Ranker owns predictor objects and uses a config for initialization.

Ranker also takes care of logging and deals with field trials internally.

Bug: 786472, 778468
Change-Id: Ie583616643ab8ad169df4739a4a18b81a950553f
Reviewed-on: https://chromium-review.googlesource.com/788331
Commit-Queue: Philippe Hamel <hamelphi@chromium.org>
Reviewed-by: Roger McFarlane <rogerm@chromium.org>
Reviewed-by: Donn Denman <donnd@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524426}

chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java

@@ -193,7 +193,6 @@ public abstract class ChromeFeatureList {
             "ContentSuggestionsThumbnailDominantColor";
     public static final String CONTEXTUAL_SEARCH_ML_TAP_SUPPRESSION =
             "ContextualSearchMlTapSuppression";
-    public static final String CONTEXTUAL_SEARCH_RANKER_QUERY = "ContextualSearchRankerQuery";
     public static final String CONTEXTUAL_SEARCH_SECOND_TAP = "ContextualSearchSecondTap";
     public static final String CONTEXTUAL_SUGGESTIONS_CAROUSEL = "ContextualSuggestionsCarousel";
     public static final String COPYLESS_PASTE = "CopylessPaste";

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchRankerLogger.java

@@ -54,6 +54,11 @@ public interface ContextualSearchRankerLogger {
      */
     void logFeature(Feature feature, Object value);
 
+    /**
+     * Returns whether or not AssistRanker query is enabled.
+     */
+    boolean isQueryEnabled();
+
     /**
      * Logs an outcome value at training time that indicates an ML label as a key/value pair.
      * @param feature The feature to log.

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchRankerLoggerImpl.java

@@ -111,6 +111,12 @@ public class ContextualSearchRankerLoggerImpl implements ContextualSearchRankerL
         mIsLoggingReadyForPage = true;
         mBasePageWebContents = basePageWebContents;
         mHasInferenceOccurred = false;
+        nativeSetupLoggingAndRanker(mNativePointer, basePageWebContents);
+    }
+
+    @Override
+    public boolean isQueryEnabled() {
+        return nativeIsQueryEnabled(mNativePointer);
     }
 
     @Override
@@ -138,7 +144,6 @@ public class ContextualSearchRankerLoggerImpl implements ContextualSearchRankerL
         mHasInferenceOccurred = true;
         if (isEnabled() && mBasePageWebContents != null && mFeaturesToLog != null
                 && !mFeaturesToLog.isEmpty()) {
-            nativeSetupLoggingAndRanker(mNativePointer, mBasePageWebContents);
             for (Map.Entry<Feature, Object> entry : mFeaturesToLog.entrySet()) {
                 logObject(entry.getKey(), entry.getValue());
             }
@@ -260,4 +265,5 @@ public class ContextualSearchRankerLoggerImpl implements ContextualSearchRankerL
     // Returns an AssistRankerPrediction integer value.
     private native int nativeRunInference(long nativeContextualSearchRankerLoggerImpl);
     private native void nativeWriteLogAndReset(long nativeContextualSearchRankerLoggerImpl);
+    private native boolean nativeIsQueryEnabled(long nativeContextualSearchRankerLoggerImpl);
 }

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchSelectionController.java

@@ -10,7 +10,6 @@ import android.text.TextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.ChromeActivity;
-import org.chromium.chrome.browser.ChromeFeatureList;
 import org.chromium.chrome.browser.compositor.bottombar.OverlayPanel;
 import org.chromium.chrome.browser.preferences.PrefServiceBridge;
 import org.chromium.chrome.browser.tab.Tab;
@@ -380,7 +379,7 @@ public class ContextualSearchSelectionController {
 
         // Make sure Tap Suppression features are consistent.
         assert !ContextualSearchFieldTrial.isContextualSearchMlTapSuppressionEnabled()
-                || ChromeFeatureList.isEnabled(ChromeFeatureList.CONTEXTUAL_SEARCH_RANKER_QUERY)
+                || rankerLogger.isQueryEnabled()
             : "Tap Suppression requires the Ranker Query feature to be enabled!";
 
         // If we're suppressing based on heuristics then Ranker doesn't need to know about it.

chrome/browser/android/chrome_feature_list.cc

@@ -85,7 +85,6 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &kContentSuggestionsSettings,
     &kContentSuggestionsThumbnailDominantColor,
     &kContextualSearchMlTapSuppression,
-    &kContextualSearchRankerQuery,
     &kContextualSearchSecondTap,
     &kContextualSuggestionsCarousel,
     &kCustomContextMenu,
@@ -251,9 +250,6 @@ const base::Feature kContentSuggestionsThumbnailDominantColor{
 const base::Feature kContextualSearchMlTapSuppression{
     "ContextualSearchMlTapSuppression", base::FEATURE_DISABLED_BY_DEFAULT};
 
-const base::Feature kContextualSearchRankerQuery{
-    "ContextualSearchRankerQuery", base::FEATURE_DISABLED_BY_DEFAULT};
-
 const base::Feature kContextualSearchSecondTap{
     "ContextualSearchSecondTap", base::FEATURE_DISABLED_BY_DEFAULT};
 

chrome/browser/android/chrome_feature_list.h

@@ -44,7 +44,6 @@ extern const base::Feature kContentSuggestionsScrollToLoad;
 extern const base::Feature kContentSuggestionsSettings;
 extern const base::Feature kContentSuggestionsThumbnailDominantColor;
 extern const base::Feature kContextualSearchMlTapSuppression;
-extern const base::Feature kContextualSearchRankerQuery;
 extern const base::Feature kContextualSearchSecondTap;
 extern const base::Feature kContextualSuggestionsCarousel;
 extern const base::Feature kCustomContextMenu;

chrome/browser/android/contextualsearch/contextual_search_ranker_logger_impl.cc

@@ -7,23 +7,18 @@
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
 #include "base/feature_list.h"
-#include "base/metrics/field_trial_params.h"
 #include "base/metrics/histogram_functions.h"
-#include "base/metrics/metrics_hashes.h"
-#include "base/strings/stringprintf.h"
 #include "chrome/browser/android/chrome_feature_list.h"
 #include "chrome/browser/assist_ranker/assist_ranker_service_factory.h"
 #include "chrome/browser/browser_process.h"
 #include "components/assist_ranker/assist_ranker_service_impl.h"
 #include "components/assist_ranker/binary_classifier_predictor.h"
+#include "components/assist_ranker/predictor_config_definitions.h"
 #include "components/assist_ranker/proto/ranker_example.pb.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/ukm/content/source_url_recorder.h"
 #include "content/public/browser/web_contents.h"
 #include "jni/ContextualSearchRankerLoggerImpl_jni.h"
-#include "services/metrics/public/cpp/ukm_entry_builder.h"
-#include "services/metrics/public/cpp/ukm_recorder.h"
-#include "url/gurl.h"
 
 namespace content {
 class BrowserContext;
@@ -31,111 +26,61 @@ class BrowserContext;
 
 namespace {
 
-const char kContextualSearchRankerModelUrlParamName[] =
-    "contextual-search-ranker-model-url";
-const char kContextualSearchModelFilename[] = "contextual_search_model";
-const char kContextualSearchUmaPrefix[] = "Search.ContextualSearch.Ranker";
-
 const char kContextualSearchRankerDidPredict[] = "OutcomeRankerDidPredict";
 const char kContextualSearchRankerPrediction[] = "OutcomeRankerPrediction";
 
-const base::FeatureParam<std::string> kModelUrl{
-    &chrome::android::kContextualSearchRankerQuery,
-    kContextualSearchRankerModelUrlParamName, ""};
-
-// TODO(donnd, hamelphi): move hex-hash-string to Ranker.
-std::string HexHashFeatureName(const std::string& feature_name) {
-  uint64_t feature_key = base::HashMetricName(feature_name);
-  return base::StringPrintf("%016" PRIx64, feature_key);
-}
-
 }  // namespace
 
 ContextualSearchRankerLoggerImpl::ContextualSearchRankerLoggerImpl(JNIEnv* env,
                                                                    jobject obj)
-    : source_id_(ukm::kInvalidSourceId),
-      builder_(nullptr),
-      predictor_(nullptr),
-      browser_context_(nullptr),
-      ranker_example_(nullptr),
-      has_predicted_decision_(false),
-      java_object_(nullptr) {
-  java_object_.Reset(env, obj);
-}
+    : java_object_(env, obj) {}
 
