OPC-UA proxy

A proxy microservice writing OPC-UA data changes to MongoDB.

Design

See DESIGN.md.

Specifications

Public Key Infrastructure (PKI)

PKI path is configured with a CLI option (see Configuration).

OPC-UA partners configuration

This service will periodically query the configuration API, to get the configuration for all OPC-UA partners as a JSON array of objects.

Each object is expected to have the following format.

Key	Value type	Description
_id	string	OPC-UA partner ID
serverUrl	string	OPC-UA server URL
securityPolicy	string	OPC-UA security policy
securityMode	string	OPC-UA security mode
user	string | null	OPC-UA authentication username
password	string | null	OPC-UA authentication password
tags	array of objects	Description of tags to subscribe on (see below)

Each element of tags array is an object with a type property and is of one of the following formats.

Nodes container

This format allows to collect tags from an OPC-UA container node which has HasComponent forward reference(s). Each referenced node will be added to the tag set to monitor, with its DisplayName as tag name.

{
  // ...
  "tags": [
    // ...
    {
      "type": "container",
      "namespaceUri": "urn:namespace",
      "nodeIdentifier": "containerNode"
    }
    // ...
  ]
  // ...
}

Key	Value type	Description
namespaceUri	string	OPC-UA namespace URI
nodeIdentifier	string | number (positive integer)	OPC-UA NodeId identifier*

* identifier type will be inferred from JSON type.

Single tag

This format directly refers to a single tag.

{
  // ...
  "tags": [
    // ...
    {
      "type": "tag",
      "name": "tagName",
      "namespaceUri": "urn:namespace",
      "nodeIdentifier": "someNode"
    }
    // ...
  ]
  // ...
}

Key	Value type	Description
name	string	Tag name
namespaceUri	string	OPC-UA namespace URI
nodeIdentifier	string | number (positive integer)	OPC-UA NodeId identifier*

* identifier type will be inferred from JSON type.

MongoDB

Queries to MongoDB will use following parameters:

• database: as configured by service argument;
• document primary key (_id): OPC-UA partner ID.

When it starts, this service will initialize all documents in data collection.

OPC-UA data change

For each data change notification received from the OPC-UA servers, an update query will be issued to MongoDB on collection data, as a document comprising following fields:

• val: mapping of tag names to their values;
• ts: mapping of tag names to to the timestamp of last value change;
• updatedAt: MongoDB current date and time.

Health

This service subscribes to OPC-UA server current time. Each time a data change notification is received, it sends an update query on health collection to MongoDB, with following document fields:

• serverDateTime: OPC-UA server timestamp as BSON DateTime;
• updatedAt: MongoDB current date and time.

Data flow

sequenceDiagram
    participant OPCServer as OPC-UA servers
    participant opcua-proxy as OPC-UA proxy (this service)
    participant MongoDB
    participant ConfigAPI as Configuration API
    loop At start and periodically
    opcua-proxy->>+ConfigAPI: Queries configuration data
    ConfigAPI-->>-opcua-proxy: Sends configuration data
        loop For each OPC-UA partner not already handled
            opcua-proxy->>+OPCServer: Connects
            OPCServer-->>-opcua-proxy: Connection success
            opcua-proxy->>+OPCServer: Creates subscription
            OPCServer-->>-opcua-proxy: Subscription created
            opcua-proxy->>+OPCServer: Creates monitored items
            OPCServer-->>-opcua-proxy: Monitored items created
        end
    end
    loop Current time changes
        OPCServer-)+opcua-proxy: Data change notification
        opcua-proxy-)-MongoDB: Updates health document
    end
    loop Tags values changes
        OPCServer-)+opcua-proxy: Data change notification
        opcua-proxy-)-MongoDB: Updates data document
    end

Configuration

$ opcua-proxy --help
Usage: opcua-proxy [OPTIONS] --mongodb-database <MONGODB_DATABASE> --config-api-url <CONFIG_API_URL> --pki-dir <PKI_DIR>

Options:
      --mongodb-uri <MONGODB_URI>
          URL of MongoDB server [env: MONGODB_URI=] [default: mongodb://mongodb]
      --mongodb-database <MONGODB_DATABASE>
          Name of the MongoDB database to use [env: MONGODB_DATABASE=]
      --config-api-url <CONFIG_API_URL>
          Base API URL to get configuration from [env: CONFIG_API_URL=]
      --pki-dir <PKI_DIR>
          Path of the PKI directory [env: PKI_DIR=]
  -v, --verbose...
          More output per occurrence
  -q, --quiet...
          Less output per occurrence
  -h, --help
          Print help