components/sync_driver/revisit/sessions_page_revisit_observer.cc

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "components/sync_driver/revisit/sessions_page_revisit_observer.h"
   6
   7 #include "base/metrics/histogram_macros.h"
   8 #include "base/thread_task_runner_handle.h"
   9 #include "components/sessions/session_types.h"
  10 #include "components/sync_driver/glue/synced_session.h"
  11 #include "components/sync_driver/revisit/current_tab_matcher.h"
  12 #include "components/sync_driver/revisit/offset_tab_matcher.h"
  13 #include "components/sync_driver/revisit/page_equality.h"
  14
  15 namespace sync_driver {
  16
  17 SessionsPageRevisitObserver::SessionsPageRevisitObserver(
  18     scoped_ptr<ForeignSessionsProvider> provider)
  19     : provider_(provider.Pass()) {}
  20
  21 SessionsPageRevisitObserver::~SessionsPageRevisitObserver() {}
  22
  23 void SessionsPageRevisitObserver::OnPageVisit(const GURL& url,
  24                                               const TransitionType transition) {
  25   // We need to be invoked and eventually execute on the thread which owns the
  26   // session objects the provider will give us. However, this work is not
  27   // especially time sensitive, and so we post a task to perform this to get out
  28   // of the way of any currently executing logic.
  29
  30   // Bind this task to this->AsWeakPtr() so that if we're destructed this task
  31   // just vanish instead of breaking things.
  32   base::ThreadTaskRunnerHandle::Get()->PostTask(
  33       FROM_HERE, base::Bind(&SessionsPageRevisitObserver::CheckForRevisit,
  34                             this->AsWeakPtr(), url, transition));
  35 }
  36
  37 void SessionsPageRevisitObserver::CheckForRevisit(
  38     const GURL& url,
  39     const TransitionType transition) {
  40   base::TimeTicks start(base::TimeTicks::Now());
  41
  42   // We want to match tabs/navigation entries in two slightly different ways. We
  43   // value the current url/navigation entry of a tab more highly, and want to
  44   // actually seperate metrics from the backwards/forwards entries. And then
  45   // to make things a little bit messier, we only have an accurate modified time
  46   // for the tabs/current entries. So use index offset for forward/back entries.
  47   PageEquality page_equality(url);
  48   CurrentTabMatcher current_matcher(page_equality);
  49   OffsetTabMatcher offset_matcher(page_equality);
  50
  51   std::vector<const sync_driver::SyncedSession*> foreign_sessions;
  52   if (provider_->GetAllForeignSessions(&foreign_sessions)) {
  53     for (const sync_driver::SyncedSession* session : foreign_sessions) {
  54       for (const std::pair<const SessionID::id_type, sessions::SessionWindow*>&
  55                key_value : session->windows) {
  56         for (const sessions::SessionTab* tab : key_value.second->tabs) {
  57           // These matchers look identical and could easily implement an
  58           // interface and we could iterate through a vector of matchers here.
  59           // However this would cause quite a bit of overhead at the inner most
  60           // loop of something that takes linear time in relation to the number
  61           // of open foreign tabs. A small fraction of users have thousands of
  62           // open tabs.
  63           current_matcher.Check(tab);
  64           offset_matcher.Check(tab);
  65         }
  66       }
  67     }
  68   }
  69
  70   // emit even if there are no foreign sessions so that that counts all match.
  71   current_matcher.Emit(transition);
  72   offset_matcher.Emit(transition);
  73
  74   base::TimeDelta duration(base::TimeTicks::Now() - start);
  75   UMA_HISTOGRAM_TIMES("Sync.PageRevisitSessionDuration", duration);
  76 }
  77
  78 }  // namespace sync_driver