Chris Pettitt created BEAM-2704:
-----------------------------------
Summary: KafkaIO: NPE without key serializer set
Key: BEAM-2704
URL: https://issues.apache.org/jira/browse/BEAM-2704
Project: Beam
Issue Type: Bug
Components: sdk-java-extensions
Reporter: Chris Pettitt
Assignee: Davor Bonaci
The KafkaIO javadoc implies that you do not need to set a Serializer if you
only want to emit values:
{code}
* <p>Often you might want to write just values without any keys to Kafka. Use
{@code values()} to
* write records with default empty(null) key:
*
* <pre>{@code
* PCollection<String> strings = ...;
* strings.apply(KafkaIO.<Void, String>write()
* .withBootstrapServers("broker_1:9092,broker_2:9092")
* .withTopic("results")
* .withValueSerializer(new StringSerializer()) // just need serializer
for value
* .values()
* );
* }</pre>
{code}
However, if you don't set the key serializer then Kafka blows up when trying to
instantiate the key serializer (in Kafka 0.10.1, at least). It would be more
convenient if KafkaIO worked as documented and assigned a null serializer if
values() is used.
Relevant stack trace:
{code}
Caused by: java.lang.NullPointerException
at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:230)
at
org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:163)
at
org.apache.beam.sdk.io.kafka.KafkaIO$KafkaWriter.setup(KafkaIO.java:1582)
at
org.apache.beam.sdk.io.kafka.KafkaIO$KafkaWriter$DoFnInvoker.invokeSetup(Unknown
Source)
{code}
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