android: add support for spinning up multiple instances of the emulator.

Bug: 922145
Change-Id: Iabea0d27059ad64d76a72f80b4a3d88e97e6f6f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836598Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Andrew Luo <aluo@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702646}

build/android/pylib/local/emulator/local_emulator_environment.py

@@ -2,8 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import logging
 import os
 
+from devil.utils import parallelizer
 from pylib.constants import host_paths
 from pylib.local.device import local_device_environment
 
@@ -13,19 +15,55 @@ with host_paths.SysPath(AVD_DIR_PATH):
   import avd  # pylint: disable=import-error
 
 
+# Mirroring https://bit.ly/2OjuxcS#23
+_MAX_ANDROID_EMULATORS = 16
+
+
 class LocalEmulatorEnvironment(local_device_environment.LocalDeviceEnvironment):
 
   def __init__(self, args, output_manager, error_func):
     super(LocalEmulatorEnvironment, self).__init__(args, output_manager,
                                                    error_func)
     self._avd_config = avd.AvdConfig(args.avd_config)
-    self._emulator_instance = None
+    if args.emulator_count < 1:
+      error_func('--emulator-count must be >= 1')
+    elif args.emulator_count >= _MAX_ANDROID_EMULATORS:
+      logging.warning('--emulator-count capped at 16.')
+    self._emulator_count = min(_MAX_ANDROID_EMULATORS, args.emulator_count)
+    self._emulator_instances = []
+    self._device_serials = []
 
   #override
   def SetUp(self):
     self._avd_config.Install()
-    self._emulator_instance = self._avd_config.StartInstance()
-    self._device_serials = [self._emulator_instance.serial]
+
+    emulator_instances = [
+        self._avd_config.CreateInstance() for _ in range(self._emulator_count)
+    ]
+
+    def start_emulator_instance(e):
+      try:
+        e.Start()
+        return e
+      except avd.AvdException:
+        logging.exception('Failed to start emulator instance.')
+        return None
+
+    parallel_emulators = parallelizer.SyncParallelizer(emulator_instances)
+    self._emulator_instances = [
+        emu
+        for emu in parallel_emulators.pMap(start_emulator_instance).pGet(None)
+        if emu is not None
+    ]
+    self._device_serials = [e.serial for e in self._emulator_instances]
+
+    if not self._emulator_instances:
+      raise Exception('Failed to start any instances of the emulator.')
+    elif len(self._emulator_instances) < self._emulator_count:
+      logging.warning(
+          'Running with fewer emulator instances than requested (%d vs %d)',
+          len(self._emulator_instances), self._emulator_count)
+
     super(LocalEmulatorEnvironment, self).SetUp()
 
   #override
@@ -33,5 +71,4 @@ class LocalEmulatorEnvironment(local_device_environment.LocalDeviceEnvironment):
     try:
       super(LocalEmulatorEnvironment, self).TearDown()
     finally:
-      if self._emulator_instance:
-        self._emulator_instance.Stop()
+      parallelizer.SyncParallelizer(self._emulator_instances).Stop()

build/android/test_runner.py

@@ -315,6 +315,11 @@ def AddEmulatorOptions(parser):
       help='Path to the avd config textpb. '
       '(See //tools/android/avd/proto/ for message definition'
       ' and existing textpb files.)')
+  parser.add_argument(
+      '--emulator-count',
+      type=int,
+      default=1,
+      help='Number of emulators to use.')
 
 
 def AddGTestOptions(parser):

tools/android/avd/avd.py

@@ -365,15 +365,23 @@ class AvdConfig(object):
         if not os.path.exists(d):
           os.makedirs(d)
 
-  def StartInstance(self):
-    """Starts an AVD instance.
+  def CreateInstance(self):
+    """Creates an AVD instance without starting it.
 
     Returns:
       An _AvdInstance.
     """
     self._Initialize()
-    instance = _AvdInstance(
+    return _AvdInstance(
         self._emulator_path, self._config.avd_name, self._emulator_home)
+
+  def StartInstance(self):
+    """Starts an AVD instance.
+
+    Returns:
+      An _AvdInstance.
+    """
+    instance = self.CreateInstance()
     instance.Start()
     return instance
 
@@ -400,6 +408,9 @@ class _AvdInstance(object):
     self._emulator_serial = None
     self._sink = None
 
+  def __str__(self):
+    return '%s|%s' % (self._avd_name, (self._emulator_serial or id(self)))
+
   def Start(self, read_only=True):
     """Starts the emulator running an instance of the given AVD."""
     with tempfile_ext.TemporaryFileName() as socket_path, (contextlib.closing(
@@ -445,9 +456,9 @@ class _AvdInstance(object):
         self._emulator_serial = timeout_retry.Run(
             listen_for_serial, timeout=30, retries=0, args=[sock])
         logging.info('%s started', self._emulator_serial)
-      except Exception:
+      except Exception as e:
         self.Stop()
-        raise
+        raise AvdException('Emulator failed to start: %s' % str(e))
 
   def Stop(self):
     """Stops the emulator process."""