-ContextualSearchRankerLoggerImpl::~ContextualSearchRankerLoggerImpl() {
-  java_object_ = nullptr;
-}
+ContextualSearchRankerLoggerImpl::~ContextualSearchRankerLoggerImpl() {}
 
 void ContextualSearchRankerLoggerImpl::SetupLoggingAndRanker(
     JNIEnv* env,
     jobject obj,
     const base::android::JavaParamRef<jobject>& java_web_contents) {
-  content::WebContents* web_contents =
-      content::WebContents::FromJavaWebContents(java_web_contents);
-  if (!web_contents)
+  web_contents_ = content::WebContents::FromJavaWebContents(java_web_contents);
+  if (!web_contents_)
     return;
 
-  source_id_ = ukm::GetSourceIdForWebContentsDocument(web_contents);
-  ResetUkmEntry();
-
-  if (IsRankerQueryEnabled()) {
-    SetupRankerPredictor(web_contents);
+  SetupRankerPredictor();
   // Start building example data based on features to be gathered and logged.
-    ranker_example_.reset(new assist_ranker::RankerExample());
-  } else {
-    // TODO(donnd): remove when behind-the-flag bug fixed (crbug.com/786589).
-    VLOG(1) << "SetupLoggingAndRanker got IsRankerQueryEnabled false.";
-  }
+  ranker_example_ = std::make_unique<assist_ranker::RankerExample>();
 }
 
-void ContextualSearchRankerLoggerImpl::ResetUkmEntry() {
-  // Releasing the old entry triggers logging.
-  builder_ =
-      ukm::UkmRecorder::Get()->GetEntryBuilder(source_id_, "ContextualSearch");
-}
-
-void ContextualSearchRankerLoggerImpl::SetupRankerPredictor(
-    content::WebContents* web_contents) {
-  // Set up the Ranker predictor.
-  if (IsRankerQueryEnabled()) {
+void ContextualSearchRankerLoggerImpl::SetupRankerPredictor() {
   // Create one predictor for the current BrowserContext.
-    content::BrowserContext* browser_context =
-        web_contents->GetBrowserContext();
-    if (browser_context == browser_context_)
+  if (browser_context_) {
+    DCHECK(browser_context_ == web_contents_->GetBrowserContext());
     return;
+  }
+  browser_context_ = web_contents_->GetBrowserContext();
 
-    browser_context_ = browser_context;
   assist_ranker::AssistRankerService* assist_ranker_service =
       assist_ranker::AssistRankerServiceFactory::GetForBrowserContext(
-            browser_context);
-    DCHECK(assist_ranker_service);
-    std::string model_string(kModelUrl.Get());
-    DCHECK(model_string.size());
-    // TODO(donnd): remove when behind-the-flag bug fixed (crbug.com/786589).
-    VLOG(0) << "Model URL: " << model_string;
+          browser_context_);
+  if (assist_ranker_service) {
     predictor_ = assist_ranker_service->FetchBinaryClassifierPredictor(
-        GURL(model_string), kContextualSearchModelFilename,
-        kContextualSearchUmaPrefix);
-    DCHECK(predictor_);
+        assist_ranker::GetContextualSearchPredictorConfig());
   }
 }
 
+void ContextualSearchRankerLoggerImpl::LogFeature(
+    const std::string& feature_name,
+    int value) {
+  auto& features = *ranker_example_->mutable_features();
+  features[feature_name].set_int32_value(value);
+}
+
 void ContextualSearchRankerLoggerImpl::LogLong(
     JNIEnv* env,
     jobject obj,
     const base::android::JavaParamRef<jstring>& j_feature,
     jlong j_long) {
   std::string feature = base::android::ConvertJavaStringToUTF8(env, j_feature);
-  if (builder_)
-    builder_->AddMetric(feature.c_str(), j_long);
-
-  // Also write to Ranker if we're logging data needed to predict a decision.
-  if (IsRankerQueryEnabled() && !has_predicted_decision_) {
-    std::string hex_feature_key(HexHashFeatureName(feature));
-    auto& features = *ranker_example_->mutable_features();
-    features[hex_feature_key].set_int32_value(j_long);
-  }
+  LogFeature(feature, j_long);
 }
 
 AssistRankerPrediction ContextualSearchRankerLoggerImpl::RunInference(
@@ -144,19 +89,17 @@ AssistRankerPrediction ContextualSearchRankerLoggerImpl::RunInference(
   has_predicted_decision_ = true;
   bool prediction = false;
   bool was_able_to_predict = false;
-  if (IsRankerQueryEnabled()) {
+  if (IsQueryEnabledInternal()) {
     was_able_to_predict = predictor_->Predict(*ranker_example_, &prediction);
     // Log to UMA whether we were able to predict or not.
     base::UmaHistogramBoolean("Search.ContextualSearchRankerWasAbleToPredict",
                               was_able_to_predict);
-    // Log the Ranker decision to UKM, including whether we were able to make
-    // any prediction.
-    if (builder_) {
-      builder_->AddMetric(kContextualSearchRankerDidPredict,
-                          was_able_to_predict);
+    // TODO(chrome-ranker-team): this should be logged internally by Ranker.
+    LogFeature(kContextualSearchRankerDidPredict,
+               static_cast<int>(was_able_to_predict));
     if (was_able_to_predict) {
-        builder_->AddMetric(kContextualSearchRankerPrediction, prediction);
-      }
+      LogFeature(kContextualSearchRankerPrediction,
+                 static_cast<int>(prediction));
     }
   }
   AssistRankerPrediction prediction_enum;
@@ -170,21 +113,28 @@ AssistRankerPrediction ContextualSearchRankerLoggerImpl::RunInference(
     prediction_enum = ASSIST_RANKER_PREDICTION_UNAVAILABLE;
   }
   // TODO(donnd): remove when behind-the-flag bug fixed (crbug.com/786589).
-  VLOG(0) << "prediction: " << prediction_enum;
+  DVLOG(0) << "prediction: " << prediction_enum;
   return prediction_enum;
 }
 
 void ContextualSearchRankerLoggerImpl::WriteLogAndReset(JNIEnv* env,
                                                         jobject obj) {
+  if (predictor_ && ranker_example_) {
+    ukm::SourceId source_id =
+        ukm::GetSourceIdForWebContentsDocument(web_contents_);
+    predictor_->LogExampleToUkm(*ranker_example_.get(), source_id);
+  }
   has_predicted_decision_ = false;
-  // Set up another builder for the next record (in case it's needed).
-  ResetUkmEntry();
-  ranker_example_.reset();
+  ranker_example_ = std::make_unique<assist_ranker::RankerExample>();
+}
+
+bool ContextualSearchRankerLoggerImpl::IsQueryEnabled(JNIEnv* env,
+                                                      jobject obj) {
+  return IsQueryEnabledInternal();
 }
 
-bool ContextualSearchRankerLoggerImpl::IsRankerQueryEnabled() {
-  return base::FeatureList::IsEnabled(
-      chrome::android::kContextualSearchRankerQuery);
+bool ContextualSearchRankerLoggerImpl::IsQueryEnabledInternal() {
+  return predictor_ && predictor_->is_query_enabled();
 }
 
 // Java wrapper boilerplate

chrome/browser/android/contextualsearch/contextual_search_ranker_logger_impl.h

@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_ANDROID_CONTEXTUALSEARCH_CONTEXTUAL_SEARCH_RANKER_LOGGER_IMPL_H_
 
 #include "base/android/jni_android.h"
+#include "base/memory/weak_ptr.h"
 
 namespace content {
 class BrowserContext;
@@ -17,10 +18,6 @@ class BinaryClassifierPredictor;
 class RankerExample;
 }  // namespace assist_ranker
 
-namespace ukm {
-class UkmEntryBuilder;
-}  // namespace ukm
-
 // A Java counterpart will be generated for this enum.
 // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.chrome.browser.contextualsearch
 enum AssistRankerPrediction {
@@ -65,28 +62,30 @@ class ContextualSearchRankerLoggerImpl {
   // ready to start logging the next set of data.
   void WriteLogAndReset(JNIEnv* env, jobject obj);
 
