Skip to main content

Posts tagged with 'microsoft'

This is a repost that originally appeared on the Couchbase Blog: Azure Functions and Lazy Initialization with Couchbase Server.

Azure Functions are still new to me, and I’m learning as I’m going. I blogged about my foray into Azure Functions with Couchbase over a month ago. Right after I posted that, I got some helpful feedback about the way I was instantiating a Couchbase cluster (and bucket).

I had (wrongly) assumed that there was no way to save state between Azure Function calls. This is why I created a GetCluster() method that was called each time the function ran. But, initializing a Couchbase Cluster object is an expensive operation. The less often you instantiate it, the better.

You can follow along with the updated source code for this blog post on Github.

Static state

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".

Lazy initializing within Azure Functions

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>.

Lazy Initialization in Azure Functions

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

private static readonly Lazy<IBucket> Bucket = new Lazy<IBucket>(() =>
{
    var uri = ConfigurationManager.AppSettings["couchbaseUri"];
    var bucketName = ConfigurationManager.AppSettings["couchbaseBucketName"];
    var bucketPassword = ConfigurationManager.AppSettings["couchbaseBucketPassword"];
    var cluster = new Cluster(new ClientConfiguration
    {
        Servers = new List<Uri> { new Uri(uri) }
    });
    return cluster.OpenBucket(bucketName, bucketPassword);
});

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).

Using a Lazy property

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.

var lazyObject = new Lazy<string>(() =>
{
    // this code won't be called until 'lazyObject.Value' is referenced
    // for the first time
    return "I'm lazy!";
});

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

var doc = await Bucket.Value.GetAsync<MyDocument>(id);

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).

Summary

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.

Kevin Groves talks about the movie Pirates of Silicon Valley and the history of personal computing. Note: this is an extra large episode of Cross Cutting Concerns. This is a very broad, historical topic, so it could have easily gone a lot longer!

Show Notes:

I could add a million more links, but instead why don't you leave a comment with your favorite quote, clip, or story about the events that transpired in the movie?

Want to be on the next episode? You can! All you need is the willingness to talk about something technical.

Theme music is "Crosscutting Concerns" by The Dirty Truckers, check out their music on Amazon or iTunes.

Hey, did you know that I'm a Microsoft MVP? As an MVP, sometimes Microsoft lets me do some cool stuff.

Microsoft MVP logo

For instance, they let me write some blog posts about Couchbase with Windows and .NET for the MVP Award Program Blog! There are three total parts, and part 1 was just published.

So go check it out, subscribe to the MVP Award Blog, and most importantly, download Couchbase and try it out today.

I always want to thank fellow MVP Travis Smith for being the technical editor for these posts! He provided some great feedback, and he's an overall great guy!

Welcome back to another "Weekly Concerns" (after skipping a week). This is a post-a-week series of interesting links, relevant to programming and programmers. You can check out previous Weekly Concerns posts in the archive.

If you have an interesting link that you'd like to see in Weekly Concerns, leave a comment or contact me.

Matthew D. Groves

About the Author

Matthew D. Groves lives in Central Ohio. He works remotely, loves to code, and is a Microsoft MVP.

Latest Comments

Twitter