Broker Runtime Configuration
RobustMQ Kafka configuration comes in two kinds:
- Broker runtime (static) config: lives in
config/server.toml, loaded at process startup; changes require a node restart. This page covers this kind. - Cluster dynamic config: persisted in the meta layer, changeable online and preserved across restarts. See Dynamic Configuration.
Kafka-related static config lives under [kafka_runtime] (SASL in its sub-section [kafka_runtime.sasl]). Every item has a default and runs on that default when unset.
[kafka_runtime]
| Key | Default | Description |
|---|---|---|
tcp_port | 9092 | Kafka protocol listen port. Also the port of the advertised address a node registers into meta (see Advertised Address). |
max_fetch_bytes | 4194304 (4 MiB) | Per-partition upper bound on how many bytes a Fetch response may return, regardless of the client's max_bytes / partition_max_bytes. |
max_message_bytes | 1048588 (~1 MiB) | Upper bound on a single produced record batch. Larger batches are rejected with MESSAGE_TOO_LARGE, matching Kafka's message.max.bytes / topic max.message.bytes. |
max_describe_topic_partitions | 2000 | Upper bound on how many partitions a single DescribeTopicPartitions response returns, regardless of the client's response_partition_limit. |
[kafka_runtime.sasl]
| Key | Default | Description |
|---|---|---|
enabled | false | When false, connections are accepted without authentication and the SASL handshake/authenticate handlers stay inert. Set true to enable SASL. |
mechanisms | ["SCRAM-SHA-256", "SCRAM-SHA-512"] | SASL mechanisms the broker offers, advertised to clients via SaslHandshake. |
Example
toml
[kafka_runtime]
tcp_port = 9092
max_fetch_bytes = 4194304
max_message_bytes = 1048588
max_describe_topic_partitions = 2000
[kafka_runtime.sasl]
enabled = true
mechanisms = ["SCRAM-SHA-256", "SCRAM-SHA-512"]About the advertised address
The broker address a client receives is not decided by tcp_port alone: it is the broker_ip (top-level config) + tcp_port advertised address. When broker_ip is unset, the auto-detected local IP is used. In Docker / Kubernetes / NAT environments, connections fail if the advertised address is unreachable from the client. See Advertised Address.
Related
- Top-level
broker_ip,roles,grpc_port,http_port, etc. are global node config affecting all protocols. See Deployment. - Topic-level keys (e.g.
retention.ms,cleanup.policy) are dynamic config read/written over the Kafka protocol. See Topic Configuration.