[DO NOT COMMIT] Refactor systrace to support new clock sync design

systrace/systrace/tracing_controller.py

Index: systrace/systrace/tracing_controller.py
diff --git a/systrace/systrace/tracing_controller.py b/systrace/systrace/tracing_controller.py
new file mode 100644
index 0000000000000000000000000000000000000000..6858ea8644177bd5446c80ad01be75f95d1eef89
--- /dev/null
+++ b/systrace/systrace/tracing_controller.py
@@ -0,0 +1,127 @@
+#!/usr/bin/env python
+
+# Copyright (c) 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+'''Tracing controller class. This class manages
+multiple tracing agents and collects data from all of them. It also
+manages the clock sync process.
+'''
+
+import tempfile
+import trace_event
+import uuid
+from systrace import tracing_agent
+
+
+TRACE_ERR = 'Cannot enable trace_event; ensure catapult_base is in PYTHONPATH'

[nednguyen, 2016/03/14 17:48:11]

It's strange that you put this as a constant. I would just inline it directly
below.

[alexandermont, 2016/03/14 22:19:28]

Done

+
+
+class TracingController(tracing_agent.TracingAgent):
+  def __init__(self, agents):
+    """Create tracing controller. Note that the tracing
+    controller is also a tracing agent.
+
+    Args:
+       agents: List of tracing agents for this controller.
+    """
+    super(TracingController, self).__init__()
+    self._agents = agents
+    self._trace_in_progress = False
+    self._clock_sync_markers = []
+    self._log_path = None
+    self._all_results = None
+
+  #override
+  def StartAgentTracing(self):
+    """Start tracing for the controller tracing agent. Note that
+    the tracing controller records the "controller side"
+    of the clock sync records, and nothing else.
+    """
+    if not trace_event.trace_can_enable():
+      raise RuntimeError, TRACE_ERR
+    controller_log_file = tempfile.NamedTemporaryFile(delete=False)
+    self._log_path = controller_log_file.name
+    controller_log_file.close()
+    trace_event.trace_enable(self._log_path)
+    return True
+
+  @property
+  def trace_in_progress(self):
+    return self._trace_in_progress
+
+  #override
+  def StopAgentTracing(self):
+    """Stops tracing for the controller tracing agent.
+    """
+    trace_event.trace_disable()
+    return True
+
+  #override
+  def GetResults(self):
+    """Gets the log output from the controller tracing agent. Again,
+    this contains only the "controller side" of the clock sync
+    records.
+    """
+    if self._trace_in_progress:
+      raise RuntimeError, 'Cannot get results while trace is in progress'
+    with open(self._log_path, 'r') as outfile:
+      result = outfile.read() + ']'
+    return tracing_agent.TraceResults('trace-data', result, True)

[Zhen Wang, 2016/03/14 17:11:27]

s/trace-data/systrace

This will need some small trace viewer change after Charlie finish the clock
sync work there.

[alexandermont, 2016/03/14 22:19:28]

Done

+
+  #override
+  def StartTracing(self):
+    """Start tracing for all tracing agents (the controller tracing agent
+    and the child tracing agents).
+
+    Returns:
+        Boolean indicating whether or not the start tracing succeeded
+        for all agents.
+    """
+    assert not self._trace_in_progress, 'Trace already in progress.'
+    self._trace_in_progress = True
+    all_succ = True
+    all_succ = all_succ and self.StartAgentTracing()
+    for agent in self._agents:
+      all_succ = all_succ and agent.StartAgentTracing()
+
+  #override
+  def StopTracing(self):
+    """Stop tracing for all tracing agents (the controller tracing agent
+    and the child tracing agents). Issues clock sync marker prior
+    to stopping tracing.
+
+    Returns:
+        Boolean indicating whether or not the stop tracing succeeded
+        for all agents.
+    """
+    assert self._trace_in_progress, 'No trace in progress.'
+    self._trace_in_progress = False
+    self._IssueClockSyncMarker()
+    all_succ = True
+    for agent in self._agents:
+      all_succ = all_succ and agent.StopAgentTracing()
+    all_succ = all_succ and self.StopAgentTracing()
+    self._all_results = [agent.GetResults() for agent in self._agents + [self]]

[nednguyen, 2016/03/14 17:48:11]

this has to be a dictionary that conforms to
https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAy...
for trace viewer to consume the data

[Zhen Wang, 2016/03/14 17:58:23]

GetResults() here returns a tuple.

The old systrace way uses it as a list:
SystraceTracingController._WriteTraceHTML().

The new way (for clock sync) will need to use it as a dict:
SystraceTracingController._WriteTraceJSON().

Though maybe we should create a TraceResult class, so it will be clearer.

[alexandermont, 2016/03/14 22:19:28]

Changed it to use a dict. Note that I still have not written _WriteTraceJSON
yet. I will need to look at documentation on the format before writing this
function.

+
+  #override
+  def SupportsExplicitClockSync(self):
+    return False

[Zhen Wang, 2016/03/14 17:11:27]

Conceptually the controller supports explicit clock sync. I understand that it
needs to return false here because it is not an agent controlled by other
controllers. Can you add some comments here to explain why this returns false?

[alexandermont, 2016/03/14 22:19:28]

Done

+
+  #override
+  def RecordClockSyncMarker(self, sync_id, callback):
+    raise NotImplementedError
+
+  def _IssueClockSyncMarker(self):
+    """Issue clock sync markers to all the child tracing agents."""
+    for agent in self._agents:
+      if agent.SupportsExplicitClockSync():
+        sync_id = GetUniqueSyncID()
+        callback = lambda t, s: trace_event.clock_sync(s, issue_ts=t)
+        agent.RecordClockSyncMarker(sync_id, callback)
+
+def GetUniqueSyncID():
+  """Get a unique sync ID.
+  """
+  return uuid.uuid4()