Modifying prefetch to account for multi-profile.

chrome/browser/net/predictor.h

 // Copyright (c) 2011 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.
 
 // A Predictor object is instantiated once in the browser process, and manages
 // both preresolution of hostnames, as well as TCP/IP preconnection to expected
 // subresources.
 // Most hostname lists are provided by the renderer processes, and include URLs
 // that *might* be used in the near future by the browsing user.  One goal of
 // this class is to cause the underlying DNS structure to lookup a hostname
 // before it is really needed, and hence reduce latency in the standard lookup
 // paths.
 // Subresource relationships are usually acquired from the referrer field in a
 // navigation.  A subresource URL may be associated with a referrer URL.  Later
 // navigations may, if the likelihood of needing the subresource is high enough,
 // cause this module to speculatively create a TCP/IP connection. If there is
 // only a low likelihood, then a DNS pre-resolution operation may be performed.
 
 #ifndef CHROME_BROWSER_NET_PREDICTOR_H_
 #define CHROME_BROWSER_NET_PREDICTOR_H_
 #pragma once
 
 #include <map>
 #include <queue>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
-#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "chrome/browser/net/url_info.h"
 #include "chrome/browser/net/referrer.h"
 #include "chrome/common/net/predictor_common.h"
 #include "net/base/host_port_pair.h"
 
 namespace base {
 class ListValue;
 }
 
+namespace base {
+class WaitableEvent;
+}
+
 namespace net {
 class HostResolver;
 }  // namespace net
 
+class IOThread;
+class PrefService;
+class Profile;
+
 namespace chrome_browser_net {
 
 typedef chrome_common_net::UrlList UrlList;
 typedef chrome_common_net::NameList NameList;
 typedef std::map<GURL, UrlInfo> Results;
 
-// Note that Predictor is not thread safe, and must only be called from
-// the IO thread. Failure to do so will result in a DCHECK at runtime.
-class Predictor : public base::RefCountedThreadSafe<Predictor> {
+// Predictor is constructed during Profile construction (on the UI thread),
+// but it is destroyed on the IO thread when ProfileIOData goes away. All of
+// its core state and functionality happens on the IO thread. The only UI
+// methods are initialization / shutdown related (including preconnect
+// initialization), or convenience methods that internally forward calls to
+// the IO thread.
+class Predictor {
  public:
   // A version number for prefs that are saved. This should be incremented when
   // we change the format so that we discard old data.
   static const int kPredictorReferrerVersion;
 
+  // Given that the underlying Chromium resolver defaults to a total maximum of
+  // 8 paralell resolutions, we will avoid any chance of starving navigational
+  // resolutions by limiting the number of paralell speculative resolutions.
+  // This is used in the field trials and testing.
+  // TODO(jar): Move this limitation into the resolver.
+  static const size_t kMaxSpeculativeParallelResolves;
+
+  // To control the congestion avoidance system, we need an estimate of how
+  // many speculative requests may arrive at once.  Since we currently only
+  // keep 8 subresource names for each frame, we'll use that as our basis.
+  // Note that when scanning search results lists, we might actually get 10 at
+  // a time, and wikipedia can often supply (during a page scan) upwards of 50.
+  // In those odd cases, we may discard some of the later speculative requests
+  // mistakenly assuming that the resolutions took too long.
+  static const int kTypicalSpeculativeGroupSize;
+
+  // The next constant specifies an amount of queueing delay that is
+  // "too large," and indicative of problems with resolutions (perhaps due to
+  // an overloaded router, or such).  When we exceed this delay, congestion
+  // avoidance will kick in and all speculations in the queue will be discarded.
+  static const int kMaxSpeculativeResolveQueueDelayMs;
+
   // |max_concurrent| specifies how many concurrent (parallel) prefetches will
   // be performed. Host lookups will be issued through |host_resolver|.
-  Predictor(net::HostResolver* host_resolver,
-            base::TimeDelta max_queue_delay_ms, size_t max_concurrent,
-            bool preconnect_enabled);
+  explicit Predictor(bool preconnect_enabled);
+
+  virtual ~Predictor();
+
+  // This function is used to create a predictor. For testing, we can create
+  // a version which does a simpler shutdown.
+  static Predictor* CreatePredictor(bool preconnect_enabled,
+                                    bool simple_shutdown);
+
+  static void RegisterUserPrefs(PrefService* user_prefs);
+
+  // ------------- Start UI thread methods.
+
+  virtual void InitNetworkPredictor(PrefService* user_prefs,
+                                    PrefService* local_state,
+                                    IOThread* io_thread);
+
+  // The Omnibox has proposed a given url to the user, and if it is a search
+  // URL, then it also indicates that this is preconnectable (i.e., we could
+  // preconnect to the search server).
+  void AnticipateOmniboxUrl(const GURL& url, bool preconnectable);
+
+  // Preconnect a URL and all of its subresource domains.
+  void PreconnectUrlAndSubresources(const GURL& url);
+
+  static UrlList GetPredictedUrlListAtStartup(PrefService* user_prefs,
+                                              PrefService* local_state);
+
+  static void set_max_queueing_delay(int max_queueing_delay_ms);
+
+  static void set_max_parallel_resolves(size_t max_parallel_resolves);
+
+  virtual void ShutdownOnUIThread(PrefService* user_prefs);
+
+  // ------------- End UI thread methods.
+
+  // ------------- Start IO thread methods.
 
