Serverless 1.X – enable API Gateway caching on request parameters

Having previously blogged about the untrodden path to enable caching on API Gateway request parameters in the Serverless framework 0.5.X, it’s a little disappointing that it’s still not officially fixed in the 1.X versions…

The Problem

The problem is two-fold:

  1. there’s currently no way to specify caching should be enabled for path & query string parameters
  2. the CloudFormation template Serverless 1.X generates for API Gateway is missing a few optional fields, these missing fields stop you from manually enable caching in the API Gateway management console too

After you deploy your Lambda function with associated API, if you go to the management console and enable caching on path or request parameters you will get an error saying “Invalid cache key parameter specified”.

The Workaround

A friend pointed me to a neat trick to modify the CloudFormation template that Serverless 1.X auto-generates for you.

After the project is deployed, you can go to CloudFormation and view the template that Serverless has generated. These templates are pretty big (and poorly formatted), so I find it easier to open them up in the Designer view and use that view to navigate to the endpoint I’m looking for.

Once you find the resource template for the endpoint, write down its name. Now go back to the serverless.yml file in your project, and add the resource name to the resources section at the bottom. You only need to include fields that you want to update or add to the template.

The CloudFormation syntax for an API Gateway method looks like this:

We also need to fill in some blanks for the Integration section:

For more details on the CloudFormation syntax, see here and here.

After some trial-and-error, the minimum set of fields I had to add are:

Redeploy with Serverless and the path parameter is enabled for caching:

Wrap Up

I hope you have found this post useful, though I’m surprised by the lack of information out there during my research and the lack of official support from the Serverless framework.

You know of a better way to do this, please let me know in the comments.

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