- private:
-  // Log the current UKM entry (if any) and start a new one.
-  // TODO(donnd): write a test using TestAutoSetUkmRecorder.
-  void ResetUkmEntry();
+  // Returns whether or not AssistRanker query is enabled.
+  bool IsQueryEnabled(JNIEnv* env, jobject obj);
 
-  // Sets up the Ranker Predictor for the given |web_contents|.
-  void SetupRankerPredictor(content::WebContents* web_contents);
+ private:
+  // Returns whether or not AssistRanker query is enabled.
+  bool IsQueryEnabledInternal();
 
-  // Whether querying Ranker for model loading and prediction is enabled.
-  bool IsRankerQueryEnabled();
+  // Adds feature to the RankerExample.
+  void LogFeature(const std::string& feature_name, int value);
 
-  // The UKM source ID being used for this session.
-  int32_t source_id_;
+  // Sets up the Ranker Predictor for the given |web_contents|.
+  void SetupRankerPredictor();
 
-  // The entry builder for the current record, or nullptr if not yet configured.
-  std::unique_ptr<ukm::UkmEntryBuilder> builder_;
+  // The WebContents object used to produce the source_id for UKMs, and to get
+  // browser_context when fetching the predictor. The object is not owned by
+  // ContextualSearchRankerLoggerImpl.
+  content::WebContents* web_contents_ = nullptr;
 
   // The Ranker Predictor for whether a tap gesture should be suppressed or not.
-  std::unique_ptr<assist_ranker::BinaryClassifierPredictor> predictor_;
+  base::WeakPtr<assist_ranker::BinaryClassifierPredictor> predictor_;
 
   // The |BrowserContext| currently associated with the above predictor.
-  content::BrowserContext* browser_context_;
+  // The object not owned by ContextualSearchRankerLoggerImpl.
+  content::BrowserContext* browser_context_ = nullptr;
 
   // The current RankerExample or null.
   // Set of features from one example of a Tap to predict a suppression
@@ -94,7 +93,7 @@ class ContextualSearchRankerLoggerImpl {
   std::unique_ptr<assist_ranker::RankerExample> ranker_example_;
 
   // Whether Ranker has predicted the decision yet.
-  bool has_predicted_decision_;
+  bool has_predicted_decision_ = false;
 
   // The linked Java object.
   base::android::ScopedJavaGlobalRef<jobject> java_object_;

components/assist_ranker/BUILD.gn

@@ -15,6 +15,10 @@ static_library("assist_ranker") {
     "fake_ranker_model_loader.h",
     "generic_logistic_regression_inference.cc",
     "generic_logistic_regression_inference.h",
+    "predictor_config.cc",
+    "predictor_config.h",
+    "predictor_config_definitions.cc",
+    "predictor_config_definitions.h",
     "ranker_example_util.cc",
     "ranker_example_util.h",
     "ranker_model.cc",
@@ -32,6 +36,7 @@ static_library("assist_ranker") {
     "//components/data_use_measurement/core",
     "//components/keyed_service/core",
     "//net",
+    "//services/metrics/public/cpp:metrics_cpp",
     "//url",
   ]
 }
@@ -40,6 +45,7 @@ source_set("unit_tests") {
   testonly = true
 
   sources = [
+    "base_predictor_unittest.cc",
     "binary_classifier_predictor_unittest.cc",
     "generic_logistic_regression_inference_unittest.cc",
     "ranker_example_util_unittest.cc",
@@ -51,6 +57,7 @@ source_set("unit_tests") {
     ":assist_ranker",
     "//base",
     "//components/assist_ranker/proto",
+    "//components/ukm:test_support",
     "//net:test_support",
     "//testing/gtest",
   ]

components/assist_ranker/DEPS

@@ -2,5 +2,7 @@ include_rules = [
   "+components/data_use_measurement/core",
   "+components/keyed_service/core",
   "+components/metrics",
+  "+components/ukm",
   "+net",
+  "+services/metrics/public",
 ]
\ No newline at end of file

components/assist_ranker/assist_ranker_service.h

@@ -9,32 +9,25 @@
 #include <string>
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "components/keyed_service/core/keyed_service.h"
 
-class GURL;
-
 namespace assist_ranker {
 
 class BinaryClassifierPredictor;
+struct PredictorConfig;
 
-// TODO(crbug.com/778468) : Refactor this so that the service owns the predictor
-// objects and enforce model uniqueness through internal registration in order
-// to avoid cache collisions.
-//
 // Service that provides Predictor objects.
 class AssistRankerService : public KeyedService {
  public:
   AssistRankerService() = default;
 
-  // Returns a binary classification model. |model_filename| is the filename of
-  // the cached model. It should be unique to this predictor to avoid cache
-  // collision. |model_url| represents a unique ID for the desired model (see
-  // ranker_model_loader.h for more details). |uma_prefix| is used to log
-  // histograms related to the loading of the model.
-  virtual std::unique_ptr<BinaryClassifierPredictor>
-  FetchBinaryClassifierPredictor(GURL model_url,
-                                 const std::string& model_filename,
-                                 const std::string& uma_prefix) = 0;
+  // Returns a binary classification model given a PredictorConfig.
+  // The predictor is instantiated the first time a predictor is fetched. The
+  // next calls to fetch will return a pointer to the already instantiated
+  // predictor.
+  virtual base::WeakPtr<BinaryClassifierPredictor>
+  FetchBinaryClassifierPredictor(const PredictorConfig& config) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AssistRankerService);

components/assist_ranker/assist_ranker_service_impl.cc

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 #include "components/assist_ranker/assist_ranker_service_impl.h"
-
+#include "base/memory/weak_ptr.h"
 #include "components/assist_ranker/binary_classifier_predictor.h"
 #include "components/assist_ranker/ranker_model_loader_impl.h"
 #include "net/url_request/url_request_context_getter.h"
@@ -19,15 +19,27 @@ AssistRankerServiceImpl::AssistRankerServiceImpl(
 
 AssistRankerServiceImpl::~AssistRankerServiceImpl() {}
 
-std::unique_ptr<BinaryClassifierPredictor>
+base::WeakPtr<BinaryClassifierPredictor>
 AssistRankerServiceImpl::FetchBinaryClassifierPredictor(
-    GURL model_url,
-    const std::string& model_filename,
-    const std::string& uma_prefix) {
+    const PredictorConfig& config) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  return BinaryClassifierPredictor::Create(url_request_context_getter_.get(),
-                                           GetModelPath(model_filename),
-                                           model_url, uma_prefix);
+  const std::string& model_name = config.model_name;
+  auto predictor_it = predictor_map_.find(model_name);
+  if (predictor_it != predictor_map_.end()) {
+    DVLOG(1) << "Predictor " << model_name << " already initialized.";
+    return base::AsWeakPtr(
+        static_cast<BinaryClassifierPredictor*>(predictor_it->second.get()));
+  }
+
+  // The predictor does not exist yet, so we create one.
+  DVLOG(1) << "Initializing predictor: " << model_name;
+  std::unique_ptr<BinaryClassifierPredictor> predictor =
+      BinaryClassifierPredictor::Create(config, GetModelPath(model_name),
+                                        url_request_context_getter_.get());
+  base::WeakPtr<BinaryClassifierPredictor> weak_ptr =
+      base::AsWeakPtr(predictor.get());
+  predictor_map_[model_name] = std::move(predictor);
+  return weak_ptr;
 }
 
 base::FilePath AssistRankerServiceImpl::GetModelPath(

components/assist_ranker/assist_ranker_service_impl.h

@@ -7,13 +7,13 @@
 
 #include <memory>
 #include <string>
+#include <unordered_map>
 
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/sequence_checker.h"
 #include "components/assist_ranker/assist_ranker_service.h"
-
-class GURL;
+#include "components/assist_ranker/predictor_config.h"
 
 namespace net {
 class URLRequestContextGetter;
@@ -21,6 +21,7 @@ class URLRequestContextGetter;
 
 namespace assist_ranker {
 
+class BasePredictor;
 class BinaryClassifierPredictor;
 
 class AssistRankerServiceImpl : public AssistRankerService {
@@ -31,10 +32,8 @@ class AssistRankerServiceImpl : public AssistRankerService {
   ~AssistRankerServiceImpl() override;
 
