AWS Lambda - Traffic Shift

 

We all know what is AWS Lambda which is a serverless architecture. In this blog, we will discuss on what is lambda alias and how it can be used shift traffic between 2 version of AWS lambda.

What is lambda versioning?

AWS Lambda versions are immutable snapshots of your function’s code and configuration at a specific point in time.

An immutable snapshot is a frozen, unchangeable copy of something at a specific point in time.

Immutable = cannot be changed
Snapshot = point-in-time copy

Lets start by creating a simple lambda function with nodejs as runtime environment.

I updated the code as below:

Invoking the lambda function.

Let's publish this version of lambda function as "Version-1".

Now, we have our function looks like:

demo-function -> Version-1

Let's update the demo-function with the below content.

Publishing this version as "Version-2".

Now, our lambda "demo-function" has 2 versions.

demo-function -> Version-1
                           -> Version-2

Let see how to route traffic between 2 different lambda version using lambda alias. 

An alias is a pointer to one or two versions. Choose each version that you want the alias to point to.

Once we create alias, it creates alias function which routes 50%-50% traffic between Version-1 and Version-2.

Let’s invoke the lambda functions and see the result.

We could see the traffic split between 2 versions of lambda functions.