Kafka LeaveGroup Request Wire Format v1 — Binary Protocol Layout

What is LeaveGroup?

Sent on clean consumer shutdown to trigger an immediate rebalance rather than waiting for the session timeout. Without it, a departed consumer's partitions stay unassigned for up to session.timeout.ms. Static membership (group.instance.id) avoids rebalances on short restarts by skipping LeaveGroup semantics.

Schema
{
  "GroupId": string,
  "MemberId": string
}

Example
{
  "GroupId": "order-processors",
  "MemberId": "consumer-1-abc123"
}