Klag vs Burrow

Both Klag and Burrow monitor Kafka consumer lag with read-only access. They differ in philosophy: Burrow evaluates lag against built-in status rules and pushes notifications; Klag exports a richer set of lag metrics and leaves evaluation and alerting to your observability stack.

What each tool is

• Klag is a lag metrics exporter. It polls the Kafka Admin API on an interval and publishes metrics to Prometheus, Datadog, or OTLP.
• Burrow is a lag monitor with an evaluation engine. It classifies each consumer group’s status (OK / WARN / ERROR) using a sliding-window algorithm and can push notifications over email and HTTP. It exposes an HTTP API; Prometheus metrics come via a separate exporter.

At a glance

	Klag	Burrow
Category	Lag metrics exporter	Lag monitor + notifier
Runtime	Java / Vert.x / GraalVM	Go
Primary output	Prometheus, Datadog, OTLP	HTTP API + notifiers
Lag evaluation	In your alerting stack	Built-in status rules
License	Apache 2.0	Apache 2.0

Feature comparison

Feature	Klag	Burrow
Lag in messages	✅	✅
Consumer group state	✅	✅
Lag status evaluation rules	❌	✅
Built-in notifiers (email/HTTP)	❌	✅
Lag velocity (growing/shrinking)	✅	⚠️ status only
Time-based lag (ms) + time-to-catch-up	✅	❌
Hot partition detection	✅	❌
Data-loss / retention alerting	✅	❌
Commit staleness (stuck consumers)	✅	❌
MCP endpoint for AI agents	✅	❌
Prometheus native	✅	⚠️ separate exporter
Datadog / OTLP native	✅	❌
Read-only DESCRIBE ACLs	✅	✅

When to use which

• Use Burrow if you want a self-contained tool that decides “is this group healthy?” and pushes a notification, without a metrics pipeline. Its status-window algorithm is its signature feature.
• Use Klag if you already run Prometheus / Grafana / Datadog and want lag as first-class metrics — plus velocity, time-based lag, retention risk, and hot-partition signals — that you alert on with your existing rules and dashboards. Klag also exposes a read-only MCP endpoint for AI agents, which Burrow does not.

Klag was inspired by the archived kafka-lag-exporter; if you’re coming from that project, the migration guide maps every metric.

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