Android test_runner.py: Add --enable-device-cache to speed up file pushing

build/android/pylib/local/device/local_device_environment.py

Index: build/android/pylib/local/device/local_device_environment.py
diff --git a/build/android/pylib/local/device/local_device_environment.py b/build/android/pylib/local/device/local_device_environment.py
index ee0ff987afd353f22095d06d3c52f4014dddcf44..f0a6ca5c081118b86e605b45bb7ccc57a3a01aac 100644
--- a/build/android/pylib/local/device/local_device_environment.py
+++ b/build/android/pylib/local/device/local_device_environment.py
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import logging
+import os
 import threading
 
 from devil.android import device_blacklist
@@ -10,6 +11,12 @@ from devil.android import device_errors
 from devil.android import device_utils
 from devil.utils import parallelizer
 from pylib.base import environment
+from pylib import constants

[jbudorick, 2015/10/08 14:34:49]

nit: this should precede pylib.base.environment

[agrieve, 2015/10/08 16:03:28]

Done.

+
+
+def _DeviceCachePath(device):
+  file_name = 'device_cache_%s.json' % device.adb.GetDeviceSerial()
+  return os.path.join(constants.GetOutDirectory(), file_name)
 
 
 class LocalDeviceEnvironment(environment.Environment):
@@ -24,11 +31,12 @@ class LocalDeviceEnvironment(environment.Environment):
     self._devices = []
     self._max_tries = 1 + args.num_retries
     self._tool_name = args.tool
+    self._enable_device_cache = args.enable_device_cache
 
   #override
   def SetUp(self):
     available_devices = device_utils.DeviceUtils.HealthyDevices(
-        self._blacklist)
+        self._blacklist, enable_device_files_cache=self._enable_device_cache)
     if not available_devices:
       raise device_errors.NoDevicesError
     if self._device_serial:
@@ -40,6 +48,15 @@ class LocalDeviceEnvironment(environment.Environment):
     else:
       self._devices = available_devices
 
+    if self._enable_device_cache:
+      for d in self._devices:
+        cache_path = _DeviceCachePath(d)
+        if os.path.exists(cache_path):
+          logging.info('Using device cache: %s', cache_path)
+          with open(cache_path) as f:
+            d.LoadCacheData(f.read())
+          os.unlink(cache_path)
+
   @property
   def devices(self):
     if not self._devices:
@@ -60,7 +77,13 @@ class LocalDeviceEnvironment(environment.Environment):
 
   #override
   def TearDown(self):
-    pass
+    # Write the cache even when not using it so that a bad cache will be fixed

[jbudorick, 2015/10/08 14:34:49]

I lost you on the reasoning here as written. I can understand writing the cache
s.t. the cache is kept valid on each run & can be used when going from disabled
-> enabled, but I'm not following the bad cache fix part.

The possible issue I see with that is the extra time in doing this when we
aren't using the device cache -- specifically, on the bots.

[agrieve, 2015/10/08 16:03:28]

Reworded

[agrieve, 2015/10/09 00:28:31]

Should also note that the extra time is negligible compared to everything else
we're doing (it's much faster than a single adb command)

[jbudorick, 2015/10/09 00:30:31]

Fair enough.

+    # by running once without it enabled.
+    for d in self._devices:
+      cache_path = _DeviceCachePath(d)
+      with open(cache_path, 'w') as f:
+        f.write(d.DumpCacheData())
+        logging.info('Wrote device cache: %s', cache_path)
 
   def BlacklistDevice(self, device):
     if not self._blacklist: