
> org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:934)
> {code}
> Maybe it's better to remove null when doing subscription.
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