---
title: "Compatibility"
description: "The Java and Apache Kafka versions monedula-metrics-reporter supports on brokers and clients, and the version matrix tested in CI."
url: https://monedula.dev/flock/docs/metrics-reporter/concepts/compatibility/
---
## Requirements

The reporter needs Java 17 or newer in the broker or client JVM, Apache Kafka 3.7.0 to 4.3.0 on the broker or client, the range CI tested for 0.10.0, and a collector endpoint that accepts OTLP over gRPC or HTTP. Versions before 3.7 lack the `ClientTelemetry` interface from [KIP-714](https://cwiki.apache.org/confluence/display/KAFKA/KIP-714%3A+Client+metrics+and+observability) that the reporter implements, and are not tested.

## Brokers and clients

The same JAR runs in both. What it exports depends on where it runs:

| | Broker | Java client |
| --- | --- | --- |
| Kafka SPI metrics | Yes, with the `kafka_server_` prefix | Yes, with the `kafka_producer_` or `kafka_consumer_` prefix |
| Yammer metrics | Yes | No, clients have no Yammer registry |
| JVM runtime metrics | Yes | Yes |
| KIP-714 client telemetry | Received and forwarded | Not applicable |
| Broker identity labels | `kafka_cluster_id`, `kafka_node_id` or `kafka_broker_id` | No |

KRaft brokers report `kafka_node_id`, ZooKeeper-mode brokers `kafka_broker_id`.

## Versions tested in CI

For the 0.10.0 release, CI built the shadow JAR and ran the unit and integration tests on JDK 17 and 21 against Kafka 3.7.0, 3.9.0, 4.2.0 and 4.3.0, and an end-to-end test, with Kafka, an OpenTelemetry Collector and Prometheus, against Kafka 4.2.0. The main branch has since moved to the newer Kafka patch releases and added JDK 25, twelve combinations in all, with its end-to-end test against Kafka 4.2.1:

| | Kafka 3.7.2 | Kafka 3.9.2 | Kafka 4.2.1 | Kafka 4.3.1 |
| --- | :---: | :---: | :---: | :---: |
| **JDK 17** | Yes | Yes | Yes | Yes |
| **JDK 21** | Yes | Yes | Yes | Yes |
| **JDK 25** | Yes | Yes | Yes | Yes |

## KIP-714 clients

Client telemetry needs clients that push KIP-714 metrics. The Java client and librdkafka 2.5 or later push by default, because `enable.metrics.push` is on. [Collect Kafka client metrics with KIP-714](/flock/docs/metrics-reporter/how-to/collect-client-telemetry/) lists which metrics each client library pushes.

## Collectors and backends

Any collector with an OTLP receiver works; the reporter does not depend on a particular backend. The quickstart uses the OpenTelemetry Collector Contrib 0.152.0, Prometheus 3.11.3 and Grafana 13.0.1.

For Prometheus, the quickstart lets Prometheus scrape the collector's `prometheus` exporter. Pulling keeps the `# TYPE` and `# HELP` metadata, so Prometheus reports gauges, counters and histograms with their real types. If Prometheus cannot reach the collector, you can use the `prometheusremotewrite` exporter instead, but metric types will likely show up as `unknown`: the collector's remote-write 1.x metadata path is unreliable, and remote write 2.0 was still marked "in development" in collector 0.152.

## Next to other plugins

Kafka uses a single `ClientTelemetry` receiver per broker; if another telemetry plugin is configured too, which one Kafka selects is undefined. The JAR relocates its OpenTelemetry, gRPC, OkHttp and protobuf classes to its own package, so other plugins and libraries on Kafka's classpath, or in a client application, can use their own versions.