Reland r212020: Move Python setup/tear down logic into Forwarder ...

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 5bdb1cd4ce92b2598e9cff38295f19fd3950c572..adf538c731595ed23b606148ea1d33fc832f62aa 100644
--- a/build/android/pylib/forwarder.py
+++ b/build/android/pylib/forwarder.py
@@ -2,24 +2,49 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import fcntl
 import logging
 import os
+import psutil
 import re
 import sys
-import threading
 import time
 
 import android_commands
 import cmd_helper
 import constants
 
-from pylib import pexpect
+from pylib import valgrind_tools
 
 
 def _MakeBinaryPath(build_type, binary_name):
   return os.path.join(cmd_helper.OutDirectory.get(), build_type, binary_name)
 
 
+def _GetProcessStartTime(pid):
+  return psutil.Process(pid).create_time
+
+
+class _FileLock(object):
+  """With statement-aware implementation of a file lock.
+
+  File locks are needed for cross-process synchronization when the
+  multiprocessing Python module is used.
+  """
+  def __init__(self, path):
+    self._path = path
+
+  def __enter__(self):
+    self._fd = os.open(self._path, os.O_RDONLY | os.O_CREAT)
+    if self._fd < 0:
+      raise Exception('Could not open file %s for reading' % self._path)
+    fcntl.flock(self._fd, fcntl.LOCK_EX)
+
+  def __exit__(self, type, value, traceback):
+    fcntl.flock(self._fd, fcntl.LOCK_UN)
+    os.close(self._fd)
+
+
 class Forwarder(object):
   """Thread-safe class to manage port forwards from the device to the host."""
 
@@ -28,28 +53,18 @@ class Forwarder(object):
   _DEVICE_FORWARDER_PATH = (constants.TEST_EXECUTABLE_DIR +
                             '/forwarder/device_forwarder')
   _LD_LIBRARY_PATH = 'LD_LIBRARY_PATH=%s' % _DEVICE_FORWARDER_FOLDER
+  _LOCK_PATH = '/tmp/chrome.forwarder.lock'
+  _MULTIPROCESSING_ENV_VAR = 'CHROME_FORWARDER_USE_MULTIPROCESSING'
 
-  def __init__(self, adb, build_type):
-    """Forwards TCP ports on the device back to the host.
-
-    Works like adb forward, but in reverse.
+  _instance = None
 
-    Args:
-      adb: Instance of AndroidCommands for talking to the device.
-      build_type: 'Release' or 'Debug'.
-    """
-    assert build_type in ('Release', 'Debug')
-    self._adb = adb
-    self._device_to_host_port_map = dict()
-    self._host_to_device_port_map = dict()
-    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')
+  @staticmethod
+  def UseMultiprocessing():
+    """Tells the forwarder that multiprocessing is used."""
+    os.environ[Forwarder._MULTIPROCESSING_ENV_VAR] = '1'
 
-  def Run(self, port_pairs, tool):
+  @staticmethod
+  def Map(port_pairs, adb, build_type='Debug', tool=None):
     """Runs the forwarder.
 
     Args:
@@ -58,24 +73,29 @@ class Forwarder(object):
                  port will by dynamically assigned on the device. You can
                  get the number of the assigned port using the
                  DevicePortForHostPort method.
+      adb: An AndroidCommands instance.
       tool: Tool class to use to get wrapper, if necessary, for executing the
             forwarder (see valgrind_tools.py).
 
     Raises:
       Exception on failure to forward the port.
     """
-    with self._lock:
-      self._InitDeviceLocked(tool)
-      host_name = '127.0.0.1'
+    if not tool:
+      tool = valgrind_tools.CreateTool(None, adb)
+    with _FileLock(Forwarder._LOCK_PATH):
+      instance = Forwarder._GetInstanceLocked(build_type, tool)
+      instance._InitDeviceLocked(adb, tool)
+
+      device_serial = adb.Adb().GetSerialNumber()
       redirection_commands = [
-          ['--serial-id=' + self._adb.Adb().GetSerialNumber(), '--map',
-           str(device), str(host)] for device, host in port_pairs]
+          ['--serial-id=' + device_serial, '--map', str(device),
+           str(host)] for device, host in port_pairs]
       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)
+              [instance._host_forwarder_path] + redirection_command)
         except OSError as e:
           if e.errno == 2:
             raise Exception('Unable to start host forwarder. Make sure you have'
@@ -83,83 +103,203 @@ class Forwarder(object):
           else: raise
         if exit_code != 0:
           raise Exception('%s exited with %d:\n%s' % (
-              self._host_forwarder_path, exit_code, '\n'.join(output)))
+              instance._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._device_to_host_port_map[device_port] = host_port
-        self._host_to_device_port_map[host_port] = device_port
+        serial_with_port = (device_serial, device_port)
+        instance._device_to_host_port_map[serial_with_port] = host_port
+        instance._host_to_device_port_map[host_port] = serial_with_port
         logging.info('Forwarding device port: %d to host port: %d.',
                      device_port, host_port)
 
-  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' % (Forwarder._LD_LIBRARY_PATH, tool.GetUtilWrapper(),
-                      Forwarder._DEVICE_FORWARDER_PATH))
-    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):
+  @staticmethod
+  def UnmapDevicePort(device_port, adb):
     """Unmaps a previously forwarded device port.
 
