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