Version: 2.0-dev

Ignition trigger node

Ignition Trigger Node

Overview

The Ignition Trigger Node automatically initiates MaestroHub pipelines when tag values change in Inductive Automation's Ignition Gateway. Unlike polling-based approaches, this trigger provides real-time event-driven automation with intelligent debouncing—multiple rapid tag changes within 100ms are aggregated into a single pipeline execution with the latest values for all affected tags.

Core Functionality

What It Does

Ignition Trigger enables real-time, event-driven pipeline execution by:

1. Event-Driven Pipeline Execution
Start pipelines automatically when Ignition tag values change, without manual intervention or polling. Perfect for process monitoring, alarm handling, and real-time data flows.

2. Intelligent Debouncing
Multiple tag changes within a 100ms window are automatically aggregated into a single event, preventing excessive pipeline executions while ensuring you receive the latest values for all changed tags.

3. Automatic Subscription Management
Subscriptions are created and cleaned up automatically—no manual subscription management required. The system handles connection lifecycle and resubscription after reconnections.

4. Aggregated Tag Data
All tag values that changed during the debounce window are provided in a single array, making it easy to process multiple related tag changes together.

Debounce Behavior

How Debouncing Works

The Ignition Trigger uses a 100ms fixed debounce window to aggregate rapid tag changes:

First Change: When the first tag value change occurs, a 100ms timer starts
Subsequent Changes: Any additional tag changes within this window update the buffer with the latest values
Timer Expires: After 100ms, the trigger fires once with an array containing the latest values for all tags that changed
Next Window: The process repeats for the next set of changes

Benefits of Debouncing

Scenario	Without Debouncing	With Debouncing
10 rapid tag changes	10 separate pipeline executions	1 pipeline execution with all 10 tag values
Burst updates	Pipeline overload, potential queueing	Smooth processing with aggregated data
Related tag changes	Process tags individually, lose context	Process all related changes together

Debounce Window

The 100ms debounce window is fixed and cannot be configured. This value provides an optimal balance between responsiveness and aggregation for most industrial automation scenarios.

Reconnection Handling

MaestroHub automatically handles connection disruptions to ensure reliable tag monitoring.

Automatic Recovery

When an Ignition connection is lost and restored:

Connection Lost: The system detects the disconnection automatically
Connection Restored: Subscriptions are automatically re-established within seconds
Transparent Recovery: Pipelines continue to receive tag changes once the connection is restored—no manual intervention required

What This Means for Your Workflows

Scenario	Behavior
Brief network interruption	Automatic resubscription after reconnection
Gateway restart	Subscriptions automatically restored when gateway comes back online
MaestroHub restart	All triggers for enabled pipelines are restored on startup

Minimizing Data Loss

While the trigger automatically reconnects, tag changes that occur during the disconnection period may be missed. For critical data, consider implementing a complementary polling mechanism or using Ignition's built-in store-and-forward capabilities.

Configuration Options

Parameters Tab

Parameters Configuration

Settings Tab

Settings Configuration

Basic Information

Field	Type	Description
Node Label	String (Required)	Display name for the node on the pipeline canvas
Description	String (Optional)	Explains what this trigger monitors and initiates

Parameters

Parameter	Type	Required	Default	Description
Connection	Connection ID	Yes	-	The Ignition connection profile to use for subscribing
Function	Function ID	Yes	-	The Ignition Subscribe function that defines which tags to monitor
Enabled	Boolean	No	`true`	When disabled, the subscription is not created even if the pipeline is enabled

Function Requirement

The selected function must be an Ignition Subscribe function type. Read, write, or browse functions cannot be used with Ignition Trigger nodes.

Settings

Basic Settings

Setting	Options	Default	Recommendation
Retry on Fail	true / false	false	Keep disabled for triggers—retries don't apply to event-driven nodes
Error Handling	Stop Pipeline / Continue	Stop Pipeline	Use "Stop Pipeline" to halt on critical failures

Documentation Settings

Setting	Type	Default	Purpose
Notes	Text	Empty	Document the trigger's purpose, monitored tags, or operational context
Display Note in Pipeline	Boolean	false	Show notes on the pipeline canvas for quick reference

Output Data Structure

When Ignition tag changes trigger pipeline execution, the following data is available to downstream nodes via the $input variable.

