Serverless Plugin Split Stacks

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serverless-plugin-split-stacks

This plugin migrates CloudFormation resources in to nested stacks in order to work around the 200 resource limit.

There are built-in migration strategies that can be turned on or off as well as defining your own custom migrations. It is a good idea to select the best strategy for your needs from the start because the only reliable method of changing strategy later on is to recreate the deployment from scratch. You configure this in your serverless.yml (defaults shown):

custom:
  splitStacks:
    perFunction: false
    perType: true

Migration Strategies

Per Lambda

This splits resources off in to a nested stack dedicated to the associated Lambda function. This defaults to off in 1.x but will switch to enabled by default in 2.x

Per Type

This moves resources in to a nested stack for the given resource type. If Per Lambda is enabled, it takes precedence over Per Type.

Limitations

This plugin is not a substitute for fine-grained services - try to limit the size of your service. This plugin has a hard limit of 200 sub-stacks and does not try to create any kind of tree of nested stacks.

Advanced Usage

If you create a file in the root of your Serverless project called stacks-map.js this plugin will load it.

This file can customize a few things.

module.exports = {
  'AWS::DynamoDB::Table': { destination: 'Dynamodb' }
}
const ServerlessPluginSplitStacks = require('serverless-plugin-split-stacks');

ServerlessPluginSplitStacks.resolveMigration = function (resource, logicalId, serverless) {
  if (logicalId.startsWith("Foo")) return { destination: 'Foo' };

  // Fallback to default:
  return this.stacksMap[resource.Type];
};

Be careful when introducing any customizations to default config. Many kind of resources (as e.g. DynamoDB tables) cannot be freely moved between CloudFormation stacks (that can only be achieved via full removal and recreation of the stage)