There are several options for diagnosing issues with Durable Functions. Some of these options are the same for regular functions and some of them are unique to Durable Functions. Application Insights is the recommended way to do diagnostics and monitoring in Azure Functions. The same applies to Durable Functions. For an overview of how to leverage Application Insights in your function app, see Monitor Azure Functions.

The Azure Functions Durable Extension also emits tracking events that allow you to trace the end-to-end execution of an orchestration.

These tracking events can be found and queried using the Application Insights Analytics tool in the Azure portal.

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Each lifecycle event of an orchestration instance causes a tracking event to be written to the traces collection in Application Insights. This event contains a customDimensions payload with several fields. The verbosity of tracking data emitted to Application Insights can be configured in the logger Functions 1. By default, all non-replay tracking events are emitted. The volume of data can be reduced by setting Host. DurableTask to "Warning" or "Error" in which case tracking events will only be emitted for exceptional situations.

To enable emitting the verbose orchestration replay events, the LogReplayEvents can be set to true in the host. By default, Application Insights telemetry is sampled by the Azure Functions runtime to avoid emitting data too frequently. This can cause tracking information to be lost when many lifecycle events occur in a short period of time.

The Azure Functions Monitoring article explains how to configure this behavior. The following query shows historical tracking data for a single instance of the Hello Sequence function orchestration. It filters out replay execution so that only the logical execution path is shown.

Events can be ordered by sorting by timestamp and sequenceNumber as shown in the query below:. The result is a list of tracking events that shows the execution path of the orchestration, including any activity functions ordered by the execution time in ascending order.Durable Functions is an extension of Azure Functions that lets you write stateful functions in a serverless environment.

The extension manages state, checkpoints, and restarts for you. In this article, you learn how to use Visual Studio Code to locally create and test a "hello world" durable function. This function orchestrates and chains-together calls to other functions. You then publish the function code to Azure. Install Visual Studio Code. Make sure you have the latest version of the Azure Functions Core Tools.

Make sure that you have version 3. If you don't have an Azure subscriptioncreate a free account before you begin. It also creates a function app project in a folder. This project contains the host. When VS Code prompts you to select a storage account, choose Select storage account. Following the prompts, provide the following information to create a new storage account in Azure. A class containing the new functions is added to the project.

VS Code also adds the storage account connection string to local. DurableTask NuGet package to the.

azure durable functions

Open the new HelloOrchestration. This durable function is a simple function chaining example with the following methods:. Now that you've created your function project and a durable function, you can test it on your local computer.

azure durable functions

Azure Functions Core Tools lets you run an Azure Functions project on your local development computer. You're prompted to install these tools the first time you start a function from Visual Studio Code.

To test your function, set a breakpoint in the SayHello activity function code and press F5 to start the function app project. Output from Core Tools is displayed in the Terminal panel. Refer to the Durable Functions Diagnostics for more information on debugging. The response is the initial result from the HTTP function letting us know the durable orchestration has started successfully.

It is not yet the end result of the orchestration. The response includes a few useful URLs. For now, let's query the status of the orchestration. Alternatively you can also continue to use Postman to issue the GET request. The request will query the orchestration instance for the status.It allows you to write a workflow as code and have the execution run with the scalability and the reliability of serverless with high throughput. Initially, I wanted to index data from GitHub repositories.

To summarize the post, I wanted to retrieve a list of repositories that I wanted to index. Then, query each repository for more detailed information. Finally, save the data into a database. A serverless function on Azure is a unit of work that is, in Ca single method from a static class.

Azure Functions allows you only pay for what you use as well as scaling that piece of code for you.

azure durable functions

Those triggers are applied directly on a parameter of a function. Those are traditional functions that you find in a serverless application deployed on Azure. They are simple and respond to events.

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What if you need something more complicated? What about calling functions with functions? For example, invoking one function for every element of a list then reconciling the result and saving it to a file. Writing a complex workflow with simple code is where Durable Functions comes in.

An Orchestrator is an Azure Function with specific behaviors attached to them. As an example, it automatically set checkpoint during its execution, shut itself down while waiting for other functions to finish executing, then replay through the checkpoint to resume execution.

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It is important to remember how an Orchestrator function operates differently than a standard function. While a normal function only executes once per event, the orchestrator is restarted many times while waiting for other functions to complete. It must return the same result each time. More information is available on the checkpoint and replay pattern that Orchestrators are using internally.

