Revert "[Translate] Add translate ranker model loader."

components/translate/core/browser/ranker_model_loader.cc

Index: components/translate/core/browser/ranker_model_loader.cc
diff --git a/components/translate/core/browser/ranker_model_loader.cc b/components/translate/core/browser/ranker_model_loader.cc
deleted file mode 100644
index 900815b59dd4b0a8b8f6bd3f7c8b97f015cea3e3..0000000000000000000000000000000000000000
--- a/components/translate/core/browser/ranker_model_loader.cc
+++ /dev/null
@@ -1,420 +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/ranker_model_loader.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/command_line.h"
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/files/important_file_writer.h"
-#include "base/macros.h"
-#include "base/memory/ptr_util.h"
-#include "base/metrics/histogram_macros.h"
-#include "base/profiler/scoped_tracker.h"
-#include "base/sequenced_task_runner.h"
-#include "base/strings/string_util.h"
-#include "base/task_scheduler/post_task.h"
-#include "base/threading/sequenced_task_runner_handle.h"
-#include "components/translate/core/browser/proto/ranker_model.pb.h"
-#include "components/translate/core/browser/ranker_model.h"
-#include "components/translate/core/browser/translate_url_fetcher.h"
-#include "url/gurl.h"
-
-namespace translate {
-namespace {
-
-using chrome_intelligence::RankerModel;
-using chrome_intelligence::RankerModelProto;
-
-constexpr int kUrlFetcherId = 2;
-
-// The maximum number of model download attempts to make. Download may fail
-// due to server error or network availability issues.
-constexpr int kMaxRetryOn5xx = 8;
-
-// The minimum duration, in minutes, between download attempts.
-constexpr int kMinRetryDelayMins = 3;
-
-// Suffixes for the various histograms produced by the backend.
-const char kWriteTimerHistogram[] = ".Timer.WriteModel";
-const char kReadTimerHistogram[] = ".Timer.ReadModel";
-const char kDownloadTimerHistogram[] = ".Timer.DownloadModel";
-const char kParsetimerHistogram[] = ".Timer.ParseModel";
-const char kModelStatusHistogram[] = ".Model.Status";
-
-// A helper class to produce a scoped timer histogram that supports using a
-// non-static-const name.
-class MyScopedHistogramTimer {
- public:
-  MyScopedHistogramTimer(const base::StringPiece& name)
-      : name_(name.begin(), name.end()), start_(base::TimeTicks::Now()) {}
-
-  ~MyScopedHistogramTimer() {
-    base::TimeDelta duration = base::TimeTicks::Now() - start_;
-    base::HistogramBase* counter = base::Histogram::FactoryTimeGet(
-        name_, base::TimeDelta::FromMilliseconds(10),
-        base::TimeDelta::FromMilliseconds(200000), 100,
-        base::HistogramBase::kUmaTargetedHistogramFlag);
-    if (counter)
-      counter->AddTime(duration);
-  }
-
- private:
-  const std::string name_;
-  const base::TimeTicks start_;
-
-  DISALLOW_COPY_AND_ASSIGN(MyScopedHistogramTimer);
-};
-
-}  // namespace
-
-// =============================================================================
-// RankerModelLoader::Backend
-
-class RankerModelLoader::Backend {
- public:
-  // An internal version of RankerModelLoader::OnModelAvailableCallback that
-  // bundles calling the real callback with a notification of whether or not
-  // tha backend is finished.
-  using InternalOnModelAvailableCallback =
-      base::Callback<void(std::unique_ptr<RankerModel>, bool)>;
-
-  Backend(const ValidateModelCallback& validate_model_cb,
-          const InternalOnModelAvailableCallback& on_model_available_cb,
-          const base::FilePath& model_path,
-          const GURL& model_url,
-          const std::string& uma_prefix);
-  ~Backend();
-
-  // Reads the model from |model_path_|.
-  void LoadFromFile();
-
-  // Reads the model from |model_url_|.
-  void AsyncLoadFromURL();
-
- private:
-  // Log and return the result of loading a model to UMA.
-  RankerModelStatus ReportModelStatus(RankerModelStatus model_status);
-
-  // Constructs a model from the given |data|.
