Use a single Python Forwarder instance for each base test runner instance.

build/android/pylib/forwarder.py

Index: build/android/pylib/forwarder.py
diff --git a/build/android/pylib/forwarder.py b/build/android/pylib/forwarder.py
index f5cde9e29da230201fa3c4ec48408c8319f5cb3c..965823ee4dace1d0e3a33e64ecb95220771e9d24 100644
--- a/build/android/pylib/forwarder.py
+++ b/build/android/pylib/forwarder.py
@@ -6,6 +6,7 @@ import logging
 import os
 import re
 import sys
+import threading
 import time
 
 import android_commands
@@ -21,7 +22,7 @@ def _MakeBinaryPath(build_type, binary_name):
 
 
 class Forwarder(object):
-  """Class to manage port forwards from the device to the host."""
+  """Thread-safe class to manage port forwards from the device to the host."""
 
   # Unix Abstract socket path:
   _DEVICE_ADB_CONTROL_PORT = 'chrome_device_forwarder'
@@ -45,7 +46,9 @@ class Forwarder(object):
     assert build_type in ('Release', 'Debug')
     self._adb = adb
     self._host_to_device_port_map = dict()
-    self._device_process = None
+    self._device_initialized = False
+    self._host_adb_control_port = 0
+    self._lock = threading.Lock()
     self._host_forwarder_path = _MakeBinaryPath(build_type, 'host_forwarder')
     self._device_forwarder_path_on_host = os.path.join(
         cmd_helper.OutDirectory.get(), build_type, 'forwarder_dist')
@@ -67,23 +70,58 @@ class Forwarder(object):
     Raises:
       Exception on failure to forward the port.
     """
+    with self._lock:
+      self._InitDeviceLocked(tool)
+      self._InitHostLocked()
+      redirection_commands = [
+          '%d:%d:%d:%s' % (self._host_adb_control_port, device, host,
+                           host_name) for device, host in port_pairs]
+      logging.info('Command format: <ADB port>:<Device port>' +
+                   '[:<Forward to port>:<Forward to address>]')
+      logging.info('Forwarding using commands: %s', redirection_commands)
+
+      for redirection_command in redirection_commands:
+        try:
+          (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
+              [self._host_forwarder_path, redirection_command])
+        except OSError as e:
+          if e.errno == 2:
+            raise Exception('Unable to start host forwarder. Make sure you have'
+                            ' built host_forwarder.')
+          else: raise
+        if exit_code != 0:
+          raise Exception('%s exited with %d:\n%s' % (
+              self._host_forwarder_path, exit_code, '\n'.join(output)))
+        tokens = output.split(':')
+        if len(tokens) != 2:
+          raise Exception('Unexpected host forwarder output "%s", ' +
+                          'expected "device_port:host_port"' % output)
+        device_port = int(tokens[0])
+        host_port = int(tokens[1])
+        self._host_to_device_port_map[host_port] = device_port
+        logging.info('Forwarding device port: %d to host port: %d.',
+                     device_port, host_port)
+
+  def _InitHostLocked(self):
+    """Initializes the host forwarder process (only once)."""
+    if self._host_adb_control_port:
+      return
     self._host_adb_control_port = ports.AllocateTestServerPort()
     if not self._host_adb_control_port:
       raise Exception('Failed to allocate a TCP port in the host machine.')
-    self._adb.PushIfNeeded(
-        self._device_forwarder_path_on_host, Forwarder._DEVICE_FORWARDER_FOLDER)
-    redirection_commands = [
-        '%d:%d:%d:%s' % (self._host_adb_control_port, device, host,
-                         host_name) for device, host in port_pairs]
-    logging.info('Command format: <ADB port>:<Device port>' +
-                 '[:<Forward to port>:<Forward to address>]')
-    logging.info('Forwarding using commands: %s', redirection_commands)
     if cmd_helper.RunCmd(
         ['adb', '-s', self._adb._adb.GetSerialNumber(), 'forward',
          'tcp:%s' % self._host_adb_control_port,
          'localabstract:%s' % Forwarder._DEVICE_ADB_CONTROL_PORT]) != 0:
       raise Exception('Error while running adb forward.')
 
