API Gateway WebSocket API

• For real-time and stateful application in API Gateway
• Client connect to server
  • Connecting using wss://[unique-id].execute-api.[region].amazonaws.com/[stage-name]
  • We invoke the onConnect lambda function upon connection and the lambda function can store connectionId to DynamoDB for example
• Client to server
  • When client sending messages (frames) it invoke a sendMessage lambda function witht he same connectionId
• Server returns client
  • Server talk back to client using a Connection URL callback
    • Lambda function can then do a POST to the URL callback to connect back to the client
    • wss://[uniqueid].execute-api.[region].amazonaws.com/[stage]/@connections/[connectionId]
• Connection URL
  • Has the format wss://[uniqueid].execute-api.[region].amazonaws.com/[stage]/@connections/[connectionId]
    • POST: send message from Server to Client
    • GET: get the latest connection status of the connected WS Client
    • DELETE: Disconnect the client from WS connection

Routing

• Incoming JSON messages are routed to different back end
• If ther is no rount, it sends to $default
• Specify a route selection to select the field on JSON to act as route
  • For example, $request.body.action
  • The result is avaluated against route keys available in your API Gateway
  • The route then connected to backend you've setup through API gateway