   // Cancel pending requests and prevent new ones from being made.
   void Shutdown();
 
   // In some circumstances, for privacy reasons, all results should be
   // discarded.  This method gracefully handles that activity.
   // Destroy all our internal state, which shows what names we've looked up, and
   // how long each has taken, etc. etc.  We also destroy records of suggesses
   // (cache hits etc.).
   void DiscardAllResults();
 
   // Add hostname(s) to the queue for processing.
   void ResolveList(const UrlList& urls,
                    UrlInfo::ResolutionMotivation motivation);
-  void Resolve(const GURL& url,
-               UrlInfo::ResolutionMotivation motivation);
 
-  // Instigate pre-connection to any URLs, or pre-resolution of related host,
-  // that we predict will be needed after this navigation (typically
-  // more-embedded resources on a page).  This method will actually post a task
-  // to do the actual work, so as not to jump ahead of the frame navigation that
-  // instigated this activity.
-  void PredictFrameSubresources(const GURL& url);
-
-  // The Omnibox has proposed a given url to the user, and if it is a search
-  // URL, then it also indicates that this is preconnectable (i.e., we could
-  // preconnect to the search server).
-  void AnticipateOmniboxUrl(const GURL& url, bool preconnectable);
-
-  // Preconnect a URL and all of its subresource domains.
-  void PreconnectUrlAndSubresources(const GURL& url);
+  void Resolve(const GURL& url, UrlInfo::ResolutionMotivation motivation);
 
   // Record details of a navigation so that we can preresolve the host name
   // ahead of time the next time the users navigates to the indicated host.
   // Should only be called when urls are distinct, and they should already be
   // canonicalized to not have a path.
   void LearnFromNavigation(const GURL& referring_url, const GURL& target_url);
 
+  // When displaying info in about:dns, the following API is called.
+  static void PredictorGetHtmlInfo(Predictor* predictor, std::string* output);
+
   // Dump HTML table containing list of referrers for about:dns.
   void GetHtmlReferrerLists(std::string* output);
 
   // Dump the list of currently known referrer domains and related prefetchable
-  // domains.
+  // domains for about:dns.
   void GetHtmlInfo(std::string* output);
 
   // Discards any referrer for which all the suggested host names are currently
   // annotated with negligible expected-use.  Scales down (diminishes) the
   // expected-use of those that remain, so that their use will go down by a
   // factor each time we trim (moving the referrer closer to being discarded in
   // a future call).
   // The task is performed synchronously and completes before returing.
   void TrimReferrersNow();
 
