Introduction
Have you ever built an Azure Function and found yourself wondering how to handle complex workflows, maintain state, or coordinate multiple function executions? If so, you're not alone. Traditional Azure Functions are stateless by design, but what if you need a long-running process or an orchestrated workflow? That’s where Azure Durable Functions come in!
Durable Functions extend Azure Functions by enabling stateful workflows in a serverless environment. They allow you to define workflows using code, making it easier to manage complex interactions between functions. In this blog, we’ll dive deep into Durable Functions, explore their capabilities, and walk through a practical example.
What Are Azure Durable Functions?
Azure Durable Functions are an extension of Azure Functions that enable you to build stateful and serverless workflows. They are powered by the Durable Task Framework, which allows you to define workflows in code rather than using JSON or YAML-based logic apps.
Key Features:
Stateful Execution: Functions can preserve their state across executions.
Orchestration: Durable Functions allow you to define workflows using code rather than external orchestrators.
Long-Running Processes: Easily handle background jobs, waiting for external inputs, or timeouts.
Reliability: If a function crashes or restarts, it can resume from where it left off.
Built-in Patterns: Support for Function Chaining, Fan-Out/Fan-In, Async HTTP APIs, and more.
Durable Functions Patterns
Azure Durable Functions introduce several powerful patterns for handling workflows. Let’s explore some of the most common ones:
1️⃣ Function Chaining
This pattern allows one function to call another in a sequence, where the output of one function becomes the input to the next.
from azure.durable_functions import DurableOrchestrationContext
async def orchestrator_function(context: DurableOrchestrationContext):
result1 = await context.call_activity("ActivityFunction1", "input1")
result2 = await context.call_activity("ActivityFunction2", result1)
return result2
2️⃣ Fan-Out/Fan-In
Useful when multiple functions need to execute in parallel and aggregate the results.
async def orchestrator_function(context: DurableOrchestrationContext):
tasks = []
for i in range(5):
tasks.append(context.call_activity("ActivityFunction", i))
results = await context.task_all(tasks)
return sum(results)
3️⃣ Async HTTP APIs
This pattern is useful when you want to return a response immediately while continuing execution in the background.
3️⃣ Async HTTP APIs
This pattern is useful when you want to return a response immediately while continuing execution in the background.
Real-World Use Case: Processing Image Uploads
Let’s say you’re building an image processing system that applies multiple transformations (resize, watermark, compress) to an uploaded image. A Durable Function can orchestrate the entire workflow:
Receive an image upload request.
Resize the image.
Apply a watermark.
Compress the image.
Store the final image in Azure Blob Storage.
Here's how an orchestrator function might look:
async def orchestrator_function(context: DurableOrchestrationContext):
image_url = context.get_input()
resized_image = await context.call_activity("ResizeImage", image_url)
watermarked_image = await context.call_activity("ApplyWatermark", resized_image)
compressed_image = await context.call_activity("CompressImage", watermarked_image)
await context.call_activity("SaveToBlobStorage", compressed_image)
return compressed_image
Each function runs independently, ensuring modularity and scalability.
Deploying Durable Functions in Azure
Step 1: Install Azure Functions Core Tools
npm install -g azure-functions-core-tools@4 --unsafe-perm
Step 2: Create a Durable Functions Project
func init my-durable-functions-project --worker-runtime python
cd my-durable-functions-project
Step 3: Add an Orchestration Function
func new --template "Durable Functions Orchestration" --name OrchestratorFunction
Step 4: Deploy to Azure
func azure functionapp publish
Conclusion
Azure Durable Functions are a game-changer for serverless applications that require stateful workflows. Whether you’re handling long-running processes, workflow orchestration, or parallel executions, Durable Functions simplify the complexity while maintaining the benefits of serverless computing.
Are you ready to try Azure Durable Functions? Start building your first workflow today!
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