[Solved] Given the following code snippet using TopologyTestDriver: var driver = new TopologyTestDriver(topology, props);... What will be printed if the topology simply forwards input to output unchanged? | Kafka

Kafka - Advanced Stream Processing

Given the following code snippet using TopologyTestDriver:

var driver = new TopologyTestDriver(topology, props);
var inputTopic = driver.createInputTopic("input", Serdes.String().serializer(), Serdes.String().serializer());
var outputTopic = driver.createOutputTopic("output", Serdes.String().deserializer(), Serdes.String().deserializer());

inputTopic.pipeInput("key1", "value1");
var result = outputTopic.readKeyValue();
System.out.println(result.key + ":" + result.value);

What will be printed if the topology simply forwards input to output unchanged?

Akey1:value1

Bnull:null

Cvalue1:key1

DException thrown

Step-by-Step Solution

Solution:

Step 1: Understand the topology behavior
The topology forwards input key-value pairs unchanged to the output topic.
Step 2: Trace the test driver code
Input "key1" and "value1" is piped in; outputTopic reads the same key-value pair.
Final Answer:
key1:value1 -> Option A
Quick Check:
Forwarded key-value = key1:value1 [OK]

Quick Trick: If topology forwards, output matches input exactly [OK]

Common Mistakes:

MISTAKES

Mixing key and value order
Expecting null output without input
Assuming exceptions without errors

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Given the following code snippet using TopologyTestDriver:

Step 1: Understand the topology behavior

Step 2: Trace the test driver code

Final Answer:

Quick Check:

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