   // AssistRankerService...
-  std::unique_ptr<BinaryClassifierPredictor> FetchBinaryClassifierPredictor(
-      GURL model_url,
-      const std::string& model_filename,
-      const std::string& uma_prefix) override;
+  base::WeakPtr<BinaryClassifierPredictor> FetchBinaryClassifierPredictor(
+      const PredictorConfig& config) override;
 
  private:
   // Returns the full path to the model cache.
@@ -46,6 +45,9 @@ class AssistRankerServiceImpl : public AssistRankerService {
   // Base path where models are stored.
   const base::FilePath base_path_;
 
+  std::unordered_map<std::string, std::unique_ptr<BasePredictor>>
+      predictor_map_;
+
   SEQUENCE_CHECKER(sequence_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(AssistRankerServiceImpl);

components/assist_ranker/base_predictor.cc

@@ -4,23 +4,40 @@
 
 #include "components/assist_ranker/base_predictor.h"
 
+#include "base/feature_list.h"
 #include "base/memory/ptr_util.h"
+#include "components/assist_ranker/proto/ranker_example.pb.h"
 #include "components/assist_ranker/proto/ranker_model.pb.h"
+#include "components/assist_ranker/ranker_example_util.h"
 #include "components/assist_ranker/ranker_model.h"
+#include "services/metrics/public/cpp/ukm_entry_builder.h"
+#include "services/metrics/public/cpp/ukm_recorder.h"
+#include "url/gurl.h"
 
 namespace assist_ranker {
 
-BasePredictor::BasePredictor() {}
+BasePredictor::BasePredictor(const PredictorConfig& config) : config_(config) {
+  // TODO(chrome-ranker-team): validate config.
+  if (config_.field_trial) {
+    is_query_enabled_ = base::FeatureList::IsEnabled(*config_.field_trial);
+  } else {
+    DVLOG(0) << "No field trial specified";
+  }
+}
+
 BasePredictor::~BasePredictor() {}
 
 void BasePredictor::LoadModel(std::unique_ptr<RankerModelLoader> model_loader) {
+  if (!is_query_enabled_)
+    return;
+
   if (model_loader_) {
-    DLOG(ERROR) << "This predictor already has a model loader.";
+    DVLOG(0) << "This predictor already has a model loader.";
     return;
   }
   // Take ownership of the model loader.
   model_loader_ = std::move(model_loader);
-  // Kick off the initial load from cache.
+  // Kick off the initial model load.
   model_loader_->NotifyOfRankerActivity();
 }
 
@@ -31,10 +48,80 @@ void BasePredictor::OnModelAvailable(
 }
 
 bool BasePredictor::IsReady() {
-  if (!is_ready_)
+  if (!is_ready_ && model_loader_)
     model_loader_->NotifyOfRankerActivity();
 
   return is_ready_;
 }
 
+void BasePredictor::LogFeatureToUkm(const std::string& feature_name,
+                                    const Feature& feature,
+                                    ukm::UkmEntryBuilder* ukm_builder) {
+  if (!ukm_builder) {
+    return;
+  }
+
+  if (!base::ContainsKey(*config_.feature_whitelist, feature_name)) {
+    DVLOG(1) << "Feature not whitelisted: " << feature_name;
+    return;
+  }
+
+  int feature_int_value;
+  if (FeatureToInt(feature, &feature_int_value)) {
+    DVLOG(3) << "Logging: " << feature_name << ": " << feature_int_value;
+    ukm_builder->AddMetric(feature_name.c_str(), feature_int_value);
+  } else {
+    DVLOG(0) << "Could not convert feature to int: " << feature_name;
+  }
+}
+
+void BasePredictor::LogExampleToUkm(const RankerExample& example,
+                                    ukm::SourceId source_id) {
+  if (config_.log_type != LOG_UKM) {
+    DVLOG(0) << "Wrong log type in predictor config: " << config_.log_type;
+    return;
+  }
+
+  if (!config_.feature_whitelist) {
+    DVLOG(0) << "No whitelist specified.";
+    return;
+  }
+  if (config_.feature_whitelist->empty()) {
+    DVLOG(0) << "Empty whitelist, examples will not be logged.";
+    return;
+  }
+
+  // Releasing the builder will trigger logging.
+  std::unique_ptr<ukm::UkmEntryBuilder> builder =
+      ukm::UkmRecorder::Get()->GetEntryBuilder(source_id, config_.logging_name);
+  if (builder) {
+    for (const auto& feature_kv : example.features()) {
+      LogFeatureToUkm(feature_kv.first, feature_kv.second, builder.get());
+    }
+  } else {
+    DVLOG(0) << "Could not get UKM Entry Builder.";
+  }
+}
+
+std::string BasePredictor::GetModelName() const {
+  return config_.model_name;
+}
+
+GURL BasePredictor::GetModelUrl() const {
+  if (!config_.field_trial_url_param) {
+    DVLOG(1) << "No URL specified.";
+    return GURL();
+  }
+
+  return GURL(config_.field_trial_url_param->Get());
+}
+
+RankerExample BasePredictor::PreprocessExample(const RankerExample& example) {
+  if (ranker_model_->proto().has_metadata() &&
+      ranker_model_->proto().metadata().input_features_names_are_hex_hashes()) {
+    return HashExampleFeatureNames(example);
+  }
+  return example;
+}
+
 }  // namespace assist_ranker

components/assist_ranker/base_predictor.h

@@ -9,30 +9,53 @@
 #include <string>
 
 #include "base/files/file_path.h"
+#include "base/memory/weak_ptr.h"
+#include "components/assist_ranker/predictor_config.h"
 #include "components/assist_ranker/ranker_model_loader.h"
+#include "services/metrics/public/cpp/ukm_source_id.h"
+
+class GURL;
+
+namespace ukm {
+class UkmEntryBuilder;
+}
 
 namespace assist_ranker {
 
+class Feature;
+class RankerExample;
 class RankerModel;
 
 // Predictors are objects that provide an interface for prediction, as well as
-// encapsulate the logic for loading the model. Sub-classes of BasePredictor
-// implement an interface that depends on the nature of the suported model.
-// Subclasses of BasePredictor will also need to implement an Initialize method
-// that will be called once the model is available, and a static validation
-// function with the following signature:
+// encapsulate the logic for loading the model and logging. Sub-classes of
+// BasePredictor implement an interface that depends on the nature of the
+// suported model. Subclasses of BasePredictor will also need to implement an
+// Initialize method that will be called once the model is available, and a
+// static validation function with the following signature:
 //
 // static RankerModelStatus ValidateModel(const RankerModel& model);
-class BasePredictor {
+class BasePredictor : public base::SupportsWeakPtr<BasePredictor> {
  public:
-  BasePredictor();
+  BasePredictor(const PredictorConfig& config);
   virtual ~BasePredictor();
 
+  // Returns true if the predictor is ready to make predictions.
   bool IsReady();
+  // Returns true if the base::Feature associated with this model is enabled.
+  bool is_query_enabled() const { return is_query_enabled_; }
+
+  // Logs the features of |example| to UKM using the given source_id.
+  void LogExampleToUkm(const RankerExample& example, ukm::SourceId source_id);
+
+  // Returns the model URL.
+  GURL GetModelUrl() const;
+  // Returns the model name.
+  std::string GetModelName() const;
 
  protected:
-  // The model used for prediction.
-  std::unique_ptr<RankerModel> ranker_model_;
+  // Preprocessing applied to an example before prediction. The original
+  // RankerExample is not modified, so it is safe to use it later for logging.
+  RankerExample PreprocessExample(const RankerExample& example);
 
   // Called when the RankerModelLoader has finished loading the model. Returns
   // true only if the model was succesfully loaded and is ready to predict.
@@ -43,9 +66,17 @@ class BasePredictor {
   // Called once the model loader as succesfully loaded the model.
   void OnModelAvailable(std::unique_ptr<RankerModel> model);
   std::unique_ptr<RankerModelLoader> model_loader_;
+  // The model used for prediction.
+  std::unique_ptr<RankerModel> ranker_model_;
 
  private:
+  void LogFeatureToUkm(const std::string& feature_name,
+                       const Feature& feature,
+                       ukm::UkmEntryBuilder* ukm_builder);
+
   bool is_ready_ = false;
+  bool is_query_enabled_ = false;
+  PredictorConfig config_;
 
