serverless-gradual-traffic-shifting/lib/cfn-template-generators/Sns.js

A Serverless plugin to implement gradual deployment of Lambda functions

function replaceTopicSubscriptionFunctionWithAlias(snsTopic, functionAlias, functionName) {
  const subscriptions = snsTopic.Properties.Subscription;

  const isTargetSubscription = (subscription) => {
    const endpoint = subscription.Endpoint || {};
    const funcDetails = (endpoint['Fn::GetAtt'] || []);
    const [funcName] = funcDetails;
    return funcName ? funcName === functionName : false;
  };

  const restOfSubscriptions = subscriptions.filter(s => !isTargetSubscription(s));
  const subscriptionWithAlias = { Endpoint: { Ref: functionAlias }, Protocol: 'lambda' };
  const newSubscriptions = [...restOfSubscriptions, subscriptionWithAlias];

  const newProperties = Object.assign({}, snsTopic.Properties, { Subscription: newSubscriptions });
  return Object.assign({}, snsTopic, { Properties: newProperties });
}

const Sns = {
  replaceTopicSubscriptionFunctionWithAlias
};

module.exports = Sns;