Vahid Hashemian created KAFKA-7026: -------------------------------------- Summary: Sticky assignor could assign a partition to multiple consumers Key: KAFKA-7026 URL: https://issues.apache.org/jira/browse/KAFKA-7026 Project: Kafka Issue Type: Bug Components: clients Reporter: Vahid Hashemian Assignee: Vahid Hashemian
In the following scenario sticky assignor assigns a topic partition to two consumers in the group: # Create a topic {{test}} with a single partition # Start consumer {{c1}} in group {{sticky-group}} ({{c1}} becomes group leader and gets {{test-0}}) # Start consumer {{c2}} in group {{sticky-group}} ({{c1}} holds onto {{test-0}}, {{c2}} does not get any partition) # Pause {{c1}} (e.g. using Java debugger) ({{c2}} becomes leader and takes over {{test-0}}, {{c1}} leaves the group) # Resume {{c1}} At this point both {{c1}} and {{c2}} will have {{test-0}} assigned to them. The reason is {{c1}} still has kept its previous assignment ({{test-0}}) from the last assignment it received from the leader (itself) and did not get the next round of assignments (when {{c2}} became leader) because it was paused. Both {{c1}} and {{c2}} enter the rebalance supplying {{test-0}} as their existing assignment. The sticky assignor code does not currently check for this duplication. Note: This issue was originally reported on [StackOverflow|https://stackoverflow.com/questions/50761842/kafka-stickyassignor-breaking-delivery-to-single-consumer-in-the-group]. -- This message was sent by Atlassian JIRA (v7.6.3#76005)