Win 10 Inactive toast experiment metrics and storage modifications.

chrome/installer/util/experiment.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 "chrome/installer/util/experiment.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+
+namespace installer {
+
+// Returns closest integer of logarithm of |x| with base |b|.

[grt (UTC plus 2), 2017/05/31 12:24:09]

put these helpers in an unnamed namespace (and drop "static").

[nikunjb, 2017/06/02 05:11:22]

Done.

+static double LogFloor(double x, double b) {
+  return std::round(std::log(x) / std::log(b));
+}
+
+// Returns the base to use for exponential buckets so that buckets
+// 0,1,.. 2^|bits|-1 cover range [0, max_val]. If this function return b
+// then Bucket value i will store values from [b^i, b^(i+1)]
+static double ExpBucketBase(int max_val, int bits) {
+  return std::exp(std::log(max_val - 1) / (1 << bits));
+}
+
+// Invert bucket to the approximate value that the bucket may correspond to.
+static int BucketToValue(int bucket, double bucket_base) {
+  return static_cast<int>(std::round(std::pow(bucket_base, bucket) - 1));
+}
+
+Experiment::Experiment() = default;
+Experiment::Experiment(Experiment&&) = default;
+Experiment::Experiment(const Experiment&) = default;
+Experiment::~Experiment() = default;
+
+void Experiment::InitializeFromMetrics(const ExperimentMetrics& metrics) {

[grt (UTC plus 2), 2017/05/31 12:24:09]

this will only be called when |metrics| is in an initial state so it doesn't
need to be able to reconstitute any of the fields that are set from group
assignment on. may as well add a DCHECK that |metrics| is in the initial state
here.

[nikunjb, 2017/06/02 05:11:22]

Done.

+  *this = Experiment();
+  metrics_ = metrics;
+  state_ = metrics.state;
+  group_ = metrics.group;
+  toast_location_ = metrics.toast_location;
+  toast_count_ = metrics.toast_count;
+  if (metrics_.last_used_bucket > 0) {
+    double log_base = ExpBucketBase(ExperimentMetrics::kMaxLastUsed,
+                                    ExperimentMetrics::kLastUsedBucketBits);
+    inactive_days_ = BucketToValue(metrics_.last_used_bucket, log_base);
+    if (inactive_days_ > ExperimentMetrics::kMaxLastUsed) {
+      inactive_days_ = ExperimentMetrics::kMaxLastUsed;
+    }
+  }
+  if (metrics_.session_length_bucket > 0) {
+    double log_base = ExpBucketBase(ExperimentMetrics::kMaxSessionLength,
+                                    ExperimentMetrics::kSessionLengthBits);
+    user_session_uptime_ = base::TimeDelta::FromMinutes(
+        BucketToValue(metrics_.session_length_bucket, log_base));
+    if (user_session_uptime_.InMinutes() >
+        ExperimentMetrics::kMaxSessionLength) {
+      user_session_uptime_ =
+          base::TimeDelta::FromMinutes(ExperimentMetrics::kMaxSessionLength);
+    }
+  }
+
+  if (metrics_.display_time_bucket > 0) {
+    double log_base = ExpBucketBase(ExperimentMetrics::kMaxDisplayTime,
+                                    ExperimentMetrics::kDisplayTimeBucketBits);
+    action_delay_ = base::TimeDelta::FromSeconds(
+        BucketToValue(metrics_.display_time_bucket, log_base));
+    if (action_delay_.InSeconds() > ExperimentMetrics::kMaxDisplayTime) {
+      action_delay_ =
+          base::TimeDelta::FromSeconds(ExperimentMetrics::kMaxDisplayTime);
+    }
+  }
+
+  if (metrics_.first_toast_offset > 0) {
+    // Accurate time information is not kept in |metrics|. Reconstruct
+    // the toast display time to the closest day.
+    first_display_time_ =
+        (base::Time::UnixEpoch() +
+         base::TimeDelta::FromSeconds(
+             ExperimentMetrics::kExperimentStartSeconds) +
+         base::TimeDelta::FromDays(metrics_.first_toast_offset));
+    DCHECK_LE(metrics_.first_toast_offset,
+              ExperimentMetrics::kExperimentStartSeconds);
+  }
+  // Latest display time is not stored in experiment metrics. So, it will
+  // be initialized to be same as |first_display_time_| for now.
+  latest_display_time_ = first_display_time_;
+}
+
+void Experiment::SetState(ExperimentMetrics::State state) {
+  state_ = state;
+  metrics_.SetState(state);

[grt (UTC plus 2), 2017/05/31 12:24:09]

may has well drop this setter and use metrics_.state = state; for consistency
with the other setters.

[nikunjb, 2017/06/02 05:11:22]

Done.

