Working with Azure Functions in Visual Studio Code like a boss

So after a while I decided to finally check Azure Functions extensions out in Visual Studio Code. I often want to check something really quickly and being forced to open Visual Studio each time makes me furious. I must say that initially I was a bit skeptical regarding Code functionality, but it turns out to be superb. Let's check what it offers for now.

Installing

Installing the extensions is super easy. Just go to the Extensions menu and search for Azure Functions:

Once extensions is installed you can easily disable or uninstall it

For now - that's really all!

Creating a function

With Azure Functions plugin installed you should be able to see available subscriptions in the Explorer area. If not left-click on the status bar where your username is displayed and select the ones you're interested in:

Workspace with only one subscription selected

 

Installing the extension gives you some more features. Now you're able to work with a project, create a function and publish it. Let's start with a function triggered by a HTTP request. Click on "Create New Project Button":

Now you're able to select a current location or create a new one where your project will be placed. Once you're satisfied you can select a language and... that's all, your workspace is ready to start working on a function.

Empty Functions project ready to rock!

Now let's create a function. You can create in in a similar way as a project. After providing all necessary data(like a name, a type of trigger, security level), a template will be created so you can start modyfing it as you wish.

A template, very similar to the one created in Visual Studio

Running a function

You can easily start testing your function by pressing F5. It'll start runtime and you'll be given an endpoint, which you can call anytime:

Publishing a function

Publishing a function from Visual Studio Code is as easy as other tasks. Once more go to the Azure Functions workspace and select "Deploy to Function App". You'll be asked about many different parameters like a subscription, resource group or storage account. Once everything's configured wait a second(or maybe two) until a function is published. You can start using it!

Function published along with a storage account and consumption plan

Summary

In the current shape VS Code will not replace full Visual Studio(at least for me personally), but I found Azure Functions extension extremely helpful in the smaller projects, which are developed fully in Code. If I don't have to switch between IDEs, I'm more than happy. 

Don't be afraid to store it twice

In most cases we try to follow DRY approach - Don't Repeat Yourself. This simple yet powerful statement, which - if executed correctly - has the power of changing meh projects to good ones, doesn't work well in all scenarios and use cases. As one once said "One size doesn't fit all", you shouldn't always follow each pattern or approach blindly. You can easily get burnt.

Problem

Imagine following scenario(or rather requirement):

We have following concepts in the application: Company, Group and User. User can have access to multiple Companies(from which one is his main). Group is a logical thing, which exists within a Company

The question is - how to store data in Table Storage, so we can easily query both all Groups within a Company and a single Group. 

Let's skip User for a second and consider following implementation:

/
[FunctionName("GroupList")]
public static Task<HttpResponseMessage> GroupList(
	[HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "group")] HttpRequestMessage req,
	[Table(TableName, "AzureWebJobsStorage")] IQueryable<GroupEntity> groups,
	[Table(Company.TableName, "AzureWebJobsStorage")] IQueryable<Company.CompanyEntity> companies,
	TraceWriter log)
{
	var groupsQuery = groups.Take(100).ToList().Select(_ => new
	{
		Id = _.RowKey,
		Name = _.Name,
		Description = _.Description,
		// ReSharper disable once ReplaceWithSingleCallToFirst
		CompanyName = companies.Where(company => company.RowKey == _.CompanyId.ToString()).FirstOrDefault()?.Name
	}).ToList();

	var response = req.CreateResponse(HttpStatusCode.OK,
		groupsQuery);

	return Task.FromResult(response);
}

[FunctionName("GroupGet")]
public static Task<HttpResponseMessage> GroupGet(
	[HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "group/{id}")] HttpRequestMessage req,
	[Table(TableName, "{partitionKey}", "{id}", Connection = "AzureWebJobsStorage")] GroupEntity group,
	TraceWriter log)
{
	var response = req.CreateResponse(HttpStatusCode.OK, group);
	return Task.FromResult(response);
}

public class GroupEntity : TableEntity
{
	public GroupEntity(Guid companyId)
	{
		PartitionKey = companyId.ToString();
		RowKey = Guid.NewGuid().ToString();
	}

	public string Name { get; set; }
	public Guid CompanyId { get; set; }
	public string Description { get; set; }
}

All right, initially it all looks fine. If we want to get a list of User specific Groups, we'll just add some context(e.g. store all user's companies somewhere and just use their identifiers as a parameter in a query). Now let's request a single Group. We have a Group identifier, we can get the whole row from a database...

NO WE CAN'T!

Since GroupEntity's PK is equal to Company's identifier, we'd have to make one query per each company a user has access to. Not very smart, not very clean. What to do? Change PK in GroupEntity to a generic one? We'll lost the possibility to make fast queries for all groups within a company. Make a combined identifier and user it as a PK? We still have to perform multiple queries. Go for SQL and perform proper JOINs? This is definitely a possibility - but we don't need other features of a relative database. Is it a dead end? 

Solution

One thing in Azure Storage is really cheap - it's the storage itself. How can we remodel our tables so we can improve both performance and lower transactions amount? Well, we can store our data twice!

Before you start throwing tomatoes at me, consider following example:

/
[FunctionName("GroupCreate")]
public static async Task<HttpResponseMessage> GroupCreate(
	[HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "group")] HttpRequestMessage req,
	[Table(TableName, "AzureWebJobsStorage")] IAsyncCollector<GroupEntity> groups,
	TraceWriter log)
{
	var data = JsonConvert.DeserializeObject<GroupEntity>(await req.Content.ReadAsStringAsync());

	var group = new GroupEntity(data.CompanyId)
	{
		Name = data.Name,
		CompanyId = data.CompanyId,
		Description = data.Description
	};

	await groups.AddAsync(group);
	await groups.AddAsync(new GroupEntity
	{
		RowKey = group.RowKey,
		Name = data.Name,
		CompanyId = data.CompanyId,
		Description = data.Description
	});

	var response = req.CreateResponse(HttpStatusCode.OK, group);
	return response;
}

Here we're storing a row twice but with slight changes. The first insert stores data with no changes to the previous version. The second one is the crucial one - it performs one change, which is changing PK to a generic one named "group". Thanks to this solution we can have two almost the same rows, one for being displayed as a part of a list, one for storing all info regarding a row. 

Now you may ask - how it secures a row from being displayed if a User doesn't have access to a given Company? That's why we're storing company identifier along with a row in CompanyId column. This is much quickier and cleaner solution than performing several requests to Table Storage - we can cache the data locally and just check whether identifiers match.

Summary

Modeling Table Storage is both challenging and rewarding - you can easily hit performance problems if tables are not designed carefully, on the other hand wise design allow you to really push the limit. Those redesigns are important also because of one more thing - they save time. And in a cloud time = money. Make sure you pay only as much as needed.