A negative lag value in CMAK (Cluster Manager for Apache Kafka) usually indicates a bug, timing issue, or inconsistency in how offsets are being calculated or reported. Here's a breakdown of what could cause it:

🔍 Possible Reasons for Negative Lag in CMAK

1. Race condition in offset updates

• CMAK computes lag as:

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  lag = logEndOffset (latest offset) - consumerOffset (committed offset)

• If the consumer offset is updated slightly after CMAK fetches the log end offset, but the values aren't synchronized properly, it can briefly show as negative.

2. Offset reset or manual intervention

• If an admin or app manually sets the consumer offset ahead of the current log end offset (e.g., via kafka-consumer-groups.sh --reset-offsets), CMAK may temporarily report negative lag.

3. CMAK bug or version-specific glitch

• Some CMAK versions have known bugs or quirks related to lag calculation, especially under high load or with large offset ranges.

• Check CMAK GitHub issues for related bugs (search "negative lag").

4. Clock sync issues between brokers and CMAK

• If your Kafka cluster and the server running CMAK have out-of-sync clocks, timestamp comparisons might lead to incorrect lag readings.

5. Compacted topics or partition leadership changes

• Lag calculations can become inconsistent if:

  • Topics are log-compacted

  • Partition leadership changes quickly

  • Consumer group rebalancing is in progress

✅ How to Fix / Mitigate

1. Ensure consumers commit offsets properly and consistently

2. Upgrade CMAK – bugs are often fixed in newer versions

3. Check broker and CMAK server clocks – sync them using NTP

4. Monitor offset commits and topic configurations

5. Restart CMAK – sometimes a stale cache can cause issues

Would you like a script or a dashboard tip to track offsets outside of CMAK as a comparison tool?