Client Quotas

RobustMQ Kafka implements the client-quota management APIs (AlterClientQuotas / DescribeClientQuotas): quotas can be set, queried, and persisted to meta-service.

Current state (please note): quotas can be set, queried, and persisted, but they are not yet wired into throttling. The Produce / Fetch paths never read quotas, so setting one does not actually throttle; quotas are loaded into the broker cache, but no call site consults them to rate-limit a producer or consumer. Quotas are "manageable metadata" today.

Supported scope

Dimension	Support
Entity type	client-id only; others (e.g. user) return InvalidRequest
Entity dimensions	single-dimension only; multi-dimension returns InvalidRequest
Quota keys	producer_byte_rate, consumer_byte_rate
Key value	for non-remove ops, the value must be positive and finite, else InvalidRequest
Entity name	may not be empty, may not be the reserved __default__

CLI examples

# Set producer/consumer byte-rate limits (bytes/sec) for client-id = svc-a
kafka-configs.sh --bootstrap-server localhost:9092 \
  --alter --entity-type clients --entity-name svc-a \
  --add-config 'producer_byte_rate=1048576,consumer_byte_rate=2097152'

# Describe
kafka-configs.sh --bootstrap-server localhost:9092 \
  --describe --entity-type clients --entity-name svc-a

# Delete a key
kafka-configs.sh --bootstrap-server localhost:9092 \
  --alter --entity-type clients --entity-name svc-a \
  --delete-config 'producer_byte_rate'

DescribeClientQuotas filter matching supports EXACT, DEFAULT, and ANY match types, with an optional strict flag.

Quotas are persisted through Raft and broadcast to every broker's cache (see Overview).

Limitations at a glance

Limitation	Detail
Not enforced	no throttling; setting a quota does not rate-limit produce/consume
Entity type	client-id only; no user or user+client-id
Quota keys	byte-rate only; no request rate (request_percentage), etc.