Serverless custom Visual Studio gallery with Azure Functions

There are a few online services that offer custom VS galleries, but given that it’s just a plain Atom feed with some storage for the payloads, I figured it made for an excelent use case for Azure Functions.

The online Azure Functions code “editor” is extremely basic, more a textbox than an editor at the moment :).

So I’d much rather create an actual .NET project, with unit tests and create a nuget package that I consume on one-liner functions instead :)

AzureFunctions.VisualStudioGallery

This package makes it trivial to create a custom Visual Studio gallery feed using plain Azure Blob Storage to persist the feed as well as automatically update it from VSIX payloads pushed to the same storage container.

The service requires two functions: one for updating the feed blob, and another for returning the feed to the users.

Feed Updating Function

1. Create a new Azure Functions app, if you don’t have one already.

2. Create a new Azure Funcion using the BlobTrigger-CSharp template.

   a. Name your function appropriately, like vsgallery or the like.

   b. The Path property should have a container name and name patterns for both the blob name and extension, like vsgallery/{name}.{extension}. This is needed for generating appropriate blob name for the extension icon, if any is found in the VSIX.

   c. Name the Azure Storage connection appropriately too, say, vsgallery_STORAGE

3. Once created, open the View files panel to the right of the functions blade, and click Add to add a file named project.json. Add the following content to the project.json file to reference the AzureFunctions.VisualStudioGallery package:

{
  "frameworks": {
    "net46": {
      "dependencies": {
        "AzureFunctions.VisualStudioGallery": "*"
      }
    }
  }
}

1. You can manually add the input and output bindings from the Functions UI, but it’s much faster to just open the function.json file, which would look like the following at this point:

{
  "bindings": [
    {
      "name": "myBlob",
      "type": "blobTrigger",
      "direction": "in",
      "path": "vsgallery/{name}.{extension}",
      "connection": "vsgallery_STORAGE"
    }
  ],
  "disabled": false
}

Update the contents to contain all the required bindings, as follows:

{
  "bindings": [
    {
      "type": "blobTrigger",
      "name": "blob",
      "path": "vsgallery/{name}.{extension}",
      "connection": "vsgallery_STORAGE",
      "direction": "in"
    },
    {
      "type": "blob",
      "name": "currentFeed",
      "path": "feed/vsgallery.xml",
      "connection": "vsgallery_STORAGE",
      "direction": "in"
    },
    {
      "type": "blob",
      "name": "updatedFeed",
      "path": "feed/vsgallery.xml",
      "connection": "vsgallery_STORAGE",
      "direction": "out"
    },
    {
      "type": "blob",
      "name": "icon",
      "path": "alpha/{name}.png",
      "connection": "vsgallery_STORAGE",
      "direction": "out"
    }
  ],
  "disabled": false
}

NOTE: update the vsgallery_STORAGE connection value to whatever you had before in the for the myBlob default binding that was generated.

NOTE: also note that the feed XML itself (bindings currentFeed and updatedFeed) should be in another storage container, to avoid unnecessarily re-triggering the same function when you update the feed.

1. Finally, open the run.csx file that contains the actual function code and replace it entirely with:

const string storageUrl = "[YOUR BLOB STORAGE CONTAINER URL WHERE VSIXes ARE UPLOADED]";
const string feedId = "[OPTIONAL FEED ID, DEFAULTS TO 'Gallery']";
const string feedTitle = "[OPTIONAL FEED TITLE, DEFAULTS TO 'Gallery']";

public static void Run(Stream blob, string name, Stream currentFeed, Stream updatedFeed, Stream icon, TraceWriter log)
{
    new VisualStudioGallery(storageUrl, feedId, feedTitle)
        .UpdateFeed(blob, name, currentFeed, updatedFeed, icon);
}

That’s all that’s needed.

You can test your function by using the Azure Storage Explorer to upload a VSIX, and see the function run almost in real-time and create the initial atom feed for you.

Feed Retrieving Function

Technically, you don’t need another function to retrieve the Atom feed for VS to consume. You can just make the storage container/blob publicly accessible and then just use that instead, such as https://vsgallery.blob.core.windows.net/feed/vsgallery.xml.

Since functions can additionally have a custom domain assigned, you may prefer to have a function with a custom domain to retrieve it. If so, the function is quite trivial.

1. Create another Azure Funcion using the HttpTrigger-CSharp template.

   a. Name your function appropriately, like feed or the like.

   b. Set the Authorization level to Anonymous (or whatever is appropriate for your gallery).

2. Add a Blob input binding to the function, either from the UI or by adjusting the function.json as follows:

{
  "bindings": [
    {
      "authLevel": "anonymous",
      "name": "req",
      "type": "httpTrigger",
      "direction": "in"
    },
    {
      "name": "$return",
      "type": "http",
      "direction": "out"
    },
    {
      "type": "blob",
      "name": "feed",
      "path": "feed/vsgallery.xml",
      "connection": "vsgallery_STORAGE",
      "direction": "in"
    }
  ],
  "disabled": false
}

NOTE: update the vsgallery_STORAGE connection value to whatever you have in the function that updates the feed. Update the feed path too.

1. Replace run.csx with the following code to just return the feed as an Atom XML content:

#r "System.Xml.Linq"

using System.Net;
using System.Text;
using System.Xml.Linq;

public static HttpResponseMessage Run(HttpRequestMessage req, Stream feed, TraceWriter log) =>  
    new HttpResponseMessage(HttpStatusCode.OK)
    {
        Content = new StringContent(XDocument.Load(feed).ToString(), Encoding.UTF8, "application/atom+xml")
    };

NOTE: you can use the cool C# lambda syntax since it’s a one-liner ;)

With that, you can now head over to the MSDN documentation on how to add a private Gallery to Visual Studio and try it out!