Implementing a Monsoon power monitor trace agent, utilizing the UI infrastructure that the BattOr a…

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
index d0d2d7c3735988f4b4904a0a980ae87baeee86c7..cf3764e09a9868668f1b67af78c89320c39682dc 100644
--- a/systrace/systrace/tracing_controller.py
+++ b/systrace/systrace/tracing_controller.py
@@ -18,6 +18,7 @@ import uuid
 
 from systrace import trace_result
 from systrace import tracing_agents
+from systrace.tracing_agents import monsoon_agent
 from py_trace_event import trace_event
 
 
@@ -117,9 +118,28 @@ class TracingController(object):
     self._child_agents_with_config = agents_with_config
     self._controller_agent = TracingControllerAgent()
     self._controller_config = controller_config
+    self._monsoon_agent = None
     self._trace_in_progress = False
     self.all_results = None
 
+    # If we have a monsoon power monitor controller in the group, make an

[Chris Craik, 2017/09/19 18:47:02]

I'm not especially happy with this, but I don't have other ideas. Zhen,
thoughts? May be nice to abstract this to a "connectionOwnerAgent" or something
like that, instead of hard coding this as a monsoon agent, then have only
monsoon return 'true' from an isConnectionOwner method.

Zhen, do we know if there are other agents that expect to use USB while tracing?

Alternately, we could consider another 'lifecycle' callback that happens after
all the starts, and before all the stops, and monsoon could put its code there.

[Zhen Wang, 2017/09/19 23:53:50]

I see --usbpassthrough is set to off for monsoon. Looks like it also affects
other agents?

For systrace and adb_profile_chrome, I think agents do not need to use USB while
tracing. For Telemetry, it will need USB, but that has separate controlling
logic. So it should be fine.

Another lifecycle callback may not work well. It seems that the sequence is:
1. start tracing for other agents
2. disable usb
3. start tracing for monsoon
So it seems that monsoon's start cannot be grouped into step 1. 

ConnectionOwnerAgent is probably the only way, so it will always start last and
stop first.

+    # explicit reference to it.  We need to collect data from it before any
+    # other collectors as it re-enables USB for the subsequent collectors to
+    # collect their data.
+    # In addition, move this agent to the end of the list so it is the last
+    # to start (it disables USB).
+    monsoon_agent_with_config = None
+    sorted_agents_with_config = []
+    for agent_with_config in self._child_agents_with_config:
+      if isinstance(agent_with_config.agent, monsoon_agent.MonsoonTracingAgent):
+        monsoon_agent_with_config = agent_with_config
+      else:
+        sorted_agents_with_config.append(agent_with_config)
+    if monsoon_agent_with_config:
+      sorted_agents_with_config.append(monsoon_agent_with_config)
+      self._monsoon_agent = monsoon_agent_with_config.agent
+    self._child_agents_with_config = sorted_agents_with_config
+
   @property
   def get_child_agents(self):
     return self._child_agents
@@ -163,6 +183,7 @@ class TracingController(object):
     if ns < na:
       print 'Warning: Only %d of %d tracing agents started.' % (ns, na)
     self._child_agents = succ_agents
+
     return True
 
   def StopTracing(self):
@@ -179,6 +200,13 @@ class TracingController(object):
     assert self._trace_in_progress, 'No trace in progress.'
     self._trace_in_progress = False
 
+    # Explicity stop Monsoon tracing first, as it re-enables USB.
+    if self._monsoon_agent:
+      sync_id = GetUniqueSyncID()
+      if not self._monsoon_agent.StopCollectionWithClockSync(sync_id,
+        ControllerAgentClockSync):
+        print 'Monsoon agent failed to stop collection.'
+
     # Issue the clock sync marker and stop the child tracing agents.
     self._IssueClockSyncMarker()
     succ_agents = []