[YARN-8763] Add WebSocket logic to the Node Manager web server to establish servlet

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Labels: Docker
• Assignee: Zian Chen
• Reporter: Zian Chen
• Created: 10/Sep/18 23:45
• Updated: 08/Nov/18 23:14
• Resolved: 08/Oct/18 17:59

Description

The reason we want to use WebSocket servlet to serve the backend instead of establishing the connection through HTTP is that WebSocket solves a few issues with HTTP which needed for our scenario,

1. In HTTP, the request is always initiated by the client and the response is processed by the server — making HTTP a unidirectional protocol, while web socket provides the Bi-directional protocol which means either client/server can send a message to the other party.
2. Full-duplex communication — client and server can talk to each other independently at the same time
3. Single TCP connection — After upgrading the HTTP connection in the beginning, client and server communicate over that same TCP connection throughout the lifecycle of WebSocket connection