@mapbox/cloudfriend/lib/shortcuts/log-subscription-lambda.js

Helper functions for assembling CloudFormation templates in JavaScript

'use strict';

const Lambda = require('./lambda');

/**
 * A Lambda function that runs in response to a log subscription filter.
 * Includes a Log Group, a Role, an Alarm on function errors, a CloudWatch Subscription Filter,
 * and a Lambda permission.
 *
 * @param {Object} options - Extends the options for [`Lambda`](#lambda) with the following additional attributes:
 * @param {String} options.LogGroupName - See [AWS documentation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-logs-subscriptionfilter.html#cfn-cwl-subscriptionfilter-loggroupname).
 * @param {String} [options.FilterPattern=''] - See [AWS documentation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-logs-subscriptionfilter.html#cfn-cwl-subscriptionfilter-filterpattern).
 *
 * @example
 * const cf = require('@mapbox/cloudfriend');
 *
 * const myTemplate = { ... };
 *
 * const lambda = new cf.shortcuts.LogSubscriptionLambda({
 *   LogicalName: 'MyLambda',
 *   Code: {
 *     S3Bucket: 'my-code-bucket',
 *     S3Key: 'path/to/code.zip'
 *   },
 *   LogGroupName: 'my-log-group'
 * });
 *
 * module.exports = cf.merge(myTemplate, lambda);
 */
class LogSubscriptionLambda extends Lambda {
  constructor(options) {
    if (!options) throw new Error('Options required');
    super(options);

    const {
      FilterPattern = '',
      LogGroupName
    } = options;

    const required = [LogGroupName];
    if (required.some((variable) => !variable))
      throw new Error('You must provide a LogGroupName');

    this.Resources[`${this.LogicalName}SubscriptionFilter`] = {
      Type: 'AWS::Logs::SubscriptionFilter',
      Condition: this.Condition,
      Properties: {
        DestinationArn: { 'Fn::GetAtt': [this.LogicalName, 'Arn'] },
        FilterPattern: FilterPattern,
        LogGroupName: LogGroupName
      }
    };

    this.Resources[`${this.LogicalName}Permission`] = {
      Type: 'AWS::Lambda::Permission',
      Condition: this.Condition,
      Properties: {
        Action: 'lambda:InvokeFunction',
        FunctionName: {
          'Fn::GetAtt': [this.LogicalName, 'Arn']
        },
        Principal: {
          'Fn::Sub': 'logs.${AWS::URLSuffix}'
        },
        SourceArn: {
          'Fn::Sub': ['arn:${AWS::Partition}:logs:${AWS::Region}:${AWS::AccountId}:log-group:${Name}:*', {
            Name: LogGroupName
          }]
        }
      }
    };
  }
}

module.exports = LogSubscriptionLambda;