+}
+
+void Experiment::AssignGroup(int group) {
+  DCHECK_GE(group, 0);
+  DCHECK_LT(group, ExperimentMetrics::kNumGroups);
+  DCHECK(metrics_.InInitialState());
+
+  group_ = group;
+  metrics_.group = group;
+  SetState(ExperimentMetrics::kGroupAssigned);
+}
+
+void Experiment::SetToastLocation(ExperimentMetrics::ToastLocation location) {
+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  toast_location_ = location;
+  metrics_.toast_location = location;
+}
+
+void Experiment::SetInactiveDays(int days) {
+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  DCHECK_GE(days, 0);
+  inactive_days_ = days;
+  double log_base = ExpBucketBase(ExperimentMetrics::kMaxLastUsed,
+                                  ExperimentMetrics::kLastUsedBucketBits);
+  metrics_.last_used_bucket = LogFloor(1 + days, log_base);

[grt (UTC plus 2), 2017/05/31 12:24:09]

how about:
  LogFloor(std::min(days, ExperimentMetrics::kMaxLastUsed) + 1, log_base);
and get rid of the if below?

comment applies to other setters below, too

[nikunjb, 2017/06/02 05:11:22]

Done.

+  if (days > ExperimentMetrics::kMaxLastUsed) {
+    metrics_.last_used_bucket =
+        LogFloor(1 + ExperimentMetrics::kMaxLastUsed, log_base);
+  }
+}
+
+void Experiment::SetToastCount(int count) {
+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  toast_count_ = count;
+  metrics_.toast_count = count;

[grt (UTC plus 2), 2017/05/31 12:24:09]

std::min(count, ExperimentMetrics::kMaxToastCount)

also, wdyt of moving this into a setter on ExperimentMetrics? or maybe creating
a setter that DCHECKs that |count| <= kMaxToastCount? comment applies to all EM
fields.

[nikunjb, 2017/06/02 05:11:22]

Done.

+  if (count > ExperimentMetrics::kMaxToastCount) {
+    metrics_.toast_count = ExperimentMetrics::kMaxToastCount;
+  }
+}
+
+void Experiment::SetDisplayTime(const base::Time& time) {

[grt (UTC plus 2), 2017/05/31 12:24:09]

Time and TimeTicks should be passed by value rather than constref as per comment
in base/time.h

[nikunjb, 2017/06/02 05:11:22]

Done.

+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  if (metrics_.first_toast_offset == 0) {
+    // This is the first time toast is shown so add user to today's cohort.
+    first_display_time_ = time;
+    metrics_.first_toast_offset =
+        (time - base::Time::UnixEpoch() -
+         base::TimeDelta::FromSeconds(
+             ExperimentMetrics::kExperimentStartSeconds))
+            .InDays();
+    if (metrics_.first_toast_offset > ExperimentMetrics::kMaxFirstToastOffset ||
+        metrics_.first_toast_offset < 0) {
+      // First display time is outside the experiment range. Invalid local time.
+      // Reset to highest value of first display time.
+      metrics_.first_toast_offset = ExperimentMetrics::kMaxFirstToastOffset;
+    }
+  }
+  latest_display_time_ = time;
+  metrics_.toast_hour = (time - time.LocalMidnight()).InHours();
+  DCHECK_LE(metrics_.toast_hour, 24);
+  DCHECK_GE(metrics_.toast_hour, 0);
+}
+
+void Experiment::SetUserSessionUptime(const base::TimeDelta& time_delta) {
+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  user_session_uptime_ = time_delta;
+  double log_base = ExpBucketBase(ExperimentMetrics::kMaxSessionLength,
+                                  ExperimentMetrics::kSessionLengthBits);
+  metrics_.session_length_bucket =
+      LogFloor(1 + time_delta.InMinutes(), log_base);
+  if (time_delta.InMinutes() > ExperimentMetrics::kMaxSessionLength) {
+    metrics_.session_length_bucket =
+        LogFloor(1 + ExperimentMetrics::kMaxSessionLength, log_base);
+  }
+}
+
+void Experiment::SetActionDelay(const base::TimeDelta& time_delta) {
+  DCHECK(!metrics_.InTerminalState());
+  DCHECK(!metrics_.InInitialState());
+  action_delay_ = time_delta;
+  double log_base = ExpBucketBase(ExperimentMetrics::kMaxDisplayTime,
+                                  ExperimentMetrics::kDisplayTimeBucketBits);
+  metrics_.display_time_bucket = LogFloor(1 + time_delta.InSeconds(), log_base);
+  if (time_delta.InSeconds() > ExperimentMetrics::kMaxDisplayTime) {
+    metrics_.display_time_bucket =
+        LogFloor(1 + ExperimentMetrics::kMaxDisplayTime, log_base);
+  }
+}
+
+}  // namespace installer