Azure Function HTTP Trigger

Azure Function is an Azure Service from Microsoft that helps you to run some pieces of code smoothly without getting worried about the infrastructure for your application. Check out some more information on Azure Function before starting with the Azure Function HTTP Trigger.

The main work of the Azure Function HTTP Trigger is to invoke the Azure Function with the HTTP Request. HTTP Trigger is the basic and simplest trigger of an Azure Function. Mostly, People use the HTTP Trigger while performing the operation with the Azure Function.

Basically, there are two response codes that HTTP Triggered functions return

It returns the response code as HTTP 204 if in case there is no content.
It returns the response code as HTTP 200 OK in case everything is ok and the Successful execution of the Azure Function.

The HttpTrigger attribute is available in the case of C# language, Java, etc to configure your Azure Function.

Azure function HTTP Trigger authorization level

To execute the HTTP-triggered Azure function, you need to specify the authorization types. If you are running the Azure Function locally, in that case, the authorization attribute will get ignored. Once you will publish your Azure Function into the Azure cloud then the authorization will work. There are a few authorization types available as below

Function: This is the default authorization type option available. This is the key-based authorization type. A function-specific API key is required for this authorization type.
Anonymous: There is no restriction, anyone can access and No API key is needed in the case of the Anonymous Authorization type.
Admin: For the Admin authorization type, the master key is required to access the Azure function.

You can provide the HTTP-triggered Azure function parameter value along with the query string in the function URL or in the Body in a JSON format.

When you will create an HTTP-triggered Azure function, by default, the URL of the function is in the below format

http://<APP_NAME>.azurewebsites.net/api/<FUNCTION_NAME>

One of the Examples for an HTTP triggered Azure function URL with the authorization type as Function is as below

https://mydemoazurefunction1220200810210756.azurewebsites.net/api/Function1?code=CNZkNlmz3xpQRhgu7DIKcRiMiTtLv7bTOvhcip82GdfCkormbvCqjw==

Below is the example of an HTTP-triggered Azure function function.json file

{
  "bindings": [
    {
      "authLevel": "function",
      "name": "req",
      "type": "httpTrigger",
      "direction": "in",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "name": "$return",
      "type": "http",
      "direction": "out"
    }
  ]
}

If we will discuss a little bit on the above function.json file,

type: The type property is must required to mention and the value will be httpTrigger.

direction: The property direction is also required and the value must be set to in.

name: The property name is required and needs to mention the variable name in the code for the Azure function. authLevel: The property authLevel needs to specify the authorization level for the Azure function. You can provide the auth level property value as Function, Anonymous, or Admin. The default option is Function.

methods: You can specify the HTTP methods that you want the Azure Function to respond to. If you will not mention any specific method then your Azure function will respond to all the HTTP methods available. This is about the Azure function HTTP trigger authentication.

Let’s create an Azure Function HTTP Trigger using Visual Studio 2019

Create An HTTP Trigger Azure Function Using Visual Studio 2019

Well, let’s create an HTTP-triggered Azure Function using Visual Studio 2019. Follow the below steps to create the Azure function.

Step-1: The first step is to open Visual Studio 2019.

Step-2: Once the Visual Studio will be loaded successfully, Now you need to click on the Create a new Project button from the Get Started window.

Create An HTTP Trigger Azure Function Using Visual Studio 2019

Step-3: On the Create a new project window, Now search for the Azure Functions template and choose the Azure Functions and then click on the Next button to go to the next screen.

How to Create An HTTP Trigger Azure Function Using Visual Studio 2019

Step-4: Enter your Project name, and choose a location where you want to save the Azure function project On the Configure Your new Project window, and then click on the Create button.

Step-5: We need to choose the trigger for our Azure Function, so choose the Http trigger as the trigger option For the Storage Account (AzureWebJobsStorage) option, select the Storage Emulator option and Choose the Authorization level option as Anonymous On the Create a new Azure Functions Application window. Now click on the Create button to create the HTTP-triggered Azure function as shown below.

Now, you can see the project got created successfully.

Create An HTTP Trigger Azure Function in Visual Studio 2019

Now if you can see the local.settings.json file and it contains the below code with a key-value pair for the Azure Storage connection string to access the Azure storage account.