Not every function can be used with an orchestrator. Activities are part of the checkpoint and replay pattern described previously. Among the differences with other functions, they do not respond to other triggers than an orchestrator calling them. An activity is a perfect place to have code accessing a database, sending emails, or any other external systems.

Activities that have been called and returned have their results cached. As an example, our sample uses an activity function to retrieve the list of repositories from which we want to extract more data. An Activity Function is not re-executed for the same Orchestrator instance. In this scenario, we preserve the list of repositories without invoking the API again.You build the extension on top of the open-source Durable Task Framework.

Furthermore, the extension takes care of managing the state, checkpoint, and replays for you. With Azure Durable Functions, you can write stateful workflows in a new function type called an orchestrator function. This orchestration function provides you more control for building workflows than using, for instance, a designer for Microsoft Flow or Logic Apps. It is strictly coded, and developers like that.

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Therefore, you as a developer can build durable functions with the code the same way as you are familiar with Visual Studio or Code. Furthermore, other benefits of using Azure Durable Functions are:. The Orchestrator client is responsible for starting and stopping orchestrator functions and monitoring them.

You can, for example, have an HTTP-triggered function as orchestrator client, which accepts an HTTP request and starts an orchestrator function, or a Service Bus triggered function, which listens to a queue and each message begins an orchestrator function.

In the introduction, we already mentioned the orchestrator function. This function is the heart when building a durable function solution.

Creating distributed workflows with Azure Durable Functions

Moreover, in the orchestrator function, you write your workflow in code. The workflow can consist of code statements calling other functions like activity, or other orchestration functions sub orchestrationsor waits for other events to occur callbacks or human interactionor timers. Furthermore, an orchestration function itself is triggered by an orchestration trigger.

You start an orchestration by a so-called orchestrator client, a function that on its turn can be triggered by a message in a queue, an HTTP request, or any other trigger mechanism you are familiar with using functions.

Every instance of an orchestration function will have an instance identifier, which can be auto- or user-generated. You can for example with the DurableFunctionsHubHistory Table of the storage account attached to the Function App, examine an orchestration run from a given instance identifier. You can call so-called activity functions from an orchestration function.

These activity functions are the basic unit of work in a durable function solution. Each activity function executes one task, which can be anything you want.Develop more efficiently with Functions, an event-driven serverless compute platform that can also solve complex orchestration problems.

Build and debug locally without additional setup, deploy and operate at scale in the cloud, and integrate services using triggers and bindings. Automated and flexible scaling based on your workload volume, keeping the focus on adding value instead of managing infrastructure. Integrated programming model based on triggers and bindings that help you respond to events and seamlessly connect to other services. End-to-end development experience, from building and debugging to deploying and monitoring with integrated tools and built-in DevOps capabilities.

Variety of programming languages and hosting options—always pick the best one for each scenario and quickly adjust to meet business needs.

Take advantage of a complete, end-to-end development experience with Functions—from building and debugging locally on major platforms like Windows, macOS, and Linux to deploying and monitoring in the cloud.

Use Functions extensions and templates on Visual Studio and Visual Studio Code for a faster and more efficient development on your local machine, fully integrated with the whole Azure platform.

Develop using your favorite code editor and the Azure Functions Core Tools. Serverless functions are meant to be short-lived and stateless—until you need them to solve stateful problems.

azure durable functions

Remove this limitation in a fully managed way without provisioning more resources, just by coding your workflow definition. Simplify complex, stateful coordination requirements programmatically in event-driven applications with the Durable Functions extension.

Durable Functions versions overview

Use your functions also on declarative workflows that can take advantage of over connectors with Azure Logic Apps. Write only the code that truly matters to your business. Save coding time with a programming model based on triggers and bindings that enable your serverless applications to respond to events and connect to other services seamlessly. Build more scalable and stable event-driven applications with a microservices-friendly approach using Functions. Not all applications are the same, and one hosting plan won't fit them all.

Pick the Functions plan that matches your business needs, and deploy the same code to multiple targets - from pay-per-execution in the cloud to your Kubernetes cluster or IoT devices for edge computing. Start coding right away with the technology stack you already know and love, no new languages or frameworks to learn. Pick the programming languages you like best for each unique scenario—from web apps and APIs with.

