Sink connectors in Kafka - Mini Project: Build & Apply

Sink Connectors with Kafka

📖 Scenario: You are working with Apache Kafka to move data from a Kafka topic to an external system using sink connectors. This is common in real-world data pipelines where data collected in Kafka needs to be stored or processed elsewhere.

🎯 Goal: Build a simple Kafka sink connector configuration step-by-step to send messages from a Kafka topic to a file system.

📋 What You'll Learn

Create a Kafka topic configuration

Set up a sink connector configuration variable

Write the connector configuration JSON with required fields

Print the final connector configuration JSON

💡 Why This Matters

🌍 Real World

Kafka sink connectors are used to move data from Kafka topics to external systems like files, databases, or search engines automatically.

💼 Career

Understanding sink connectors is important for data engineers and developers who build data pipelines and integrate Kafka with other systems.

1

Create Kafka topic configuration

Create a variable called topic_config as a dictionary with these exact entries: "name": "test-topic", "partitions": 3, "replication_factor": 1.

Kafka

# Your code here

Hint

Use a Python dictionary with keys exactly as shown.

2

Set up sink connector configuration variable

Create a variable called sink_connector_config as an empty dictionary to hold the sink connector settings.

Kafka

topic_config = {
    "name": "test-topic",
    "partitions": 3,
    "replication_factor": 1
}
# Your code here

Hint

Just create an empty dictionary named sink_connector_config.

3

Write sink connector configuration JSON

Add these exact key-value pairs to sink_connector_config: "name": "file-sink-connector", "connector.class": "FileStreamSink", "tasks.max": "1", "topics": "test-topic", "file": "/tmp/output.txt".

Kafka

topic_config = {
    "name": "test-topic",
    "partitions": 3,
    "replication_factor": 1
}
sink_connector_config = {}
# Your code here

Hint

Assign all required keys and values exactly as shown inside sink_connector_config.

4

Print the sink connector configuration

Write a print statement to display the sink_connector_config dictionary.

Kafka

topic_config = {
    "name": "test-topic",
    "partitions": 3,
    "replication_factor": 1
}
sink_connector_config = {
    "name": "file-sink-connector",
    "connector.class": "FileStreamSink",
    "tasks.max": "1",
    "topics": "test-topic",
    "file": "/tmp/output.txt"
}
# Your code here

Hint

Use print(sink_connector_config) to show the dictionary.

Practice

1.

What is the main purpose of a Kafka sink connector?

easy

A. To create new Kafka topics dynamically

B. To move data from external systems into Kafka topics

C. To monitor Kafka cluster health

D. To move data from Kafka topics to external systems automatically

Solution

1. Step 1: Understand the role of sink connectors

   Sink connectors are designed to export data from Kafka topics to other systems.

2. Step 2: Differentiate from source connectors

   Source connectors import data into Kafka, while sink connectors export data out.

3. Final Answer:

   To move data from Kafka topics to external systems automatically -> Option D

4. Quick Check:

   Sink connector = export data from Kafka [OK]

Hint: Sink connectors export data out of Kafka topics [OK]

Common Mistakes:

• Confusing sink with source connectors
• Thinking sink connectors create topics
• Assuming sink connectors monitor Kafka health

2.

Which of the following is a correct JSON field to specify the Kafka topic for a sink connector configuration?

{
  "name": "my-sink-connector",
  "config": {
    "connector.class": "io.confluent.connect.jdbc.JdbcSinkConnector",
    "topics": "my_topic",
    "connection.url": "jdbc:mysql://localhost:3306/mydb"
  }
}

easy

A. "topics"

B. "topic"

C. "topic_name"

D. "source.topics"

Solution

1. Step 1: Check the standard Kafka Connect config field

   The field to specify Kafka topics in sink connector config is "topics" (plural).

2. Step 2: Verify the example JSON

   The example uses "topics": "my_topic", which is correct syntax.

3. Final Answer:

   "topics" -> Option A

4. Quick Check:

   Kafka sink config uses "topics" field [OK]

Hint: Use "topics" (plural) to list Kafka topics in config [OK]

Common Mistakes:

• Using "topic" (singular) instead of "topics"
• Using non-standard fields like "topic_name"
• Confusing source connector fields with sink

3.

Given this sink connector config snippet, what will be the destination system?

{
  "name": "file-sink-connector",
  "config": {
    "connector.class": "FileStreamSink",
    "topics": "logs",
    "file": "/tmp/output.log"
  }
}

medium

A. A Kafka topic named 'logs'

B. A file located at /tmp/output.log

C. A database table named 'logs'

D. A remote HTTP endpoint

Solution

1. Step 1: Identify the connector class

   The connector class is "FileStreamSink", which writes data to a file.

2. Step 2: Check the "file" config field

   The "file" field specifies the destination file path "/tmp/output.log".

3. Final Answer:

   A file located at /tmp/output.log -> Option B

4. Quick Check:

   FileStreamSink writes to file path [OK]

Hint: FileStreamSink writes Kafka data to a file path [OK]

Common Mistakes:

• Assuming data goes back to Kafka topic
• Confusing sink with source connectors
• Thinking it writes to a database or HTTP

4.

Identify the error in this sink connector config JSON:

{
  "name": "jdbc-sink",
  "config": {
    "connector.class": "io.confluent.connect.jdbc.JdbcSinkConnector",
    "topic": "orders",
    "connection.url": "jdbc:postgresql://localhost:5432/shop"
  }
}

medium

A. Invalid JDBC URL format

B. Connector class name is incorrect

C. Missing 'topics' field; uses 'topic' instead

D. Missing 'name' field

Solution

1. Step 1: Check the topic field name

   The config uses "topic" (singular), but Kafka sink connectors require "topics" (plural).

2. Step 2: Verify other fields

   The JDBC URL and connector class are correctly formatted, and "name" is present.

3. Final Answer:

   Missing 'topics' field; uses 'topic' instead -> Option C

4. Quick Check:

   Use "topics" not "topic" in sink config [OK]

Hint: Use plural "topics" field in sink connector config [OK]

Common Mistakes:

• Using singular "topic" instead of "topics"
• Assuming JDBC URL is wrong without checking
• Thinking connector class name is invalid

5.

You want to export data from multiple Kafka topics to a single database table using a JDBC sink connector. Which configuration approach is correct?

{
  "name": "multi-topic-jdbc-sink",
  "config": {
    "connector.class": "io.confluent.connect.jdbc.JdbcSinkConnector",
    "topics": "topic1,topic2,topic3",
    "connection.url": "jdbc:mysql://localhost:3306/mydb",
    "table.name.format": "combined_table"
  }
}

hard

A. This config exports all topics to one table named 'combined_table'

B. Each topic will create a separate table ignoring 'table.name.format'

C. The connector will fail because multiple topics are not allowed

D. Data will be merged but only from 'topic1'

Solution

1. Step 1: Understand 'topics' field with multiple topics

   The "topics" field lists multiple topics separated by commas, which is valid.

2. Step 2: Check 'table.name.format' usage

   Setting "table.name.format" to a fixed table name causes all data to go into that single table.

3. Step 3: Confirm connector behavior

   The JDBC sink connector supports writing multiple topics to one table if configured this way.

4. Final Answer:

   This config exports all topics to one table named 'combined_table' -> Option A

5. Quick Check:

   Multiple topics + fixed table name = single table export [OK]

Hint: Use comma-separated topics and fixed table name for single table export [OK]

Common Mistakes:

• Assuming multiple topics create separate tables automatically
• Thinking multiple topics are not allowed in sink config
• Ignoring 'table.name.format' effect