fix(app-shell): use a wrapping stream for usb (#14214)

Implement the tcp socket emulator by creating a separate stream
that is piped through to the usb connection via its downward interface
rather than using the same stream for both the port and the socket or
pipelining the two streams together.

This implementation allows the lifecycles of the USB port connection,
which we want to be the same as the physical robot connection; and the
tcp socket emulators, which we want to be more like tcp sockets; to be
separate, which really increases reliability because we don't have the
port going up and down all the time anymore. This reduces spurious
disconnects.

It will also allow us to add socket activity timeouts to help with the
windows dropping data problem, though we can't really do that until the
http requests that cause synchronous actions that we make get keep alive
streaming responses.

app-shell/src/usb.ts

@@ -34,25 +34,50 @@ let usbFetchInterval: NodeJS.Timeout
 export function getSerialPortHttpAgent(): SerialPortHttpAgent | undefined {
   return usbHttpAgent
 }
-export function createSerialPortHttpAgent(path: string): void {
-  const serialPortHttpAgent = new SerialPortHttpAgent({
-    maxFreeSockets: 1,
-    maxSockets: 1,
-    maxTotalSockets: 1,
-    keepAlive: true,
-    keepAliveMsecs: Infinity,
-    path,
-    logger: usbLog,
-    timeout: 100000,
-  })
-  usbHttpAgent = serialPortHttpAgent
+export function createSerialPortHttpAgent(
+  path: string,
+  onComplete: (err: Error | null, agent?: SerialPortHttpAgent) => void
+): void {
+  if (usbHttpAgent != null) {
+    onComplete(
+      new Error('Tried to make a USB http agent when one already existed')
+    )
+  } else {
+    usbHttpAgent = new SerialPortHttpAgent(
+      {
+        maxFreeSockets: 1,
+        maxSockets: 1,
+        maxTotalSockets: 1,
+        keepAlive: true,
+        keepAliveMsecs: Infinity,
+        path,
+        logger: usbLog,
+        timeout: 100000,
+      },
+      (err, agent?) => {
+        if (err != null) {
+          usbHttpAgent = undefined
+        }
+        onComplete(err, agent)
+      }
+    )
+  }
 }
 
-export function destroyUsbHttpAgent(): void {
+export function destroyAndStopUsbHttpRequests(dispatch: Dispatch): void {
   if (usbHttpAgent != null) {
     usbHttpAgent.destroy()
   }
   usbHttpAgent = undefined
+  ipcMain.removeHandler('usb:request')
+  dispatch(usbRequestsStop())
+  // handle any additional invocations of usb:request
+  ipcMain.handle('usb:request', () =>
+    Promise.resolve({
+      status: 400,
+      statusText: 'USB robot disconnected',
+    })
+  )
 }
 
 function isUsbDeviceOt3(device: UsbDevice): boolean {
@@ -115,42 +140,11 @@ function pollSerialPortAndCreateAgent(dispatch: Dispatch): void {
   }
   usbFetchInterval = setInterval(() => {
     // already connected to an Opentrons robot via USB
-    if (getSerialPortHttpAgent() != null) {
-      return
-    }
-    usbLog.debug('fetching serialport list')
-    fetchSerialPortList()
-      .then((list: PortInfo[]) => {
-        const ot3UsbSerialPort = list.find(
-          port =>
-            port.productId?.localeCompare(DEFAULT_PRODUCT_ID, 'en-US', {
-              sensitivity: 'base',
-            }) === 0 &&
-            port.vendorId?.localeCompare(DEFAULT_VENDOR_ID, 'en-US', {
-              sensitivity: 'base',
-            }) === 0
-        )
-
-        if (ot3UsbSerialPort == null) {
-          usbLog.debug('no OT-3 serial port found')
-          return
-        }
-
-        createSerialPortHttpAgent(ot3UsbSerialPort.path)
-        // remove any existing handler
-        ipcMain.removeHandler('usb:request')
-        ipcMain.handle('usb:request', usbListener)
-
-        dispatch(usbRequestsStart())
-      })
-      .catch(e =>
-        // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
-        usbLog.debug(`fetchSerialPortList error ${e?.message ?? 'unknown'}`)
-      )
+    tryCreateAndStartUsbHttpRequests(dispatch)
   }, 10000)
 }
 
-function startUsbHttpRequests(dispatch: Dispatch): void {
+function tryCreateAndStartUsbHttpRequests(dispatch: Dispatch): void {
   fetchSerialPortList()
     .then((list: PortInfo[]) => {
       const ot3UsbSerialPort = list.find(
@@ -165,17 +159,22 @@ function startUsbHttpRequests(dispatch: Dispatch): void {
 
       // retry if no OT-3 serial port found - usb-detection and serialport packages have race condition
       if (ot3UsbSerialPort == null) {
-        usbLog.debug('no OT-3 serial port found, retrying')
-        setTimeout(() => startUsbHttpRequests(dispatch), 1000)
+        usbLog.debug('no OT-3 serial port found')
         return
       }
-
-      createSerialPortHttpAgent(ot3UsbSerialPort.path)
-      // remove any existing handler
-      ipcMain.removeHandler('usb:request')
-      ipcMain.handle('usb:request', usbListener)
-
-      dispatch(usbRequestsStart())
+      if (usbHttpAgent == null) {
+        createSerialPortHttpAgent(ot3UsbSerialPort.path, (err, agent?) => {
+          if (err != null) {
+            const message = err?.message ?? err
+            usbLog.error(`Failed to create serial port: ${message}`)
+          }
+          if (agent) {
+            ipcMain.removeHandler('usb:request')
+            ipcMain.handle('usb:request', usbListener)
+            dispatch(usbRequestsStart())
+          }
+        })
+      }
     })
     .catch(e =>
       // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
@@ -188,27 +187,18 @@ export function registerUsb(dispatch: Dispatch): (action: Action) => unknown {
     switch (action.type) {
       case SYSTEM_INFO_INITIALIZED:
         if (action.payload.usbDevices.find(isUsbDeviceOt3) != null) {
-          startUsbHttpRequests(dispatch)
+          tryCreateAndStartUsbHttpRequests(dispatch)
         }
         pollSerialPortAndCreateAgent(dispatch)
         break
       case USB_DEVICE_ADDED:
         if (isUsbDeviceOt3(action.payload.usbDevice)) {
-          startUsbHttpRequests(dispatch)
+          tryCreateAndStartUsbHttpRequests(dispatch)
         }
         break
       case USB_DEVICE_REMOVED:
         if (isUsbDeviceOt3(action.payload.usbDevice)) {
-          destroyUsbHttpAgent()
-          ipcMain.removeHandler('usb:request')
-          dispatch(usbRequestsStop())
-          // handle any additional invocations of usb:request
-          ipcMain.handle('usb:request', () =>
-            Promise.resolve({
-              status: 400,
-              statusText: 'USB robot disconnected',
-            })
-          )
+          destroyAndStopUsbHttpRequests(dispatch)
         }
         break
     }