{
    "IsEncrypted": false,
    "Values": {
        "AzureWebJobsStorage": "UseDevelopmentStorage=true",
        "FUNCTIONS_WORKER_RUNTIME": "dotnet"
    }
}

azure function http trigger authorization level — azure functions route parameters

Now If you will open the Function1.cs file and see that it contains our HTTP-triggered Azure Function. I am renaming the function from Function1 to HTTPAzureFunction

public static class Function1
    {
        [FunctionName("Function1")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req,
            ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string name = req.Query["name"];

            string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            dynamic data = JsonConvert.DeserializeObject(requestBody);
            name = name ?? data?.name;

            string responseMessage = string.IsNullOrEmpty(name)
                ? "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response."
                : $"Hello, {name}. This HTTP triggered function executed successfully.";

            return new OkObjectResult(responseMessage);
        }
    }

azure function http trigger authentication — azure functions http trigger route parameters

Now our Azure function HTTP Trigger is ready. Let’s run the function to check if it is working as expected. Press F5 to run the project. You can able to see the project ran successfully without any issues and provides us with the Http Azure Function URL to access the function.

The URL is like below

http://localhost:7071/api/HTTPAzureFunction

Now to check, if the function is working fine, To check that copy that URL and paste it into the Browser and press enter

azure function http trigger with parameters c# — azure function http trigger example

Now we can see the default message it is showing, It is expecting value for the name parameter in the query string. Let’s provide that. So now append ?name=Azure and press enter. You can able to see it provides the output as expected.

Let’s check the function URL in the Postman app and see if it is working as expected. You can see below it executed the function URL successfully.

azure function http trigger query parameters

Deploy An HTTP Trigger Azure Function from Visual Studio 2019

You can deploy the HTTP trigger Azure function from Visual Studio 2019. You can check to Deploy an HTTP Trigger Azure Function from Visual Studio 2019 to Azure. you can check Deploying the Azure Function using Visual Studio 2019 section for the detailed steps.

Azure Function HTTP Trigger Route

Well, here we will discuss the HTTP-triggered Azure Functions Routing options. Before that, We should know What is routing?

Routing basically refers to how an application responds to the user request to an endpoint address with the particular HTTP request method like “GET” and “POST“, etc. In the case of Azure Functions, the route says, with the help of the Azure function URL, which function is going to react as per your HTTP request. Finally, routing is all about the endpoint or the application URL.

HTTP triggered Azure Functions Default Routing

If we will consider the above function, we have created a named as HTTPAzureFunction.By running that function locally, you can see that the default URL generated to access the function is http://localhost:7071/api/HTTPAzureFunction. If you will closely look at the function URL, you can see that the URL is comprised of a route prefix of /API/, then the actual name of your function, in my case it is HTTPAzureFunction.

So, this is the default URL to access the HTTPAzureFunction, Now if we are accessing the URL with the value of a parameter as a query string with the function URL. You will get the expected output as below

How to change the Azure Function Route Prefix With host.json

We can change the default routing of /API/ for the HTTP triggered Azure Function with the help of a few modifications on the host.json file in your project. You can find the host.json file in your solution. Open that file and do the changes and save it.

{
  "version": "2.0",
  "extensions": {
    "http": {
      "routePrefix": "Name"

    }
  }
}

Your host.json file should exactly look like below.

How to change the Route Prefix With host.json — azure function http trigger with parameters c#

Now after the host.json file modification, if you will run the Azure Function project again, you can see the URL is changed now, Earlier before changing the host.json file, the function URL was http://localhost:7071/api/HTTPAzureFunction and now after the modification, the Function URL is http://localhost:7071/Name/HTTPAzureFunction. see below.

Now let’s try to open the new URL in the Browser and see if it is working fine. You can able to see it is working as expected.

Azure Function Remove API From Route

If you want to remove the route prefix completely from the function URL then you need to modify the host.json file like below

{
  "version": "2.0",
  "extensions": {
    "http": {
      "routePrefix": ""

    }
  }
}

Now your host.json file should be like the below

Azure Function Remove API From Route — azure functions http trigger example

Now if you will run the Project again after the above modification, Then you can see the URL changed now.

Now the URL is http://localhost:7071/HTTPAzureFunction

Now let’s try to open the new URL in the Browser and see if it is working fine. You can able to see it is working as expected.

