Which command starts consuming messages from a topic starting from the beginning?

Which command starts consuming messages from a topic starting from the beginning?

• A. bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic my-first-topic --from-end
• B. bin/kafka-console-consumer.sh --broker-list localhost:9092 --topic my-first-topic
• C. bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic my-first-topic --from-beginning
• D. bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic my-first-topic --group my-group

Answer: (C)

You control where a Kafka console consumer starts reading from. The flag that guarantees reading all existing messages from every partition is --from-beginning. When you include this option, the consumer starts at the very first offset of each partition in the topic, ignoring any previously stored offsets or group state. That’s why the command that contains --from-beginning is the one that starts from the beginning. Without this flag, the consumer relies on the current offset for the consumer group. If there’s a committed offset, it resumes from there; if there isn’t one yet, it typically starts at the end of the log, which means you’d miss earlier messages. The option to start from the end is a different behavior, while using a group without --from-beginning ties the starting point to group offsets rather than the start of the log. So, to guarantee starting from the very first message, use the command with --from-beginning. If the topic already has messages, you’ll read from the start; if not, you’ll wait for new messages to arrive.

You control where a Kafka console consumer starts reading from. The flag that guarantees reading all existing messages from every partition is --from-beginning. When you include this option, the consumer starts at the very first offset of each partition in the topic, ignoring any previously stored offsets or group state. That’s why the command that contains --from-beginning is the one that starts from the beginning.

Without this flag, the consumer relies on the current offset for the consumer group. If there’s a committed offset, it resumes from there; if there isn’t one yet, it typically starts at the end of the log, which means you’d miss earlier messages. The option to start from the end is a different behavior, while using a group without --from-beginning ties the starting point to group offsets rather than the start of the log. So, to guarantee starting from the very first message, use the command with --from-beginning. If the topic already has messages, you’ll read from the start; if not, you’ll wait for new messages to arrive.