Add UMA stats for Chromoting connection details.

remoting/webapp/base/js/client_session.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Class handling creation and teardown of a remoting client session.
  *
  * The ClientSession class controls lifetime of the client plugin
  * object and provides the plugin with the functionality it needs to
@@ skipping 117 matching lines @@
 
 // Note that the positive values in both of these enums are copied directly
 // from connection_to_host.h and must be kept in sync. Code in
 // chromoting_instance.cc converts the C++ enums into strings that must match
 // the names given here.
 // The negative values represent state transitions that occur within the
 // web-app that have no corresponding plugin state transition.
 //
 // TODO(kelvinp): Merge this enum with remoting.ChromotingEvent.SessionState
 // once we have migrated away from XMPP-based logging (crbug.com/523423).
+// NOTE: The enums here correspond to the Chromoting.Connections enumerated
+// histogram defined in src/tools/metrics/histograms/histograms.xml. UMA
+// histograms don't work well with negative values, so only non-negative values
+// have been used for Chromoting.Connections.
+// The maximum values for the UMA enumerated histogram is included here for use
+// when uploading values to UMA.
+// The 2 lists should be kept in sync, and any new enums should be append-only.
 /** @enum {number} */
 remoting.ClientSession.State = {
+  MIN_STATE_ENUM: -3,
   CONNECTION_CANCELED: -3,  // Connection closed (gracefully) before connecting.
   CONNECTION_DROPPED: -2,  // Succeeded, but subsequently closed with an error.
   CREATED: -1,
   UNKNOWN: 0,
   INITIALIZING: 1,
   CONNECTING: 2,
   AUTHENTICATED: 3,
   CONNECTED: 4,
   CLOSED: 5,
-  FAILED: 6
+  FAILED: 6,
+  MAX_STATE_ENUM: 6,
 };
 
 /**
  * @param {string} state The state name.
  * @return {remoting.ClientSession.State} The session state enum value.
  */
 remoting.ClientSession.State.fromString = function(state) {
   if (!remoting.ClientSession.State.hasOwnProperty(state)) {
     throw "Invalid ClientSession.State: " + state;
   }
@@ skipping 375 matching lines @@
     if (this.plugin_.hasCapability(
           remoting.ClientSession.Capability.TOUCH_EVENTS)) {
       this.plugin_.enableTouchEvents(true);
     }
   } else if (this.isFinished()) {
     base.dispose(this.connectedDisposables_);
     this.connectedDisposables_ = null;
   }
 
   this.notifyStateChanges_(oldState, this.state_);
+  // Record state count in an UMA enumerated histogram.
+  recordState(this.state_);
   this.logger_.logClientSessionStateChange(
       this.state_, this.error_, this.xmppErrorCache_.getFirstError());
 };
 
 /**
+ * Records a Chromoting Connection State, stored in an UMA enumerated histogram.
+ * @param {remoting.ClientSession.State} state State identifier.
+ */
+function recordState(state) {
+  // According to src/base/metrics/histogram.h, for a UMA enumerated histogram,
+  // the upper limit should be 1 above the max-enum. Because SessionState's
+  // minimum enum value is negative, we'll just take the difference of the max
+  // and min enums.
+  var histogram_max = (remoting.ClientSession.State.MAX_STATE_ENUM -
+    remoting.ClientSession.State.MIN_STATE_ENUM);

[Ilya Sherman, 2015/08/25 01:34:25]

I'm pretty sure you're missing a "+1" in this computation :(

+
+  var metricDescription = {
+    metricName: 'Chromoting.Connections',
+    type: 'histogram-linear',
+    // According to histogram.h, minimum should be 1. Values less than minimum
+    // end up in the 0th bucket.
+    min: 1,
+    max: histogram_max,
+    // The # of buckets should include 1 for underflow.
+    buckets: histogram_max + 1
+  };
+
+  chrome.metricsPrivate.recordValue(metricDescription, state -
+      remoting.ClientSession.State.MIN_STATE_ENUM);
+}
+
+/**
  * @param {remoting.ClientSession.State} oldState The new state for the session.
  * @param {remoting.ClientSession.State} newState The new state for the session.
  * @private
  */
 remoting.ClientSession.prototype.notifyStateChanges_ =
     function(oldState, newState) {
   /** @type {remoting.Error} */
   var error;
   switch (this.state_) {
     case remoting.ClientSession.State.CONNECTED:
@@ skipping 57 matching lines @@
   } else if (previous == State.CONNECTED && current == State.FAILED) {
     return State.CONNECTION_DROPPED;
   }
   return current;
 };
 
 /** @private */
 remoting.ClientSession.prototype.reportStatistics = function() {
   this.logger_.logStatistics(this.plugin_.getPerfStats());
 };