-  std::unique_ptr<chrome_intelligence::RankerModel> CreateModel(
-      const std::string& data);
-
-  // Accepts downloaded model data. This signature is mandated by the callback
-  // defined by TransalteURLFetcher.
-  //
-  // id - the id given to the TranslateURLFetcher on creation
-  // success - true of the download was successful
-  // data - the body of the downloads response
-  void OnDownloadComplete(int id, bool success, const std::string& data);
-
-  // Transfers ownership of |model| to the client using the
-  // |internal_on_model_available_cb_|. |is_finished| denotes whether the
-  // backend is finished (or has given up on) loading the model.
-  void TransferModelToClient(
-      std::unique_ptr<chrome_intelligence::RankerModel> model,
-      bool is_finished);
-
-  // Validates that ranker model loader backend tasks are all performed on the
-  // same sequence.
-  base::SequenceChecker sequence_checker_;
-
-  // The TaskRunner on which |this| was constructed.
-  const scoped_refptr<base::SequencedTaskRunner> origin_task_runner_;
-
-  // Validates a ranker model on behalf of the model loader client. This may
-  // be called on any sequence and must, therefore, be thread-safe.
-  const ValidateModelCallback validate_model_cb_;
-
-  // Transfers ownership of a loaded model back to the model loader client.
-  // This will be called on the sequence on which the model loader was
-  // constructed.
-  const InternalOnModelAvailableCallback internal_on_model_available_cb_;
-
-  // The path at which the model is (or should be) cached.
-  const base::FilePath model_path_;
-
-  // The URL from which to download the model if the model is not in the cache
-  // or the cached model is invalid/expired.
-  const GURL model_url_;
-
-  // This will prefix all UMA metrics generated by the model loader.
-  const std::string uma_prefix_;
-
-  // Used to download model data from |model_url_|.
-  // TODO(rogerm): Use net::URLFetcher directly?
-  std::unique_ptr<TranslateURLFetcher> url_fetcher_;
-
-  // The next time before which no new attempts to download the model should be
-  // attempted.
-  base::TimeTicks next_earliest_download_time_;
-
-  // Tracks the last time of the last attempt to download a model. Used for UMA
-  // reporting of download duration.
-  base::TimeTicks download_start_time_;
-
-  DISALLOW_COPY_AND_ASSIGN(Backend);
-};
-
-RankerModelLoader::Backend::Backend(
-    const ValidateModelCallback& validate_model_cb,
-    const InternalOnModelAvailableCallback& internal_on_model_available_cb,
-    const base::FilePath& model_path,
-    const GURL& model_url,
-    const std::string& uma_prefix)
-    : origin_task_runner_(base::SequencedTaskRunnerHandle::Get()),
-      validate_model_cb_(validate_model_cb),
-      internal_on_model_available_cb_(internal_on_model_available_cb),
-      model_path_(model_path),
-      model_url_(model_url),
-      uma_prefix_(uma_prefix) {
-  sequence_checker_.DetachFromSequence();
-}
-
-RankerModelLoader::Backend::~Backend() {}
-
-RankerModelStatus RankerModelLoader::Backend::ReportModelStatus(
-    RankerModelStatus model_status) {
-  base::HistogramBase* histogram = base::LinearHistogram::FactoryGet(
-      uma_prefix_ + kModelStatusHistogram, 1,
-      static_cast<int>(RankerModelStatus::MAX),
-      static_cast<int>(RankerModelStatus::MAX) + 1,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-  if (histogram)
-    histogram->Add(static_cast<int>(model_status));
-  return model_status;
-}
-
-std::unique_ptr<chrome_intelligence::RankerModel>
-RankerModelLoader::Backend::CreateModel(const std::string& data) {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  MyScopedHistogramTimer timer(uma_prefix_ + kParsetimerHistogram);
-  auto model = RankerModel::FromString(data);
-  if (ReportModelStatus(model ? validate_model_cb_.Run(*model)
-                              : RankerModelStatus::PARSE_FAILED) !=
-      RankerModelStatus::OK) {
-    return nullptr;
-  }
-  return model;
-}
-
-void RankerModelLoader::Backend::LoadFromFile() {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-
-  // If there is not cache path set, move on to loading the model by URL.
