ERR XReadGroup is cancelled

Fix the Upstash Redis XReadGroup is cancelled error by acknowledging pending stream messages with XACK to free the consumer PEL.

Symptom

The client gets an exception similar to:

ReplyError: ERR XReadGroup is cancelled. Pending Entries List limit per consumer is about to be reached. Limit: 1000, Current PEL size: 90, Requested Read: 20, Key: mstream, Group: group1, Consumer: consumer1.

Diagnosis

Pending Entries List of the stream for the consumer is full. For each consumer in a consumer group, there is a pending entries list. This list keeps the messages that are delivered to a consumer but not yet acknowledged via XACK. This list is populated via XREADGROUP.

Solution

Acknowledge the consumed messages via XACK from the list of the associated group and consumer.