[Android] Tune DeviceUtils commands that are prone to large outputs.

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index 3ad767b51951c59f526be272d2dac5e38cb0a2a5..8fc2f6b687624dad758afeb99ba1b2c8e663b824 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -574,6 +574,28 @@ class DeviceUtils(object):
     else:
       return output
 
+  def _RunPipedShellCommand(self, script, **kwargs):
+    PIPESTATUS_LEADER = 'PIPESTATUS: '
+
+    script += '; echo "%s${PIPESTATUS[@]}"' % PIPESTATUS_LEADER
+    output = self.RunShellCommand(script, **kwargs)
+    pipestatus_line = output[-1]
+
+    if not pipestatus_line.startswith(PIPESTATUS_LEADER):
+      logging.error('Pipe exit statuses of shell script missing.')
+      raise device_errors.AdbShellCommandFailedError(
+          script, output, status=None,
+          device_serial=self.adb.GetDeviceSerial())
+
+    output = output[:-1]
+    statuses = [
+        int(s) for s in pipestatus_line[len(PIPESTATUS_LEADER):].split()]
+    if any(statuses):
+      raise device_errors.AdbShellCommandFailedError(
+          script, output, status=statuses,
+          device_serial=self.adb.GetDeviceSerial())
+    return output
+
   @decorators.WithTimeoutAndRetriesFromInstance()
   def KillAll(self, process_name, signum=9, as_root=False, blocking=False,
               timeout=None, retries=None):
@@ -595,7 +617,7 @@ class DeviceUtils(object):
       CommandTimeoutError on timeout.
       DeviceUnreachableError on missing device.
     """
-    pids = self._GetPidsImpl(process_name)
+    pids = self.GetPids(process_name)
     if not pids:
       raise device_errors.CommandFailedError(
           'No process "%s"' % process_name, str(self))
@@ -605,7 +627,7 @@ class DeviceUtils(object):
 
     if blocking:
       wait_period = 0.1
-      while self._GetPidsImpl(process_name):
+      while self.GetPids(process_name):
         time.sleep(wait_period)
 
     return len(pids)
@@ -1020,7 +1042,7 @@ class DeviceUtils(object):
     else:
       logging.warning('Could not determine size of %s.', device_path)
 
-    if size is None or size <= self._MAX_ADB_OUTPUT_LENGTH:
+    if 0 < size <= self._MAX_ADB_OUTPUT_LENGTH:
       return _JoinLines(self.RunShellCommand(
           ['cat', device_path], as_root=as_root, check_return=True))
     elif as_root and self.NeedsSU():
@@ -1355,11 +1377,20 @@ class DeviceUtils(object):
       CommandTimeoutError on timeout.
       DeviceUnreachableError on missing device.
     """
-    return self._GetPidsImpl(process_name)
-
-  def _GetPidsImpl(self, process_name):
     procs_pids = {}
-    for line in self.RunShellCommand('ps', check_return=True):
+    try:
+      ps_output = self._RunPipedShellCommand(
+          cmd_helper.SingleQuote('ps | grep -F %s' % process_name),
+          check_return=False)

[perezju, 2015/04/14 14:13:35]

nit: I'm ok with this, but maybe _RunPipedShellCommand should set
kwargs['check_return'] = False?

[jbudorick, 2015/04/14 16:56:13]

After our offline discussion, I realized that check_return will only check the
PIPESTATUS echo, not the actual command. We do care if that fails, so I'm
actually going the other way and setting kwargs['check_return'] = True.

+    except device_errors.AdbShellCommandFailedError as e:
+      if e.status and not e.status[0]:
+        # If ps succeeded but grep failed, there were no processes with the
+        # given name.
+        return procs_pids
+      else:
+        raise
+
+    for line in ps_output:
       try:
         ps_data = line.split()
         if process_name in ps_data[-1]:
@@ -1431,10 +1462,9 @@ class DeviceUtils(object):
         'Size', 'Rss', 'Pss', 'Shared_Clean', 'Shared_Dirty', 'Private_Clean',
         'Private_Dirty')
 
-    showmap_out = self.RunShellCommand(
-        ['showmap', str(pid)], as_root=True, check_return=True)
-    if not showmap_out:
-      raise device_errors.CommandFailedError('No output from showmap')
+    showmap_out = self._RunPipedShellCommand(
+        'showmap %d | grep TOTAL' % int(pid),
+        as_root=True, check_return=False)
 
     split_totals = showmap_out[-1].split()
     if (not split_totals