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Prevent site engagement scores from decaying when Chrome isn't in use.
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The site engagement service decays origins which have not been accessed
in a week. However, if a user isn't using Chrome at all, the decay still
occurs.

This CL addresses this issue by persisting the last recorded time that
any engagement occurred. If too long a period passes (currently 10 days)
without *any* engagement, all scores have their last accessed time
adjusted to be relative to some number of decay periods prior to now
(currently set at 1 decay period), based on their offset to the last known
engagement time.

BUG=575504

Review-Url: https://codereview.chromium.org/2082953002
Cr-Commit-Position: refs/heads/master@{#402653}
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dominickn authored and Commit bot committed Jun 29, 2016
1 parent e6ea446 commit 709246a
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Showing 8 changed files with 436 additions and 70 deletions.
14 changes: 14 additions & 0 deletions chrome/browser/engagement/site_engagement_score.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,8 @@ const char* kVariationNames[] = {
"first_daily_engagement_points",
"medium_engagement_boundary",
"high_engagement_boundary",
"max_decays_per_score",
"last_engagement_grace_period_in_hours",
};

bool DoublesConsideredDifferent(double value1, double value2, double delta) {
Expand Down Expand Up @@ -83,6 +85,8 @@ double SiteEngagementScore::param_values[] = {
8, // BOOTSTRAP_POINTS
5, // MEDIUM_ENGAGEMENT_BOUNDARY
50, // HIGH_ENGAGEMENT_BOUNDARY
1, // MAX_DECAYS_PER_SCORE
72, // LAST_ENGAGEMENT_GRACE_PERIOD_IN_HOURS
};

const char* SiteEngagementScore::kRawScoreKey = "rawScore";
Expand Down Expand Up @@ -139,6 +143,14 @@ double SiteEngagementScore::GetHighEngagementBoundary() {
return param_values[HIGH_ENGAGEMENT_BOUNDARY];
}

double SiteEngagementScore::GetMaxDecaysPerScore() {
return param_values[MAX_DECAYS_PER_SCORE];
}

double SiteEngagementScore::GetLastEngagementGracePeriodInHours() {
return param_values[LAST_ENGAGEMENT_GRACE_PERIOD_IN_HOURS];
}

// static
void SiteEngagementScore::UpdateFromVariations(const char* param_name) {
double param_vals[MAX_VARIATION];
Expand Down Expand Up @@ -337,6 +349,8 @@ void SiteEngagementScore::SetParamValuesForTesting() {
param_values[BOOTSTRAP_POINTS] = 8;
param_values[MEDIUM_ENGAGEMENT_BOUNDARY] = 5;
param_values[HIGH_ENGAGEMENT_BOUNDARY] = 50;
param_values[MAX_DECAYS_PER_SCORE] = 1;
param_values[LAST_ENGAGEMENT_GRACE_PERIOD_IN_HOURS] = 72;

// This is set to zero to avoid interference with tests and is set when
// testing this functionality.
Expand Down
27 changes: 23 additions & 4 deletions chrome/browser/engagement/site_engagement_score.h
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,18 @@ class SiteEngagementScore {
MEDIUM_ENGAGEMENT_BOUNDARY,
HIGH_ENGAGEMENT_BOUNDARY,

// The maximum number of decays that a SiteEngagementScore can incur before
// entering a grace period. MAX_DECAYS_PER_SCORE * DECAY_PERIOD_IN_DAYS is
// the max decay period, i.e. the maximum duration permitted for
// (clock_->Now() - score.last_engagement_time()).
MAX_DECAYS_PER_SCORE,

// If a SiteEngagamentScore has not been accessed or updated for a period
// longer than the max decay period + LAST_ENGAGEMENT_GRACE_PERIOD_IN_HOURS
// (see above), its last engagement time will be reset to be max decay
// period prior to clock_->Now().
LAST_ENGAGEMENT_GRACE_PERIOD_IN_HOURS,

