TSK-728: Server reconnect support

plugins/client-resources/src/connection.ts

@@ -24,6 +24,7 @@ import core, {
   Domain,
   FindOptions,
   FindResult,
+  generateId,
   Ref,
   Tx,
   TxHandler,
@@ -48,6 +49,7 @@ class Connection implements ClientConnection {
   private readonly requests = new Map<ReqId, DeferredPromise>()
   private lastId = 0
   private readonly interval: number
+  private readonly sessionId = generateId() as string
 
   constructor (
     private readonly url: string,
@@ -106,7 +108,7 @@ class Connection implements ClientConnection {
       const clientSocketFactory =
         getMetadata(client.metadata.ClientSocketFactory) ?? ((url: string) => new WebSocket(url) as ClientSocket)
 
-      const websocket = clientSocketFactory(this.url)
+      const websocket = clientSocketFactory(this.url + `?sessionId=${this.sessionId}`)
       const socketId = this.sockets++
       websocket.onmessage = (event: MessageEvent) => {
         const resp = readResponse(event.data)

server/ws/src/server.ts

@@ -58,7 +58,8 @@ class SessionManager {
     ws: WebSocket,
     token: Token,
     pipelineFactory: PipelineFactory,
-    productId: string
+    productId: string,
+    sessionId?: string
   ): Promise<Session> {
     const wsString = toWorkspaceString(token.workspace, '@')
 
@@ -98,7 +99,22 @@ class SessionManager {
     }
 
     const pipeline = await workspace.pipeline
+
+    if (sessionId !== undefined) {
+      // try restore session
+      const existingSession = workspace.sessions.find((it) => it[0].sessionId === sessionId)
+      if (existingSession !== undefined) {
+        if (LOGGING_ENABLED) console.log('found existing session', existingSession)
+        // Update websocket
+        clearTimeout(existingSession[0].closeTimeout)
+        existingSession[0].closeTimeout = undefined
+        existingSession[1] = ws
+        return existingSession[0]
+      }
+    }
+
     const session = this.createSession(token, pipeline)
+    session.sessionId = sessionId
     workspace.sessions.push([session, ws])
     await this.setStatus(ctx, session, true)
     return session
@@ -210,6 +226,7 @@ class SessionManager {
     workspace.sessions = []
 
     const closeS = async (s: Session, webSocket: WebSocket): Promise<void> => {
+      clearTimeout(s.closeTimeout)
       // await for message to go to client.
       await new Promise((resolve) => {
         // Override message handler, to wait for upgrading response from clients.
@@ -283,6 +300,12 @@ async function handleRequest<S extends Session> (
   const request = readRequest(msg)
   if (request.id === -1 && request.method === 'hello') {
     ws.send(serialize({ id: -1, result: 'hello' }))
+
+    // Push result buffer messages to client.
+    for (const r of service.resultBuffer ?? []) {
+      ws.send(serialize(r))
+    }
+    service.resultBuffer = []
     return
   }
   if (request.id === -1 && request.method === '#upgrade') {
@@ -294,7 +317,12 @@ async function handleRequest<S extends Session> (
     const params = [ctx, ...request.params]
     const result = await f.apply(service, params)
     const resp: Response<any> = { id: request.id, result }
-    ws.send(serialize(resp))
+    ws.send(serialize(resp), (err) => {
+      if (err !== undefined) {
+        // It seems we failed to send to client.
+        service.resultBuffer = [...(service.resultBuffer ?? []), resp]
+      }
+    })
   } catch (err: any) {
     const resp: Response<any> = {
       id: request.id,
@@ -337,18 +365,21 @@ export function start (
     }
   })
   // eslint-disable-next-line @typescript-eslint/no-misused-promises
-  wss.on('connection', async (ws: WebSocket, request: any, token: Token) => {
+  wss.on('connection', async (ws: WebSocket, request: any, token: Token, sessionId?: string) => {
     let buffer: string[] | undefined = []
 
     ws.on('message', (msg: string) => {
       buffer?.push(msg)
     })
-    const session = await sessions.addSession(ctx, ws, token, pipelineFactory, productId)
+    const session = await sessions.addSession(ctx, ws, token, pipelineFactory, productId, sessionId)
     // eslint-disable-next-line @typescript-eslint/no-misused-promises
     ws.on('message', async (msg: string) => await handleRequest(ctx, session, ws, msg))
     // eslint-disable-next-line @typescript-eslint/no-misused-promises
     ws.on('close', (code: number, reason: string) => {
-      void sessions.close(ctx, ws, token.workspace, code, reason)
+      // remove session after 1seconds, give a time to reconnect.
+      session.closeTimeout = setTimeout(() => {
+        void sessions.close(ctx, ws, token.workspace, code, reason)
+      }, 1000)
     })
     const b = buffer
     buffer = undefined
@@ -359,16 +390,19 @@ export function start (
 
   const server = createServer()
   server.on('upgrade', (request: IncomingMessage, socket: any, head: Buffer) => {
-    const token = request.url?.substring(1) // remove leading '/'
+    const url = new URL('http://localhost' + (request.url ?? ''))
+    const token = url.pathname.substring(1)
+
     try {
       const payload = decodeToken(token ?? '')
       console.log('client connected with payload', payload)
+      const sessionId = url.searchParams.get('sessionId')
 
       if (payload.workspace.productId !== productId) {
         throw new Error('Invalid workspace product')
       }
 
-      wss.handleUpgrade(request, socket, head, (ws) => wss.emit('connection', ws, request, payload))
+      wss.handleUpgrade(request, socket, head, (ws) => wss.emit('connection', ws, request, payload, sessionId))
     } catch (err) {
       console.error('invalid token', err)
       wss.handleUpgrade(request, socket, head, (ws) => {

server/ws/src/types.ts

@@ -27,6 +27,11 @@ export interface Session {
     options?: FindOptions<T>
   ) => Promise<FindResult<T>>
   tx: (ctx: MeasureContext, tx: Tx) => Promise<TxResult>
+
+  // Session restore information
+  sessionId?: string
+  resultBuffer?: TxResult[]
+  closeTimeout?: any
 }
 
 /**