NET, Node. Scale automatically and only pay for compute resources when your functions are running. On the Consumption plan, instances of the Functions host are dynamically added and removed based on the number of incoming events. While automatically scaling based on demand, use pre-warmed workers to run applications with no delay after being idle, run on more powerful instances, and connect to VNETs.

Good fit for long running operations, as well as when more predictive scaling and costs are required. See documentation. Learn to create serverless applications. Get the e-book. Serverless APIs with Node.

Serverless web application for static websites and single-page applications. Serverless microservices for event-driven scenarios.Durable Functions is an extension of Azure Functions that lets you write stateful functions in a serverless compute environment.

The extension lets you define stateful workflows by writing orchestrator functions and stateful entities by writing entity functions using the Azure Functions programming model.

Behind the scenes, the extension manages state, checkpoints, and restarts for you, allowing you to focus on your business logic. Durable Functions has a goal of supporting all Azure Functions languages. See the Durable Functions issues list for the latest status of work to support additional languages. The primary use case for Durable Functions is simplifying complex, stateful coordination requirements in serverless applications.

The following sections describe typical application patterns that can benefit from Durable Functions:. In the function chaining pattern, a sequence of functions executes in a specific order. In this pattern, the output of one function is applied to the input of another function. You can use Durable Functions to implement the function chaining pattern concisely as shown in the following example. In this example, the values F1F2F3and F4 are the names of other functions in the same function app.

You can implement control flow by using normal imperative coding constructs. Code executes from the top down. The code can involve existing language control flow semantics, like conditionals and loops. You can use the context parameter to invoke other functions by name, pass parameters, and return function output.

Each time the code calls awaitthe Durable Functions framework checkpoints the progress of the current function instance. If the process or virtual machine recycles midway through the execution, the function instance resumes from the preceding await call. You can use the context. Each time the code calls yieldthe Durable Functions framework checkpoints the progress of the current function instance.

If the process or virtual machine recycles midway through the execution, the function instance resumes from the preceding yield call. The context object in JavaScript represents the entire function context. Access the Durable Functions context using the df property on the main context.

Often, some aggregation work is done on the results that are returned from the functions. With normal functions, you can fan out by having the function send multiple messages to a queue. Fanning back in is much more challenging. To fan in, in a normal function, you write code to track when the queue-triggered functions end, and then store function outputs.

The fan-out work is distributed to multiple instances of the F2 function. The work is tracked by using a dynamic list of tasks. WhenAll is called to wait for all the called functions to finish.

HTTP Triggered Azure Functions

Then, the F2 function outputs are aggregated from the dynamic task list and passed to the F3 function. The automatic checkpointing that happens at the await call on Task. WhenAll ensures that a potential midway crash or reboot doesn't require restarting an already completed task.

The automatic checkpointing that happens at the yield call on context. In rare circumstances, it's possible that a crash could happen in the window after an activity function completes but before its completion is saved into the orchestration history. If this happens, the activity function would re-run from the beginning after the process recovers. A common way to implement this pattern is by having an HTTP endpoint trigger the long-running action.

Then, redirect the client to a status endpoint that the client polls to learn when the operation is finished. Durable Functions provides built-in support for this pattern, simplifying or even removing the code you need to write to interact with long-running function executions.

The following example shows REST commands that start an orchestrator and query its status.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I'm stepping through Azure training. When I got to "Verify that the durable functions workflow starts" I noticed something was wrong.

Instead of the json response that it predicted, I got a blank screen. Then, I checked the log of the HttpStart function, and I saw this:. I'm not sure where I would do that, but at this point I went through all of the previous instructions looking for variances. The only thing I noticed was that in the instructions, where it showed what the "function.

What I have seems more correct, in any case, so I think what was shown in the instructions was incorrect. I also noticed that the instructions described installing the "Azure DurableTask extension", but I didn't see any prompt to install this. I then googled the error message. I have changed my runtime version to version 2 and this time the HTTP Trigger was successful in running. To change the runtime version, I clicked on the "Function App settings" link underneath the Configured features heading on the Overview tab of the durable function I created.

Another workaround without changing the azure SDK version is to add a compatibility app setting and setting it to true. This seems to do the trick while the azure-functions-durable package gets this fixed to deal with synchronous calls within the library, see the issue on GitHub.

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Learn more. Azure durable functions sample says sync functions are not allowed Ask Question. Asked 2 months ago.