Cannot update a WSSWSSharedDoc when no browser client is connected

1

I have successfully created a node server that uses the WSSharedDoc class from utils.js from y-websocket-server. I am running a spawned process that writes its stdout to a document that then syncs up (beautifully) with a client browser. This is the node side updater:

//get the right document
  output = utils.docs.get(data['code']).getText('output')

//clear the document before starting spawn
  output.delete(0,output.length);

//spawn process
  ps[data['code']] = spawn("python3",[`-u`,`code/${data['code']}.py`])

//stream spawned process into ytext
  ps[data['code']].stdout.on('data',(data) => {output.insert(output.length,`${data}`)
  })

And this is the client listener

const yO = ydoc.getText('output')
yO.observe(event => { $("#output").html(yO.toString());})

So long as a client is open, this works beautifully and the spawned stream updates in the browser in real time. But if I close all clients, the spawned process continues, but the ytext in the WSSharedDoc no longer receives the updates. If I restart the process with the client attached it works fine. To be clear, if I have multiple browser windows open the spawn stream updates continute, but if I close all browsers and then reopen I only see the ytext as recent as the last browser tab was closed.

I am guessing there is some flag that prevents the ytext from receiving updates if there is no client attached to the websocketserver, if so how can I override

Thanks for taking the time to help me.

2

Sometimes typing out the problem and then eating a bag of potato chips brings clarity. Upon inspection of utils.js I found

    if (doc.conns.size === 0 && persistence !== null) {
      // if persisted, we store state and destroy ydocument
      persistence.writeState(doc.name, doc).then(() => {
        doc.destroy()
      })

I changed the 0 to -1 and voila, hacky hacky worky worky. But I’m guessing this is going to bite me later. Curious how. Any advice would be most appreciated.

3

For this type of application you probably want to create a client that connects to a server. The client can be a nodejs process (see https://github.com/yjs/y-websocket#client-code-in-nodejs). The node application that uses input from python connects to the default y-websocket server.

If you never want to close rooms, you can also just disable the if-condition, like you are already doing. In that case, just remove the if-condition including its content.

4

Thanks @dmonad: my challenge is that I want to serve websocket-server from the same express instance and I don’t know now how to connect to myself in that context. I suppose my hack is the functional equivalent.

Anyway appreciate your time, and the more I use Y.js the better it gets. Really appreciate your effort and talent here.

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