[translate] Add translate ranker model loader.

components/translate/core/browser/translate_ranker.cc

Index: components/translate/core/browser/translate_ranker.cc
diff --git a/components/translate/core/browser/translate_ranker.cc b/components/translate/core/browser/translate_ranker.cc
deleted file mode 100644
index 1341652f64293c9037dce916c4e903456a084ed5..0000000000000000000000000000000000000000
--- a/components/translate/core/browser/translate_ranker.cc
+++ /dev/null
@@ -1,311 +0,0 @@
-// Copyright 2016 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.
-
-#include "components/translate/core/browser/translate_ranker.h"
-
-#include <cmath>
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/command_line.h"
-#include "base/metrics/histogram_macros.h"
-#include "base/profiler/scoped_tracker.h"
-#include "base/strings/string_util.h"
-#include "components/metrics/proto/translate_event.pb.h"
-#include "components/translate/core/browser/proto/translate_ranker_model.pb.h"
-#include "components/translate/core/browser/translate_download_manager.h"
-#include "components/translate/core/browser/translate_prefs.h"
-#include "components/translate/core/browser/translate_url_fetcher.h"
-#include "components/translate/core/common/translate_switches.h"
-
-namespace translate {
-
-namespace {
-
-typedef google::protobuf::Map<std::string, float> WeightMap;
-
-const double kTranslationOfferThreshold = 0.5;
-
-// Parameters for model fetching.
-const char kTranslateRankerModelURL[] =
-    "https://chromium-i18n.appspot.com/ssl-translate-ranker-model";
-const int kMaxRetryOn5xx = 3;
-const int kDownloadRefractoryPeriodMin = 15;
-const char kUnknown[] = "UNKNOWN";
-
-// Enumeration denoting the outcome of an attempt to download the translate
-// ranker model. This must be kept in sync with the TranslateRankerModelStatus
-// enum in histograms.xml
-enum ModelStatus {
-  MODEL_STATUS_OK = 0,
-  MODEL_STATUS_DOWNLOAD_THROTTLED = 1,
-  MODEL_STATUS_DOWNLOAD_FAILED = 2,
-  MODEL_STATUS_PARSE_FAILED = 3,
-  MODEL_STATUS_VALIDATION_FAILED = 4,
-  // Insert new values above this line.
-  MODEL_STATUS_MAX
-};
-
-double Sigmoid(double x) {
-  return 1.0 / (1.0 + exp(-x));
-}
-
-double ScoreComponent(const WeightMap& weights, const std::string& key) {
-  WeightMap::const_iterator i = weights.find(base::ToLowerASCII(key));
-  if (i == weights.end())
-    i = weights.find(kUnknown);
-  return i == weights.end() ? 0.0 : i->second;
-}
-
-GURL GetTranslateRankerURL() {
-  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-  return GURL(command_line->HasSwitch(switches::kTranslateRankerModelURL)
-                  ? command_line->GetSwitchValueASCII(
-                        switches::kTranslateRankerModelURL)
-                  : kTranslateRankerModelURL);
-}
-
-void ReportModelStatus(ModelStatus model_status) {
-  UMA_HISTOGRAM_ENUMERATION("Translate.Ranker.Model.Status", model_status,
-                            MODEL_STATUS_MAX);
-}
-
-}  // namespace
-
-const base::Feature kTranslateRankerQuery{"TranslateRankerQuery",
-                                          base::FEATURE_DISABLED_BY_DEFAULT};
-
-const base::Feature kTranslateRankerEnforcement{
-    "TranslateRankerEnforcement", base::FEATURE_DISABLED_BY_DEFAULT};
-
-const base::Feature kTranslateRankerLogging{"TranslateRankerLogging",
-                                            base::FEATURE_DISABLED_BY_DEFAULT};
-
-TranslateRanker::~TranslateRanker() {}
-
-// static
-bool TranslateRanker::IsEnabled() {
-  return IsQueryEnabled() || IsEnforcementEnabled();
-}
-
-// static
-bool TranslateRanker::IsLoggingEnabled() {
-  return base::FeatureList::IsEnabled(kTranslateRankerLogging);
-}
-
-// static
-bool TranslateRanker::IsQueryEnabled() {
-  return base::FeatureList::IsEnabled(kTranslateRankerQuery);
-}
-
-// static
-bool TranslateRanker::IsEnforcementEnabled() {
-  return base::FeatureList::IsEnabled(kTranslateRankerEnforcement);
-}
-
-// static
-TranslateRanker* TranslateRanker::GetInstance() {
-  return base::Singleton<TranslateRanker>::get();
-}
-
-std::unique_ptr<TranslateRanker> TranslateRanker::CreateForTesting(
-    const std::string& model_data) {
-  std::unique_ptr<TranslateRanker> ranker(new TranslateRanker());
-  CHECK(ranker != nullptr);
-  ranker->ParseModel(0, true, model_data);
-  CHECK(ranker->model_ != nullptr);
-  return ranker;
-}
-
-bool TranslateRanker::ShouldOfferTranslation(
-    const TranslatePrefs& translate_prefs,
-    const std::string& src_lang,
-    const std::string& dst_lang) {
-  // The ranker is a gate in the "show a translation prompt" flow. To retain
-  // the pre-existing functionality, it defaults to returning true in the
-  // absence of a model or if enforcement is disabled. As this is ranker is
-  // subsumed into a more general assist ranker, this default will go away
-  // (or become False).
