How is fault tolerance implemented in Storm?

The fault-tolerance mechanism in Storm is implemented using an ACK mechanism and timers.

ACK mechanism: In Storm, each tuple is assigned a unique ID. When a tuple is successfully processed by a bolt, it sends an ACK message to the spout to confirm the processing. If a tuple does not receive an ACK message, the spout will resend the tuple to the next bolt for processing.

Timer: Storm will set a timeout for each tuple during processing. If a tuple does not receive an ACK message within the set timeout, it will be considered as failed and resent to the next bolt for processing.

通过这两种方式，Storm能够保证在出现问题或失败时能够及时进行恢复和重新处理，以实现容错性。