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4) Update Add new CSV file to support multiple consumer groups. Thus, we will have to update table format by adding a consumer group column. . Backwards compatibility with old CSV file format should be preserved.  

New CSV file format:

Old CSV file format for a single group (leaving as is):

Proposed Changes

• Providing the command line tool kafka-consumer-groups.sh with support of repeating --group parameter for operations --describe, --delete, --reset-offsets
• Providing the command line tool kafka-consumer-groups.sh with an optional --all-groups parameter for operations --describe, --delete, --reset-offsets
• Extending data output table format by adding "GROUP" column for all --describe queries
• Update CSV file to support multiple consumer groups.
• We will also have to make sure CSV generation is done properly since there are no restrictions on consumer group names and symbols like commas and quotes are allowed. That is, CSV file generation with export/import of consumer offsets needs some rework. 

...

• Positive impact on existing users
• We are not changing behavior but adding new features
• Support backwards compatibility with old CSV file format for a single group case

Rejected Alternatives

None.