     Args:
-      device_port: A previously forwarded port (through Run()).
+      adb: An AndroidCommands instance.
+      device_port: A previously forwarded port (through Map()).
+    """
+    with _FileLock(Forwarder._LOCK_PATH):
+      Forwarder._UnmapDevicePortLocked(device_port, adb)
+
+  @staticmethod
+  def UnmapAllDevicePorts(adb):
+    """Unmaps all the previously forwarded ports for the provided device.
+
+    Args:
+      adb: An AndroidCommands instance.
+      port_pairs: A list of tuples (device_port, host_port) to unmap.
+    """
+    with _FileLock(Forwarder._LOCK_PATH):
+      port_map = Forwarder._GetInstanceLocked(
+          None, None)._device_to_host_port_map
+      adb_serial = adb.Adb().GetSerialNumber()
+      for ((device_serial, device_port), _) in port_map:
+        if adb_serial == device_serial:
+          Forwarder._UnmapDevicePortLocked(device_port, adb)
+
+  @staticmethod
+  def DevicePortForHostPort(host_port):
+    """Returns the device port that corresponds to a given host port."""
+    with _FileLock(Forwarder._LOCK_PATH):
+      (device_serial, device_port) = Forwarder._GetInstanceLocked(
+          None, None)._host_to_device_port_map.get(host_port)
+      return device_port
+
+  @staticmethod
+  def _GetInstanceLocked(build_type, tool):
+    """Returns the singleton instance.
+
+    Note that the global lock must be acquired before calling this method.
+
+    Args:
+      build_type: 'Release' or 'Debug'
+      tool: Tool class to use to get wrapper, if necessary, for executing the
+            forwarder (see valgrind_tools.py).
     """
-    with self._lock:
-      self._UnmapDevicePortInternalLocked(device_port)
+    if not Forwarder._instance:
+      Forwarder._instance = Forwarder(build_type, tool)
+    return Forwarder._instance
+
+  def __init__(self, build_type, tool):
+    """Constructs a new instance of Forwarder.
 
-  def _UnmapDevicePortInternalLocked(self, device_port):
-    if not device_port in self._device_to_host_port_map:
+    Note that Forwarder is a singleton therefore this constructor should be
+    called only once.
+
+    Args:
+      build_type: 'Release' or 'Debug'
+      tool: Tool class to use to get wrapper, if necessary, for executing the
+            forwarder (see valgrind_tools.py).
+    """
+    assert not Forwarder._instance
+    self._build_type = build_type
+    self._tool = tool
+    self._initialized_devices = set()
+    self._device_to_host_port_map = dict()
+    self._host_to_device_port_map = dict()
+    self._host_forwarder_path = _MakeBinaryPath(
+        self._build_type, 'host_forwarder')
+    if not os.path.exists(self._host_forwarder_path):
+      self._build_type = 'Release' if self._build_type == 'Debug' else 'Debug'
+      self._host_forwarder_path = _MakeBinaryPath(
+          self._build_type, 'host_forwarder')
+      assert os.path.exists(
+          self._host_forwarder_path), 'Please build forwarder2'
+    self._device_forwarder_path_on_host = os.path.join(
+        cmd_helper.OutDirectory.get(), self._build_type, 'forwarder_dist')
+    self._InitHostLocked()
+
+  @staticmethod
+  def _UnmapDevicePortLocked(device_port, adb):
+    """Internal method used by UnmapDevicePort().
+
+    Note that the global lock must be acquired before calling this method.
+    """
+    instance = Forwarder._GetInstanceLocked(None, None)
+    serial = adb.Adb().GetSerialNumber()
+    serial_with_port = (serial, device_port)
+    if not serial_with_port in instance._device_to_host_port_map:
+      logging.error('Trying to unmap non-forwarded port %d' % device_port)
       return
-    redirection_command = [
-        '--serial-id=' + self._adb.Adb().GetSerialNumber(), '--unmap',
-        str(device_port)]
+    redirection_command = ['--serial-id=' + serial, '--unmap', str(device_port)]
     (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
-        [self._host_forwarder_path] + redirection_command)
+        [instance._host_forwarder_path] + redirection_command)
     if exit_code != 0:
       logging.error('%s exited with %d:\n%s' % (
-          self._host_forwarder_path, exit_code, '\n'.join(output)))
-    host_port = self._device_to_host_port_map[device_port]
-    del self._device_to_host_port_map[device_port]
-    del self._host_to_device_port_map[host_port]
+          instance._host_forwarder_path, exit_code, '\n'.join(output)))
+    host_port = instance._device_to_host_port_map[serial_with_port]
+    del instance._device_to_host_port_map[serial_with_port]
+    del instance._host_to_device_port_map[host_port]
 
