Configuration

Each configuration key can be overridden with an environment variable prefixed with KARAPACE_, the exception being keys that already start with the karapace string. For example, to override the bootstrap_uri value, use the environment variable KARAPACE_BOOTSTRAP_URI.

An example configuration file in the repository gives you an idea of what you can change.

At least one of karapace_registry and karapace_rest must be enabled for the service to start.

Common keys

Parameter	Default	Description
bootstrap_uri	localhost:9092	The Kafka service where schemas are stored and coordination among Karapace instances runs.
host	127.0.0.1	Listening host. Use an empty string to listen on all networks.
port	8081	Listening port for the Karapace server.
topic_name	_schemas	The Kafka topic where schemas are stored.
group_id	schema-registry	Kafka group name used to elect a master for storing schemas.
client_id	sr-1	The client id used when coordinating with other Karapace instances.
replication_factor	1	Replication factor for the schema topic.
karapace_registry	true	Include the registry part of the app in the starting process.
karapace_rest	true	Include the REST part of the app in the starting process.
log_level	DEBUG	Logging level.
log_handler	stdout	Log handler: stdout or systemd.

High availability / master election

Parameter	Default	Description
advertised_hostname	socket.gethostname()	Hostname advertised to other Karapace instances in the same Kafka group.
advertised_port	None	Port advertised to other instances. Falls back to port.
advertised_protocol	http	Protocol advertised to other instances.
master_eligibility	true	Whether the instance can be promoted to master.
master_election_strategy	lowest	Basis on which the cluster master is chosen.
waiting_time_before_acting_as_master_ms	5000	Time a master waits before becoming active. Should be an upper bound of the time to write and consume a message in the Kafka topic.

REST proxy

Parameter	Default	Description
consumer_enable_autocommit	true	Enable auto commit on REST proxy consumers.
consumer_request_max_bytes	67108864	Maximum bytes fetched per consumer request.
consumer_request_timeout_ms	11000	Timeout for consumer reads without their own timeout.
fetch_min_bytes	1	Minimum bytes fetched per consumer request.
producer_acks	1	Consistency level for each produced message.
producer_compression_type	None	Compression used by REST proxy producers.
producer_max_request_size	1048576	Maximum size of a request in bytes.
name_strategy	topic_name	Name strategy for storing schemas: topic_name, record_name, or topic_record_name.
rest_authorization	false	Delegate REST proxy authorization to Kafka over SASL using the caller's credentials.
rest_base_uri	None	Publicly available URI advertised to clients for stateful operations.

TLS / security

Parameter	Default	Description
security_protocol	PLAINTEXT	Kafka security protocol: PLAINTEXT, SSL, SASL_PLAINTEXT, or SASL_SSL.
sasl_mechanism	None	SASL mechanism (PLAIN, SCRAM-SHA-512, OAUTHBEARER).
ssl_cafile / ssl_certfile / ssl_keyfile	None	SSL CA / cert / key used when security_protocol is SSL.
server_tls_cafile / server_tls_certfile / server_tls_keyfile	None	TLS files for the Karapace server in HTTPS mode.
server_tls_client_auth	none	Client certificate requirement: none, optional, or required.
registry_authfile	None	Users and access-control rules for HTTP basic auth. See Authentication.

Protobuf

Parameter	Default	Description
protobuf_runtime_directory	runtime	Runtime directory for the protoc parser and code generator.
use_protobuf_formatter	false	Normalize and persist Protobuf schemas in a formatted state.

For the full list of keys, see the README.