Environment

• kminion version: 2.3.0 (also reproduced on 2.2.17)
• MINION_CONSUMERGROUPS_SCRAPEMODE: adminApi (also reproduced with offsetsTopic)
• MINION_CONSUMERGROUPS_GRANULARITY: partition
• Kafka brokers: 3 nodes
  Problem
  When a Kafka cluster has consumer groups with a large number of members (38+)
  subscribed to multiple topics (5+ topics), kminion fails to serve any metrics
  with the following error on every scrape:
  An error has occurred while serving metrics:
  19 error(s) occurred:

• collected metric "kminion_kafka_consumer_group_info" { label:{name:"coordinator_id"
  value:"1"} label:{name:"group_id" value:"my-group"} ... } was collected before
  with the same name and label values
• collected metric "kminion_kafka_consumer_group_members" { label:{name:"group_id"
  value:"my-group"} ... } was collected before with the same name and label values
  ...
  Impact
  The Prometheus registry rejects the entire scrape when duplicates are detected,
  meaning zero metrics are exported from kminion during affected scrape cycles.
  Steps to Reproduce

1. Have a Kafka consumer group with 38+ active members
2. The group subscribes to 5+ topics simultaneously
3. Deploy kminion with either adminApi or offsetsTopic scrape mode
4. Hit /metrics endpoint — error is consistent, not intermittent
   Root Cause (hypothesis)
   In concurrent metric collection, the same consumer group is being processed by
   multiple goroutines simultaneously:

• In offsetsTopic mode: the group's offset data is spread across multiple
  __consumer_offsets partitions, each processed by a separate goroutine.
  Group-level metrics (group_info, group_members) are emitted once per partition
  that contains data for that group, instead of once per group.
• In adminApi mode: similar concurrent DescribeGroups processing causes the same
  group to emit group-level metrics more than once.
  Expected Behavior
  Each consumer group emits group-level metrics exactly once per scrape cycle,
  regardless of how many topics it subscribes to or how many goroutines process its data.
  Suggested Fix
  Add a deduplication guard (e.g., sync.Map) in the consumer group metric emission
  logic to ensure group-level metrics (group_info, group_members, empty_members)
  are only written to the metrics channel once per group per collection cycle.
  Workaround
  Exclude affected groups via:
  MINION_CONSUMERGROUPS_IGNOREDGROUPS=my-group-1|my-group-2
  This causes complete loss of visibility for those groups.