   DISALLOW_COPY_AND_ASSIGN(BasePredictor);
 };

components/assist_ranker/base_predictor_unittest.cc

+// Copyright 2017 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/assist_ranker/base_predictor.h"
+
+#include <memory>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/memory/ptr_util.h"
+#include "base/test/scoped_feature_list.h"
+#include "base/test/scoped_task_environment.h"
+#include "components/assist_ranker/fake_ranker_model_loader.h"
+#include "components/assist_ranker/predictor_config.h"
+#include "components/assist_ranker/proto/ranker_example.pb.h"
+#include "components/assist_ranker/ranker_model.h"
+#include "components/ukm/test_ukm_recorder.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+namespace assist_ranker {
+
+using ::assist_ranker::testing::FakeRankerModelLoader;
+
+namespace {
+
+// Predictor config for testing.
+const char kTestModelName[] = "test_model";
+const char kTestLoggingName[] = "TestLoggingName";
+const char kTestUmaPrefixName[] = "Test.Ranker";
+const char kTestUrlParamName[] = "ranker-model-url";
+const char kTestDefaultModelUrl[] = "https://foo.bar/model.bin";
+
+const char kBoolFeature[] = "bool_feature";
+const char kIntFeature[] = "int_feature";
+const char kFloatFeature[] = "float_feature";
+const char kStringFeature[] = "string_feature";
+const char kFeatureNotWhitelisted[] = "not_whitelisted";
+
+const char kTestNavigationUrl[] = "https://foo.com";
+
+const base::flat_set<std::string> kFeatureWhitelist({kBoolFeature, kIntFeature,
+                                                     kFloatFeature,
+                                                     kStringFeature});
+
+const base::Feature kTestRankerQuery{"TestRankerQuery",
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
+
+const base::FeatureParam<std::string> kTestRankerUrl{
+    &kTestRankerQuery, kTestUrlParamName, kTestDefaultModelUrl};
+
+const PredictorConfig kTestPredictorConfig = PredictorConfig{
+    kTestModelName,     kTestLoggingName,  kTestUmaPrefixName, LOG_UKM,
+    &kFeatureWhitelist, &kTestRankerQuery, &kTestRankerUrl};
+
+// Class that implements virtual functions of the base class.
+class FakePredictor : public BasePredictor {
+ public:
+  static std::unique_ptr<FakePredictor> Create();
+  ~FakePredictor() override{};
+  // Validation will always succeed.
+  static RankerModelStatus ValidateModel(const RankerModel& model);
+
+ protected:
+  // Not implementing any inference logic.
+  bool Initialize() override { return true; };
+
+ private:
+  FakePredictor(const PredictorConfig& config);
+  DISALLOW_COPY_AND_ASSIGN(FakePredictor);
+};
+
+FakePredictor::FakePredictor(const PredictorConfig& config)
+    : BasePredictor(config) {}
+
+RankerModelStatus FakePredictor::ValidateModel(const RankerModel& model) {
+  return RankerModelStatus::OK;
+}
+
+std::unique_ptr<FakePredictor> FakePredictor::Create() {
+  std::unique_ptr<FakePredictor> predictor(
+      new FakePredictor(kTestPredictorConfig));
+  auto ranker_model = base::MakeUnique<RankerModel>();
+  auto fake_model_loader = base::MakeUnique<FakeRankerModelLoader>(
+      base::BindRepeating(&FakePredictor::ValidateModel),
+      base::BindRepeating(&FakePredictor::OnModelAvailable,
+                          base::Unretained(predictor.get())),
+      std::move(ranker_model));
+  predictor->LoadModel(std::move(fake_model_loader));
+  return predictor;
+}
+
+}  // namespace
+
+class BasePredictorTest : public ::testing::Test {
+ protected:
+  BasePredictorTest() = default;
+  // Disables Query for the test predictor.
+  void DisableQuery();
+
+  ukm::SourceId GetSourceId();
+
+  ukm::TestUkmRecorder* GetTestUkmRecorder() { return &test_ukm_recorder_; }
+
+ private:
+  // Sets up the task scheduling/task-runner environment for each test.
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
+
+  // Sets itself as the global UkmRecorder on construction.
+  ukm::TestAutoSetUkmRecorder test_ukm_recorder_;
+
+  // Manages the enabling/disabling of features within the scope of a test.
+  base::test::ScopedFeatureList scoped_feature_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(BasePredictorTest);
+};
+
+ukm::SourceId BasePredictorTest::GetSourceId() {
+  ukm::SourceId source_id = ukm::UkmRecorder::GetNewSourceID();
+  test_ukm_recorder_.UpdateSourceURL(source_id, GURL(kTestNavigationUrl));
+  return source_id;
+}
+
+void BasePredictorTest::DisableQuery() {
+  scoped_feature_list_.InitWithFeatures({}, {kTestRankerQuery});
+}
+
+TEST_F(BasePredictorTest, BaseTest) {
+  auto predictor = FakePredictor::Create();
+  EXPECT_EQ(kTestModelName, predictor->GetModelName());
+  EXPECT_EQ(kTestDefaultModelUrl, predictor->GetModelUrl());
+  EXPECT_TRUE(predictor->is_query_enabled());
+  EXPECT_TRUE(predictor->IsReady());
+}
+
+TEST_F(BasePredictorTest, QueryDisabled) {
+  DisableQuery();
+  auto predictor = FakePredictor::Create();
+  EXPECT_EQ(kTestModelName, predictor->GetModelName());
+  EXPECT_EQ(kTestDefaultModelUrl, predictor->GetModelUrl());
+  EXPECT_FALSE(predictor->is_query_enabled());
+  EXPECT_FALSE(predictor->IsReady());
+}
+
+TEST_F(BasePredictorTest, LogExampleToUkm) {
+  auto predictor = FakePredictor::Create();
+  RankerExample example;
+  auto& features = *example.mutable_features();
+  features[kBoolFeature].set_bool_value(true);
+  features[kIntFeature].set_int32_value(42);
+  features[kFloatFeature].set_float_value(42.0f);
+  features[kStringFeature].set_string_value("42");
+  // This feature will not be logged.
+  features[kFeatureNotWhitelisted].set_bool_value(false);
+
+  predictor->LogExampleToUkm(example, GetSourceId());
+
+  EXPECT_EQ(1U, GetTestUkmRecorder()->sources_count());
+  EXPECT_EQ(1U, GetTestUkmRecorder()->entries_count());
+  std::vector<const ukm::mojom::UkmEntry*> entries =
+      GetTestUkmRecorder()->GetEntriesByName(kTestLoggingName);
+  EXPECT_EQ(1U, entries.size());
+  GetTestUkmRecorder()->ExpectEntryMetric(entries[0], kBoolFeature, 1);
+  GetTestUkmRecorder()->ExpectEntryMetric(entries[0], kIntFeature, 42);
+  // TODO(crbug.com/794187) Float and string features are not logged yet.
+  EXPECT_FALSE(GetTestUkmRecorder()->EntryHasMetric(entries[0], kFloatFeature));
+  EXPECT_FALSE(
+      GetTestUkmRecorder()->EntryHasMetric(entries[0], kStringFeature));
+  EXPECT_FALSE(
+      GetTestUkmRecorder()->EntryHasMetric(entries[0], kFeatureNotWhitelisted));
+}
+
+}  // namespace assist_ranker

components/assist_ranker/binary_classifier_predictor.cc

@@ -15,26 +15,33 @@
 #include "components/assist_ranker/ranker_model.h"
 #include "components/assist_ranker/ranker_model_loader_impl.h"
 #include "net/url_request/url_request_context_getter.h"
-#include "url/gurl.h"
 
 namespace assist_ranker {
 
-BinaryClassifierPredictor::BinaryClassifierPredictor(){};
+BinaryClassifierPredictor::BinaryClassifierPredictor(
+    const PredictorConfig& config)
+    : BasePredictor(config){};
 BinaryClassifierPredictor::~BinaryClassifierPredictor(){};
 
