AWS Serverless and Microservices — Part 3

  1. Polling Pattern — Client makes a call every X second to get the status. In our example, on submission of the New Order, Server responds back with a unique ID (UUID in our case). Client can use this ID to get the status. Easy but not efficient.
  2. WebSocket’s Pattern — After getting a unique ID of the order, client can initiate a WebSocket connection. Once the connection is established, Server can start pushing the status of the order as and when it gets changed on the server side. Yes, data starts flowing from Server to Client without client requesting for it. On receiving the Notification, client can take further action. For instance, it can invoke additional Status API call to get detailed status of the order. This approach has got some effort involved but is much more efficient than the earlier approach and also provides good User Experience as it provides real time updates to the end user.
WebSocket Pattern to communicate Order Status change
  1. On submission of a new Order, unique UUID is returned back to the client.
  2. Client initiates a WebSocket persistent connection with Notification API Gateway endpoint.
  3. WebSocket API Gateway sends an OnConnect event to the OnConnect Lambda function passing the connection details.
  4. WebSocket API invokes the Lambda Authorizer before step #3. If the Authorizer allows the request, step #3 gets executed, else the request is Denied.
  5. OnConnect Lambda function saves the unique Connection ID and User ID in the DynamoDB.
  6. Whenever Notification Service wants to communicate anything to the end user, it searches the Connection ID attached with the User ID from the Connection DynamoDB table.
  7. Once it gets hold of the Connection ID, it makes Post API call on the WebSocket Gateway passing the payload as input.
  8. WebSocket Gateway then delivers the Notification to the caller.
  9. On receiving the Notification, depending on the payload content, client can make additional Status API call to get more details.
  1. Design of Notification Service &
  2. Saga Choreograph Pattern for Order Placement (I know, this is pending from part #2)



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Naresh Waswani

Naresh Waswani

#AWS #CloudArchitect #CloudMigration #Microservices #Mobility #IoT