Refs #16: Global property section and property to retain functions

You can now apply global properties by adding the `lambdaAtEdge` property to your `custom` section of your `serverless.yml`. **Note:** This section currently only supports the follow option:

   * **`retain`** (optional): a boolean, default is `false`, which
     sets the DeletionPolicy of the function resource to `Retain`. Can be
     used to avoid the currently inevitable CloudFormation stack deletion failure. There are at least two schools of though on how to handle this issue. Hopefully AWS will have this fixed soon. Use at your own discretion.

feat(deletionPolicy): Add deletionPolicy setting

fix(readme): Correct deletionPolicy replication del time

fix(nit): Fix spacing nits

fix(global): add function to global location

Author: iDVB

README.md

@@ -72,6 +72,12 @@ objects, the objects all have the same fields, each of which is explained here:
      with a specific cache behavior. If the path pattern is not defined here, the function
      will be associated with the default cache behavior for the specified distribution.
 
+You can also apply global properties by adding the `lambdaAtEdge` property to your `custom` section of your `serverless.yml`. **Note:** This section currently only supports the follow option:
+
+   * **`retain`** (optional): a boolean, default is `false`, which 
+     sets the [DeletionPolicy][DeletionPolicy] of the function resource to `Retain`. Can be 
+     used to avoid the currently inevitable [CloudFormation stack deletion failure][ReplicaDeleteFail]. There are at least [two schools of though][HandlingCFNFailure] on how to handle this issue. Hopefully AWS will have this fixed soon. Use at your own discretion. 
+
 For example:
 
 ```yml
@@ -89,6 +95,10 @@ functions:
 Or:
 
 ```yml
+custom:
+   lambdaAtEdge:
+      retain: true
+
 functions:
    someImageHandlingFunction:
       name: '${self:custom.objectPrefix}-image-handling'
@@ -242,3 +252,6 @@ details.
 
 [contributing]: https://github.com/silvermine/silvermine-info#contributing
 [FnAssoc]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-cloudfront-distribution-cachebehavior.html#cfn-cloudfront-distribution-cachebehavior-lambdafunctionassociations
+[DeletionPolicy]: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-attribute-deletionpolicy.html
+[ReplicaDeleteFail]: https://forums.aws.amazon.com/thread.jspa?threadID=260242&tstart=0
+[HandlingCFNFailure]: https://github.com/silvermine/serverless-plugin-cloudfront-lambda-edge/pull/19

src/index.js

@@ -10,6 +10,7 @@ module.exports = Class.extend({
       this._serverless = serverless;
       this._provider = serverless ? serverless.getProvider('aws') : null;
       this._opts = opts;
+      this._custom = serverless.service && serverless.service.custom;
 
       if (!this._provider) {
          throw new Error('This plugin must be used with AWS');
@@ -90,10 +91,12 @@ module.exports = Class.extend({
           pathPattern = lambdaAtEdge.pathPattern,
           outputName = this._provider.naming.getLambdaVersionOutputLogicalId(fnName),
           distName = lambdaAtEdge.distribution,
+          fnObj = template.Resources[fnLogicalName],
           fnProps = template.Resources[fnLogicalName].Properties,
           evtType = lambdaAtEdge.eventType,
           output = template.Outputs[outputName],
           dist = template.Resources[distName],
+          retainFunctions = this._custom && this._custom.lambdaAtEdge && (this._custom.lambdaAtEdge.retain === true),
           distConfig, cacheBehavior, fnAssociations, versionLogicalID;
 
       if (!_.contains(VALID_EVENT_TYPES, evtType)) {
@@ -130,6 +133,10 @@ module.exports = Class.extend({
          }
       }
 
+      if (retainFunctions) {
+         fnObj.DeletionPolicy = 'Retain';
+      }
+
       distConfig = dist.Properties.DistributionConfig;
 
       if (pathPattern) {