fastiot_core_services.opc_ua_reader.env module¶

class fastiot_core_services.opc_ua_reader.env.OPCUARetrievalMode(value)[source]¶

An enumeration.

subscription = 'subscription'¶

polling = 'polling'¶

polling_always = 'polling_always'¶

class fastiot_core_services.opc_ua_reader.env.OPCUAEnv[source]¶

Environment variables for opc ua monitoring

property endpoint_url: str¶

FASTIOT_OPCUA_ENDPOINT_URL¶

The Endpoint Url to the OPC-UA Server, e.g. “opc.tcp://127.0.0.1:5000”

property security_string: str¶

FASTIOT_OPCUA_SECURITY_STRING¶

A security string if its needed, e.g. “Basic256Sha256,Sign,/path/to/certificate/test_certificate.der,/path/to/key/test_key.pem”

It is recommended to place needed certificates inside a config dir and locate it there.

property user: str¶

FASTIOT_OPCUA_USER¶

Username for the OPC UA connection.

property password: str¶

FASTIOT_OPCUA_PASSWORD¶

Password for the OPC UA Connection.

property application_uri: str¶

FASTIOT_OPCUA_APPLICATION_URI¶

In rare cases it is needed to specify an application uri to connect to an OPC-UA Server which can be set with this env variable, e.g. “urn:freeopcua:client”

property max_allowed_data_delay: float¶

FASTIOT_OPCUA_MAX_ALLOWED_DATA_DELAY¶

The maximum allowed data delay for opc-ua connections in seconds. If no data changes happen over this timespan, the connection to the machine is considered lost. This value must be positive. A value of zero means the connection is never considered lost.

property polling_delay: float¶

FASTIOT_OPCUA_POLLING_DELAY¶

The polling delay specifies the delay between polling opcua node cycles. This value is only applied if retrieval mode is polling, which is the default behavior, or polling_always. Otherwise this variable is ignored. Must be positive. A value of zero means no wait interval which may result in high server load.

property retrieval_mode: OPCUARetrievalMode¶

FASTIOT_OPCUA_RETRIEVAL_MODE¶

Can be one of ‘polling’ (default), ‘polling_always’ or ‘subscription’.

Polling mode requests all OPC-UA nodes in a loop. You can specify the loop delay via ‘FASTIOT_OPCUA_POLLING_DELAY’. If you use ‘polling_always’, it will publish a value for each value retrieved. Running in ‘polling’ will only publish all values in the first run and in consecutive loop runs it will only publish value changes.

If using subscriptions mode, it will utilize OPC-UA Subscriptions to publish retrieved value changes; depending on the OPC-UA Server implementation. This can be useful when working with many OPC-UA nodes where polling takes too long to complete. Please note that Subscriptions are an optional OPC-UA feature and not all Servers might support it nor might provide a stable implementation. It is recommended when using subscriptions, to also use ‘FASTIOT_OPCUA_MAX_ALLOWED_DATA_DELAY’ to handle connection errors.

Generally speaking, polling is useful for a small number of nodes <10 and subscriptions for many nodes >1000 depending on the usecase. (There is no general answer what is better for values between 10 and 1000.)

property opc_ua_reader_config_dir: str¶

FASTIOT_OPC_UA_CONFIG_NAME¶

Specify a config name. This can be useful when running multiple instances of machine monitoring with a different opc-ua node configuration inside the config_dir. Defaults to “opc_ua_reader” and is relative to the config dir.

property opc_ua_reader_error_logfile: str¶

FASTIOT_OPC_UA_ERROR_LOGFILE¶

Specify an error log file. In this error log file are connection errors logged. If there is any error logged, the machine monitor is marked as unhealthy and depending on the deployment is restarted.

This can be useful if the OPC-UA Server has unstable subscriptions - so when they break the service is restarted.