Serverless Cloud Formation Strip

This Serverless plugin replaces all cloud formation references in a serverless.yml file with hardcoded values when running in offline mode. This allows simulating an offline stack without having to purge the service file from all cloud formation references, which may not exist yet (or will never exist if running on a novel stage). The plugin can be configured to generate fake ARNs so that other offline plugins that rely on ARN values can still emulate the offline behavior (e.g. serverless-offline-kinesis)

Installation

First, add the plugin to your project:

npm install --save-dev serverless-offline-cfstrip

Then, inside your project's serverless.yml file add serverless-offline-cfstrip to the top-level plugins section. If there is no plugin section you will need to add it to the file.

plugins:
  - serverless-offline-cfstrip

Configuration

The plugin's behavior is configured with values in the custom.serverless-offline-cfstrip section of your serverless.yml file. The possible values are:

custom:
  serverless-offline-cfstrip:
    regexFlags: i               # Flags to use for regex matching (defaults to 'i')
    replacements:               # Mapping of regex replacements
      streamArn: arn:aws:kinesis:$REGION:00000000:stream/$STACK

The most important section is the replacements configuration entry. This entry contains a mapping of Regex (RE) to a replacement string (RS). Each RE is matched against the cloud formation reference (CFR) output name (ON). If the RE matches the ON, the entire CFR will be replaced with the RS. The following special tokens may be included in the RS which will be replaced by the appropriate value:

• $REGION
• $STACK
• $OUTPUT

Keep in mind that CFRs are of the form ${cf.REGION:STACK.OUTPUT} or ${cf:STACK.OUTPUT}

Troubleshooting

The plugin will log all applied replacements if the environment variable SLS_DEBUG is set. By convention, this variable is set to the value *, e.g.:

SLS_DEBUG=* sls offline