   @staticmethod
-  def KillHost(build_type='Debug'):
-    """Kills the forwarder process running on the host.
+  def _GetPidForLock():
+    """Returns the PID used for host_forwarder initialization.
+
+    In case multi-process sharding is used, the PID of the "sharder" is used.
+    The "sharder" is the initial process that forks that is the parent process.
+    By default, multi-processing is not used. In that case the PID of the
+    current process is returned.
+    """
+    use_multiprocessing = Forwarder._MULTIPROCESSING_ENV_VAR in os.environ
+    return os.getppid() if use_multiprocessing else os.getpid()
+
+  def _InitHostLocked(self):
+    """Initializes the host forwarder daemon.
+
+    Note that the global lock must be acquired before calling this method. This
+    method kills any existing host_forwarder process that could be stale.
+    """
+    # See if the host_forwarder daemon was already initialized by a concurrent
+    # process or thread (in case multi-process sharding is not used).
+    pid_for_lock = Forwarder._GetPidForLock()
+    fd = os.open(Forwarder._LOCK_PATH, os.O_RDWR | os.O_CREAT)
+    with os.fdopen(fd, 'r+') as pid_file:
+      pid_with_start_time = pid_file.readline()
+      if pid_with_start_time:
+        (pid, process_start_time) = pid_with_start_time.split(':')
+        if pid == str(pid_for_lock):
+          if process_start_time == str(_GetProcessStartTime(pid_for_lock)):
+            return
+      self._KillHostLocked()
+      pid_file.seek(0)
+      pid_file.write(
+          '%s:%s' % (pid_for_lock, str(_GetProcessStartTime(pid_for_lock))))
+
+  def _InitDeviceLocked(self, adb, tool):
+    """Initializes the device_forwarder daemon for a specific device (once).
+
+    Note that the global lock must be acquired before calling this method. This
+    method kills any existing device_forwarder daemon on the device that could
+    be stale, pushes the latest version of the daemon (to the device) and starts
+    it.
 
     Args:
-      build_type: 'Release' or 'Debug' (default='Debug')
+      adb: An AndroidCommands instance.
+      tool: Tool class to use to get wrapper, if necessary, for executing the
+            forwarder (see valgrind_tools.py).
+    """
+    device_serial = adb.Adb().GetSerialNumber()
+    if device_serial in self._initialized_devices:
+      return
+    Forwarder._KillDeviceLocked(adb, tool)
+    adb.PushIfNeeded(
+        self._device_forwarder_path_on_host,
+        Forwarder._DEVICE_FORWARDER_FOLDER)
+    (exit_code, output) = adb.GetShellCommandStatusAndOutput(
+        '%s %s %s' % (Forwarder._LD_LIBRARY_PATH, tool.GetUtilWrapper(),
+                      Forwarder._DEVICE_FORWARDER_PATH))
+    if exit_code != 0:
+      raise Exception(
+          'Failed to start device forwarder:\n%s' % '\n'.join(output))
+    self._initialized_devices.add(device_serial)
+
+  def _KillHostLocked(self):
+    """Kills the forwarder process running on the host.
+
+    Note that the global lock must be acquired before calling this method.
     """
     logging.info('Killing host_forwarder.')
-    host_forwarder_path = _MakeBinaryPath(build_type, 'host_forwarder')
-    if not os.path.exists(host_forwarder_path):
-      host_forwarder_path = _MakeBinaryPath(
-          'Release' if build_type == 'Debug' else 'Debug', 'host_forwarder')
-    assert os.path.exists(host_forwarder_path), 'Please build forwarder2'
     (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
-        [host_forwarder_path, '--kill-server'])
+        [self._host_forwarder_path, '--kill-server'])
     if exit_code != 0:
       (exit_code, output) = cmd_helper.GetCmdStatusAndOutput(
-          ['pkill', 'host_forwarder'])
+          ['pkill', '-9', 'host_forwarder'])
       if exit_code != 0:
         raise Exception('%s exited with %d:\n%s' % (
-              host_forwarder_path, exit_code, '\n'.join(output)))
+              self._host_forwarder_path, exit_code, '\n'.join(output)))
 
   @staticmethod
-  def KillDevice(adb, tool):
+  def _KillDeviceLocked(adb, tool):
     """Kills the forwarder process running on the device.
 
+    Note that the global lock must be acquired before calling this method.
+
     Args:
       adb: Instance of AndroidCommands for talking to the device.
       tool: Wrapper tool (e.g. valgrind) that can be used to execute the device
@@ -180,14 +320,3 @@ class Forwarder(object):
       pids = adb.ExtractPid('device_forwarder')
       if pids:
         raise Exception('Timed out while killing device_forwarder')
-
-  def DevicePortForHostPort(self, 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)
-
-  def Close(self):
-    """Releases the previously forwarded ports."""
-    with self._lock:
-      for device_port in self._device_to_host_port_map.copy():
-        self._UnmapDevicePortInternalLocked(device_port)