One-time reset of UMA client ids and low entropy source.

chrome/browser/metrics/metrics_service.cc

 // 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.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 418 matching lines @@
   virtual ~MetricsMemoryDetails() {}
 
   base::Closure callback_;
   DISALLOW_COPY_AND_ASSIGN(MetricsMemoryDetails);
 };
 
 // static
 void MetricsService::RegisterPrefs(PrefRegistrySimple* registry) {
   DCHECK(IsSingleThreaded());
   registry->RegisterStringPref(prefs::kMetricsClientID, std::string());
+  registry->RegisterInt64Pref(prefs::kMetricsReportingEnabledTimestamp, 0);
   registry->RegisterIntegerPref(prefs::kMetricsLowEntropySource,
                                 kLowEntropySourceNotSet);
-  registry->RegisterInt64Pref(prefs::kMetricsClientIDTimestamp, 0);
   registry->RegisterInt64Pref(prefs::kStabilityLaunchTimeSec, 0);
   registry->RegisterInt64Pref(prefs::kStabilityLastTimestampSec, 0);
   registry->RegisterStringPref(prefs::kStabilityStatsVersion, std::string());
   registry->RegisterInt64Pref(prefs::kStabilityStatsBuildTime, 0);
   registry->RegisterBooleanPref(prefs::kStabilityExitedCleanly, true);
   registry->RegisterIntegerPref(prefs::kStabilityExecutionPhase,
                                 UNINITIALIZED_PHASE);
   registry->RegisterBooleanPref(prefs::kStabilitySessionEndCompleted, true);
   registry->RegisterIntegerPref(prefs::kMetricsSessionID, -1);
   registry->RegisterIntegerPref(prefs::kStabilityLaunchCount, 0);
@@ skipping 24 matching lines @@
   registry->RegisterListPref(prefs::kMetricsInitialLogs);
   registry->RegisterListPref(prefs::kMetricsOngoingLogs);
 
   registry->RegisterInt64Pref(prefs::kInstallDate, 0);
   registry->RegisterInt64Pref(prefs::kUninstallMetricsPageLoadCount, 0);
   registry->RegisterInt64Pref(prefs::kUninstallLaunchCount, 0);
   registry->RegisterInt64Pref(prefs::kUninstallMetricsUptimeSec, 0);
   registry->RegisterInt64Pref(prefs::kUninstallLastLaunchTimeSec, 0);
   registry->RegisterInt64Pref(prefs::kUninstallLastObservedRunTimeSec, 0);
 
+  // TODO(asvitkine): Remove these once a couple of releases have passed.

[Ilya Sherman, 2014/03/28 18:23:06]

nit: Please add a specific milestone target to this TODO, and file a bug, so
that future readers of the code don't have to dig through history to figure out
when this TODO was added.

[Alexei Svitkine (slow), 2014/03/28 18:40:19]

Done. The milestone is on the bug.

+  registry->RegisterStringPref(prefs::kMetricsOldClientID, std::string());
+  registry->RegisterIntegerPref(prefs::kMetricsOldLowEntropySource, 0);
+
 #if defined(OS_ANDROID)
   RegisterPrefsAndroid(registry);
 #endif  // defined(OS_ANDROID)
 }
 
 // static
 void MetricsService::DiscardOldStabilityStats(PrefService* local_state) {
   local_state->SetBoolean(prefs::kStabilityExitedCleanly, true);
   local_state->SetInteger(prefs::kStabilityExecutionPhase, UNINITIALIZED_PHASE);
   local_state->SetBoolean(prefs::kStabilitySessionEndCompleted, true);
@@ skipping 138 matching lines @@
   if (!client_id_.empty())
     return;
   PrefService* pref = g_browser_process->local_state();
   client_id_ = pref->GetString(prefs::kMetricsClientID);
   if (!client_id_.empty())
     return;
 
   client_id_ = GenerateClientID();
   pref->SetString(prefs::kMetricsClientID, client_id_);
 
-  // Might as well make a note of how long this ID has existed
-  pref->SetString(prefs::kMetricsClientIDTimestamp,
-                  base::Int64ToString(Time::Now().ToTimeT()));
+  // Record the timestamp of when the user opted in to UMA.

[Ilya Sherman, 2014/03/28 18:23:06]

nit: Move this inside the if branch, since it doesn't apply to the else branch.

[Alexei Svitkine (slow), 2014/03/28 18:40:19]

Done.

+  if (pref->GetString(prefs::kMetricsOldClientID).empty()) {
+    pref->SetInt64(prefs::kMetricsReportingEnabledTimestamp,
+                   Time::Now().ToTimeT());
+  } else {
+    UMA_HISTOGRAM_BOOLEAN("UMA.MigratedClientID", true);

[Ilya Sherman, 2014/03/28 18:23:06]

You don't seem to ever emit a |false| value to this histogram.  What's the
purpose of tracking this as a histogram?

[Alexei Svitkine (slow), 2014/03/28 18:40:19]

This will allow analysis of when users migrated their ids. (We don't care about
the actual counts of this, since all UMA users on M35 will be affected by this.)
But we may want to know when a given "new" UMA client id we see is a result of
migration.

[Ilya Sherman, 2014/03/28 19:22:48]

Fair 'nuff.

+  }
+  pref->ClearPref(prefs::kMetricsOldClientID);
 }
 
 void MetricsService::EnableRecording() {
   DCHECK(IsSingleThreaded());
 
   if (recording_active_)
     return;
   recording_active_ = true;
 
   ForceClientIdCreation();
@@ skipping 534 matching lines @@
   // value has been set or not.
   if (low_entropy_source_ != kLowEntropySourceNotSet)
     return low_entropy_source_;
 
   PrefService* local_state = g_browser_process->local_state();
   const CommandLine* command_line(CommandLine::ForCurrentProcess());
   // Only try to load the value from prefs if the user did not request a reset.
   // Otherwise, skip to generating a new value.
   if (!command_line->HasSwitch(switches::kResetVariationState)) {
     int value = local_state->GetInteger(prefs::kMetricsLowEntropySource);
-    // Old versions of the code would generate values in the range of [1, 8192],
-    // before the range was switched to [0, 8191] and then to [0, 7999]. Map
-    // 8192 to 0, so that the 0th bucket remains uniform, while re-generating
-    // the low entropy source for old values in the [8000, 8191] range.
-    if (value == 8192)
-      value = 0;
     // If the value is outside the [0, kMaxLowEntropySize) range, re-generate
     // it below.
     if (value >= 0 && value < kMaxLowEntropySize) {
       low_entropy_source_ = value;
       UMA_HISTOGRAM_BOOLEAN("UMA.GeneratedLowEntropySource", false);
       return low_entropy_source_;
     }
   }
 
   UMA_HISTOGRAM_BOOLEAN("UMA.GeneratedLowEntropySource", true);
   low_entropy_source_ = GenerateLowEntropySource();
   local_state->SetInteger(prefs::kMetricsLowEntropySource, low_entropy_source_);
+  local_state->ClearPref(prefs::kMetricsOldLowEntropySource);
   metrics::CachingPermutedEntropyProvider::ClearCache(local_state);
 
   return low_entropy_source_;
 }
 
 // static
 std::string MetricsService::GenerateClientID() {
   return base::GenerateGUID();
 }
 
@@ skipping 869 matching lines @@
   // Android has its own settings for metrics / crash uploading.
   const PrefService* prefs = g_browser_process->local_state();
   return prefs->GetBoolean(prefs::kCrashReportingEnabled);
 #else
   return MetricsServiceHelper::IsMetricsReportingEnabled();
 #endif
 #else
   return false;
 #endif
 }