 // static
 std::unique_ptr<BinaryClassifierPredictor> BinaryClassifierPredictor::Create(
-    net::URLRequestContextGetter* request_context_getter,
+    const PredictorConfig& config,
     const base::FilePath& model_path,
-    GURL model_url,
-    const std::string& uma_prefix) {
+    net::URLRequestContextGetter* request_context_getter) {
   std::unique_ptr<BinaryClassifierPredictor> predictor(
-      new BinaryClassifierPredictor());
+      new BinaryClassifierPredictor(config));
+  if (!predictor->is_query_enabled()) {
+    DVLOG(1) << "Query disabled, bypassing model loading.";
+    return predictor;
+  }
+  const GURL& model_url = predictor->GetModelUrl();
+  DVLOG(1) << "Creating predictor instance for " << predictor->GetModelName();
+  DVLOG(1) << "Model URL: " << model_url;
   auto model_loader = base::MakeUnique<RankerModelLoaderImpl>(
-      base::Bind(&BinaryClassifierPredictor::ValidateModel),
-      base::Bind(&BinaryClassifierPredictor::OnModelAvailable,
+      base::BindRepeating(&BinaryClassifierPredictor::ValidateModel),
+      base::BindRepeating(&BinaryClassifierPredictor::OnModelAvailable,
                           base::Unretained(predictor.get())),
-      request_context_getter, model_path, model_url, uma_prefix);
+      request_context_getter, model_path, model_url, config.uma_prefix);
   predictor->LoadModel(std::move(model_loader));
   return predictor;
 }
@@ -42,18 +49,23 @@ std::unique_ptr<BinaryClassifierPredictor> BinaryClassifierPredictor::Create(
 bool BinaryClassifierPredictor::Predict(const RankerExample& example,
                                         bool* prediction) {
   if (!IsReady()) {
+    DVLOG(1) << "Predictor " << GetModelName() << " not ready for prediction.";
     return false;
   }
-  *prediction = inference_module_->Predict(example);
+
+  *prediction = inference_module_->Predict(PreprocessExample(example));
+  DVLOG(1) << "Predictor " << GetModelName() << " predicted: " << *prediction;
   return true;
 }
 
 bool BinaryClassifierPredictor::PredictScore(const RankerExample& example,
                                              float* prediction) {
   if (!IsReady()) {
+    DVLOG(1) << "Predictor " << GetModelName() << " not ready for prediction.";
     return false;
   }
-  *prediction = inference_module_->PredictScore(example);
+  *prediction = inference_module_->PredictScore(PreprocessExample(example));
+  DVLOG(1) << "Predictor " << GetModelName() << " predicted: " << prediction;
   return true;
 }
 
@@ -61,17 +73,22 @@ bool BinaryClassifierPredictor::PredictScore(const RankerExample& example,
 RankerModelStatus BinaryClassifierPredictor::ValidateModel(
     const RankerModel& model) {
   if (model.proto().model_case() != RankerModelProto::kLogisticRegression) {
+    DVLOG(0) << "Model is incompatible.";
     return RankerModelStatus::INCOMPATIBLE;
   }
   return RankerModelStatus::OK;
 }
 
 bool BinaryClassifierPredictor::Initialize() {
-  // TODO(hamelphi): move the GLRM proto up one layer in the proto in order to
-  // be independent of the client feature.
+  if (ranker_model_->proto().model_case() ==
+      RankerModelProto::kLogisticRegression) {
     inference_module_.reset(new GenericLogisticRegressionInference(
         ranker_model_->proto().logistic_regression()));
     return true;
+  }
+
+  DVLOG(0) << "Could not initialize inference module.";
+  return false;
 }
 
 }  // namespace assist_ranker

components/assist_ranker/binary_classifier_predictor.h

@@ -9,8 +9,6 @@
 #include "components/assist_ranker/base_predictor.h"
 #include "components/assist_ranker/proto/ranker_example.pb.h"
 
-class GURL;
-
 namespace base {
 class FilePath;
 }
@@ -28,11 +26,13 @@ class BinaryClassifierPredictor : public BasePredictor {
  public:
   ~BinaryClassifierPredictor() override;
 
+  // Returns an new predictor instance with the given |config| and initialize
+  // its model loader. The |request_context getter| is passed to the
+  // predictor's model_loader which holds it as scoped_refptr.
   static std::unique_ptr<BinaryClassifierPredictor> Create(
-      net::URLRequestContextGetter* request_context_getter,
+      const PredictorConfig& config,
       const base::FilePath& model_path,
-      GURL model_url,
-      const std::string& uma_prefix);
+      net::URLRequestContextGetter* request_context_getter) WARN_UNUSED_RESULT;
 
   // Fills in a boolean decision given a RankerExample. Returns false if a
   // prediction could not be made (e.g. the model is not loaded yet).
@@ -53,7 +53,7 @@ class BinaryClassifierPredictor : public BasePredictor {
 
  private:
   friend class BinaryClassifierPredictorTest;
-  BinaryClassifierPredictor();
+  BinaryClassifierPredictor(const PredictorConfig& config);
 
   // TODO(hamelphi): Use an abstract BinaryClassifierInferenceModule in order to
   // generalize to other models.

components/assist_ranker/binary_classifier_predictor_unittest.cc

@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/feature_list.h"
 #include "base/memory/ptr_util.h"
 #include "components/assist_ranker/fake_ranker_model_loader.h"
 #include "components/assist_ranker/proto/ranker_model.pb.h"
@@ -21,11 +22,14 @@ using ::assist_ranker::testing::FakeRankerModelLoader;
 class BinaryClassifierPredictorTest : public ::testing::Test {
  public:
   std::unique_ptr<BinaryClassifierPredictor> InitPredictor(
-      std::unique_ptr<RankerModel> ranker_model);
+      std::unique_ptr<RankerModel> ranker_model,
+      const PredictorConfig& config);
 
   // This model will return the value of |feature| as a prediction.
   GenericLogisticRegressionModel GetSimpleLogisticRegressionModel();
 
+  PredictorConfig GetConfig();
+
  protected:
   const std::string feature_ = "feature";
   const float threshold_ = 0.5;
@@ -33,10 +37,11 @@ class BinaryClassifierPredictorTest : public ::testing::Test {
 
 std::unique_ptr<BinaryClassifierPredictor>
 BinaryClassifierPredictorTest::InitPredictor(
-    std::unique_ptr<RankerModel> ranker_model) {
+    std::unique_ptr<RankerModel> ranker_model,
+    const PredictorConfig& config) {
   std::unique_ptr<BinaryClassifierPredictor> predictor(
-      new BinaryClassifierPredictor());
-  auto fake_model_loader = base::MakeUnique<FakeRankerModelLoader>(
+      new BinaryClassifierPredictor(config));
+  auto fake_model_loader = std::make_unique<FakeRankerModelLoader>(
       base::Bind(&BinaryClassifierPredictor::ValidateModel),
       base::Bind(&BinaryClassifierPredictor::OnModelAvailable,
                  base::Unretained(predictor.get())),
@@ -45,6 +50,20 @@ BinaryClassifierPredictorTest::InitPredictor(
   return predictor;
 }
 
+const base::Feature kTestRankerQuery{"TestRankerQuery",
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
+
+const base::FeatureParam<std::string> kTestRankerUrl{
+    &kTestRankerQuery, "url-param-name", "https://default.model.url"};
+
+PredictorConfig BinaryClassifierPredictorTest::GetConfig() {
+  PredictorConfig config("model_name", "logging_name", "uma_prefix", LOG_NONE,
+                         GetEmptyWhitelist(), &kTestRankerQuery,
+                         &kTestRankerUrl);
+
+  return config;
+}
+
 GenericLogisticRegressionModel
 BinaryClassifierPredictorTest::GetSimpleLogisticRegressionModel() {
   GenericLogisticRegressionModel lr_model;
@@ -58,7 +77,7 @@ BinaryClassifierPredictorTest::GetSimpleLogisticRegressionModel() {
 
