Monitor Kafka Consumer Lag
Kafma provides Kafka consumer lag monitoring at the group, topic, partition, and member levels. Start with the group total, then narrow the investigation to the partition where progress has slowed.
What is Kafka consumer lag?
Kafka consumer lag is the difference between a partition's end offset and the consumer group's committed offset. Lag increases when new records arrive faster than the group advances its committed position.
Kafma measures lag from committed offsets. After a consumer processes records, lag decreases only when the group commits a new offset.
Lag belongs to a group, topic, and partition—not to a topic alone. Two consumer groups reading the same partition can therefore report different lag.
A partition without a committed offset is shown as Not committed. In group details, total and max lag include only partitions with committed offsets. Not committed or Partial indicates that other partitions do not yet have a reliable lag value.
Read Kafka consumer lag metrics
Open a group to compare three signals:
| Metric | Use it to |
|---|---|
| Total lag | See the combined committed lag across the group |
| Max lag | Find the committed partition with the largest lag |
| Trend | See whether recent lag samples are rising or falling |
The trend uses recent samples collected while group details refresh; it is not long-term monitoring history.
Find lag by topic, partition, and member
Expand Topic Assignments to compare topic totals and individual partitions. Each partition shows its committed offset, lag, and whether a member is assigned. An Unassigned partition has no current member, but its saved offset can still fall behind as new records arrive.
Member lag is the sum of lag across that member's committed partitions. Expand a member to find which assigned partition contributes the backlog. A partition can be assigned to only one member of the group at a time.
Diagnose increasing Kafka consumer lag
Use these signals to decide what to check next:
| Signal | Check next |
|---|---|
| Lag rises across many assigned partitions | Consumer throughput, processing time, or downstream dependencies |
| Lag is concentrated in one partition | Key distribution, partition traffic, or repeated processing failures |
| Lag appears on an unassigned partition | Whether the group is rebalancing or no active member subscribes to the topic |
| Group is Empty and lag rises | Whether the consumer application is stopped or failing |
Kafka retention can move a partition's earliest available offset forward. Records already removed by retention cannot be recovered by the consumer or by resetting its offsets.
Inspect lagging messages in the Console
From an expanded topic in the group drawer, open the Console in Watch Group mode. For an assigned partition, hover over the partition and select Inspect to watch only that partition. Kafma shows a bounded window around the committed position of each partition without joining the group or changing its offsets.
The view separates records before the committed position from pending records at the front of the backlog. Use it to inspect the keys and values near a stalled position.