Output Format

{
  "type": "ignition_trigger",
  "connectionId": "bf29be94-fc0a-4dc4-8e5c-092f1b74eb4b",
  "functionId": "aef374c3-aa2b-454e-aabc-5657faac5950",
  "enabled": true,
  "node_id": "trigger.ignition-1",
  "message": "Ignition trigger provides configuration for event-based triggering",
  "values": [
    {
      "path": "[default]Line1/Temperature",
      "value": 78.5,
      "quality": "Good",
      "timestamp": 1704067200000
    },
    {
      "path": "[default]Line1/Pressure",
      "value": 145.2,
      "quality": "Good",
      "timestamp": 1704067200050
    }
  ]
}

Accessing Tag Data

In downstream nodes, use the $input variable to access the trigger output:

Field	Expression	Description
Tag Values Array	`$input.values`	Array of all tag values that changed during the debounce window
Individual Tag	`$input.values[0]`	Access a specific tag by array index
Tag Path	`$input.values[0].path`	The full tag path including provider
Tag Value	`$input.values[0].value`	The current value of the tag
Tag Quality	`$input.values[0].quality`	Quality indicator (Good, Bad, Uncertain, etc.)
Tag Timestamp	`$input.values[0].timestamp`	Unix timestamp in milliseconds when the value changed
Connection ID	`$input.connectionId`	The Ignition connection profile used
Function ID	`$input.functionId`	The Subscribe function that received the changes
Node ID	`$input.node_id`	The trigger node identifier
Trigger Type	`$input.type`	Always `ignition_trigger`

Processing Multiple Tags

Use a JavaScript node or loop to iterate through $input.values and process each tag change:

$input.values.forEach(tag => {
  if (tag.quality === 'Good') {
    // Process good quality tag values
  }
});

Validation Rules

The Ignition Trigger Node enforces these validation requirements:

Parameter Validation

Connection ID

Must be provided and non-empty
Must reference a valid Ignition connection profile
Error: "Ignition connection is required"

Function ID

Must be provided and non-empty
Must reference a valid Ignition Subscribe function
Function must belong to the specified connection
Error: "Subscribe function is required"

Enabled Flag

Must be a boolean if provided
Error: "Enabled must be a boolean value"

Settings Validation

On Error

Must be one of: stopPipeline, continueExecution, retryNode
Error: "onError must be a valid error handling option"

Usage Examples

Production Line Monitoring

Scenario: Monitor critical process parameters on a production line and trigger alerts when values exceed thresholds.

Configuration:

Label: Production Line Monitor
Connection: Plant Floor Ignition Gateway
Function: Subscribe to [default]Line1/* (all tags on Line 1)
Enabled: true

Downstream Processing:

Iterate through $input.values array
Check each tag value against configured thresholds
Generate alerts for out-of-range values
Log all changes to time-series database
Update real-time dashboard

Equipment State Change Handler

Scenario: React to equipment state changes and coordinate downstream systems.

Configuration:

Label: Equipment State Handler
Connection: Manufacturing Ignition
Function: Subscribe to [default]Equipment/*/State (state tags for all equipment)
Enabled: true

Downstream Processing:

Extract equipment ID from tag path
Determine state transition (Running → Stopped, etc.)
Update maintenance schedule if needed
Notify operators of critical state changes
Trigger dependent equipment adjustments

Alarm Acknowledgment Workflow

Scenario: Automatically process alarm acknowledgments and update external systems.

Configuration:

Label: Alarm Ack Processor
Connection: SCADA Ignition Gateway
Function: Subscribe to [default]Alarms/*/Acknowledged (acknowledgment status for all alarms)
Enabled: true

Downstream Processing:

Filter for newly acknowledged alarms (value changed to true)
Extract alarm details from tag path
Log acknowledgment to audit database
Send notification to maintenance system
Update alarm dashboard

Multi-Tag Batch Processing

Scenario: Process related tag changes together for batch operations.