 TEST_F(BinaryClassifierPredictorTest, EmptyRankerModel) {
   auto ranker_model = base::MakeUnique<RankerModel>();
-  auto predictor = InitPredictor(std::move(ranker_model));
+  auto predictor = InitPredictor(std::move(ranker_model), GetConfig());
   EXPECT_FALSE(predictor->IsReady());
 
   RankerExample ranker_example;
@@ -78,7 +97,7 @@ TEST_F(BinaryClassifierPredictorTest, NoInferenceModuleForModel) {
       ->mutable_translate()
       ->mutable_translate_logistic_regression_model()
       ->set_bias(1);
-  auto predictor = InitPredictor(std::move(ranker_model));
+  auto predictor = InitPredictor(std::move(ranker_model), GetConfig());
   EXPECT_FALSE(predictor->IsReady());
 
   RankerExample ranker_example;
@@ -94,7 +113,7 @@ TEST_F(BinaryClassifierPredictorTest, GenericLogisticRegressionModel) {
   auto ranker_model = base::MakeUnique<RankerModel>();
   *ranker_model->mutable_proto()->mutable_logistic_regression() =
       GetSimpleLogisticRegressionModel();
-  auto predictor = InitPredictor(std::move(ranker_model));
+  auto predictor = InitPredictor(std::move(ranker_model), GetConfig());
   EXPECT_TRUE(predictor->IsReady());
 
   RankerExample ranker_example;

components/assist_ranker/generic_logistic_regression_inference.cc

@@ -29,7 +29,7 @@ float GenericLogisticRegressionInference::PredictScore(
     const FeatureWeight& feature_weight = weight_it.second;
     switch (feature_weight.feature_type_case()) {
       case FeatureWeight::FEATURE_TYPE_NOT_SET: {
-        DVLOG(1) << "Feature type not set for " << feature_name;
+        DVLOG(0) << "Feature type not set for " << feature_name;
         break;
       }
       case FeatureWeight::kScalar: {
@@ -37,6 +37,8 @@ float GenericLogisticRegressionInference::PredictScore(
         if (GetFeatureValueAsFloat(feature_name, example, &value)) {
           const float weight = feature_weight.scalar();
           activation += value * weight;
+        } else {
+          DVLOG(1) << "Feature not in example: " << feature_name;
         }
         break;
       }
@@ -50,19 +52,22 @@ float GenericLogisticRegressionInference::PredictScore(
           } else {
             // If the category is not found, use the default weight.
             activation += feature_weight.one_hot().default_weight();
+            DVLOG(1) << "Unknown feature value for " << feature_name << ": "
+                     << value;
           }
         } else {
           // If the feature is missing, use the default weight.
           activation += feature_weight.one_hot().default_weight();
+          DVLOG(1) << "Feature not in example: " << feature_name;
         }
         break;
       }
       case FeatureWeight::kSparse: {
-        DVLOG(1) << "Sparse features not implemented yet.";
+        DVLOG(0) << "Sparse features not implemented yet.";
         break;
       }
       case FeatureWeight::kBucketized: {
-        DVLOG(1) << "Bucketized features not implemented yet.";
+        DVLOG(0) << "Bucketized features not implemented yet.";
         break;
       }
     }

components/assist_ranker/predictor_config.cc

+// Copyright 2017 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/assist_ranker/predictor_config.h"
+
+namespace assist_ranker {
+
+const base::flat_set<std::string>* GetEmptyWhitelist() {
+  static auto* whitelist = new base::flat_set<std::string>();
+  return whitelist;
+}
+
+}  // namespace assist_ranker

components/assist_ranker/predictor_config.h

+// Copyright 2017 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.
+
+#ifndef COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_H_
+#define COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_H_
+
+#include <string>
+
+#include "base/containers/flat_set.h"
+#include "base/metrics/field_trial_params.h"
+
+namespace assist_ranker {
+
+// TODO(chrome-ranker-team): Implement other logging types.
+enum LogType {
+  LOG_NONE = 0,
+  LOG_UKM = 1,
+};
+
+// Empty feature whitelist used for testing.
+const base::flat_set<std::string>* GetEmptyWhitelist();
+
+// This struct holds the config options for logging, loading and field trial
+// for a predictor.
+struct PredictorConfig {
+  PredictorConfig(const char* model_name,
+                  const char* logging_name,
+                  const char* uma_prefix,
+                  const LogType log_type,
+                  const base::flat_set<std::string>* feature_whitelist,
+                  const base::Feature* field_trial,
+                  const base::FeatureParam<std::string>* field_trial_url_param)
+      : model_name(model_name),
+        logging_name(logging_name),
+        uma_prefix(uma_prefix),
+        log_type(log_type),
+        feature_whitelist(feature_whitelist),
+        field_trial(field_trial),
+        field_trial_url_param(field_trial_url_param) {}
+  const char* model_name;
+  const char* logging_name;
+  const char* uma_prefix;
+  const LogType log_type;
+  const base::flat_set<std::string>* feature_whitelist;
+  const base::Feature* field_trial;
+  const base::FeatureParam<std::string>* field_trial_url_param;
+};
+
+}  // namespace assist_ranker
+
+#endif  // COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_H_

components/assist_ranker/predictor_config_definitions.cc

+// Copyright 2017 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/assist_ranker/predictor_config_definitions.h"
+
+namespace assist_ranker {
+
+#if defined(OS_ANDROID)
+const base::Feature kContextualSearchRankerQuery{
+    "ContextualSearchRankerQuery", base::FEATURE_DISABLED_BY_DEFAULT};
+
+namespace {
+
+const char kContextualSearchModelName[] = "contextual_search_model";
+const char kContextualSearchLoggingName[] = "ContextualSearch";
+const char kContextualSearchUmaPrefixName[] = "Search.ContextualSearch.Ranker";
+
+const char kContextualSearchDefaultModelUrl[] =
+    "https://www.gstatic.com/chrome/intelligence/assist/ranker/models/"
+    "contextual_search/test_ranker_model_20171109_short_words_v2.pb.bin";
+
+const base::FeatureParam<std::string>*
+GetContextualSearchRankerUrlFeatureParam() {
+  static auto* kContextualSearchRankerUrl = new base::FeatureParam<std::string>(
+      &kContextualSearchRankerQuery, "contextual-search-ranker-model-url",
+      kContextualSearchDefaultModelUrl);
+  return kContextualSearchRankerUrl;
+}
+
+// This list needs to be kept in sync with tools/metrics/ukm/ukm.xml.
+// Only features within this list will be logged to UKM.
+// TODO(chrome-ranker-team) Deprecate the whitelist once it is available through
+// the UKM generated API.
+const base::flat_set<std::string>* GetContextualSearchFeatureWhitelist() {
+  static auto* kContextualSearchFeatureWhitelist =
+      new base::flat_set<std::string>(
+          {"DidOptIn", "DurationAfterScrollMs", "IsEntity", "IsLongWord",
+           "IsShortWord", "IsWordEdge", "OutcomeWasCardsDataShown",
+           "OutcomeWasPanelOpened", "OutcomeWasQuickActionClicked",
+           "OutcomeWasQuickAnswerSeen", "Previous28DayCtrPercent",
+           "Previous28DayImpressionsCount", "PreviousWeekCtrPercent",
+           "PreviousWeekImpressionsCount", "ScreenTopDps", "TapDuration",
+           "WasScreenBottom"});
+  return kContextualSearchFeatureWhitelist;
+}
+
+}  // namespace
+
+const PredictorConfig GetContextualSearchPredictorConfig() {
+  static auto kContextualSearchPredictorConfig = *(new PredictorConfig(
+      kContextualSearchModelName, kContextualSearchLoggingName,
+      kContextualSearchUmaPrefixName, LOG_UKM,
+      GetContextualSearchFeatureWhitelist(), &kContextualSearchRankerQuery,
+      GetContextualSearchRankerUrlFeatureParam()));
+  return kContextualSearchPredictorConfig;
+}
+#endif  // OS_ANDROID
+
+}  // namespace assist_ranker

components/assist_ranker/predictor_config_definitions.h

+// Copyright 2017 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.
+
+#ifndef COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_DEFINITIONS_H_
+#define COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_DEFINITIONS_H_
+
+#include <memory>
+#include <string>
+#include <unordered_map>
+
+#include "base/feature_list.h"
+#include "base/metrics/field_trial_params.h"
+#include "build/build_config.h"
+#include "components/assist_ranker/predictor_config.h"
+
+namespace assist_ranker {
+
+#if defined(OS_ANDROID)
+extern const base::Feature kContextualSearchRankerQuery;
+const PredictorConfig GetContextualSearchPredictorConfig();
+#endif  // OS_ANDROID
+
+}  // namespace assist_ranker
+
+#endif  // COMPONENTS_ASSIST_RANKER_PREDICTOR_CONFIG_DEFINITIONS_H_

components/assist_ranker/proto/ranker_example.proto

@@ -32,5 +32,9 @@ message RankerExample {
   // This field represents the ground truth that the ranker is
   // expected to predict, and is typically derived from user feedback. It is
   // used for training only and is not required for inference.
+  // NOTE: this field will not be logged. If you want to log an outcome, add it
+  // to the features field before calling LogExample.
+  // TODO(chrome-ranker-team) Add a metadata field to log metrics that are not
+  // used as model input.
   optional Feature target = 2;
 }
\ No newline at end of file

components/assist_ranker/ranker_example_util.cc

@@ -3,7 +3,10 @@
 // found in the LICENSE file.
 
