XACK command in Redis is used with stream data structures. It's specifically utilized to acknowledge the processing of a message from a stream by a consumer. When consumers read messages, they can ensure that no message gets lost during processing by using
XACK. Typically, this is used in a system where reliability is required and message loss cannot be tolerated such as in messaging queues, event-driven architectures, etc.
Consider a scenario where your application is consuming messages from a stream named "mystream" and the consumer group is named "mygroup".
For the purpose of this example, let's assume that you have already connected to your Redis instance and created a new stream and consumer group.
Let's say that you have read a message and its ID is "1577836800000-0", now you want to acknowledge it:
This script connects to the Redis server running on localhost and acknowledges the processing of the message with ID "1577836800000-0" in "mystream" by "mygroup".
XACK. If an error occurs and it's not handled, your application might behave unexpectedly.
context.Background()which never expires and can cause a goroutine leak if the redis server doesn't respond.
Q: Can I acknowledge multiple messages at once?
A: Yes, you can pass multiple IDs to the
XAck function to acknowledge multiple messages in one command.
Q: What happens if I try to acknowledge a message that does not exist or has already been acknowledged?
A: Redis will silently ignore non-existing IDs or IDs for messages that have already been acknowledged. The
XACK command returns the count of IDs actually acknowledged.