How to Alert on Room Booking Conflicts with N8n

Workflows > New Workflow

Create New N8n Workflow

Start a fresh workflow in N8n specifically for room conflict monitoring. This will house all the logic for detecting overlaps and sending alerts.

1. 1Click 'New Workflow' from the N8n dashboard
2. 2Name it 'Room Booking Conflicts'
3. 3Click the + icon to add your first node

Add Node > Trigger > Google Calendar Trigger

Add Google Calendar Trigger

Set up a trigger that fires when calendar events are created or updated. This catches new bookings that might conflict with existing ones.

1. 1Search for 'Google Calendar' in the node menu
2. 2Select 'Google Calendar Trigger'
3. 3Choose 'Event Created or Updated' as the trigger type
4. 4Set 'Resource' to the specific room calendar ID

Node Settings > Credentials > Google Calendar OAuth2 API

Connect Google Calendar Account

Authenticate with Google to access your calendar data. N8n needs permission to read calendar events and check for scheduling conflicts.

1. 1Click 'Create New Credential' in the Google Calendar node
2. 2Select 'Google Calendar OAuth2 API'
3. 3Click 'Connect my account' and authorize N8n
4. 4Test the connection with 'Test Step'

Add Node > Regular > Google Calendar

Add Calendar Query Node

Query all existing events for the same time period to find overlaps. This node pulls events that might conflict with the new booking.

1. 1Add a new 'Google Calendar' action node after the trigger
2. 2Set operation to 'Get Many' events
3. 3Configure 'Time Min' to {{ $node['Google Calendar Trigger'].json['start']['dateTime'] }}
4. 4Set 'Time Max' to {{ $node['Google Calendar Trigger'].json['end']['dateTime'] }}

Add Node > Regular > Code

Add JavaScript Code Node for Conflict Detection

Write logic to compare event times and detect actual overlaps. N8n's built-in nodes can't handle complex time comparisons, so custom code is required.

1. 1Add a 'Code' node and select 'JavaScript'
2. 2Paste the conflict detection logic into the code editor
3. 3Set the node to process 'Each Item Separately'
4. 4Configure input data from both calendar nodes

Drop this into an n8n Code node.

// Detect time overlap with 15-minute buffer
const newStart = new Date($node['Google Calendar Trigger'].json.start.dateTime);
const newEnd = new Date($node['Google Calendar Trigger'].json.end.dateTime);

// Detect time overlap with 15-minute buffer
const newStart = new Date($node['Google Calendar Trigger'].json.start.dateTime);
const newEnd = new Date($node['Google Calendar Trigger'].json.end.dateTime);
const buffer = 15 * 60 * 1000; // 15 minutes in milliseconds

const conflicts = $node['Google Calendar'].json.filter(event => {
  if (event.status === 'cancelled') return false;
  const existingStart = new Date(event.start.dateTime);
  const existingEnd = new Date(event.end.dateTime);
  
  return (newStart < existingEnd + buffer) && (newEnd > existingStart - buffer);
});

return [{ conflictCount: conflicts.length, conflictDetails: conflicts }];

Add Node > Regular > IF

Configure IF Node for Conflict Filter

Only proceed to Slack notification if conflicts are actually found. This prevents spam notifications for non-conflicting bookings.

1. 1Add an 'IF' node after the code node
2. 2Set condition to 'Number' > 'Larger' > 0
3. 3Reference {{ $node['Code'].json['conflictCount'] }}
4. 4Connect 'true' output to continue the workflow

Add Node > Regular > Slack

Add Slack Node

Configure Slack to post conflict alerts to your office channel. This sends the actual notification when room booking conflicts are detected.

1. 1Add a 'Slack' node connected to the IF node's 'true' output
2. 2Set operation to 'Post Message'
3. 3Choose your #office channel from the dropdown
4. 4Configure the message template with event details

Node Settings > Credentials > Slack OAuth2 API

Connect Slack Workspace

Authenticate N8n with your Slack workspace to enable message posting. You need bot permissions to post in channels.

1. 1Click 'Create New Credential' in the Slack node
2. 2Select 'Slack OAuth2 API'
3. 3Click 'Connect my account' and authorize the N8n app
4. 4Grant 'chat:write' and 'channels:read' permissions

Slack Node > Message Text Field

Format Conflict Alert Message

Create a clear message template that shows exactly which events conflict and when. Include enough detail for someone to resolve the booking issue.

1. 1Set message text to include event names, times, and organizers
2. 2Add conflict details using {{ $node['Code'].json['conflictDetails'] }}
3. 3Include room name and booking duration
4. 4Add a call-to-action for resolving the conflict

Workflow > Execute Workflow

Test the Complete Workflow

Run end-to-end testing with real calendar events to verify conflict detection and Slack notifications work correctly.

1. 1Create two overlapping test events in your room calendar
2. 2Click 'Execute Workflow' to trigger the flow manually
3. 3Check that conflicts are detected in the code node output
4. 4Verify the Slack message appears in your #office channel

Workflow > Activation Toggle

Activate the Workflow

Turn on the workflow to monitor for room conflicts continuously. Once active, it will check every new or updated calendar event automatically.

1. 1Click the workflow toggle switch to 'Active'
2. 2Verify the status shows 'Active' with a green indicator
3. 3Check the execution log to confirm it's listening for events