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The following description provides more clarity on the states that make up the CGMSM:

NEW

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NEW is the initial state for a CGSM

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upon its creation. The Consumer will remain in this state until the next pass of the background thread loop.

JOINING

A state of JOINING signifies that a Consumer wants to join a consumer group. On the next pass of the background thread, the Consumer will enter this state

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to begin communicating with the Kafka broker node that was elected as the group coordinator. A ConsumerGroupHeartbeatRequest will be sent to the coordinator with specific values in the request:

• MemberId is set to null
• MemberEpoch is set to the hard-coded value of 0

Since this is the first request to the coordinator, the ConsumerGroupHeartbeatRequest will be a full request, including values for the following:

• InstanceId is set to the configured value of client.instance.id
• RackId is set to null
• RebalanceTimeoutMs is set to XXXXX
• SubscribedTopicNames is set to XXXXX
• SubscribedTopicRegex is set to XXXXX
• ServerAssignor is set to XXXXX
• ClientAssignors is set to XXXXX
• TopicPartitions is set to null since there are no assigned partitions yet

Per KIP-848's description of the request schema, the above values are only sent with the ConsumerGroupHeartbeatRequest when they change on the client.

JOINED

afsdfsa

ASSIGNING

TBD

TERMINATING

TBD

TERMINATED

TBD

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Consumer API Internal Changes 

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