MAX_VARIATION
};

Expand All @@ -80,6 +92,8 @@ class SiteEngagementScore {
static double GetBootstrapPoints();
static double GetMediumEngagementBoundary();
static double GetHighEngagementBoundary();
static double GetMaxDecaysPerScore();
static double GetLastEngagementGracePeriodInHours();

// Update the default engagement settings via variations.
static void UpdateFromVariations(const char* param_name);
Expand Down Expand Up @@ -108,10 +122,7 @@ class SiteEngagementScore {
bool MaxPointsPerDayAdded() const;

// Resets the score to |points| and resets the daily point limit. If
// |updated_time| is non-null, sets the last engagement time and last
// shortcut launch time (if it is non-null) to |updated_time|. Otherwise, last
// engagement time is set to the current time and last shortcut launch time is
// left unchanged.
// |updated_time| is non-null, sets the last engagement time to that value.
void Reset(double points, const base::Time updated_time);

// Get/set the last time this origin was launched from an installed shortcut.
Expand All @@ -122,6 +133,14 @@ class SiteEngagementScore {
last_shortcut_launch_time_ = time;
}

// Get/set the last time this origin recorded an engagement change.
base::Time last_engagement_time() const {
return last_engagement_time_;
}
void set_last_engagement_time(const base::Time& time) {
last_engagement_time_ = time;
}

private:
FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, PartiallyEmptyDictionary);
FRIEND_TEST_ALL_PREFIXES(SiteEngagementScoreTest, PopulatedDictionary);
Expand Down
111 changes: 98 additions & 13 deletions chrome/browser/engagement/site_engagement_service.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -25,10 +25,13 @@
#include "chrome/browser/engagement/site_engagement_score.h"
#include "chrome/browser/engagement/site_engagement_service_factory.h"
#include "chrome/browser/history/history_service_factory.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/common/chrome_switches.h"
#include "chrome/common/pref_names.h"
#include "components/content_settings/core/browser/host_content_settings_map.h"
#include "components/content_settings/core/common/content_settings_pattern.h"
#include "components/history/core/browser/history_service.h"
#include "components/prefs/pref_service.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/web_contents.h"
#include "url/gurl.h"
Expand Down Expand Up @@ -221,6 +224,11 @@ void SiteEngagementService::SetLastShortcutLaunchTime(const GURL& url) {
}

double SiteEngagementService::GetScore(const GURL& url) const {
// Ensure that if engagement is stale, we clean things up before fetching the
// score.
if (IsLastEngagementStale())
CleanupEngagementScores(true);

return CreateEngagementScore(url).GetScore();
}

Expand All @@ -245,32 +253,81 @@ SiteEngagementService::SiteEngagementService(Profile* profile,
}

void SiteEngagementService::AddPoints(const GURL& url, double points) {
SiteEngagementScore score = CreateEngagementScore(url);
// Trigger a cleanup and date adjustment if it has been a substantial length
// of time since *any* engagement was recorded by the service. This will
// ensure that we do not decay scores when the user did not use the browser.
if (IsLastEngagementStale())
CleanupEngagementScores(true);

SiteEngagementScore score = CreateEngagementScore(url);
score.AddPoints(points);
score.Commit();

SetLastEngagementTime(score.last_engagement_time());
}

void SiteEngagementService::AfterStartupTask() {
CleanupEngagementScores();
// Check if we need to reset last engagement times on startup - we want to
// avoid doing this in AddPoints() if possible. It is still necessary to check
// in AddPoints for people who never restart Chrome, but leave it open and
// their computer on standby.
CleanupEngagementScores(IsLastEngagementStale());
RecordMetrics();
}

void SiteEngagementService::CleanupEngagementScores() {
void SiteEngagementService::CleanupEngagementScores(
bool update_last_engagement_time) const {
// This method should not be called with |update_last_engagement_time| = true
// if the last engagement time isn't stale.
DCHECK(!update_last_engagement_time || IsLastEngagementStale());

HostContentSettingsMap* settings_map =
HostContentSettingsMapFactory::GetForProfile(profile_);
std::unique_ptr<ContentSettingsForOneType> engagement_settings =
GetEngagementContentSettings(settings_map);

// We want to rebase last engagement times relative to MaxDecaysPerScore
// periods of decay in the past.
base::Time now = clock_->Now();
base::Time last_engagement_time = GetLastEngagementTime();
base::Time rebase_time = now - GetMaxDecayPeriod();
base::Time new_last_engagement_time;
for (const auto& site : *engagement_settings) {
GURL origin(site.primary_pattern.ToString());
if (origin.is_valid() && GetScore(origin) != 0)
continue;

if (origin.is_valid()) {
SiteEngagementScore score = CreateEngagementScore(origin);
if (update_last_engagement_time) {
// Work out the offset between this score's last engagement time and the
// last time the service recorded any engagement. Set the score's last
// engagement time to rebase_time - offset to preserve its state,
// relative to the rebase date. This ensures that the score will decay
// the next time it is used, but will not decay too much.
DCHECK_LE(score.last_engagement_time(), rebase_time);
base::TimeDelta offset =
last_engagement_time - score.last_engagement_time();
base::Time rebase_score_time = rebase_time - offset;
score.set_last_engagement_time(rebase_score_time);
if (rebase_score_time > new_last_engagement_time)
new_last_engagement_time = rebase_score_time;

score.Commit();
}

if (score.GetScore() != 0)
continue;
}

// This origin has a score of 0. Wipe it from content settings.
settings_map->SetWebsiteSettingDefaultScope(
origin, GURL(), CONTENT_SETTINGS_TYPE_SITE_ENGAGEMENT, std::string(),
nullptr);
}

// Set the last engagement time to be consistent with the scores. This will
// only occur if |update_last_engagement_time| is true.
if (!new_last_engagement_time.is_null())
SetLastEngagementTime(new_last_engagement_time);
}

void SiteEngagementService::RecordMetrics() {
Expand Down Expand Up @@ -307,6 +364,29 @@ void SiteEngagementService::RecordMetrics() {
}
}

base::Time SiteEngagementService::GetLastEngagementTime() const {
return base::Time::FromInternalValue(
profile_->GetPrefs()->GetInt64(prefs::kSiteEngagementLastUpdateTime));
}

void SiteEngagementService::SetLastEngagementTime(
base::Time last_engagement_time) const {
profile_->GetPrefs()->SetInt64(prefs::kSiteEngagementLastUpdateTime,
last_engagement_time.ToInternalValue());
}

base::TimeDelta SiteEngagementService::GetMaxDecayPeriod() const {
return base::TimeDelta::FromDays(
SiteEngagementScore::GetDecayPeriodInDays()) *
SiteEngagementScore::GetMaxDecaysPerScore();
}

base::TimeDelta SiteEngagementService::GetStalePeriod() const {
return GetMaxDecayPeriod() +
base::TimeDelta::FromHours(
SiteEngagementScore::GetLastEngagementGracePeriodInHours());
}

double SiteEngagementService::GetMedianEngagement(
const std::map<GURL, double>& score_map) const {
if (score_map.size() == 0)
Expand Down Expand Up @@ -372,6 +452,16 @@ void SiteEngagementService::HandleUserInput(
OnEngagementIncreased(web_contents, url, GetScore(url)));
}

bool SiteEngagementService::IsLastEngagementStale() const {
// This only happens when Chrome is first run and the user has never recorded
// any engagement.
base::Time last_engagement_time = GetLastEngagementTime();
if (last_engagement_time.is_null())
return false;

return (clock_->Now() - last_engagement_time) >= GetStalePeriod();
}

void SiteEngagementService::OnURLsDeleted(
history::HistoryService* history_service,
bool all_history,
Expand All @@ -391,15 +481,8 @@ void SiteEngagementService::OnURLsDeleted(
weak_factory_.GetWeakPtr(), hs, origins, expired));
}

const SiteEngagementScore SiteEngagementService::CreateEngagementScore(
const GURL& origin) const {
return SiteEngagementScore(
clock_.get(), origin,
HostContentSettingsMapFactory::GetForProfile(profile_));
}

