Azure Event Grid in Logic Apps

Event-Driven Workflows with Event Grid Triggers

Introduction

Azure Logic Apps can be triggered by events from Azure Event Grid, enabling you to build powerful event-driven workflows that respond to changes in your Azure resources. Whether it's a new file uploaded to blob storage, a VM state change, or custom application events, Logic Apps can process them all through the Event Grid trigger.

This comprehensive guide covers:

Event Grid trigger — Setting up the trigger in Logic Apps
Event types — Available event types from Azure services
Configuration — Webhook vs polling modes
Processing events — Extracting and using event data
Real-world examples — Complete workflow patterns

Understanding the Trigger

How It Works

┌─────────────────────────────────────────────────────────────────────┐
│                  EVENT GRID TRIGGER FLOW                            │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│   Azure Resource Change                                             │
│        │                                                            │
│        ▼                                                            │
│   Event Grid Topic ───────────┐                                     │
│                                │                                    │
│        ┌───────────────────────┼───────────────────────┐            │
│        │                       │                       │            │
│        ▼                       ▼                       ▼            │
│   ┌─────────┐           ┌─────────┐           ┌─────────┐           │
│   │ Function│           │ Logic   │           │ Custom  │           │
│   │ Handler │           │   App   │           │   App   │           │
│   └─────────┘           └────┬────┘           └─────────┘           │
│                                │                                    │
│                                ▼                                    │
│   ┌──────────────────────────────────────────────────────────┐      │
│   │              LOGIC APP WORKFLOW                          │      │
│   │                                                          │      │
│   │  [Event Grid Trigger]                                    │      │
│   │       ↓                                                  │      │
│   │  [Parse Event] ─ Extract event data                      │      │
│   │       ↓                                                  │      │
│   │  [Condition] ─ Filter based on event type                │      │
│   │       ↓                                                  │      │
│   │  [Action 1] ─ Process the event                          │      │
│   │       ↓                                                  │      │
│   │  [Action 2] ─ Take action                                │      │
│   └──────────────────────────────────────────────────────────┘      │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

Trigger Types

Trigger Name	Description	Use Case
Event Grid	Generic event trigger	Custom topics, any event
Azure Blob	Specific blob events	File uploads
Azure Data Lake	Data lake events	Analytics triggers
Event Hub	Event Hub messages	Stream processing

Configure Event Grid Trigger

Step-by-Step Setup

Create Logic App — Standard or Consumption plan
Open Designer — Navigate to Logic App designer
Add Trigger — Search for "Event Grid"
Select Trigger — "When a resource event occurs"

Basic Configuration

Subscription: Azure subscription
Resource Type: Microsoft.Storage.StorageAccounts
Resource Name: my-storage-account
Event Type: Microsoft.Storage.BlobCreated

Advanced Filters

{
  "filter": {
    "subjectBeginsWith": "uploads/",
    "includedEventTypes": [
      "Microsoft.Storage.BlobCreated",
      "Microsoft.Storage.BlobDeleted"
    ]
  }
}

Configuration Parameters

Parameter	Description	Example
Subscription	Azure subscription	Pay-as-you-go
Resource Group	Resource group	rg-production
Resource Type	Azure resource type	Microsoft.Storage.StorageAccounts
Resource Name	Specific resource	mystorageaccount
Event Type	Event to trigger on	Microsoft.Storage.BlobCreated

Webhook vs Polling

Webhook Mode (Push - Recommended)

┌─────────────────────────────────────────────────────────────────────┐
│                         WEBHOOK MODE                                │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│   Event Grid ────── Push ──────▶ Logic App                          │
│                            (Real-time)                              │
│                                                                     │
│   Pros:                                                             │
│   ✓ Real-time response (seconds)                                    │
│   ✓ No polling overhead                                             │
│   ✓ Lower cost                                                      │
│   ✓ Immediate processing                                            │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

Polling Mode (Pull - Legacy)

┌─────────────────────────────────────────────────────────────────────┐
│                         POLLING MODE                                │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│   Logic App ────── Poll every X ──────▶ Event Grid                  │
│                   minutes                  (Not recommended)        │
│                                                                     │
│   Cons:                                                             │
│   ✗ Delay in processing (X minutes)                                 │
│   ✗ Higher cost (continuous polling)                                │
│   ✗ May miss events                                                 │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

Enable Webhook

The Event Grid trigger automatically uses webhook push when:

Logic App is in the same region as the event source
Logic App has HTTPS endpoint (not HTTP)
Premium/Standard hosting plan is used

Processing Events

Access Event Data

{
  "fullEvent": "@triggerBody()",
  "eventType": "@triggerBody()?['eventType']",
  "subject": "@triggerBody()?['subject']",
  "eventTime": "@triggerBody()?['eventTime']",
  "dataUrl": "@triggerBody()?['data']?['api']",
  "blobUrl": "@triggerBody()?['data']?['url']"
}

Parse Event Data

{
  "Parse_Event": {
    "type": "ParseJson",
    "inputs": {
      "content": "@triggerBody()"
    },
    "schema": {
      "type": "object",
      "properties": {
        "eventType": { "type": "string" },
        "subject": { "type": "string" },
        "data": {
          "type": "object",
          "properties": {
            "url": { "type": "string" },
            "api": { "type": "string" }
          }
        }
      }
    }
  }
}

