Dynamic Configuration

Beyond topic-level config (Topic Configuration), RobustMQ has a category of cluster dynamic config: it applies to the whole cluster, is persisted in the meta layer, can be changed online, and survives restarts. It does not live in config/server.toml (that is static config).

How it works

1. Write a config blob through the admin HTTP API, specifying a config_type (KafkaDynamic for Kafka cluster switches).
2. The config is persisted into the meta layer (Raft-backed), guaranteeing it survives restarts.
3. The change is broadcast to each node's in-memory cache (node_cache); subsequent requests read the cache without querying meta again.

Example: auto.create.topics.enable

This is currently the most representative Kafka cluster dynamic config item: whether to auto-create a topic when a client requests one that does not exist.

Item	Value
Default	true (matches Kafka's broker default)
Hot-changeable	Yes
Persistence	Meta layer, survives restarts

Decision logic

Auto-creation happens only when both conditions hold:

client request carries allow_auto_topic_creation = true
        AND
cluster switch auto.create.topics.enable = true

That is: the client (e.g. a Metadata request) explicitly allows auto-creation, and the cluster switch is on. If either is false, no topic is auto-created.

Set via admin HTTP

curl -X POST http://<admin-host>:<http_port>/api/cluster/config/set \
  -H 'Content-Type: application/json' \
  -d '{
        "config_type": "KafkaDynamic",
        "config": "{\"auto_create_topics_enable\": false}"
      }'

• config_type is fixed to KafkaDynamic.
• config is a JSON string (mind the escaping); the field is auto_create_topics_enable.

Once overridden, the default no longer applies

true is the fallback default used when the value has never been set explicitly. Once you set a value through the API (whether true or false), it is persisted and the built-in default logic no longer participates — only the persisted value counts from then on, until you change it again.

Difference from other config

Aspect	Broker static config	Cluster dynamic config	Topic config
Scope	Single node process	Whole cluster	A single topic
Storage	config/server.toml	Meta layer	Meta layer
Hot-change	No (restart)	Yes	Yes
Entry point	File	admin HTTP	Kafka protocol

Related: Broker Configuration · Topic Configuration.