+  def _InitDeviceLocked(self, tool):
+    """Initializes the device forwarder process (only once)."""
+    if self._device_initialized:
+      return
+    self._adb.PushIfNeeded(
+        self._device_forwarder_path_on_host,
+        Forwarder._DEVICE_FORWARDER_FOLDER)
     (exit_code, output) = self._adb.GetShellCommandStatusAndOutput(
         '%s %s %s %s' % (Forwarder._LD_LIBRARY_PATH, tool.GetUtilWrapper(),
                          Forwarder._DEVICE_FORWARDER_PATH,
@@ -91,40 +129,31 @@ class Forwarder(object):
     if exit_code != 0:
       raise Exception(
           'Failed to start device forwarder:\n%s' % '\n'.join(output))
+    self._device_initialized = True
+
+  def UnmapDevicePort(self, device_port):
+    """Unmaps a previously forwarded device port.
 
-    for redirection_command in redirection_commands:
-      try:
-        (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
-            [self._host_forwarder_path, redirection_command])
-      except OSError as e:
-        if e.errno == 2:
-          raise Exception('Unable to start host forwarder. Make sure you have '
-                          'built host_forwarder.')
-        else: raise
+    Args:
+      device_port: A previously forwarded port (through Run()).
+    """
+    with self._lock:
+      # Please note the minus sign below.
+      redirection_command = '%d:-%d' % (
+          self._host_adb_control_port, device_port)
+      (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
+          [self._host_forwarder_path, redirection_command])
       if exit_code != 0:
         raise Exception('%s exited with %d:\n%s' % (
             self._host_forwarder_path, exit_code, '\n'.join(output)))
-      tokens = output.split(':')
-      if len(tokens) != 2:
-        raise Exception('Unexpected host forwarder output "%s", ' +
-                        'expected "device_port:host_port"' % output)
-      device_port = int(tokens[0])
-      host_port = int(tokens[1])
-      self._host_to_device_port_map[host_port] = device_port
-      logging.info('Forwarding device port: %d to host port: %d.', device_port,
-                   host_port)
-
-  def UnmapDevicePort(self, device_port):
-    # Please note the minus sign below.
-    redirection_command = '%d:-%d' % (self._host_adb_control_port, device_port)
-    (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
-        [self._host_forwarder_path, redirection_command])
-    if exit_code != 0:
-      raise Exception('%s exited with %d:\n%s' % (
-          self._host_forwarder_path, exit_code, '\n'.join(output)))
 
   @staticmethod
   def KillHost(build_type):
+    """Kills the forwarder process running on the host.
+
+    Args:
+      build_type: 'Release' or 'Debug'
+    """
     logging.info('Killing host_forwarder.')
     host_forwarder_path = _MakeBinaryPath(build_type, 'host_forwarder')
     assert os.path.exists(host_forwarder_path), 'Please build forwarder2'
@@ -139,6 +168,13 @@ class Forwarder(object):
 
   @staticmethod
   def KillDevice(adb, tool):
+    """Kills the forwarder process running on the device.
+
+    Args:
+      adb: Instance of AndroidCommands for talking to the device.
+      tool: Wrapper tool (e.g. valgrind) that can be used to execute the device
+            forwarder (see valgrind_tools.py).
+    """
     logging.info('Killing device_forwarder.')
     if not adb.FileExistsOnDevice(Forwarder._DEVICE_FORWARDER_PATH):
       return
@@ -156,11 +192,12 @@ class Forwarder(object):
         raise Exception('Timed out while killing device_forwarder')
 
   def DevicePortForHostPort(self, host_port):
-    """Get the device port that corresponds to a given host port."""
-    return self._host_to_device_port_map.get(host_port)
+    """Returns the device port that corresponds to a given host port."""
+    with self._lock:
+      return self._host_to_device_port_map.get(host_port)
 
+  # Deprecated.
   def Close(self):
-    """Terminate the forwarder process."""
-    if self._device_process:
-      self._device_process.close()
-      self._device_process = None
+    """Terminates the forwarder process."""
+    # TODO(pliard): Remove references in client code.
+    pass