Kafka guarantees message durability by replicating messages across multiple brokers in a Kafka cluster. When a message is written to Kafka, it is first written to the leader broker for the corresponding partition. The leader broker then replicates the message to the other brokers in the cluster that are assigned to the same partition.
Kafka uses a quorum-based replication mechanism to ensure that messages are written to a sufficient number of brokers before they are acknowledged as committed. This mechanism ensures that messages are not lost even in the event of hardware failures or other issues.
Kafka also provides configurable options for message retention and cleanup, which allow administrators to control how long messages are retained in Kafka and when they are deleted. This ensures that messages are available for processing for a configurable period of time, even in the event of hardware or software failures.
Finally, Kafka provides a mechanism for clients to acknowledge when they have successfully processed a message, which allows Kafka to remove the message from the log. This mechanism ensures that messages are not duplicated or lost during processing.
Overall, Kafka’s replication mechanism, message retention policies, and acknowledgement mechanisms provide a high degree of message durability, making Kafka a reliable platform for handling real-time data processing and streaming applications.