I had a hard time finding documentation on whether I could use a static object for reuse between function calls. I suppose I should have experimented, like fellow Microsoft MVP Mark Heath did. Instead, I posed the question to StackOverflow.

In short: yes. A Cluster, instantiated and saved to a static member, can is reusable between function calls. According to Mark’s post above, there’s no guarantee how long this value will survive. But that’s an expected trade-off that you make when going "serverless".

Simply using a static member would work, but it’s not thread-safe. There are a few ways to tackle that issue, but an easy way that’s built right into the .NET framework is to use Lazy Initialization with Lazy<T>.

First, I removed the GetBucket and GetCluster methods. Next, I created a Lazy<IBucket> property to replace them.

I just made a single property for a bucket, since that’s all I need for this example. But if you need to use the cluster, you can easily make that its own Lazy property. (Once you have a cluster, getting a bucket is a relatively cheap operation).

When you instantiate a Lazy<T> object, you supply it with an initialization lambda. That lambda won’t execute until the Value property is actually called for the first time.

For instance, notice the Value between Bucket and GetAsync in the updated version of my Azure Functions:

If that’s the first time Value is used, the cluster will be initialized. Otherwise, it will use the already initialized cluster (try experimenting with a Guid instead of a Bucket).

State can be saved between Azure Function calls by using a static member. Make sure that it’s thread-safe (by using Lazy<T> or something like it). Don’t make any assumptions about how long that object will be around.

Anything else I missed? Are you using Azure Functions with Couchbase? I would love to hear from you. Please leave a comment below or ping me on Twitter @mgroves.

For this blog post, I decided to try Visual Studio Preview.

I did this because there is a handy tool for creating Azure Function projects in Visual Studio.

But it only works for the preview version at this time. You don’t have to use these tools to develop Azure Functions, but it made the process simpler for me.

Once I had this tooling in place, all I had to was to File→New→Project. Then under "Cloud", select "Azure Functions".

Once you do this, you’ll have an empty looking project with a couple of JSON files. Right click on the project, add item, and select "Azure Function".

Next, you’ll need to select what kind of Azure Function you want to create. I chose "HttpTrigger". I also chose "Anonymous" to keep this post simple, but depending on your use case, you may want to require an authentication token. After you do this, a very simple shell of a function will be generated (as a C# class). You can execute this function locally (indeed, that is what the local.settings.json file is for) so you can test it out without deploying to Azure yet.

First, I decided that I wanted two Azure Functions: one to "get" a piece of data by ID, and one to "set" a new piece of given data. I started by defining the shape of my data with a simple C# POCO:

Here is the Azure function that I wrote to "get" that document from Couchbase Server:

Some things to note:

Next, run this function locally, and you’ll get a console screen that looks similar to this:

At the bottom, you’ll notice that it tells you the Azure Function URL(s). Assuming I had a document in Couchbase (I don’t yet), I could create an HTTP request with a tool like Postman to: http://localhost:7071/api/HttpTriggerCsharpGet?id=123456

Currently, if I do that, I’ll get "null" as a response (since I don’t have any validation or error checking code). So let’s move on and create a "Set" function.

The "Set" function will be slightly different. I want document information POSTed to it, and I want it to return a message like "New document inserted with ID 123456".

This function has a similar shape to the Get, but some important things to note:

To create a request in Postman, I’ll use a URL of http://localhost:7071/api/HttpTriggerCsharpSet. In the headers, I’ll set Content-Type to "application/json". Finally, the body will be JSON:

Now, when I POST that to the endpoint, I’ll get a response message of "New document inserted with ID f05ea97e-7c2f-4f88-b72d-19756f6a6f35".

I have glossed over how these functions connect to Couchbase Server.

Previously, I mentioned two methods, GetCluster and GetBucket that will connect to the cluster and bucket, respectively.

At this point, most of this code should be familiar if you’ve used Couchbase Server and the Couchbase .NET SDK before. I’m connecting to a single node cluster, and then connecting a bucket that has a password set (I’m using Couchbase Server 4.6).

But, the important thing to point out here is the use of Configuration.AppSettings. In the local.settings.json file, I’ve added these Couchbase settings to the Value section:

When running Azure Functions locally, this file is used for configuration. I have Couchbase Server running locally with a bucket called "azurefunctions". Anything in "Values" can be accessed via Configuration.AppSettings.

Before deploying the Azure Functions, I’ll need to create a Couchbase Cluster on Azure. This is very easy to do, thanks to Ben Lackey’s great work on the Azure Marketplace. Once that’s deployed, deploying the Azure Functions are also easy, thanks to Visual Studio.

This is my first time trying out Azure Functions. This blog post shows a simple demo, but there are other factors to consider before you start using this in production:

Anything I missed? Any more tips or suggestions to share to make this process easier or better? Please leave a comment below or ping me on Twitter @mgroves.

For the purposes of this tutorial, I’m going to use a very simple XML example. If your XML is more complex (multiple attributes, for instance), then your approach will also have to be more complex. (Json.NET can handle all XML to Json conversions, but it follows a specific set of conversion rules). Here’s a sample piece of data:

Notice that I’ve got this XML as a hardcoded string in C#. In a real-life situation, you would likely be pulling XML from a database, a REST API, XML files, etc.

Once you have the raw XML, you can create an XmlDocument object (XmlDocument lives in the System.Xml namespace).

Once you have an XmlDocument object, you can use Json.NET to convert that object into a Json representation.

In this example, I’m asking Json.NET to serialize an XML node:

Finally, let’s put the Json into Couchbase. The easiest way to do this would be to again call on JsonConvert to deserialize the Json into a C# object. That object would then be used with Couchbase’s bucket.Insert(…​) method.

With this method, the Json would be stored in Couchbase like so:

That might be fine, but often times you’re going to want more control of the format. With Json.NET, we can serialize to a given class, instead of just object. Let’s create an Invoice class like so:

Notice that there is some type information now. The Timestamp is a DateTime and the AcctNumber is an int. The conversion will still work, but the result will be different, according to Json.NET’s conversion rules. (Also check out the full Json.NET documentation if you aren’t familiar with it already).

The result of that insert will look like:

One more minor thing to point out: I used Guid.NewGuid().ToString() to create arbitrary keys for the documents. If you have value(s) in the XML data that you want to use for a key, you could/should use those value(s) instead.

This blog post was inspired by an email conversation with a Couchbase user. If you have any suggestions on tools, tips, or tricks to make this process easier, please let me know. Or, contact me if there’s something you’d like to see me blog about! You can email me or contact me @mgroves on Twitter.