How can I know if all users have disconnected from y-websocket?

Amaan2210 · January 2, 2024, 1:09pm

Is there any way to know when all of the users have disconnected from y-websocket?

raine · January 2, 2024, 2:44pm

On the server, I think you can import docs used internally by y-websocket and directly check if it is empty.

yjs/y-websocket/blob/1f6716b32d00b7c6d64d855c4cd0673b3b357141/bin/utils.js#L68


      
          * @return {null|{bindState: function(string,WSSharedDoc):void,
           * writeState:function(string,WSSharedDoc):Promise<any>}|null} used persistence layer
           */
          exports.getPersistence = () => persistence
          
          
/**
          * @type {Map<string,WSSharedDoc>}
          */
          const docs = new Map()
          // exporting docs so that others can use it
          exports.docs = docs
          
          
const messageSync = 0
          const messageAwareness = 1
          // const messageAuth = 2
          
          
/**
          * @param {Uint8Array} update
          * @param {any} origin
          * @param {WSSharedDoc} doc
          */

Docs are removed from the docs Map on disconnect:

github.com

yjs/y-websocket/blob/1f6716b32d00b7c6d64d855c4cd0673b3b357141/bin/utils.js#L208


      
               */
              // @ts-ignore
              const controlledIds = doc.conns.get(conn)
              doc.conns.delete(conn)
              awarenessProtocol.removeAwarenessStates(doc.awareness, Array.from(controlledIds), null)
              if (doc.conns.size === 0 && persistence !== null) {
                // if persisted, we store state and destroy ydocument
                persistence.writeState(doc.name, doc).then(() => {
                  doc.destroy()
                })
                docs.delete(doc.name)
              }
            }
            conn.close()
          }
          
          
/**
           * @param {WSSharedDoc} doc
           * @param {any} conn
           * @param {Uint8Array} m
           */

If you are using the built-in server, you may need to copy server.js into your project and extend it to import docs.

Amaan2210 · January 3, 2024, 9:57am

Thanks for the reply, will try out this solution!

Amaan2210 · January 8, 2024, 11:47am

Is there any way I can do this on client side as well?
I’m using yjs.awareness to hold the data for users.
So I initially tried the .on(‘update’) but when the last user is disconnected it won’t be fired

raine · January 8, 2024, 1:28pm

Yes, you can use Awareness for that.

awareness.getStates() for getting the number of clients on-demand.

awareness.on(‘update’, …) for reactivity.

If it the last client is disconnected, then nobody is left to get an update event.

You can subscribe to WebsocketProvider status changes fwiw, and detect when a given client is disconnected. But necessarily a disconnected client cannot know which others clients are still connected.

Amaan2210 · January 9, 2024, 8:00am

Got it. Thanks for the help!