[jira] [Created] (KAFKA-10503) MockProducer doesn't throw ClassCastException when no partition for topic

["Gonzalo Muñoz Fernández (Jira)" <ji...@apache.org>]

Gonzalo Muñoz Fernández created KAFKA-10503:
-----------------------------------------------

             Summary: MockProducer doesn't throw ClassCastException when no partition for topic
                 Key: KAFKA-10503
                 URL: https://issues.apache.org/jira/browse/KAFKA-10503
             Project: Kafka
          Issue Type: Improvement
          Components: clients, producer 
    Affects Versions: 2.6.0
            Reporter: Gonzalo Muñoz Fernández


Though {{MockProducer}} admits serializers in its constructors, it doesn't check during {{send}} method that those serializers are the proper ones to serialize key/value included into the {{ProducerRecord}}.

[This check|https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/producer/MockProducer.java#L499-L500] is only done if there is a partition assigned for that topic.

It would be an enhancement if these serialize methods were also invoked in simple scenarios, where no partition is assigned to a topic.

eg:
{code:java}
    @Test
    public void shouldThrowClassCastException() {
        MockProducer<Integer, String> producer = new MockProducer<>(true, new IntegerSerializer(), new StringSerializer());
        ProducerRecord record = new ProducerRecord(TOPIC, "key1", "value1");
        try {
            producer.send(record);
            fail("Should have thrown ClassCastException because record cannot be casted with serializers");
        } catch (ClassCastException e) {}
    }
{code}

Currently, for obtaining the ClassCastException is needed to define the topic into a partition:

{code:java}
PartitionInfo partitionInfo = new PartitionInfo(TOPIC, 0, null, null, null);
Cluster cluster = new Cluster(null, emptyList(), asList(partitionInfo),
                                  emptySet(), emptySet());
 producer = new MockProducer(cluster, 
                                true, 
                                new DefaultPartitioner(), 
                                new IntegerSerializer(), 
                                new StringSerializer());
{code}





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