Filter Events

{
  "Filter_Events": {
    "type": "Condition",
    "expression": "@equals(triggerBody()?['eventType'], 'Microsoft.Storage.BlobCreated')",
    "actions": {
      "Process_Blob": { ... }
    }
  }
}

Real-World Examples

Example 1: Blob Upload Processing Pipeline

┌─────────────────────────────────────────────────────────────────────┐
│              BLOB UPLOAD PROCESSING WORKFLOW                        │
├─────────────────────────────────────────────────────────────────────┤
│                                                                     │
│   [Trigger: Event Grid]                                             │
│   │  Event: Microsoft.Storage.BlobCreated                           │
│   │  Filter: uploads/*                                              │
│   └──────┬────────────────────────────────────────────────────────┘ │
│          │                                                          │
│          ▼                                                          │
│   [Get Blob Content]                                                │
│   │  URI: from trigger                                              │
│   └──────┬────────────────────────────────────────────────────────┘ │
│          │                                                          │
│          ▼                                                          │
│   [Parse CSV/JSON]                                                  │
│   └──────┬────────────────────────────────────────────────────────┘ │
│          │                                                          │
│          ▼                                                          │
│   [Switch - File Type]                                              │
│   ├─ CSV: [Insert to SQL Database]                                  │
│   ├─ JSON: [Process as Orders]                                      │
│   └─ XML: [Transform to JSON]                                       │
│   └──────┬────────────────────────────────────────────────────────┘ │
│          │                                                          │
│          ▼                                                          │
│   [Send Success Email]                                              │
│   └──────┬────────────────────────────────────────────────────────  │
│          │                                                          │
│          ▼                                                          │
│   [Update Status to Table]                                          │
│                                                                     │
└─────────────────────────────────────────────────────────────────────┘

Example 2: VM State Change Notifications

{
  "trigger": {
    "type": "EventGridTrigger",
    "inputs": {
      "subscription": {
        "subscriptionName": "production-sub"
      },
      "resourceType": "Microsoft.Compute/virtualMachines",
      "resourceName": "prod-vm-01",
      "eventTypes": [
        "Microsoft.Compute/virtualMachines/write",
        "Microsoft.Compute/virtualMachines/deallocation"
      ]
    }
  },
  "actions": {
    "Log_Event": {
      "type": "AzureTable",
      "inputs": {
        "method": "post",
        "path": "/tables/vm-events",
        "body": {
          "PartitionKey": "@triggerBody()?['eventType']",
          "RowKey": "@guid()",
          "vmName": "@triggerBody()?['subject']",
          "eventTime": "@triggerBody()?['eventTime']",
          "newState": "@triggerBody()?['data']?['newState']",
          "oldState": "@triggerBody()?['data']?['oldState']"
        }
      }
    },
    "Notify_Team": {
      "type": "Condition",
      "expression": "@equals(triggerBody()?['eventType'], 'Microsoft.Compute/virtualMachines/deallocation')",
      "actions": {
        "Send_Slack": {
          "type": "Slack",
          "inputs": {
            "message": "VM deallocated: @triggerBody()?['subject']"
          }
        }
      }
    }
  }
}

Example 3: Custom Topic Events

{
  "trigger": {
    "type": "EventGridTrigger",
    "inputs": {
      "topic": "/subscriptions/xxx/resourceGroups/my-rg/providers/Microsoft.EventGrid/topics/orders-topic"
    }
  },
  "actions": {
    "Process_Order": {
      "type": "Switch",
      "expression": "@triggerBody()?['eventType']",
      "cases": {
        "Order.Created": {
          "actions": {
            "Create_Order_Record": {
              "type": "Sql",
              "inputs": {
                "databaseName": "ordersdb",
                "query": "INSERT INTO orders VALUES (...)"
              }
            }
          }
        },
        "Order.Shipped": {
          "actions": {
            "Update_Status": {
              "type": "Sql",
              "inputs": {
                "databaseName": "ordersdb",
                "query": "UPDATE orders SET status='Shipped' WHERE id=..."
              }
            },
            "Send_Notification": {
              "type": "SendEmail"
            }
          }
        }
      }
    }
  }
}

Best Practices

Practice	Description
Use webhook mode	Enable real-time processing
Filter events	Subscribe only to needed events
Parse once	Extract event data early in workflow
Add error handling	Handle failed events gracefully
Log all events	Track for debugging and auditing

Performance Considerations

Use Standard plan for high throughput
Implement ** batching** for many events
Set up dead-letter for failed processing
Monitor trigger frequency in Analytics

Monitoring

Trigger Runs

# Get Logic App trigger history
az logic workflow run list \
  --resource-group my-rg \
  --name my-logic-app \
  --query "[].{Status: status, Start: startTime, Trigger: triggerName}"

Application Insights

traces
| where timestamp > ago(1h)
| where customDimensions.Category == "LogicApp"
| project timestamp, message, customDimensions