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.

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OPC UA Read Node

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	Bound on this operation; the connection's Request Timeout still applies and the shorter one wins

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 delivers the value under result and execution facts under _metadata:

{
  "result": {
    "value": 72.5,
    "sourceTimestamp": "2026-01-15T08:30:00.123456789Z",
    "serverTimestamp": "2026-01-15T08:30:00.125Z",
    "statusCode": "0x00000000",
    "quality": "good",
    "dataType": "Double"
  },
  "_metadata": {
    "success": true,
    "functionId": "<function-id>",
    "durationMs": 42,
    "timestamp": "2026-01-15T08:30:00Z"
  }
}

Field	Type	Description
result.value	any	The node value — typed as the OPC UA data type. This is the reading: $node["Name"].result.value
result.sourceTimestamp	string	When the value was sampled at the source (RFC 3339, UTC)
result.serverTimestamp	string	When the OPC UA server processed it (RFC 3339, UTC)
result.statusCode	string	OPC UA status code in 0x hex format
result.quality	string	The status mapped to the canonical band: good, uncertain or bad — the same scale every connector uses
result.dataType	string	OPC UA data type name (e.g., Boolean, Int32, Double, String, DateTime); Structure for a decoded structure
_metadata.success	boolean	true when the function executed without errors
_metadata.functionId	string	ID of the executed function
_metadata.durationMs	number	Execution time in milliseconds
_metadata.timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

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OPC UA Write Node

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	Bound on this operation; the connection's Request Timeout still applies and the shorter one wins

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[0].result.value }} to pass dynamic values to write parameters.

Output Structure

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

Field	Type	Description
result.statusCode	string	The OPC UA status code the server answered with, 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.

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OPC UA Browse Node

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

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

Field	Type	Description
result.namespace	number	Namespace index of the browsed node
result.identifier	string	Identifier of the browsed node
result.nodeClass	string	OPC UA node class: Object, Variable, Method, ObjectType, VariableType, ReferenceType, DataType, View
result.browseName	string	The node's browse name
result.description	string	Node description, empty when the server gives none
result.accessLevel	string	Access level as reported (CurrentRead, CurrentWrite, …); empty for a non-Variable node
result.userAccessLevel	string	Access level for the connected user
result.dataType	string	OPC UA data type for a Variable node; empty otherwise
result.readable	boolean	Whether the node's value can be read
result.writable	boolean	Whether the node accepts writes
result.children	array	One entry per child, with the same fields as the browsed node (without children, continuationPoint, hasMore)
result.continuationPoint	string	Opaque cursor for the next page of children; empty when there is none
result.hasMore	boolean	true when more children remain — pass continuationPoint to the next browse

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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, an All Functions mode, and parallel or sequential execution.

Node Configuration

Parameter	Type	Required	Default	Description
Connection	Selection	Yes	—	OPC UA connection profile
Function Selection	Selection	No	Select Functions	Select Functions reads the functions you list. All Functions reads every read function on the connection. By Labels reads every function whose labels match the labels you pick.
Functions	Array of {functionId, alias}	When Function Selection is Select Functions	[]	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

All Functions Mode

When Function Selection is All Functions, the function list is ignored. The node automatically discovers and executes every read function defined on the selected connection.

Read function types that All Functions runs:

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

The node output is the canonical {result, _metadata} envelope: result holds one entry per function read, keyed by the function's output key; _metadata holds the group's accounting.

{
  "result": {
    "Temperature Sensor": {
      "value": 72.5,
      "success": true,
      "error": "",
      "duration": 45,
      "timestamp": "2026-09-07T08:30:00Z"
    },
    "Batch Read - Line 1": {
      "value": { "results": [{ "nodeId": "ns=2;s=Line1.Speed", "value": 1450, "statusCode": "0x00000000" }], "totalNodes": 1, "successCount": 1, "failureCount": 0 },
      "success": true,
      "error": "",
      "duration": 62,
      "timestamp": "2026-09-07T08:30:00Z"
    }
  },
  "_metadata": {
    "connectionId": "conn-123",
    "connectionName": "OPC Server 1",
    "total": 2,
    "successful": 2,
    "failed": 0,
    "totalDuration": 83,
    "executionMode": "parallel",
    "originalRequests": 2
  }
}

Each entry under result is one function's read — keyed by the function's alias, else its name, else its id (see Output Key Resolution):

Field	Type	Description
result.<alias>.value	any	What the function read — its own result.value when it has one (the node's value for opcua.read, since its result carries value; the whole {results, totalNodes, successCount, failureCount} object for opcua.batchread), otherwise its whole result. null when the read failed
result.<alias>.success	boolean	true when this function's read succeeded
result.<alias>.error	string	Why the read failed; empty when it succeeded — always present
result.<alias>.duration	number	How long this function's read took, in milliseconds
result.<alias>.timestamp	string	When the read was issued, RFC 3339 UTC
result.<alias>.sourceTimestamp	string	When the device sampled the value, RFC 3339 UTC — the server's SourceTimestamp. Present only when the read succeeded and the server stamped the value. timestamp moves on every poll whatever the device does; this one stands still when the device's value does — a hung communications card or a gateway serving its cache keeps answering good with an old sourceTimestamp. Publish with it (system.uns.publish → Timestamp: {{ $item.ts }}) so a reading never looks fresher than it is
result.<alias>.quality	string	The device's verdict on the value — good, uncertain or bad, from the OPC UA status severity. Present only when the read succeeded and the server classified the value. A read can succeed and still be doubtful: Uncertain_LastUsableValue is a server saying "this is the last thing I knew" — success stays true, quality says uncertain. Publish with it (system.uns.publish → Quality: {{ $item.q }}); the publish node folds it worst-of with the trigger's own verdict

The _metadata object is the group's execution summary:

Field	Type	Description
_metadata.connectionId	string	The connection every function was read on
_metadata.connectionName	string	That connection's display name
_metadata.total	number	How many functions the group ran
_metadata.successful	number	How many read successfully — including the ones onChange then suppressed
_metadata.failed	number	How many failed; successful + failed = total
_metadata.totalDuration	number	Wall-clock time of the whole group, in milliseconds
_metadata.executionMode	string	parallel or sequential
_metadata.originalRequests	number	How many functions were selected to run
_metadata.keyCollisions	string[]	Output keys that two or more functions resolved to — the later read overwrote the earlier under that key. Present only when it happened
_metadata.configWarnings	string[]	Non-fatal problems in the node's config, each saying what was ignored. Present only when there were any
_metadata.outputMode	string	onChange — present only in that mode
_metadata.suppressedCount	number	onChange mode: how many successful reads were unchanged since the last run and left out of result
_metadata.emittedCount	number	onChange mode: how many entries result carries — total − suppressedCount
_metadata.suppressedKeys	string[]	onChange mode: the output keys left out as unchanged. Present only when at least one was
_metadata.reason	string	onChange mode, when every successful read was unchanged: why result is empty — the node buffers instead of waking downstream

Output Key Resolution

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

1. Alias — the custom alias set in the function entry
2. Function Name — the name defined on the connection function
3. 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.
• With Select Functions, at least one function entry is required; with By Labels, at least one label is required.
• Duplicate functionId values are not allowed.
• Duplicate alias values are not allowed.
• The connection type must be opcua.

Best Practices

• Use All Functions 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.

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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: Pipeline Default (the pipeline's Error Handling setting), Stop Pipeline or Continue Execution

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