   // Construct a ListValue object that contains all the data in the referrers_
   // so that it can be persisted in a pref.
   void SerializeReferrers(base::ListValue* referral_list);
 
   // Process a ListValue that contains all the data from a previous reference
   // list, as constructed by SerializeReferrers(), and add all the identified
   // values into the current referrer list.
   void DeserializeReferrers(const base::ListValue& referral_list);
 
   void DeserializeReferrersThenDelete(base::ListValue* referral_list);
 
-  // For unit test code only.
-  size_t max_concurrent_dns_lookups() const {
-    return max_concurrent_dns_lookups_;
-  }
+  void DiscardInitialNavigationHistory();
 
-  // Flag setting to use preconnection instead of just DNS pre-fetching.
-  bool preconnect_enabled() const { return preconnect_enabled_; }
+  void FinalizeInitializationOnIOThread(
+      const std::vector<GURL>& urls_to_prefetch,
+      base::ListValue* referral_list,
+      IOThread* io_thread,
+      bool predictor_enabled);
+
+  // During startup, we learn what the first N urls visited are, and then
+  // resolve the associated hosts ASAP during our next startup.
+  void LearnAboutInitialNavigation(const GURL& url);
+
+  // Renderer bundles up list and sends to this browser API via IPC.
+  // TODO(jar): Use UrlList instead to include port and scheme.
+  void DnsPrefetchList(const NameList& hostnames);
+
+  // May be called from either the IO or UI thread and will PostTask
+  // to the IO thread if necessary.
+  void DnsPrefetchMotivatedList(const UrlList& urls,
+                                UrlInfo::ResolutionMotivation motivation);
+
+  // May be called from either the IO or UI thread and will PostTask
+  // to the IO thread if necessary.
+  void SaveStateForNextStartupAndTrim(PrefService* prefs);
+
+  void SaveDnsPrefetchStateForNextStartupAndTrim(
+      base::ListValue* startup_list,
+      base::ListValue* referral_list,
+      base::WaitableEvent* completion);
+
+  // May be called from either the IO or UI thread and will PostTask
+  // to the IO thread if necessary.
+  void EnablePredictor(bool enable);
+
+  void EnablePredictorOnIOThread(bool enable);
+
+  // ------------- End IO thread methods.
+
+  // The following methods may be called on either the IO or UI threads.
+
+  // Instigate pre-connection to any URLs, or pre-resolution of related host,
+  // that we predict will be needed after this navigation (typically
+  // more-embedded resources on a page).  This method will actually post a task
+  // to do the actual work, so as not to jump ahead of the frame navigation that
+  // instigated this activity.
+  void PredictFrameSubresources(const GURL& url);
 
   // Put URL in canonical form, including a scheme, host, and port.
   // Returns GURL::EmptyGURL() if the scheme is not http/https or if the url
   // cannot be otherwise canonicalized.
   static GURL CanonicalizeUrl(const GURL& url);
 
+  // Used for testing.
+  void SetHostResolver(net::HostResolver* host_resolver) {
+    host_resolver_ = host_resolver;
+  }
+  // Used for testing.
+  size_t max_concurrent_dns_lookups() const {
+    return max_concurrent_dns_lookups_;
+  }
+  // Used for testing.
+  void SetShutdown(bool shutdown) {
+    shutdown_ = shutdown;
+  }
+
+  // Flag setting to use preconnection instead of just DNS pre-fetching.
+  bool preconnect_enabled() const {
+    return preconnect_enabled_;
+  }
+
+  // Flag setting for whether we are prefetching dns lookups.
+  bool predictor_enabled() const {
+    return predictor_enabled_;
+  }
+
+
  private:
-  friend class base::RefCountedThreadSafe<Predictor>;
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, BenefitLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ShutdownWhenResolutionIsPendingTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, SingleLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, MassiveConcurrentLookupTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueuePushPopTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, PriorityQueueReorderTest);
   FRIEND_TEST_ALL_PREFIXES(PredictorTest, ReferrerSerializationTrimTest);
   friend class WaitForResolutionHelper;  // For testing.
 
