blob: 3f8eb1282510a41db67a460cfd1f5d5fd831dad1 [file] [log] [blame]
# Copyright 2014 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.
import six
from py_trace_event import trace_event
class TracingAgent(six.with_metaclass(trace_event.TracedMetaClass, object)):
"""A tracing agent provided by the platform.
A tracing agent can gather data from StartAgentTracing() until
StopAgentTracing(), the trade data itself should then be collected with
CollectAgentTraceData(). Note, after calling StartAgentTracing, clients
*must* also make sure to call StopAgentTracing + CollectAgentTraceData in
order to free up any resources that the agents might hold.
Before constructing an TracingAgent, check whether it's supported on the
platform with IsSupported method first.
NOTE: All subclasses of TracingAgent must not change the constructor's
parameters so the agents can be dynamically constructed in
def __init__(self, platform_backend, config):
del config # unused
self._platform_backend = platform_backend
def IsSupported(cls, platform_backend):
del platform_backend # unused
return False
def StartAgentTracing(self, config, timeout):
""" Override to add tracing agent's custom logic to start tracing.
Depending on trace_options and category_filter, the tracing agent may choose
to start or not start tracing.
config: tracing_config instance that contains trace_option and
trace_options: an instance of tracing_options.TracingOptions that
control which core tracing systems should be enabled.
category_filter: an instance of
timeout: number of seconds that this tracing agent should try to start
tracing until time out.
True if tracing agent started successfully.
raise NotImplementedError
def StopAgentTracing(self):
""" Override to add tracing agent's custom logic to stop tracing.
StopAgentTracing() should guarantee tracing is stopped, even if there may
be exception.
raise NotImplementedError
def SupportsFlushingAgentTracing(self):
""" Override to indicate support of flushing tracing. """
return False
def FlushAgentTracing(self, config, timeout, trace_data_builder):
""" Override to add tracing agent's custom logic to flush tracing. """
del config, timeout, trace_data_builder # unused
raise NotImplementedError
def SupportsExplicitClockSync(self):
""" Override to indicate support of explicit clock syncing. """
return False
def RecordClockSyncMarker(self, sync_id,
""" Override to record clock sync marker.
Only override if supports explicit clock syncing.
sync_id: Unqiue id for sync event.
record_controller_clocksync_marker_callback: Function that accepts two
arguments: a sync ID and a timestamp taken immediately before the
controller requested that the agent write a clock sync marker into its
trace. Any tracing agent that implements this method must invoke this
callback immediately after receiving confirmation from the agent that
the clock sync marker was recorded.
We use a callback here rather than just calling this function after
RecordClockSyncMarker because it's important for clock sync accuracy
reasons that the "issued" timestamp and "received confirmation"
timestamp be as accurate as possible, and some agents are forced to do
additional time-consuming cleanup work in RecordClockSyncMarker after
receiving this confirmation.
del sync_id # unused
del record_controller_clocksync_marker_callback # unused
raise NotImplementedError
def CollectAgentTraceData(self, trace_data_builder, timeout=None):
""" Override to add agent's custom logic to collect tracing data. """
del trace_data_builder
del timeout
raise NotImplementedError