-  if (model_path_.empty()) {
-    AsyncLoadFromURL();
-    return;
-  }
-
-  DVLOG(2) << "Attempting to load model from: " << model_path_.value();
-
-  std::string data;
-
-  {
-    MyScopedHistogramTimer timer(uma_prefix_ + kReadTimerHistogram);
-    if (!base::ReadFileToString(model_path_, &data) || data.empty()) {
-      DVLOG(2) << "Failed to read model from: " << model_path_.value();
-      data.clear();
-    }
-  }
-
-  // If model data was loaded, check if it can be parsed to a valid model.
-  if (!data.empty()) {
-    auto model = CreateModel(data);
-    if (model) {
-      // The model is valid. The client is willing/able to use it. Keep track
-      // of where it originated and whether or not is has expired.
-      std::string url_spec = model->GetSourceURL();
-      bool is_expired = model->IsExpired();
-      bool is_finished = url_spec == model_url_.spec() && !is_expired;
-
-      DVLOG(2) << (is_expired ? "Expired m" : "M") << "odel in '"
-               << model_path_.value() << "' was originally downloaded from '"
-               << url_spec << "'.";
-
-      // Transfer the model to the client. Beyond this line, |model| is invalid.
-      TransferModelToClient(std::move(model), is_finished);
-
-      // If the cached model came from currently configured |model_url_| and has
-      // not expired, there is no need schedule a model download.
-      if (is_finished)
-        return;
-
-      // Otherwise, fall out of this block to schedule a download. The client
-      // can continue to use the valid but expired model until the download
-      // completes.
-    }
-  }
-
-  // Reaching this point means that a model download is required. If there is
-  // no download URL configured, then there is nothing further to do.
-  AsyncLoadFromURL();
-}
-
-void RankerModelLoader::Backend::AsyncLoadFromURL() {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-
-  if (!model_url_.is_valid())
-    return;
-
-  // Do nothing if the download attempts should be throttled.
-  if (base::TimeTicks::Now() < next_earliest_download_time_) {
-    DVLOG(2) << "Last download attempt was too recent.";
-    return;
-  }
-
-  // Otherwise, initialize the model fetcher to be non-null and trigger an
-  // initial download attempt.
-  if (!url_fetcher_) {
-    url_fetcher_ = base::MakeUnique<TranslateURLFetcher>(kUrlFetcherId);
-    url_fetcher_->set_max_retry_on_5xx(kMaxRetryOn5xx);
-  }
-
-  // If a request is already in flight, do not issue a new one.
-  if (url_fetcher_->state() == TranslateURLFetcher::REQUESTING) {
-    DVLOG(2) << "Download is in progress.";
-    return;
-  }
-
-  DVLOG(2) << "Downloading model from: " << model_url_;
-
-  // Reset the time of the next earliest allowable download attempt.
-  next_earliest_download_time_ =
-      base::TimeTicks::Now() + base::TimeDelta::FromMinutes(kMinRetryDelayMins);
-
-  // Kick off the next download attempt.
-  download_start_time_ = base::TimeTicks::Now();
-  bool result = url_fetcher_->Request(
-      model_url_, base::Bind(&RankerModelLoader::Backend::OnDownloadComplete,
-                             base::Unretained(this)));
-
-  // The maximum number of download attempts has been surpassed. Don't make
-  // any further attempts.
-  if (!result) {
-    DVLOG(2) << "Model download abandoned.";
-    ReportModelStatus(RankerModelStatus::DOWNLOAD_FAILED);
-    url_fetcher_.reset();
-
-    // Notify the loader that model loading has been abandoned.
-    TransferModelToClient(nullptr, true);
-  }
-}
-
-void RankerModelLoader::Backend::OnDownloadComplete(int /* id */,
-                                                    bool success,
-                                                    const std::string& data) {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-
-  // Record the duration of the download.
