Add process lifetime annotations to stack samples.

components/metrics/proto/call_stack_profile.proto

 // Copyright 2015 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.
 
 // Call stack sample data for a given profiling session.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 option java_outer_classname = "CallStackProfileProtos";
@@ skipping 14 matching lines @@
 
   // A sample consisting of one or more callstacks with the same stack frames
   // and instruction pointers.
   message Sample {
     // The callstack. Sample.entries[0] represents the call on the top of the
     // stack.
     repeated Entry entry = 1;
 
     // Number of times this stack signature occurs.
     optional int64 count = 2;
+
+    // This bit-field provide information about the current phase of the system
+    // such as whether it is in startup, general operation, or shutdown. This
+    // field is not present if it is unchanged from the previous Sample.
+    optional fixed32 process_phases = 3;

[Mike Wittman, 2016/10/24 22:28:14]

The individual phases and activities should be explicitly specified in the
proto, so we have agreement on meaning between the Chrome side and and the
server side.

My understanding is that it's not practical to define bitmask constants in
protos, and the standard way of representing data like this is fields of
repeated enums (as mentioned by Alexei in the bug). We'll need to translate
between the two representations in the metrics provider.

[bcwhite, 2016/10/25 14:45:23]

As I understand it, this will require the constants to be defined in at least
three places:

stack_sampling_profiler.h (in Chrome)
call_stack_profiles.proto (in Chrome)
call_stack_profile.proto (in Google3)
(another in Google3?)

Wouldn't it be better to _not_ define it in the .proto at all and define it only
twice:

stack_sampling_profiler.h (in Chrome)
stack_sampling_profiler.h (or whatever it's called -- in Google3)

[Mike Wittman, 2016/10/25 17:24:22]

The interpretation of the phases/activities is part of the interface between
Chrome and the UMA server, so it really should be explicitly specified. Without
it there's no good mechanism to manage changes to the data being sent/processed
across versions of Chrome and the server code. The duplication is unfortunately
unavoidable, but as far as I know doing things this way is standard practice.

If the enums are in a standalone proto -- execution_context.proto probably would
be a good home -- then the constants will be defined in two places, one of which
gets copied to Google3. The Google3 stack_sampling_profiler.h equivalent is a
proto definition rather than anything defined in source code, so there's no
additional duplication there.

[bcwhite, 2016/10/25 21:10:42]

I'll work on it.

+
+    // This bit-field provide information about current activities of the system
+    // such as whether it is (for example) writing out profile information or
+    // uploading metrics. This field is not present if it is unchanged from the
+    // previous Sample.
+    optional fixed32 current_activities = 4;
   }
 
   // Uniquely identifies a module.
   message ModuleIdentifier {
     // A hash that uniquely identifies a particular program version with high
     // probability. This is parsed from headers of the loaded module.
     // For binaries generated by GNU tools:
     //   Contents of the .note.gnu.build-id field.
     // On Windows:
     //   GUID + AGE in the debug image headers of a module.
     optional string build_id = 1;
 
     // MD5Sum Prefix of the module name. This is the same hashing scheme as used
     // to hash UMA histogram names.
     optional fixed64 name_md5_prefix = 2;
   }
 
   // The callstack and counts.
   repeated Sample sample = 1;
 
   // List of module ids found in this sample.
   repeated ModuleIdentifier module_id = 2;
 
   // Duration of this profile.
   optional int32 profile_duration_ms = 3;
 
   // Time between samples.
   optional int32 sampling_period_ms = 4;
 }