SPA: using websockets only. Why not?

Question

I am redesigning a web application which previously has been rendered server side to a Single Page Application and started to read about websockets . The web application will be using sockets to have new records and/or messages pushed to the client. I have been wondering why most pages which make use of sockets don't handle all their communication over the socket. Most of the times there is RESTful backend in addition to the websocket. Would it be a bad idea to have the client query for new resources over the socket? If so why - other than that a RESTful api might be easier to use with other devices?

I can imagine that using websockets would probably not be the best idea in case the network connection is kind of bad like on mobile devices, but that probably should work quite well with a reasonable connection to the web.

I found this related question, however it is from 2011 and seems a little outdated: websocket api to replace rest api?

Answer 1

Coming back to this question a few years later, I would like to point out a few aspects to illustrate that having all your communication through websockets does have its drawbacks:

• there is no common support for compression. You can easily configure your webserver to compress http requests and browsers have been known to happily accept compressed responses for years, however for web sockets it is still not that easy (even though the situation has improved)
• client frameworks often are build upon commonly used standards like rest. The further away you move from frameworks expectations, the less addons or features will be available.
• caching in the browser is not as easy. By now this goes a long way, reaching into the realm of offline availability and PWAs.

Answer 2

No, it won´t be a bad idea. Actually I work in an application that uses a WebSocket connection for all what is data interaction, the web server only handles requests for resources, views under different languages, dimensions .. etc..

The problem may be the lack of frameworks/tools based on a persistent connection. For many years most of frameworks, front and back end, have been designed and built around the request/response model. The approach shift may be no so easy to accept.