@@ skipping 19 matching lines @@
    private:
     // The names in the queue that should be serviced (popped) ASAP.
     std::queue<GURL> rush_queue_;
     // The names in the queue that should only be serviced when rush_queue is
     // empty.
     std::queue<GURL> background_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(HostNameQueue);
   };
 
+  // The InitialObserver monitors navigations made by the network stack. This
+  // is only used to identify startup time resolutions (for re-resolution
+  // during our next process startup).
+  // TODO(jar): Consider preconnecting at startup, which may be faster than
+  // waiting for render process to start and request a connection.
+  class InitialObserver {
+   public:
+    InitialObserver();
+    ~InitialObserver();
+    // Recording of when we observed each navigation.
+    typedef std::map<GURL, base::TimeTicks> FirstNavigations;
+
+    // Potentially add a new URL to our startup list.
+    void Append(const GURL& url, Predictor* predictor);
+
+    // Get an HTML version of our current planned first_navigations_.
+    void GetFirstResolutionsHtml(std::string* output);
+
+    // Persist the current first_navigations_ for storage in a list.
+    void GetInitialDnsResolutionList(base::ListValue* startup_list);
+
+    // Discards all initial loading history.
+    void DiscardInitialNavigationHistory() { first_navigations_.clear(); }
+
+   private:
+    // List of the first N URL resolutions observed in this run.
+    FirstNavigations first_navigations_;
+
+    // The number of URLs we'll save for pre-resolving at next startup.
+    static const size_t kStartupResolutionCount = 10;
+  };
+
   // A map that is keyed with the host/port that we've learned were the cause
   // of loading additional URLs.  The list of additional targets is held
   // in a Referrer instance, which is a value in this map.
   typedef std::map<GURL, Referrer> Referrers;
 
   // Depending on the expected_subresource_use_, we may either make a TCP/IP
   // preconnection, or merely pre-resolve the hostname via DNS (or even do
   // nothing).  The following are the threasholds for taking those actions.
   static const double kPreconnectWorthyExpectedValue;
   static const double kDNSPreresolutionWorthyExpectedValue;
   // Referred hosts with a subresource_use_rate_ that are less than the
   // following threshold will be discarded when we Trim() the list.
   static const double kDiscardableExpectedValue;
   // During trimming operation to discard hosts for which we don't have likely
   // subresources, we multiply the expected_subresource_use_ value by the
   // following ratio until that value is less than kDiscardableExpectedValue.
   // This number should always be less than 1, an more than 0.
   static const double kReferrerTrimRatio;
 
   // Interval between periodic trimming of our whole referrer list.
   // We only do a major trimming about once an hour, and then only when the user
   // is actively browsing.
   static const base::TimeDelta kDurationBetweenTrimmings;
   // Interval between incremental trimmings (to avoid inducing Jank).
   static const base::TimeDelta kDurationBetweenTrimmingIncrements;
   // Number of referring URLs processed in an incremental trimming.
   static const size_t kUrlsTrimmedPerIncrement;
 
-  ~Predictor();
-
-  // Perform actual resolution or preconnection to subresources now.  This is
-  // an internal worker method that is reached via a post task from
-  // PredictFrameSubresources().
-  void PrepareFrameSubresources(const GURL& url);
-
   // Only for testing. Returns true if hostname has been successfully resolved
   // (name found).
   bool WasFound(const GURL& url) const {
     Results::const_iterator it(results_.find(url));
     return (it != results_.end()) &&
             it->second.was_found();
   }
 
   // Only for testing. Return how long was the resolution
   // or UrlInfo::kNullDuration if it hasn't been resolved yet.
   base::TimeDelta GetResolutionDuration(const GURL& url) {
     if (results_.find(url) == results_.end())
       return UrlInfo::kNullDuration;
     return results_[url].resolve_duration();
   }
 
   // Only for testing;
   size_t peak_pending_lookups() const { return peak_pending_lookups_; }
 