Configuration:

Label: Batch Recipe Monitor
Connection: Recipe Management Ignition
Function: Subscribe to [default]Recipe/Active/* (all active recipe parameters)
Enabled: true

Downstream Processing:

Receive all recipe parameter changes in single event
Validate complete recipe configuration
Update PLC setpoints as a batch
Log recipe change event
Confirm successful application

Best Practices

Connection Health Monitoring

Configure your Ignition connection with appropriate Keep Alive intervals
Enable Auto Reconnect on the connection profile for automatic recovery
Monitor connection status through MaestroHub's connection health dashboard
Test reconnection behavior during maintenance windows

Designing Subscriptions

Practice	Rationale
Group related tags	Leverage debouncing to process related changes together
Use specific tag paths	Reduces unnecessary processing and improves performance
Consider tag update rates	High-frequency tags may benefit from additional filtering
Monitor subscription count	Each subscription consumes gateway resources

Working with Debounced Data

Processing the Values Array:

Always check $input.values.length before processing
Validate tag quality before using values
Handle missing or null values gracefully
Consider tag timestamps when ordering is important

Performance Considerations:

The debounce window aggregates changes, reducing pipeline executions
Process all tags in the array efficiently to maintain throughput
Avoid heavy processing in tight loops over large tag arrays

Error Handling Strategies

For Critical Monitoring:

Set On Error to stopPipeline
Implement alerting for stopped pipelines
Monitor pipeline execution failures
Consider backup monitoring mechanisms

For Best-Effort Processing:

Set On Error to continueExecution
Log failed events for later analysis
Ensure downstream nodes handle partial failures gracefully
Implement retry logic for critical operations

Tag Quality Handling

Always check tag quality before processing values:

$input.values.forEach(tag => {
  switch(tag.quality) {
    case 'Good':
      // Process reliable data
      break;
    case 'Bad':
      // Log error, skip processing
      break;
    case 'Uncertain':
      // Decide based on use case
      break;
  }
});

Enable vs. Disable

Use the trigger's Enabled parameter to temporarily pause monitoring without changing pipeline state
Disable triggers during maintenance windows to prevent unnecessary processing
Document the reason for disabled triggers in the node's Notes field
Re-enable triggers after testing configuration changes

Performance Optimization

Scenario	Recommendation
High-frequency tags	Use specific subscriptions; consider additional filtering in Ignition
Large tag counts	Monitor pipeline execution queue; optimize downstream processing
Multiple triggers on same tags	MaestroHub optimizes with shared subscriptions—no action needed
Burst updates	Debouncing handles this automatically; ensure downstream can process arrays efficiently

Troubleshooting

Common Issues

No Pipeline Executions

Verify the trigger is enabled
Check that the pipeline is enabled
Confirm the Ignition connection is active
Verify tags are actually changing values
Check subscription function configuration

Missing Tag Changes

Connection was down during changes (expected behavior)
Tag quality may be Bad (filtered by subscription)
Subscription function may not include the tag path
Check Ignition Gateway subscription status

Too Many Pipeline Executions

Debouncing should prevent this; verify 100ms window is working
Check if multiple triggers are configured for same tags
Review tag update rates in Ignition

Empty Values Array

Subscription may have no matching tags
All tag changes may have Bad quality
Connection issue during debounce window

Overview​

Core Functionality​

What It Does​

Debounce Behavior​

How Debouncing Works​

Benefits of Debouncing​

Reconnection Handling​

Automatic Recovery​

What This Means for Your Workflows​

Configuration Options​

Parameters Configuration

Settings Configuration

Basic Information​

Parameters​

Settings​

Output Data Structure​

Output Format​

Accessing Tag Data​

Validation Rules​

Parameter Validation​

Settings Validation​

Usage Examples​

Production Line Monitoring​

Equipment State Change Handler​

Alarm Acknowledgment Workflow​

Multi-Tag Batch Processing​

Best Practices​

Connection Health Monitoring​

Designing Subscriptions​

Working with Debounced Data​

Error Handling Strategies​

Tag Quality Handling​

Enable vs. Disable​

Performance Optimization​

Troubleshooting​

Common Issues​

Overview

Core Functionality

What It Does

Debounce Behavior

How Debouncing Works

Benefits of Debouncing

Reconnection Handling

Automatic Recovery

What This Means for Your Workflows

Configuration Options

Basic Information

Parameters

Settings

Output Data Structure

Output Format

Accessing Tag Data

Validation Rules

Parameter Validation

Settings Validation

Usage Examples

Production Line Monitoring

Equipment State Change Handler

Alarm Acknowledgment Workflow

Multi-Tag Batch Processing

Best Practices

Connection Health Monitoring

Designing Subscriptions

Working with Debounced Data

Error Handling Strategies

Tag Quality Handling

Enable vs. Disable

Performance Optimization

Troubleshooting

Common Issues