components/metrics/cloned_install_detector.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/metrics/cloned_install_detector.h"
   6
   7 #include <string>
   8
   9 #include "base/bind.h"
  10 #include "base/location.h"
  11 #include "base/metrics/histogram_macros.h"
  12 #include "base/prefs/pref_registry_simple.h"
  13 #include "base/prefs/pref_service.h"
  14 #include "base/single_thread_task_runner.h"
  15 #include "base/task_runner_util.h"
  16 #include "components/metrics/machine_id_provider.h"
  17 #include "components/metrics/metrics_hashes.h"
  18 #include "components/metrics/metrics_pref_names.h"
  19
  20 namespace metrics {
  21
  22 namespace {
  23
  24 uint32 HashRawId(const std::string& value) {
  25   uint64 hash = HashMetricName(value);
  26
  27   // Only use 24 bits from the 64-bit hash.
  28   return hash & ((1 << 24) - 1);
  29 }
  30
  31 // State of the generated machine id in relation to the previously stored value.
  32 // Note: UMA histogram enum - don't re-order or remove entries
  33 enum MachineIdState {
  34   ID_GENERATION_FAILED,
  35   ID_NO_STORED_VALUE,
  36   ID_CHANGED,
  37   ID_UNCHANGED,
  38   ID_ENUM_SIZE
  39 };
  40
  41 // Logs the state of generating a machine id and comparing it to a stored value.
  42 void LogMachineIdState(MachineIdState state) {
  43   UMA_HISTOGRAM_ENUMERATION("UMA.MachineIdState", state, ID_ENUM_SIZE);
  44 }
  45
  46 }  // namespace
  47
  48 ClonedInstallDetector::ClonedInstallDetector(MachineIdProvider* raw_id_provider)
  49     : raw_id_provider_(raw_id_provider), weak_ptr_factory_(this) {
  50 }
  51
  52 ClonedInstallDetector::~ClonedInstallDetector() {
  53 }
  54
  55 void ClonedInstallDetector::CheckForClonedInstall(
  56     PrefService* local_state,
  57     scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
  58   base::PostTaskAndReplyWithResult(
  59       task_runner.get(),
  60       FROM_HERE,
  61       base::Bind(&MachineIdProvider::GetMachineId, raw_id_provider_),
  62       base::Bind(&ClonedInstallDetector::SaveMachineId,
  63                  weak_ptr_factory_.GetWeakPtr(),
  64                  local_state));
  65 }
  66
  67 void ClonedInstallDetector::SaveMachineId(PrefService* local_state,
  68                                           std::string raw_id) {
  69   if (raw_id.empty()) {
  70     LogMachineIdState(ID_GENERATION_FAILED);
  71     local_state->ClearPref(prefs::kMetricsMachineId);
  72     return;
  73   }
  74
  75   int hashed_id = HashRawId(raw_id);
  76
  77   MachineIdState id_state = ID_NO_STORED_VALUE;
  78   if (local_state->HasPrefPath(prefs::kMetricsMachineId)) {
  79     if (local_state->GetInteger(prefs::kMetricsMachineId) != hashed_id) {
  80       id_state = ID_CHANGED;
  81       // TODO(jwd): Use a callback to set the reset pref. That way
  82       // ClonedInstallDetector doesn't need to know about this pref.
  83       local_state->SetBoolean(prefs::kMetricsResetIds, true);
  84     } else {
  85       id_state = ID_UNCHANGED;
  86     }
  87   }
  88
  89   LogMachineIdState(id_state);
  90
  91   local_state->SetInteger(prefs::kMetricsMachineId, hashed_id);
  92 }
  93
  94 // static
  95 void ClonedInstallDetector::RegisterPrefs(PrefRegistrySimple* registry) {
  96   registry->RegisterIntegerPref(prefs::kMetricsMachineId, 0);
  97 }
  98
  99 }  // namespace metrics