-  const bool kDefaultResponse = true;
-
-  // If we don't have a model, request one and return the default.
-  if (model_ == nullptr) {
-    FetchModelData();
-    return kDefaultResponse;
-  }
-
-  DCHECK(model_->has_logistic_regression_model());
-  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.ShouldOfferTranslation");
-
-  // TODO(rogerm): Remove ScopedTracker below once crbug.com/646711 is closed.
-  tracked_objects::ScopedTracker tracking_profile(
-      FROM_HERE_WITH_EXPLICIT_FUNCTION(
-          "646711 translate::TranslateRanker::ShouldOfferTranslation"));
-
-  const std::string& app_locale =
-      TranslateDownloadManager::GetInstance()->application_locale();
-  const std::string& country = translate_prefs.GetCountry();
-  int accept_count = translate_prefs.GetTranslationAcceptedCount(src_lang);
-  int decline_count = translate_prefs.GetTranslationDeniedCount(src_lang);
-  int ignore_count = translate_prefs.GetTranslationIgnoredCount(src_lang);
-  DVLOG(3) << "TranslateRanker: features=["
-           << "src_lang='" << src_lang << "', dst_lang='" << dst_lang
-           << "', country='" << country << "', locale='" << app_locale
-           << ", accept_count=" << accept_count
-           << ", decline_count=" << decline_count
-           << ", ignore_count=" << ignore_count << "]";
-
-  double score = CalculateScore(accept_count, decline_count, ignore_count,
-                                src_lang, dst_lang, app_locale, country);
-
-  DVLOG(2) << "TranslateRanker Score: " << score;
-
-  bool result = (score >= kTranslationOfferThreshold);
-
-  UMA_HISTOGRAM_BOOLEAN("Translate.Ranker.QueryResult", result);
-
-  return result;
-}
-
-TranslateRanker::TranslateRanker() {}
-
-double TranslateRanker::CalculateScore(int accept_count,
-                                       int decline_count,
-                                       int ignore_count,
-                                       const std::string& src_lang,
-                                       const std::string& dst_lang,
-                                       const std::string& locale,
-                                       const std::string& country) {
-  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.CalculateScore");
-  DCHECK(model_ != nullptr);
-  DCHECK(model_->has_logistic_regression_model());
-
-  int total_count = accept_count + decline_count + ignore_count;
-  double accept_ratio =
-      (total_count == 0) ? 0.0 : (double(accept_count) / total_count);
-  double decline_ratio =
-      (total_count == 0) ? 0.0 : (double(decline_count) / total_count);
-  double ignore_ratio =
-      (total_count == 0) ? 0.0 : (double(ignore_count) / total_count);
-  DVLOG(3) << "TranslateRanker: ratios=["
-           << ", accept_ratio=" << accept_ratio
-           << ", decline_ratio=" << decline_ratio
-           << ", ignore_ratio=" << ignore_ratio << "]";
-
-  const chrome_intelligence::TranslateRankerModel::LogisticRegressionModel&
-      logit = model_->logistic_regression_model();
-  double dot_product =
-      (accept_ratio * logit.accept_ratio_weight()) +
-      (decline_ratio * logit.decline_ratio_weight()) +
-      (ignore_ratio * logit.ignore_ratio_weight()) +
-      (accept_count * logit.accept_count_weight()) +
-      (decline_count * logit.decline_count_weight()) +
-      (ignore_count * logit.ignore_count_weight()) +
-      ScoreComponent(logit.source_language_weight(), src_lang) +
-      ScoreComponent(logit.dest_language_weight(), dst_lang) +
-      ScoreComponent(logit.country_weight(), country) +
-      ScoreComponent(logit.locale_weight(), locale);
-  return Sigmoid(dot_product + logit.bias());
-}
-
-int TranslateRanker::GetModelVersion() const {
-  return (model_ == nullptr) ? 0 : model_->version();
-}
-
-void TranslateRanker::FetchModelData() {
-  // Exit if the model has already been successfully loaded.
