Creating a Function app

All of the work we are going to be doing to create our first Function app will be using the web-based control panel. Once you have your account, you should see something like the following page:

One thing you should note about the Microsoft Azure control panel is that it scrolls horizontally, so if you lose where you are on a page you can typically find your way back to where you need to by scrolling to the right.

As you can see from the preceding screenshot, there are quite a few options. To make a start creating your first Function, you should click on + New at the top of the left-hand side menu.

From here, you will be taken to the Azure Marketplace. Click on Compute and then in the list of featured marketplace items you should see Function App. Click on this and you will be taken to a form which asks for some basic information about the Function you want to create:

• App name: Call this what you want; in my case I called it russ-test-version. This has to be a unique name and, if your desired App name has already been used by another user, you will receive a message that your chosen App name is not available.
• Subscription: Choose the Azure subscription you would like your Function to be launched in.
• Resource Group: This will be automatically populated as you type in the App name.
• Hosting Plan: Leave this at the default option.
• Location: Choose the region which is closest to you.
• Storage: This will automatically be populated based on the App name you give, for our purpose leave Create New selected.
• Pin to dashboard: Tick this as it will allow us to quickly find our Function once it has been created.

If you are not following along in your account, my completed form looks like the following screenshot:

Once you have filled out the form, click on the Create button at the bottom of the form and you will be taken back to your Dashboard. You will receive a notification that your Function is being deployed as you can see from the box at the right-hand side in the following screenshot:

Clicking on the square in the Dashboard or on the notification in the top menu (the bell icon with the 1 on it) will take you to an Overview page; here you can view the status of the deployment:

Once deployed, you should have an empty Function app ready for you to deploy your code into:

To deploy some test code, you need to click on the + icon next to Functions in the left-hand side menu; this will take you to the following page:

With Webhook + API and CSharp selected, click on Create this function; this will add the following code to your Function app:

using System.Net;

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log)
{
    log.Info("C# HTTP trigger function processed a request.");

    // parse query parameter
    string name = req.GetQueryNameValuePairs()
        .FirstOrDefault(q => string.Compare(q.Key, "name", true) == 0)
        .Value;

    // Get request body
    dynamic data = await req.Content.ReadAsAsync<object>();

    // Set name to query string or body data
    name = name ?? data?.name;

    return name == null
        ? req.CreateResponse(HttpStatusCode.BadRequest, "Please pass
        a name on the query string or in the request body")
        : req.CreateResponse(HttpStatusCode.OK, "Hello " + name);
}

This code simply reads in the variable name, which it has passed via the URL and then prints back to the user as Hello <name>.

We can test this by clicking on the Run button at the top of the page. This will execute our Function as well as giving you the output and logs:

The logs for the test run look like this:

2017-09-09T15:28:08 Welcome, you are now connected to log-streaming service.2017-09-09T15:29:07.145 Function started (Id=4db505c2-5a94-4ab4-8e12-c45d29e9cf9c)2017-09-09T15:29:07.145 C# HTTP trigger function processed a request.2017-09-09T15:29:07.176 Function completed (Success, Id=4db505c2-5a94-4ab4-8e12-c45d29e9cf9c, Duration=28ms)

You can also view more information on your Function app by clicking on Monitor in the inner left-hand side menu. As you can see from the following screenshot, we have details on how many times your Function has been called, as well as the status of each execution and the duration for each invocation:

For more detailed information on the invocation of your Function app, you can enable Azure Application Insights, and for more information on this service, please see https://azure.microsoft.com/en-gb/services/application-insights/.

Being able to test within the safety of the Azure Dashboard is all well and good, but how do you directly access your Function app?

If you click on HttpTriggerCSharp1, which will take you back to your code, above the code block you will have a button which says Get function URL, and clicking on this will pop up an overlay box with a URL in it. Copy this:

For me, the URL was:

https://russ-test-function.azurewebsites.net/api/HttpTriggerCSharp1?code=2kIZUVH8biwHjM3qzNYqwwaP6O6gPxSTHuybdNZaD36cq3HptD5OUw==

The preceding URL will no longer work as the Function has been removed; it has been provided for illustration purposes only, and you should replace it with your URL.

To interact with URLs on the command line, I am going to be using HTTPie, which is a command-line HTTP client. For more detail on HTTPie, see the project's homepage at https://httpie.org/.

Call that URL on the command line using HTTPie with the following command:

$ http "https://russ-test-function.azurewebsites.net/api/HttpTriggerCSharp1?code=2kIZUVH8biwHjM3qzNYqwwaP6O6gPxSTHuybdNZaD36cq3HptD5OUw=="

This gives us the following result:

As you can see from what is returned, our Function app has returned the HttpStatusCode BadRequest message. This is because we are not passing the name variable. To do this, we need to update our command to:

$ http "https://russ-test-function.azurewebsites.net/api/HttpTriggerCSharp1?code=2kIZUVH8biwHjM3qzNYqwwaP6O6gPxSTHuybdNZaD36cq3HptD5OUw==&name=kubernetes_for_serverless_applications"

As you would expect, this returns the correct message:

You can also enter the URL in your browser and see the message: