Add metrics for calculating precision/recall of link navigation pre-connect triggers.

chrome/browser/net/predictor.cc

Index: chrome/browser/net/predictor.cc
diff --git a/chrome/browser/net/predictor.cc b/chrome/browser/net/predictor.cc
index b7061c748b6479e801c1d9eacb63744ae752df38..d7d6a6eaf5fbaad5c4424ccf2bf45b47f0eaac8c 100644
--- a/chrome/browser/net/predictor.cc
+++ b/chrome/browser/net/predictor.cc
@@ -9,9 +9,11 @@
 #include <set>
 #include <sstream>
 
+#include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
+#include "base/containers/mru_cache.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
@@ -125,6 +127,129 @@ class Predictor::LookupRequest {
   DISALLOW_COPY_AND_ASSIGN(LookupRequest);
 };
 
+// This records UMAs for preconnect usage based on navigation URLs to
+// gather precision/recall for user-event based preconnect triggers.
+// Stats are gathered via two LRU caches that remembers all preconnect and
+// user link navigations within the last N seconds.
+// A preconnect trigger is considered as used iff a navigation including
+// access to the preconnected host occurs within a time period specified by
+// kMaxUnusedSocketLifetimeSecondsWithoutAGet.
+class Predictor::PreconnectUsage {
+ public:
+  PreconnectUsage();
+  ~PreconnectUsage();
+
+  // Record a preconnect trigger to the url.
+  void ObservePreconnect(const GURL& url);
+
+  // Record a user link navigation to the url.
+  void ObserveNavigation(const GURL& url, const GURL& original_url);
+
+ private:
+  // This tracks whether a preconnect was used in some navigation or not
+  class PreconnectPrecisionStat {
+   public:
+    PreconnectPrecisionStat()
+        : timestamp_(base::TimeTicks::Now()),
+          was_used_(false) {
+    }
+
+    const base::TimeTicks& timestamp() { return timestamp_; }
+
+    void set_was_used() { was_used_ = true; }
+    bool was_used() const { return was_used_; }
+
+   private:
+    base::TimeTicks timestamp_;
+    bool was_used_;
+  };
+
+  typedef base::MRUCache<GURL, PreconnectPrecisionStat> MRUPreconnects;
+  MRUPreconnects mru_preconnects_;
+
+  // This tracks whether a navigation used a preconnected session or not
+  class PreconnectRecallStat {
+   public:
+    PreconnectRecallStat()
+        : timestamp_(base::TimeTicks::Now()),
+          did_use_preconnect_(false) {
+    }
+
+    const base::TimeTicks& timestamp() { return timestamp_; }
+
+    void set_did_use_preconnect() { did_use_preconnect_ = true; }
+    bool did_use_preconnect() const { return did_use_preconnect_; }
+
+   private:
+    base::TimeTicks timestamp_;
+    bool did_use_preconnect_;
+  };
+
+  typedef base::MRUCache<GURL, PreconnectRecallStat> MRUNavigations;
+  MRUNavigations mru_navigations_;
+
+  // The longest time an entry can persist in mru_preconnect_/mru_navigations_
+  const base::TimeDelta max_duration_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreconnectUsage);
+};
+
+Predictor::PreconnectUsage::PreconnectUsage()
+    : mru_preconnects_(MRUPreconnects::NO_AUTO_EVICT),
+      mru_navigations_(MRUNavigations::NO_AUTO_EVICT),
+      max_duration_(base::TimeDelta::FromSeconds(
+          Predictor::kMaxUnusedSocketLifetimeSecondsWithoutAGet)) {
+}
+
+Predictor::PreconnectUsage::~PreconnectUsage() {}
+
+void Predictor::PreconnectUsage::ObservePreconnect(const GURL& url) {
+  GURL canonical_url(Predictor::CanonicalizeUrl(url));
+  mru_preconnects_.Put(canonical_url, PreconnectPrecisionStat());
+}
+
+void Predictor::PreconnectUsage::ObserveNavigation(const GURL& url,
+                                                   const GURL& original_url) {
+  GURL canonical_url(Predictor::CanonicalizeUrl(url));
+
+  // Evict any overly old entries and record stats
+  base::TimeTicks now = base::TimeTicks::Now();
+
+  MRUPreconnects::reverse_iterator eldestPreconnect = mru_preconnects_.rbegin();
+  while (!mru_preconnects_.empty()) {
+    DCHECK(eldestPreconnect == mru_preconnects_.rbegin());
+    if (now - eldestPreconnect->second.timestamp() < max_duration_)
+      break;
+
+    UMA_HISTOGRAM_BOOLEAN("Net.PreconnectTriggerUsed",
+                          eldestPreconnect->second.was_used());
+    eldestPreconnect = mru_preconnects_.Erase(eldestPreconnect);
+  }
+
+  MRUNavigations::reverse_iterator eldestNavigation = mru_navigations_.rbegin();
+  while (!mru_navigations_.empty()) {
+    DCHECK(eldestNavigation == mru_navigations_.rbegin());
+    if (now - eldestNavigation->second.timestamp() < max_duration_)
+      break;
+
+    UMA_HISTOGRAM_BOOLEAN("Net.PreconnectedNavigation",
+                          eldestNavigation->second.did_use_preconnect());
+    eldestNavigation = mru_navigations_.Erase(eldestNavigation);
+  }
+
+  // Record the preconnect trigger for the url as used if exist
+  MRUNavigations::iterator itNavigation = mru_navigations_.Peek(original_url);
+  if (itNavigation == mru_navigations_.end())
+    itNavigation = mru_navigations_.Put(original_url, PreconnectRecallStat());
+
+  MRUPreconnects::iterator itPreconnect = mru_preconnects_.Peek(canonical_url);
+  bool wasPreconnected = (itPreconnect != mru_preconnects_.end());
+  if (wasPreconnected) {
+    itPreconnect->second.set_was_used();
+    itNavigation->second.set_did_use_preconnect();
+  }
+}
+
 Predictor::Predictor(bool preconnect_enabled)
     : url_request_context_getter_(NULL),
       predictor_enabled_(true),
@@ -136,8 +261,6 @@ Predictor::Predictor(bool preconnect_enabled)
       host_resolver_(NULL),
       preconnect_enabled_(preconnect_enabled),
       consecutive_omnibox_preconnect_count_(0),
-      recent_preconnects_(
-          TimeDelta::FromSeconds(kMaxUnusedSocketLifetimeSecondsWithoutAGet)),
       next_trim_time_(base::TimeTicks::Now() +
                       TimeDelta::FromHours(kDurationBetweenTrimmingsHours)) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ -667,6 +790,7 @@ void Predictor::FinalizeInitializationOnIOThread(
   predictor_enabled_ = predictor_enabled;
   initial_observer_.reset(new InitialObserver());
   host_resolver_ = io_thread->globals()->host_resolver.get();
+  preconnect_usage_.reset(new PreconnectUsage());
 
   // base::WeakPtrFactory instances need to be created and destroyed
   // on the same thread. The predictor lives on the IO thread and will die
@@ -845,9 +969,6 @@ void Predictor::PreconnectUrl(const GURL& url,
 void Predictor::PreconnectUrlOnIOThread(
     const GURL& url, const GURL& first_party_for_cookies,
     UrlInfo::ResolutionMotivation motivation, int count) {
-  GURL canonical_url(CanonicalizeUrl(url));
-  recent_preconnects_.SetRecentlySeen(canonical_url);
-
   PreconnectOnIOThread(url,
                        first_party_for_cookies,
                        motivation,
@@ -855,10 +976,47 @@ void Predictor::PreconnectUrlOnIOThread(
                        url_request_context_getter_.get());
 }
 
-void Predictor::RecordPreconnectNavigationStats(const GURL& url) {
-  UMA_HISTOGRAM_BOOLEAN(
-      "Net.PreconnectedNavigation",
-      recent_preconnects_.WasRecentlySeen(url));
+void Predictor::RecordPreconnectTrigger(const GURL& url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
+         BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  if (BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    RecordPreconnectTriggerOnIOThread(url);
+  } else {
+    BrowserThread::PostTask(
+        BrowserThread::IO,
+        FROM_HERE,
+        base::Bind(&Predictor::RecordPreconnectTriggerOnIOThread,
+                   base::Unretained(this), url));
+  }
+}
+
+void Predictor::RecordPreconnectTriggerOnIOThread(const GURL& url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  preconnect_usage_->ObservePreconnect(url);
+}
+
+void Predictor::RecordPreconnectNavigationStat(const GURL& url,
+                                               const GURL& original_url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI) ||
+         BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  if (BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    RecordPreconnectNavigationStatOnIOThread(url, original_url);
+  } else {
+    BrowserThread::PostTask(
+        BrowserThread::IO,
+        FROM_HERE,
+        base::Bind(&Predictor::RecordPreconnectNavigationStatOnIOThread,
+                   base::Unretained(this), url, original_url));
+  }
+}
+
+void Predictor::RecordPreconnectNavigationStatOnIOThread(
+    const GURL& url,
+    const GURL& original_url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  preconnect_usage_->ObserveNavigation(url, original_url);
 }
 
 void Predictor::PredictFrameSubresources(const GURL& url,