 #include "components/assist_ranker/ranker_example_util.h"
+#include "base/format_macros.h"
 #include "base/logging.h"
+#include "base/metrics/metrics_hashes.h"
+#include "base/strings/stringprintf.h"
 
 namespace assist_ranker {
 
@@ -42,6 +45,26 @@ bool GetFeatureValueAsFloat(const std::string& key,
   return true;
 }
 
+bool FeatureToInt(const Feature& feature, int* int_value) {
+  switch (feature.feature_type_case()) {
+    case Feature::kBoolValue:
+      *int_value = static_cast<int>(feature.bool_value());
+      return true;
+    case Feature::kInt32Value:
+      *int_value = feature.int32_value();
+      return true;
+    case Feature::kFloatValue:
+      // TODO(crbug.com/794187): Implement this.
+      return false;
+    case Feature::kStringValue:
+      // TODO(crbug.com/794187): Implement this.
+      return false;
+    default:
+      NOTREACHED();
+      return false;
+  }
+}
+
 bool GetOneHotValue(const std::string& key,
                     const RankerExample& example,
                     std::string* value) {
@@ -60,4 +83,20 @@ bool GetOneHotValue(const std::string& key,
   return true;
 }
 
+// Converts string to a hex hash string.
+std::string HashFeatureName(const std::string& feature_name) {
+  uint64_t feature_key = base::HashMetricName(feature_name);
+  return base::StringPrintf("%016" PRIx64, feature_key);
+}
+
+RankerExample HashExampleFeatureNames(const RankerExample& example) {
+  RankerExample hashed_example;
+  auto& output_features = *hashed_example.mutable_features();
+  for (const auto& feature : example.features()) {
+    output_features[HashFeatureName(feature.first)] = feature.second;
+  }
+  *hashed_example.mutable_target() = example.target();
+  return hashed_example;
+}
+
 }  // namespace assist_ranker

components/assist_ranker/ranker_example_util.h

@@ -25,6 +25,10 @@ bool GetFeatureValueAsFloat(const std::string& key,
                             const RankerExample& example,
                             float* value) WARN_UNUSED_RESULT;
 
+// Returns a int value for this feature. Float values are multiplied by a given
+// constant that defines the precision. String features are hashed.
+bool FeatureToInt(const Feature& feature, int* int_value) WARN_UNUSED_RESULT;
+
 // Extract category from one-hot feature. Returns true and fills
 // in |value| if the feature is found and is of type string_value. Returns false
 // otherwise.
@@ -32,6 +36,15 @@ bool GetOneHotValue(const std::string& key,
                     const RankerExample& example,
                     std::string* value) WARN_UNUSED_RESULT;
 
+// Converts a string to a hex ahsh string.
+std::string HashFeatureName(const std::string& feature_name);
+
+// Hashes feature names to an hex string.
+// Features logged through UKM will apply this transformation when logging
+// features, so models trained on UKM data are expected to have hashed input
+// feature names.
+RankerExample HashExampleFeatureNames(const RankerExample& example);
+
 }  // namespace assist_ranker
 
 #endif  // COMPONENTS_ASSIST_RANKER_RANKER_EXAMPLE_UTIL_H_

components/assist_ranker/ranker_example_util_unittest.cc

@@ -103,4 +103,53 @@ TEST_F(RankerExampleUtilTest, GetOneHotValue) {
   EXPECT_FALSE(GetOneHotValue("foo", example_, &value));
 }
 
+TEST_F(RankerExampleUtilTest, FeatureToInt) {
+  Feature feature;
+  int int_value;
+  feature.set_bool_value(true);
+  EXPECT_TRUE(FeatureToInt(feature, &int_value));
+  EXPECT_EQ(1, int_value);
+  feature.set_bool_value(false);
+  EXPECT_TRUE(FeatureToInt(feature, &int_value));
+  EXPECT_EQ(0, int_value);
+
+  feature.set_int32_value(42);
+  EXPECT_TRUE(FeatureToInt(feature, &int_value));
+  EXPECT_EQ(42, int_value);
+  feature.set_int32_value(-3);
+  EXPECT_TRUE(FeatureToInt(feature, &int_value));
+  EXPECT_EQ(-3, int_value);
+
+  // Float and string values are not implemented yet.
+  feature.set_float_value(12.345f);
+  EXPECT_FALSE(FeatureToInt(feature, &int_value));
+  feature.set_string_value("foo");
+  EXPECT_FALSE(FeatureToInt(feature, &int_value));
+}
+
+TEST_F(RankerExampleUtilTest, HashExampleFeatureNames) {
+  auto hashed_example = HashExampleFeatureNames(example_);
+  // Hashed example has the same number of features.
+  EXPECT_EQ(example_.features().size(), hashed_example.features().size());
+
+  // But the feature names have changed.
+  EXPECT_FALSE(SafeGetFeature(bool_name_, hashed_example, nullptr));
+  EXPECT_FALSE(SafeGetFeature(int32_name_, hashed_example, nullptr));
+  EXPECT_FALSE(SafeGetFeature(float_name_, hashed_example, nullptr));
+  EXPECT_FALSE(SafeGetFeature(one_hot_name_, hashed_example, nullptr));
+
+  EXPECT_TRUE(
+      SafeGetFeature(HashFeatureName(bool_name_), hashed_example, nullptr));
+
+  // Values have not changed.
+  float float_value;
+  EXPECT_TRUE(GetFeatureValueAsFloat(HashFeatureName(float_name_),
+                                     hashed_example, &float_value));
+  EXPECT_EQ(float_value_, float_value);
+  std::string string_value;
+  EXPECT_TRUE(GetOneHotValue(HashFeatureName(one_hot_name_), hashed_example,
+                             &string_value));
+  EXPECT_EQ(one_hot_value_, string_value);
+}
+
 }  // namespace assist_ranker

services/metrics/public/cpp/ukm_recorder.h

@@ -17,7 +17,6 @@
 #include "services/metrics/public/interfaces/ukm_interface.mojom.h"
 #include "url/gurl.h"
 
-class ContextualSearchRankerLoggerImpl;
 class DocumentWritePageLoadMetricsObserver;
 class FromGWSPageLoadMetricsLogger;
 class PluginInfoHostImpl;
@@ -27,6 +26,10 @@ class UkmPageLoadMetricsObserver;
 class UseCounterPageLoadMetricsObserver;
 class LocalNetworkRequestsPageLoadMetricsObserver;
 
+namespace assist_ranker {
+class BasePredictor;
+}
+
 namespace blink {
 class AutoplayUmaHelper;
 }
@@ -85,7 +88,7 @@ class METRICS_EXPORT UkmRecorder {
   virtual void UpdateSourceURL(SourceId source_id, const GURL& url) = 0;
 
  private:
-  friend ContextualSearchRankerLoggerImpl;
+  friend assist_ranker::BasePredictor;
   friend DelegatingUkmRecorder;
   friend DocumentWritePageLoadMetricsObserver;
   friend FromGWSPageLoadMetricsLogger;