Bug 1231981 - Part 2: A websocket-to-process bridge script that can be used by JS to launch an ICE server for testing. r=ahal

MozReview-Commit-ID: FbfNzyw9SZp

testing/tools/websocketprocessbridge/websocketprocessbridge.py

@@ -0,0 +1,100 @@
+# vim: set ts=4 et sw=4 tw=80
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from twisted.internet import protocol, reactor
+from twisted.internet.task import LoopingCall
+import txws
+import psutil
+
+import sys
+import os
+
+# maps a command issued via websocket to running an executable with args
+commands = {
+    'iceserver' : [sys.executable,
+                   "-u",
+                   os.path.join("iceserver", "iceserver.py")]
+}
+
+class ProcessSide(protocol.ProcessProtocol):
+    """Handles the spawned process (I/O, process termination)"""
+
+    def __init__(self, socketSide):
+        self.socketSide = socketSide
+
+    def outReceived(self, data):
+        if self.socketSide:
+            lines = data.splitlines()
+            for line in lines:
+                self.socketSide.transport.write(line)
+
+    def errReceived(self, data):
+        self.outReceived(data)
+
+    def processEnded(self, reason):
+        if self.socketSide:
+            self.outReceived(str(reason))
+            self.socketSide.processGone()
+
+    def socketGone(self):
+        self.socketSide = None
+        self.transport.loseConnection()
+        self.transport.signalProcess("KILL")
+
+
+class SocketSide(protocol.Protocol):
+    """
+    Handles the websocket (I/O, closed connection), and spawning the process
+    """
+
+    def __init__(self):
+        self.processSide = None
+
+    def dataReceived(self, data):
+        if not self.processSide:
+            self.processSide = ProcessSide(self)
+            # We deliberately crash if |data| isn't on the "menu",
+            # or there is some problem spawning.
+            reactor.spawnProcess(self.processSide,
+                                 commands[data][0],
+                                 commands[data],
+                                 env=os.environ)
+
+    def connectionLost(self, reason):
+        if self.processSide:
+            self.processSide.socketGone()
+
+    def processGone(self):
+        self.processSide = None
+        self.transport.loseConnection()
+
+
+class ProcessSocketBridgeFactory(protocol.Factory):
+    """Builds sockets that can launch/bridge to a process"""
+
+    def buildProtocol(self, addr):
+        return SocketSide()
+
+# Parent process could have already exited, so this is slightly racy. Only
+# alternative is to set up a pipe between parent and child, but that requires
+# special cooperation from the parent.
+parent_process = psutil.Process(os.getpid()).parent()
+
+def check_parent():
+    """ Checks if parent process is still alive, and exits if not """
+    if not parent_process.is_running():
+        print("websocket/process bridge exiting because parent process is gone")
+        reactor.stop()
+
+if __name__ == "__main__":
+    parent_checker = LoopingCall(check_parent)
+    parent_checker.start(1)
+
+    bridgeFactory = ProcessSocketBridgeFactory()
+    reactor.listenTCP(8191, txws.WebSocketFactory(bridgeFactory))
+    print("websocket/process bridge listening on port 8191")
+    reactor.run()
+
+