+  // ------------- Start IO thread methods.
+
+  // Perform actual resolution or preconnection to subresources now.  This is
+  // an internal worker method that is reached via a post task from
+  // PredictFrameSubresources().
+  void PrepareFrameSubresources(const GURL& url);
+
   // Access method for use by async lookup request to pass resolution result.
   void OnLookupFinished(LookupRequest* request, const GURL& url, bool found);
 
   // Underlying method for both async and synchronous lookup to update state.
   void LookupFinished(LookupRequest* request,
                       const GURL& url, bool found);
 
   // Queue hostname for resolution.  If queueing was done, return the pointer
   // to the queued instance, otherwise return NULL.
   UrlInfo* AppendToResolutionQueue(const GURL& url,
@@ skipping 25 matching lines @@
   void LoadUrlsForTrimming();
 
   // Posts a task to do additional incremental trimming of referrers_.
   void PostIncrementalTrimTask();
 
   // Calls Trim() on some or all of urls_being_trimmed_.
   // If it does not process all the URLs in that vector, it posts a task to
   // continue with them shortly (i.e., it yeilds and continues).
   void IncrementalTrimReferrers(bool trim_all_now);
 
+  // ------------- End IO thread methods.
+
+  scoped_ptr<InitialObserver> initial_observer_;
+
+  // Status of speculative DNS resolution and speculative TCP/IP connection
+  // feature.
+  bool predictor_enabled_;
+
   // work_queue_ holds a list of names we need to look up.
   HostNameQueue work_queue_;
 
   // results_ contains information for existing/prior prefetches.
   Results results_;
 
   std::set<LookupRequest*> pending_lookups_;
 
   // For testing, to verify that we don't exceed the limit.
   size_t peak_pending_lookups_;
 
   // When true, we don't make new lookup requests.
   bool shutdown_;
 
   // The number of concurrent speculative lookups currently allowed to be sent
   // to the resolver.  Any additional lookups will be queued to avoid exceeding
   // this value.  The queue is a priority queue that will accelerate
   // sub-resource speculation, and retard resolutions suggested by page scans.
   const size_t max_concurrent_dns_lookups_;
 
   // The maximum queueing delay that is acceptable before we enter congestion
   // reduction mode, and discard all queued (but not yet assigned) resolutions.
   const base::TimeDelta max_dns_queue_delay_;
 
   // The host resolver we warm DNS entries for.
-  net::HostResolver* const host_resolver_;
+  net::HostResolver* host_resolver_;
 
   // Are we currently using preconnection, rather than just DNS resolution, for
   // subresources and omni-box search URLs.
   bool preconnect_enabled_;
 
   // Most recent suggestion from Omnibox provided via AnticipateOmniboxUrl().
   std::string last_omnibox_host_;
 
   // The time when the last preresolve was done for last_omnibox_host_.
   base::TimeTicks last_omnibox_preresolve_;
@@ skipping 11 matching lines @@
   // orginial hostname.
   Referrers referrers_;
 
   // List of URLs in referrers_ currently being trimmed (scaled down to
   // eventually be aged out of use).
   std::vector<GURL> urls_being_trimmed_;
 
   // A time after which we need to do more trimming of referrers.
   base::TimeTicks next_trim_time_;
 
-  ScopedRunnableMethodFactory<Predictor> trim_task_factory_;
+  scoped_ptr<ScopedRunnableMethodFactory<Predictor> > trim_task_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Predictor);
 };
 
+// This version of the predictor is used for testing.
+class SimplePredictor : public Predictor {
+ public:
+  explicit SimplePredictor(bool preconnect_enabled)
+      : Predictor(preconnect_enabled) {}
+  virtual ~SimplePredictor() {}
+  virtual void InitNetworkPredictor(PrefService* user_prefs,
+                                    PrefService* local_state,
+                                    IOThread* io_thread);
+  virtual void ShutdownOnUIThread(PrefService* user_prefs);
+};
+
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_PREDICTOR_H_