Lab 3: Create a function that's triggered by an HTTP request

Task 1: Create an HTTP-triggered function

On the taskbar, select the Windows Terminal icon.
Run the following command to change the current directory to the $HOME\training-az204\Labs\02\Starter\func directory:
```
 cd $HOME\training-az204\Labs\02\Starter\func
```
Run the following command to use the Azure Functions Core Tools to create a new function named Echo using the HTTP trigger template:
```
 func new --template "HTTP trigger" --name "Echo"
```
Note: You can review the documentation to [create a new function][azure-functions-core-tools-new-function] using the Azure Functions Core Tools.
Close the currently running Windows Terminal application.

Task 2: Write HTTP-triggered function code

On the Start screen, select the Visual Studio Code tile.
On the File menu, select Open Folder.
In the File Explorer window that opens, browse to $HOME\training-az204\Labs\02\Starter\func, and then select Select Folder.
On the Explorer pane of the Visual Studio Code window, open the Echo.cs file.

In the code editor, observe the example implementation:

 using System;
 using System.IO;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Azure.WebJobs;
 using Microsoft.Azure.WebJobs.Extensions.Http;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
 namespace func
 {
     public static class Echo
     {
         [FunctionName("Echo")]
         public static async Task<IActionResult> Run(
             [HttpTrigger(AuthorizationLevel.Function, "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);
         }
     }
 }

Delete all the content within the Echo.cs file.
Add the following lines of code to add using directives for the Microsoft.AspNetCore.Mvc, Microsoft.Azure.WebJobs, Microsoft.AspNetCore.Http, and Microsoft.Extensions.Logging namespaces:
```
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Azure.WebJobs;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
```
Create a new public static class named Echo:
```
 public static class Echo
 { }
```

Observe the Echo.cs file again, which should now include:

 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Azure.WebJobs;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 public static class Echo
 { }

Within the Echo class, add the following code block to create a new public static method named Run that returns a variable of type IActionResult and that also takes in variables of type HttpRequest and ILogger as parameters named request and logger:
```
 public static IActionResult Run(
     HttpRequest request,
     ILogger logger)
 { }
```
Add the following code to append an attribute to the Run method of type FunctionNameAttribute that has its name parameter set to a value of Echo:
```
 [FunctionName("Echo")]
 public static IActionResult Run(
     HttpRequest request,
     ILogger logger)
 { }
```
Add the following code to append an attribute to the request parameter of type HttpTriggerAttribute that has its methods parameter array set to a single value of POST:
```
 [FunctionName("Echo")]
 public static IActionResult Run(
     [HttpTrigger("POST")] HttpRequest request,
     ILogger logger)
 { }
```

Observe the Echo.cs file again, which should now include the following code:

 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Azure.WebJobs;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 public static class Echo
 {
     [FunctionName("Echo")]
     public static IActionResult Run(
         [HttpTrigger("POST")] HttpRequest request,
         ILogger logger)
     { }
 }

In the Run method, enter the following line of code to log a fixed message:
```
 logger.LogInformation("Received a request");
```
Enter the following line of code to echo the body of the HTTP request as the HTTP response:
```
 return new OkObjectResult(request.Body);
```

Observe the Echo.cs file again, which should now include the following code:

 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Azure.WebJobs;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 public static class Echo
 {
     [FunctionName("Echo")]
     public static IActionResult Run(
         [HttpTrigger("POST")] HttpRequest request,
         ILogger logger)
     {
         logger.LogInformation("Received a request");
         return new OkObjectResult(request.Body);
     }
 }

Select Save to save your changes to the Echo.cs file.

Task 3: Test the HTTP-triggered function by using httprepl

On the taskbar, select the Windows Terminal icon.
Run the following command to change the current directory to the $HOME\training-az204\Labs\02\Starter\func directory:
```
 cd $HOME\training-az204\Labs\02\Starter\func
```
Run the following command to run the function app project:
```
 func start --build
```
Note: You can review the documentation to start the function app project locally using the Azure Functions Core Tools.
On the taskbar, select the Windows Terminal icon again to open a new instance of the application. Run the following command to change the current directory to the $HOME\training-az204\Labs\02\Starter\func empty directory:
```
 cd $HOME\training-az204\Labs\02\Starter\func
```
From the command prompt, run the following command to install and start the httprepl tool, setting the base Uniform Resource Identifier (URI) to http://localhost:7071:
```
 dotnet tool install -g Microsoft.dotnet-httprepl
 httprepl http://localhost:7071
```
Note: An error message is displayed by the httprepl tool. This message occurs because the tool is searching for a Swagger definition file to use to traverse the API. Because your function project doesn't produce a Swagger definition file, you'll need to traverse the API manually.
From the tool's prompt, run the following command to browse to the relative api directory:
```
 cd api
```
Run the following command to browse to the relative echo directory:
```
 cd echo
```
Run the following command to run the post command, sending in an HTTP request body set to a numeric value of 3 by using the --content option:
```
 post --content 3
```
Run the following command to run the post command, sending in an HTTP request body set to a numeric value of 5 by using the --content option:
```
 post --content 5
```
Run the following command to run the post command, sending in an HTTP request body set to a string value of Hello by using the --content option:
```
 post --content "Hello"
```
Run the following command to run the post command, sending in an HTTP request body set to a JavaScript Object Notation (JSON) value of {"msg": "Successful"} by using the --content option:
```
 post --content "{"msg": "Successful"}"
```
Run the following command to exit the httprepl application:
```
 exit
```
Close all currently running instances of the Windows Terminal application.

Review

In this exercise, you created a basic function that echoes the content sent through an HTTP POST request.

LAB 3 - Create a function that’s triggered by an HTTP request

Lab 3: Create a function that's triggered by an HTTP request

Task 1: Create an HTTP-triggered function

Task 2: Write HTTP-triggered function code

Task 3: Test the HTTP-triggered function by using httprepl

Review

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