SiteEngagementScore SiteEngagementService::CreateEngagementScore(
const GURL& origin) {
const GURL& origin) const {
return SiteEngagementScore(
clock_.get(), origin,
HostContentSettingsMapFactory::GetForProfile(profile_));
Expand Down Expand Up @@ -503,4 +586,6 @@ void SiteEngagementService::GetCountsAndLastVisitForOriginsComplete(

engagement_score.Commit();
}

SetLastEngagementTime(now);
}
36 changes: 31 additions & 5 deletions chrome/browser/engagement/site_engagement_service.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,7 @@ class SiteEngagementService : public KeyedService,
FRIEND_TEST_ALL_PREFIXES(SiteEngagementServiceTest, EngagementLevel);
FRIEND_TEST_ALL_PREFIXES(SiteEngagementServiceTest, Observers);
FRIEND_TEST_ALL_PREFIXES(SiteEngagementServiceTest, ScoreDecayHistograms);
FRIEND_TEST_ALL_PREFIXES(SiteEngagementServiceTest, LastEngagementTime);
FRIEND_TEST_ALL_PREFIXES(AppBannerSettingsHelperTest, SiteEngagementTrigger);

// Only used in tests.
Expand All @@ -140,15 +141,34 @@ class SiteEngagementService : public KeyedService,
void AddPoints(const GURL& url, double points);

// Retrieves the SiteEngagementScore object for |origin|.
SiteEngagementScore CreateEngagementScore(const GURL& origin);
const SiteEngagementScore CreateEngagementScore(const GURL& origin) const;
SiteEngagementScore CreateEngagementScore(const GURL& origin) const;

// Post startup tasks: cleaning up origins which have decayed to 0, and
// logging UMA statistics.
// Runs site engagement maintenance tasks.
void AfterStartupTask();
void CleanupEngagementScores();

// Removes any origins which have decayed to 0 engagement. If
// |update_last_engagement_time| is true, the last engagement time of all
// origins is reset by calculating the delta between the last engagement event
// recorded by the site engagement service and the origin. The origin's last
// engagement time is then set to clock_->Now() - delta.
//
// If a user does not use the browser at all for some period of time,
// engagement is not decayed, and the state is restored equivalent to how they
// left it once they return.
void CleanupEngagementScores(bool update_last_engagement_time) const;

// Records UMA metrics.
void RecordMetrics();

// Get and set the last engagement time from prefs.
base::Time GetLastEngagementTime() const;
void SetLastEngagementTime(base::Time last_engagement_time) const;

// Get the maximum decay period and the stale period for last engagement
// times.
base::TimeDelta GetMaxDecayPeriod() const;
base::TimeDelta GetStalePeriod() const;

// Returns the median engagement score of all recorded origins.
double GetMedianEngagement(const std::map<GURL, double>& score_map) const;

Expand All @@ -167,6 +187,12 @@ class SiteEngagementService : public KeyedService,
void HandleUserInput(content::WebContents* web_contents,
SiteEngagementMetrics::EngagementType type);

// Returns true if the last engagement increasing event seen by the site
// engagement service was sufficiently long ago that we need to reset all
// scores to be relative to now. This ensures that users who do not use the
// browser for an extended period of time do not have their engagement decay.
bool IsLastEngagementStale() const;

// Overridden from history::HistoryServiceObserver:
void OnURLsDeleted(history::HistoryService* history_service,
bool all_history,
Expand Down
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