Version: 2.1

OPC UA Nodes

OPC UA (Unified Architecture) is the modern, platform-independent standard for industrial communication. MaestroHub provides read, write, browse, and batch-read capabilities with hardened security options.

Configuration Quick Reference

Field	What you choose	Details
Parameters	`Connection`, `Function`, `Function Parameters`, `Timeout Override`	Select the connection profile, function, configure function parameters with expression support, and optionally override timeout.
Settings	`Description`, `Timeout (seconds)`, `Retry on Timeout`, `Retry on Fail`, `On Error`	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

OPC UA Read Node

Read node values from OPC UA servers with namespace-aware identifiers.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Read Node Value (`opcua.read`)	Fetch scalar or structured values from endpoints	Equipment telemetry, quality checks, energy monitoring

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	OPC UA connection profile to use
Function	Selection	Yes	Read function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your OPC UA connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

Function parameters for Read:

Parameter	Type	Required	Description
`namespaceIndex`	Number	Yes	Node namespace index (0–65535)
`identifier`	String	Yes	Node identifier. Formats: `i=123` (numeric), `s=String` (string), `g=GUID` (GUID), `b=0xHEX` (byte string)
`requestTimeoutSeconds`	Number	No	Override default request timeout for this operation

All function parameters support expression syntax ({{ expression }}) for dynamic values from the pipeline context.

Input

The node receives the output of the previous node as input. Input data can be referenced in function parameter expressions using $input.

Output Structure

On success the node produces:

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "value": 72.5,
    "sourceTimestamp": "2026-01-15T08:30:00Z",
    "serverTimestamp": "2026-01-15T08:30:00Z",
    "statusCode": "0x00000000",
    "dataType": "Double"
  },
  "durationMs": 42,
  "timestamp": "2026-01-15T08:30:00Z"
}

Field	Type	Description
`success`	boolean	`true` when the function executed without errors
`functionId`	string	ID of the executed function
`data`	object	OPC UA read result (see below)
`durationMs`	number	Execution time in milliseconds
`timestamp`	string	ISO 8601 / RFC 3339 UTC timestamp

data fields:

Field	Type	Description
`value`	any	The node value — type depends on the OPC UA data type
`sourceTimestamp`	string	Timestamp from the data source
`serverTimestamp`	string	Timestamp from the OPC UA server
`statusCode`	string	OPC UA status code in `0x` hex format
`dataType`	string	OPC UA data type name (e.g., Boolean, Int32, Double, String, DateTime)

OPC UA Write Node

Write setpoints and command values to OPC UA nodes.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Write Node Value (`opcua.write`)	Send scalar or structured values to endpoints	Adjust temperature setpoints, acknowledge alarms, update schedules

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	OPC UA connection profile to use
Function	Selection	Yes	Write function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your OPC UA connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

Function parameters for Write:

Parameter	Type	Required	Description
`namespaceIndex`	Number	Yes	Node namespace index (0–65535)
`identifier`	String	Yes	Node identifier (same formats as Read)
`value`	String	Yes	Value to write (converted to appropriate OPC UA type)
`dataType`	String	Yes	Target data type: `bool`, `int8`, `uint8`, `int16`, `uint16`, `int32`, `uint32`, `int64`, `uint64`, `float`, `double`, `string`
`requestTimeoutSeconds`	Number	No	Override default request timeout

All function parameters support expression syntax ({{ expression }}) for dynamic values.

Input

The node receives the output of the previous node as input. Use expressions like {{ $input.payload.value }} to pass dynamic values to write parameters.

Output Structure

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "success": true,
    "statusCode": "0x00000000"
  },
  "durationMs": 15,
  "timestamp": "2026-01-15T08:30:00Z"
}

data fields:

Field	Type	Description
`success`	boolean	Whether the write was accepted by the server
`statusCode`	string	OPC UA status code in `0x` hex format

Safety First

Always implement validation and safety checks before writing to industrial equipment. Consider adding condition nodes to verify values are within safe ranges.

