how does Kafka ensure that messages are not lost?

Kafka is a distributed messaging system that ensures messages are not lost by using various methods.

1. Persistence storage: Kafka stores all messages persistently on disk, even after they have been consumed, allowing them to be retained for a certain period of time based on the configured retention policy. This ensures that consumers can re-consume messages in case of any issues during message consumption, preventing message loss.
2. Replication Mechanism: Kafka employs a distributed replication mechanism by distributing messages to multiple nodes for backup. In the event of a node failure, data can be recovered from the backup nodes. This mechanism ensures high availability and fault tolerance of messages, preventing data loss.
3. Batch sending and asynchronous writing: Kafka supports batch sending of messages and asynchronous writing, allowing multiple messages to be grouped into a batch for sending, reducing network overhead and disk I/O. Additionally, Kafka’s message writing is asynchronous, so even if a failure occurs during writing, it will not immediately impact message publishing and consumption.
4. Confirmation mechanism: Producers have the option to choose whether they need a confirmation mechanism when sending messages. This mechanism ensures that a message is successfully sent before a confirmation is returned. If an error occurs during the sending process, producers can resend the message to prevent it from being lost.
5. Client configuration parameters: Kafka provides various options for configuring client settings, such as adjusting message send timeout, retry attempts, etc., in order to ensure message reliability.

In conclusion, Kafka ensures that messages are not lost through methods such as persistent storage, replication, batch sending and asynchronous writing, message acknowledgement mechanisms, and client configuration parameters.