Cycle through port pools for Android emulator.

build/android/emulator.py

 #!/usr/bin/env python
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Provides an interface to start and stop Android emulator.
 
 Assumes system environment ANDROID_NDK_ROOT has been set.
 
   Emulator: The class provides the methods to launch/shutdown the emulator with
@@ skipping 32 matching lines @@
   if not emulators:
     return
   for emu_name in emulators:
     cmd_helper.GetCmdOutput(['adb', '-s', emu_name, 'emu', 'kill'])
   logging.info('Emulator killing is async; give a few seconds for all to die.')
   for i in range(5):
     if not android_commands.GetEmulators():
       return
     time.sleep(1)
 
+
+class PortPool(object):
+  """Pool for emulator port starting position that changes over time."""
+  _port_min = 5554
+  _port_max = 5585
+  _port_current_index = 0
+
+  @classmethod
+  def port_range(cls):
+    """Return a range of valid ports for emulator use.
+
+    The port must be an even number between 5554 and 5584.  Sometimes
+    a killed emulator "hangs on" to a port long enough to prevent
+    relaunch.  This is especially true on slow machines (like a bot).
+    Cycling through a port start position helps make us resilient."""
+    ports = range(cls._port_min, cls._port_max, 2)
+    n = cls._port_current_index
+    cls._port_current_index = (n + 1) % len(ports)
+    return ports[n:] + ports[:n]
+
+
 def _GetAvailablePort():
   """Returns an available TCP port for the console."""
   used_ports = []
   emulators = android_commands.GetEmulators()
   for emulator in emulators:
     used_ports.append(emulator.split('-')[1])
-  # The port must be an even number between 5554 and 5584.
-  for port in range(5554, 5585, 2):
+  for port in PortPool.port_range():
     if str(port) not in used_ports:
       return port
 
 
 class Emulator(object):
   """Provides the methods to lanuch/shutdown the emulator.
 
   The emulator has the android virtual device named 'buildbot'.
 
   The emulator could use any even TCP port between 5554 and 5584 for the
@@ skipping 153 matching lines @@
     """Install a handler to kill the emulator when we exit unexpectedly."""
     for sig in self._SIGNALS:
       signal.signal(sig, self._ShutdownOnSignal)
 
 def main(argv):
   Emulator().launch()
 
 
 if __name__ == '__main__':
   main(sys.argv)