Define the Route in the Azure Function Header

You can also define the Route in the Azure Function header like below. Now URL will be like http://localhost:7071/api/GetNameVal

 [FunctionName("HTTPAzureFunction")]
        public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = "GetNameVal")] HttpRequest req,
            ILogger log)

Now we can test it like below

Azure Functions HTTP Trigger Route Parameters

     [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = "GetNameVal/{name}")] HttpRequest req, string name, ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string name1 = req.Query["name"];

Now you can the project and see the parameter is like below

http://localhost:7071/api/GetNameVal/{name}

Define the Route in the Azure Function Header with Adding Parameters

Now We can pass the name value directly using a route parameter

If you will not provide the route parameter in the URL, then it will return HTTP Error 404 like below.

How To Make Azure Function Route Parameters Optional

You can Make Route Parameters as Optional by adding the ? to the parameter name in the route definition and the type in the function header parameters. It looks exactly like below

[HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = "GetNameVal/{name?}")] HttpRequest req, string name, ILogger log)
        {
            log.LogInformation("C# HTTP trigger function processed a request.");

            string name1 = req.Query["name"];

How To Make Azure Function Route Parameters Optional

Now by specifying name as a URL parameter, we can see the expected output.

Now. if you will not provide the name, the parameter value defaults to null and It will display the message to provide the name parameter.

Make Route Parameters Optional in Azure HTTP triggered function

Azure Function Route Wildcard

Sometimes you might need to handle multiple routes with a single Azure function. The syntax will be like /api/{RemainingPath}. the value {RemainingPath} is a string representation of the remaining path.

The function will look like below

[FunctionName("NewWildCardFunction")]
public async Task NewWildCardFunction([HttpTrigger(AuthorizationLevel.Anonymous, "get", 
                                    Route = "{*RemainingPath}")]) string RemainingPath)
{
    // Function body
}

Azure Function HTTP Trigger Query Parameters

Sorry to say that it’s not possible as of now to put a query parameter in the Route and it’s actually a restriction of ASP.NET routing that is used by the Azure function to build the route.

Azure Function HTTP Output Binding

Azure Function HTTP Output Binding can be used to respond to the HTTP request sender. Azure Function HTTP Output Binding requires an HTTP trigger.

Configuration for Azure Function HTTP Output Binding

In order to implement the Azure Function HTTP OutPut Binding, we need to set a few properties in the function.json file. Below are few key properties.

Key Property	Value Need to Set
For the property “type“	You must have to set the value to “HTTP”.
For the property “direction“	You must have to set the value of the direction property to “out”.
For the property “name“	Need to set the variable name used in the function code for the response

What is the use of Azure Function HTTP Output Binding

This is basically used to send an HTTP response or you can tell to respond to the HTTP request sender.

host.json settings file Changes

The host.json settings file should look like the below.

{
    "extensions": {
        "http": {
            "routePrefix": "api",
            "maxOutstandingRequests": 200,
            "maxConcurrentRequests": 100,
            "dynamicThrottlesEnabled": true,
            "hsts": {
                "isEnabled": true,
                "maxAge": "10"
            },
            "customHeaders": {
                "X-Content-Type-Options": "nosniff"
            }
        }
    }
}

maxOutstandingRequests: This property value states the maximum number of outstanding requests that are held at any given point in time. The default value for the consumption plan is 200.

maxConcurrentRequests: This property states the maximum number of HTTP functions that are executed in parallel. The default value for the consumption plan is 100.

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Conclusion

Well, in this article, we discussed, Azure Function HTTP Trigger, Azure function HTTP Trigger authorization level, Create An HTTP Trigger Azure Function Using Visual Studio 2019, and then, we discussed Azure Function HTTP Trigger Route, Deploy An HTTP Trigger Azure Function from Visual Studio 2019, HTTP triggered Azure Functions Default Routing, how to change the Azure Function Route Prefix With host.json.

Now finally we discussed Azure Function Remove API From Route, Define the Route in the Azure Function Header, Azure Functions HTTP Trigger Route Parameters, How To Make Azure Function Route Parameters Optional, Azure Function HTTP Trigger Query Parameters, Azure Function HTTP Output Binding. Hope you have enjoyed this article !!!