-  base::TimeDelta duration = base::TimeTicks::Now() - download_start_time_;
-  base::HistogramBase* counter = base::Histogram::FactoryTimeGet(
-      uma_prefix_ + kDownloadTimerHistogram,
-      base::TimeDelta::FromMilliseconds(10),
-      base::TimeDelta::FromMilliseconds(200000), 100,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-  if (counter)
-    counter->AddTime(duration);
-
-  // On failure, we just abort. The TranslateRanker will retry on a subsequent
-  // translation opportunity. The TranslateURLFetcher enforces a limit for
-  // retried requests.
-  if (!success || data.empty()) {
-    DVLOG(2) << "Download from '" << model_url_ << "'' failed.";
-    return;
-  }
-
-  auto model = CreateModel(data);
-  if (!model) {
-    DVLOG(2) << "Model from '" << model_url_ << "'' not valid.";
-    return;
-  }
-
-  url_fetcher_.reset();
-
-  auto* metadata = model->mutable_proto()->mutable_metadata();
-  metadata->set_source(model_url_.spec());
-  metadata->set_last_modified_sec(
-      (base::Time::Now() - base::Time()).InSeconds());
-
-  if (!model_path_.empty()) {
-    DVLOG(2) << "Saving model from '" << model_url_ << "'' to '"
-             << model_path_.value() << "'.";
-    MyScopedHistogramTimer timer(uma_prefix_ + kWriteTimerHistogram);
-    base::ImportantFileWriter::WriteFileAtomically(model_path_,
-                                                   model->SerializeAsString());
-  }
-
-  // Notify the owner that a compatible model is available.
-  TransferModelToClient(std::move(model), true);
-}
-
-void RankerModelLoader::Backend::TransferModelToClient(
-    std::unique_ptr<chrome_intelligence::RankerModel> model,
-    bool is_finished) {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  origin_task_runner_->PostTask(
-      FROM_HERE, base::Bind(internal_on_model_available_cb_,
-                            base::Passed(std::move(model)), is_finished));
-}
-
-// =============================================================================
-// RankerModelLoader
-
-RankerModelLoader::RankerModelLoader(
-    const ValidateModelCallback& validate_model_cb,
-    const OnModelAvailableCallback& on_model_available_cb,
-    const base::FilePath& model_path,
-    const GURL& model_url,
-    const std::string& uma_prefix)
-    : backend_task_runner_(base::CreateSequencedTaskRunnerWithTraits(
-          base::TaskTraits().MayBlock().WithShutdownBehavior(
-              base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN))),
-      weak_ptr_factory_(this) {
-  auto internal_on_model_available_cb =
-      base::Bind(&RankerModelLoader::InternalOnModelAvailable,
-                 weak_ptr_factory_.GetWeakPtr(), on_model_available_cb);
-  backend_ = base::MakeUnique<Backend>(validate_model_cb,
-                                       internal_on_model_available_cb,
-                                       model_path, model_url, uma_prefix);
-}
-
-RankerModelLoader::~RankerModelLoader() {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  // This is guaranteed to be sequenced after any pending backend operation.
-  backend_task_runner_->DeleteSoon(FROM_HERE, backend_.release());
-}
-
-void RankerModelLoader::Start() {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  DCHECK_EQ(state_, LoaderState::NOT_STARTED);
-  state_ = LoaderState::RUNNING;
-  backend_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&RankerModelLoader::Backend::LoadFromFile,
-                            base::Unretained(backend_.get())));
-}
-
-void RankerModelLoader::NotifyOfRankerActivity() {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  if (state_ == LoaderState::RUNNING) {
-    backend_task_runner_->PostTask(
-        FROM_HERE, base::Bind(&RankerModelLoader::Backend::AsyncLoadFromURL,
-                              base::Unretained(backend_.get())));
-  }
-}
-
-void RankerModelLoader::InternalOnModelAvailable(
-    const OnModelAvailableCallback& callback,
-    std::unique_ptr<RankerModel> model,
-    bool finished) {
-  DCHECK(sequence_checker_.CalledOnValidSequence());
-  if (finished)
-    state_ = LoaderState::FINISHED;
-  if (model)
-    callback.Run(std::move(model));
-}
-
-}  // namespace translate