Application Configuration

LinuxForHealth connect settings and configurations are defined within a Pydantic Settings Configuration model. Pydantic settings provide robust configuration support using Python types with the convenience of overriding configurations with environment variables. Configurations are defined within the config module.

Configuration Override

Configuration settings are overriden using environment variables. Pydantic performs type conversions on the variable values to ensure compatibility with the types defined in the config module. Non-scalar values such as lists and dictionaries are encoded as JSON strings.

Example - Override Scalar Setting:

# python configuration
uvicorn_host: str = '0.0.0.0'
# environment variable override
UVICORN_HOST=some-server

Example - Override Non-scalar Setting:

# python configuration
kafka_bootstrap_servers: List[str] = ['localhost:9094']
# environment variable override
KAFKA_BOOTSTRAP_SERVERS='["kafka:9092"]'

Local/development environments may override settings using an .env file.

Supported Properties

Property	Data Type	Description	Default
uvicorn_app	String	The fully qualified uvicorn app string	‘connect.asgi:app’
uvicorn_host	String	The uvicorn host name or ip address	‘0.0.0.0’
uvicorn_port	Integer	The uvicorn listening port	5000
uvicorn_reload	Boolean	Indicates if hot debugging/reload is enabled	False
certificate_authority_path	String	Path to the directory used to house additional or intermediate Certificate Authorities	certifi package location
certificate_verify	Boolean	Indicates if x509 certificates are verified	False
connect_ca_file	String	The path to the concatenated CA certificates in PEM format	certifi package location
connect_ca_path	String	The path to the directory containing PEM formatted certificates	/usr/local/share/ca-certificates
connect_cert_name	String	The connect certificate file name	lfh-connect.pem
connect_cert_key_name	String	The connect certificate private key file name	lfh-connect.key
connect_config_directory	String	The path to the connect application configuration directory	/home/lfh/connect/config
connect_lfh_id	String	The LinuxForHealth connect node identifier - unique within the “network”	the machine host name
connect_logging_path	String	Path to logging.yaml file	logging.yaml
connect_external_fhir_server	String	External FHIR server URL
connect_rate_limit	String	Request rate limit per client	5/second
kafka_bootstrap_servers	List	List of Kafka broker/server locations	[‘kafka:9092’]
kafka_segments_purge_timeout	Float	Timemout used for Kafka segment cache	10 minutes/600 seconds
kafka_message_chunk_size	Integer	I/O read size used for streaming Kafka messages	900KB
kafka_producer_acks	String	Number of acks required before a request is considered complete	‘all’
kafka_consumer_default_group_id	String	The default Kafka consumer group id	‘lfh_consumer_group’
kafka_consumer_default_enable_auto_commit	Boolean	Indicates if the Kafka consumer auto-commits it’s current offset	False
kafka_consumer_default_enable_auto_offset_store	Boolean	Indicates if an in-memory store is used to manage Kafka consumer commit metadata	False
kafka_consumer_default_poll_timeout_secs	Float	Timeout setting for Kafka consumer polling	1.0
kafka_consumer_default_auto_offset_reset	String	Allows the Kafka consumer to set the current offset under certain conditions	‘error’
kafka_admin_new_topic_partitions	Integer	The number of partitions the Kafka Admin client creates for a new topic	1
kafka_admin_new_topic_replication_factor	Integer	Replication setting for new Kafka partitions	1
kafka_listener_timeout	Float	Kafka connection/polling timeout in seconds	1.0
kafka_topics_timeout	Float	Number of seconds Kafka consumer waits before polling a broker	0.5
nats_servers	List	List of NATS servers	[‘tls://nats-server:4222’]
nats_sync_subscribers	List	List of NATS servers to sync messages too	[]
nats_allow_reconnect	Boolean	Indicates if the NATS client will retry connections	True
nats_max_reconnect_attempts	Integer	The maximum number of retry attempts if nats_allow_reconnect is enabled	10

Secured Communications

LinuxForHealth connect is configured for secure communications by default using TLS and x509 certificates. Outbound transactions from LinuxForHealth connect to external services are expected to be secured in a similar manner. Secure transmissions are supported within the local development environment and container image.

LinuxForHealth also utilizes secure communications between LinuxForHealth nodes for data synchronization via NATS messaging. Both TLS and NATS NKeys are used to secure NATS connections between LinuxForHealth nodes.

Please see Secured Communications and Data Synchronization for detailed information about configuring secured communications.