Allow frontend and backend to be run separately.

Add the 'check_online' method to check whether the backend is accessible
or not.
Reduce the wait for running threads timeout on quit.
Add retry feature to the backend requests send.

1 files changed, 28 insertions, 2 deletions

diff --git a/src/leap/bitmask/backend/backend_proxy.py b/src/leap/bitmask/backend/backend_proxy.py
index e2611251..9de3501e 100644
--- a/src/leap/bitmask/backend/backend_proxy.py
+++ b/src/leap/bitmask/backend/backend_proxy.py
@@ -67,6 +67,7 @@ class BackendProxy(object):
         socket.curve_serverkey = public
 
         socket.setsockopt(zmq.RCVTIMEO, 1000)
+        socket.setsockopt(zmq.LINGER, 0)  # Terminate early
         socket.connect(self.SERVER)
         self._socket = socket
 
@@ -75,8 +76,23 @@ class BackendProxy(object):
 
         self._call_queue = Queue.Queue()
         self._worker_caller = threading.Thread(target=self._worker)
+
+    def start(self):
         self._worker_caller.start()
 
+    def check_online(self):
+        """
+        Return whether the backend is accessible or not.
+        You don't need to do `run` in order to use this.
+
+        :rtype: bool
+        """
+        # we use a small timeout in order to response quickly if the backend is
+        # offline
+        self._send_request(PING_REQUEST, retry=False, timeout=500)
+        self._socket.close()
+        return self.online
+
     def _worker(self):
         """
         Worker loop that processes the Queue of pending requests to do.
@@ -150,7 +166,7 @@ class BackendProxy(object):
         if api_method == STOP_REQUEST:
             self._call_queue.put(STOP_REQUEST)
 
-    def _send_request(self, request):
+    def _send_request(self, request, retry=True, timeout=None):
         """
         Send the given request to the server.
         This is used from a thread safe loop in order to avoid sending a
@@ -158,6 +174,10 @@ class BackendProxy(object):
 
         :param request: the request to send.
         :type request: str
+        :param retry: whether we should retry or not in case of timeout.
+        :type retry: bool
+        :param timeout: a custom timeout (milliseconds) to wait for a response.
+        :type timeout: int
         """
         # logger.debug("Sending request to backend: {0}".format(request))
         self._socket.send(request)
@@ -166,10 +186,16 @@ class BackendProxy(object):
         poll.register(self._socket, zmq.POLLIN)
 
         reply = None
+
         tries = 0
+        if not retry:
+            tries = self.POLL_TRIES + 1  # this means: no retries left
+
+        if timeout is None:
+            timeout = self.POLL_TIMEOUT
 
         while True:
-            socks = dict(poll.poll(self.POLL_TIMEOUT))
+            socks = dict(poll.poll(timeout))
             if socks.get(self._socket) == zmq.POLLIN:
                 reply = self._socket.recv()
                 break