OPC UA Browse Node

Discover available nodes in the OPC UA address space.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Browse Nodes (`opcua.browse`)	Traverse address space to find readable/writable nodes	Build tag catalogs, search for equipment folders

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	OPC UA connection profile to use
Function	Selection	Yes	Browse function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema. See your OPC UA connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

Function parameters for Browse:

Parameter	Type	Required	Default	Description
`namespaceIndex`	Number	No	`0`	Starting node namespace index
`identifier`	String	No	`i=85`	Starting node identifier (default is the Objects folder)
`maxChildren`	Number	No	`0`	Maximum children to return (0 = no limit)
`continuationPoint`	String	No	`""`	Continuation point from a previous browse for pagination

Input

The node receives the output of the previous node as input.

Output Structure

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "namespace": 0,
    "identifier": "i=85",
    "nodeClass": "Object",
    "browseName": "Objects",
    "description": "",
    "accessLevel": "",
    "dataType": "",
    "writable": false,
    "children": [
      {
        "namespace": 2,
        "identifier": "i=1001",
        "nodeClass": "Variable",
        "browseName": "Temperature",
        "description": "Current temperature",
        "accessLevel": "CurrentRead",
        "dataType": "Double",
        "writable": false
      }
    ],
    "continuationPoint": "",
    "hasMore": false
  },
  "durationMs": 85,
  "timestamp": "2026-01-15T08:30:00Z"
}

data fields:

Field	Type	Description
`namespace`	number	Namespace index of the browsed node
`identifier`	string	Identifier of the browsed node
`nodeClass`	string	OPC UA node class: `Object`, `Variable`, `Method`, `ObjectType`, `VariableType`, `ReferenceType`, `DataType`, `View`
`browseName`	string	Display name of the node
`description`	string	Node description (if available)
`accessLevel`	string	Access level (`CurrentRead`, `CurrentWrite`, etc.)
`dataType`	string	OPC UA data type (for Variable nodes)
`writable`	boolean	Whether the node accepts writes
`children`	array	Child nodes with the same field structure
`continuationPoint`	string	Base64-encoded continuation point for pagination
`hasMore`	boolean	`true` if more results are available via `continuationPoint`

OPC UA Read Group Node

The OPC UA Read Group node executes multiple OPC UA read operations in a single node. It supports selective function lists, a Read All mode, and parallel or sequential execution.

Node Configuration

Parameter	Type	Required	Default	Description
Connection	Selection	Yes	—	OPC UA connection profile
Read All	Toggle	No	`false`	When enabled, executes all read functions from the connection
Functions	Array of `{functionId, alias}`	When Read All is off	`[]`	List of specific functions to execute. Each entry requires a `functionId`; `alias` is optional.
Execution Mode	Selection	No	`parallel`	`parallel` — all functions run concurrently. `sequential` — functions run one after another.
Continue on Error	Toggle	No	`true`	When enabled, the node continues executing remaining functions even if one fails
Debug Mode	Toggle	No	`false`	Enable detailed logging for troubleshooting

Read All Mode

When Read All is enabled the function list is ignored. The node automatically discovers and executes every read function defined on the selected connection.

Supported read function types for Read All:

Function Type	Description
`opcua.read`	Single node read
`opcua.batchread`	Batch node read

Input

The node receives the output of the previous node as input.