-  if (model_ != nullptr) {
-    return;
-  }
-
-  // Exit if the download has been throttled.
-  if (base::Time::NowFromSystemTime() < next_earliest_download_time_) {
-    return;
-  }
-
-  // Create the model fetcher if it does not exist.
-  if (model_fetcher_ == nullptr) {
-    model_fetcher_.reset(new TranslateURLFetcher(kFetcherId));
-    model_fetcher_->set_max_retry_on_5xx(kMaxRetryOn5xx);
-  }
-
-  // If a request is already in flight, do not issue a new one.
-  if (model_fetcher_->state() == TranslateURLFetcher::REQUESTING) {
-    DVLOG(2) << "TranslateRanker: Download complete or in progress.";
-    return;
-  }
-
-  DVLOG(2) << "TranslateRanker: Downloading model...";
-
-  download_start_time_ = base::Time::Now();
-  bool result = model_fetcher_->Request(
-      GetTranslateRankerURL(),
-      base::Bind(&TranslateRanker::ParseModel, base::Unretained(this)));
-
-  if (!result) {
-    ReportModelStatus(MODEL_STATUS_DOWNLOAD_THROTTLED);
-    next_earliest_download_time_ =
-        base::Time::NowFromSystemTime() +
-        base::TimeDelta::FromMinutes(kDownloadRefractoryPeriodMin);
-  }
-}
-
-void TranslateRanker::ParseModel(int /* id */,
-                                 bool success,
-                                 const std::string& data) {
-  UMA_HISTOGRAM_MEDIUM_TIMES("Translate.Ranker.Timer.DownloadModel",
-                             base::Time::Now() - download_start_time_);
-
-  SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.ParseModel");
-
-  // We should not be here if the model has already been downloaded and parsed.
-  DCHECK(model_ == nullptr);
-
-  // On failure, we just abort. The TranslateRanker will retry on a subsequent
-  // translation opportunity. The TranslateURLFetcher enforces a limit for
-  // retried requests.
-  if (!success) {
-    ReportModelStatus(MODEL_STATUS_DOWNLOAD_FAILED);
-    return;
-  }
-
-  // Create a new model instance, parse and validate the data, and move it over
-  // to be used by the ranker.
-  std::unique_ptr<chrome_intelligence::TranslateRankerModel> new_model(
-      new chrome_intelligence::TranslateRankerModel());
-
-  bool is_parseable = new_model->ParseFromString(data);
-  if (!is_parseable) {
-    ReportModelStatus(MODEL_STATUS_PARSE_FAILED);
-    return;
-  }
-
-  bool is_valid = new_model->has_logistic_regression_model();
-  if (!is_valid) {
-    ReportModelStatus(MODEL_STATUS_VALIDATION_FAILED);
-    return;
-  }
-
-  ReportModelStatus(MODEL_STATUS_OK);
-  model_ = std::move(new_model);
-  model_fetcher_.reset();
-
-  DVLOG(3) << "Successfully loaded model version " << GetModelVersion() << ".";
-}
-
-void TranslateRanker::FlushTranslateEvents(
-    std::vector<metrics::TranslateEventProto>* translate_events) {
-  if (IsLoggingEnabled()) {
-    translate_events->swap(translate_events_cache_);
-    translate_events_cache_.clear();
-  }
-}
-
-void TranslateRanker::RecordTranslateEvent(
-    const metrics::TranslateEventProto& translate_event) {
-  if (IsLoggingEnabled())
-    translate_events_cache_.push_back(translate_event);
-}
-
-}  // namespace translate