tracing: the client lib of the tracing service

services/resource_coordinator/public/interfaces/tracing/tracing.mojom

 // Copyright 2017 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.
 
-module resource_coordinator.tracing.mojom;
+module tracing.mojom;
 
 import "mojo/common/time.mojom";
 import "mojo/common/values.mojom";
 
 // The JSON type of data coming from a tracing agents.
 //
 // - All agents with the same label should have the same type.
 // - There can be multiple agents with the same label, if their data type is
 //   ARRAY. Their data will be concatenated together and separated by commas.
 // - There can be only one agent with data type STRING.
 enum TraceDataType {
   ARRAY,
   STRING
 };
 
 // Tracing agents, like |chrome|, |etw|, |battor|, and |cros|, use this
 // interface to register themselves to the tracing service.
-interface Factory {
-  RegisterAgent(Agent agent, string name, string label, TraceDataType type,
+//
+// This is a separate interface from |Coordinator| for security and privacy
+// reasones: although we want to let almost every process be able to send

[kenrb, 2017/05/17 21:24:02]

nit: s/reasones/reasons

[chiniforooshan, 2017/05/17 21:33:17]

Done.

+// tracing data to the service, we do not want to let an untrusted child process
+// be able to collect traces from other processes using the |Coordinator|
+// interface.
+interface AgentRegistry {
+  RegisterAgent(Agent agent, string label, TraceDataType type,
                 bool supports_explicit_clock_sync_);
 };
 
-// There should be at most one implementation of this interface per process.
 // When the tracing service calls |StopAndFlush| on an agent, the agent begins
 // serializing data into the recorder that was given in the |StartTracing| call.
 // When finished, the agent should close the recorder connection to signal the
 // tracing service that no more data will be sent.
 interface Agent {
-  StartTracing(string categories, Recorder recorder);
+  StartTracing(string config, Recorder recorder) => ();
   StopAndFlush();
-  RequestClockSyncMarker() => (mojo.common.mojom.TimeTicks issue_ts,
-                               mojo.common.mojom.TimeTicks issue_end_ts);
+  RequestClockSyncMarker(string sync_id) => (
+      mojo.common.mojom.TimeTicks issue_ts,
+      mojo.common.mojom.TimeTicks issue_end_ts);
   RequestBufferStatus() => (uint32 capacity, uint32 count);
+  GetCategories() => (string categories);
 };
 
 // An agent can make several calls to |AddChunk|. Chunks will be concatenated
 // with no separator (type STRING) or using comma as the separator (type ARRAY).
 // There should be only one agent of type STRING per agent label; otherwise
 // their trace data would be mixed up.
 interface Recorder {
   AddChunk(string chunk);
   AddMetadata(mojo.common.mojom.DictionaryValue metadata);
 };
 
 // A tracing controller uses this interface to coordinate trace data collection
 // from all registered agents. At any given time, there should be at most one
 // connected controller.
 interface Coordinator {

[kenrb, 2017/05/17 21:24:02]

How do you prevent renderer processes from being able to connect to this
interface? I had a quick look through the prototype and couldn't see anything --
is the intent to add a ConnectionFilter?

[chiniforooshan, 2017/05/17 21:33:17]

Isn't it enough that we don't "provide" the Coordinator interface
to the renderer in the tracing service manifest or in
content/public/app/mojo/content_browser_manifest.json and only
provide the AgentRegistry interface?

[kenrb, 2017/05/18 02:19:52]

Yes, thanks, this is right, sorry about my confusion. More specifically, the
renderer manifest doesn't require the tracing capability, which is what the
service manager will check before allowing an interface to be bound.

[chiniforooshan, 2017/05/18 15:23:49]

Acknowledged.

-  StartTracing(handle<data_pipe_producer> stream, string categories);
+  StartTracing(handle<data_pipe_producer> stream, string config);
   StopAndFlush();
   IsTracing() => (bool is_tracing);
-  RequestBufferUsage() => (float percent_full, uint32 approximate_count);
+  RequestBufferUsage() => (bool success, float percent_full,
+                           uint32 approximate_count);
+  GetCategories() => (string categories);
 };