Output Structure

{
  "Temperature Sensor": {
    "value": {
      "value": 72.5,
      "sourceTimestamp": "2026-01-15T08:30:00Z",
      "serverTimestamp": "2026-01-15T08:30:00Z",
      "statusCode": "0x00000000",
      "dataType": "Double"
    },
    "success": true,
    "duration": 45,
    "timestamp": "2026-01-15T08:30:00Z"
  },
  "Batch Read - Line 1": {
    "value": {
      "results": [...],
      "totalNodes": 5,
      "successCount": 5,
      "failureCount": 0
    },
    "success": true,
    "duration": 62,
    "timestamp": "2026-01-15T08:30:00Z"
  },
  "_meta": {
    "connectionId": "conn-456",
    "connectionName": "OPC Server 1",
    "total": 2,
    "successful": 2,
    "failed": 0,
    "totalDuration": 107,
    "executionMode": "parallel",
    "originalRequests": 2
  }
}

Each function result contains:

Field	Type	Description
`value`	any	The function's return data (Read result or Batch Read result)
`success`	boolean	Whether this function succeeded
`error`	string	Error message (present only on failure)
`duration`	number	Execution time in milliseconds
`timestamp`	string	ISO 8601 / RFC 3339 UTC timestamp

The _meta object provides execution summary:

Field	Type	Description
`connectionId`	string	Connection profile ID
`connectionName`	string	Connection profile display name
`total`	number	Total functions executed
`successful`	number	Count of successful executions
`failed`	number	Count of failed executions
`totalDuration`	number	Wall-clock time for the entire group (ms)
`executionMode`	string	`parallel` or `sequential`
`originalRequests`	number	Number of function configs submitted
`keyCollisions`	string[]	Output keys that appeared more than once (omitted when empty)

Output Key Resolution

Each function result is keyed in the output map using the first available value:

Alias — the custom alias set in the function entry
Function Name — the name defined on the connection function
Function ID — the unique function identifier (fallback)

Execution Modes

Parallel (default)

All functions execute concurrently.
Fastest total execution time.
Best for independent read operations from different nodes.

Sequential

Functions execute one after another in list order.
More predictable timing.
When Continue on Error is off, execution stops at the first failure.

Error Handling

Continue on Error	Behavior
`true` (default)	The node completes even if individual functions fail. Failed functions include an `error` field in their result. The node output remains successful.
`false`	The node fails as soon as any function fails. In sequential mode, remaining functions are skipped. The node result is marked as failed.

Validation Rules

connectionId is required.
executionMode must be parallel or sequential.
When Read All is off, at least one function entry is required.
Duplicate functionId values are not allowed.
Duplicate alias values are not allowed.
The connection type must be opcua.

Best Practices

Use Read All when you need a full snapshot of every read function defined on a connection.
Use specific functions in production pipelines for better performance and clarity.
Assign aliases to keep output keys readable, especially when mixing opcua.read and opcua.batchread functions.
Prefer parallel mode for independent reads from different nodes in the address space.

Settings Tab

All OPC UA node types share the same Settings tab:

Setting	Type	Default	Description
Description	Text	—	Optional description displayed on the node
Timeout (seconds)	Number	Pipeline default	Maximum time the node may run before timing out
Retry on Timeout	Toggle	Pipeline default	Automatically retry the node if it times out
Retry on Fail	Toggle	Pipeline default	Automatically retry the node if it fails
On Error	Selection	Pipeline default	Error strategy: stop the pipeline, continue to the next node, or follow the error output path

When left at their defaults, these settings inherit from the pipeline-level execution configuration.

Configuration Quick Reference​

OPC UA Read Node​

Node Configuration​

Input​

Output Structure​

OPC UA Write Node​

Node Configuration​

Input​

Output Structure​

OPC UA Browse Node​

Node Configuration​

Input​

Output Structure​

OPC UA Read Group Node​

Node Configuration​

Read All Mode​

Input​

Output Structure​

Output Key Resolution​

Execution Modes​

Error Handling​

Validation Rules​

Best Practices​

Settings Tab​

Configuration Quick Reference

OPC UA Read Node

Node Configuration

Input

Output Structure

OPC UA Write Node

Node Configuration

Input

Output Structure

OPC UA Browse Node

Node Configuration

Input

Output Structure

OPC UA Read Group Node

Node Configuration

Read All Mode

Input

Output Structure

Output Key Resolution

Execution Modes

Error Handling

Validation Rules

Best Practices

Settings Tab