Status
Current state: "Draft"
Discussion thread: here
JIRA: KAFKA-5639
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
The DescribeGroups
protocol v1 currently returns this information for each consumer group:
error_code
group_id
state
protocol_type
protocol
members
(only a member summary is returned per member that misses some useful member info too)
There are additional info in a GroupMetadata
object on the server side, some of which could be useful if exposed via the DescribeGroups
protocol. Here are some examples:
generationId
leaderId
newMemberAdded
receivedConsumerOffsetCommits
receivedTransactionalOffsetCommits
supportedProtocols
per member
Enhancing the protocol with this additional info means improving the existing tools that make use of it. For example, using this additional info, the consumer group command's --describe
output will provide more information about each consumer group to help with studying the group, its monitoring, troubleshooting, etc.
Public Interfaces
This is the latest version (v1) of DescribeGroups
protocol:
DescribeGroups Request (Version: 1) => [group_ids] group_ids => STRING DescribeGroups Response (Version: 1) => throttle_time_ms [groups] throttle_time_ms => INT32 groups => error_code group_id state protocol_type protocol [members] error_code => INT16 group_id => STRING state => STRING protocol_type => STRING protocol => STRING members => member_id client_id client_host member_metadata member_assignment member_id => STRING client_id => STRING client_host => STRING member_metadata => BYTES member_assignment => BYTES
The suggestion is to enhance the protocol to version 2 and add some of these currently missing information (*
indicates suggested fields to be added to the protocol):
DescribeGroups Request (Version: 2) => [group_ids] group_ids => STRING DescribeGroups Response (Version: 2) => throttle_time_ms [groups] throttle_time_ms => INT32 groups => error_code group_id state protocol_type protocol generation_id leader_id new_member_added received_consumer_offset_commits received_transactional_offset_commits [members] error_code => INT16 group_id => STRING state => STRING protocol_type => STRING protocol => STRING * generation_id => INT32 * leader_id => STRING * new_member_added => BOOLEAN * received_consumer_offset_commits => BOOLEAN * received_transactional_offset_commits => BOOLEAN members => member_id client_id client_host member_metadata member_assignment [member_protocols] member_id => STRING client_id => STRING client_host => STRING member_metadata => BYTES member_assignment => BYTES * member_protocols => STRING
Proposed Changes
The proposal is to
- Create version 2 of
DescribeGroups
protocol to include additional information about the consumer group and also each group member for the API clients. - Update the consumer group command to provide the added information in the command output (where applicable). Note that this KIP will impact KIP-175 where group state and detailed member information will also be returned by the consumer group command using additional command line options. Therefore,
Compatibility, Deprecation, and Migration Plan
If this KIP is implemented before KIP-175, there is no compatibility concerns. This all existing protocol fields remain unchanged.
If the KIP is implemented after KIP-175, the output for sub-options --members
and --state
that are introduced in that KIP will be modified to also include the newly added fields. Therefore, clients who rely on the output for those sub-options may need to be adjusted.
Rejected Alternatives