Precache tracking database

components/precache/core/precache_database.cc

+// Copyright 2013 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 "components/precache/core/precache_database.h"
+
+#include "base/metrics/histogram.h"
+#include "base/time/time.h"
+#include "components/precache/core/precache_statistics_table.h"
+#include "components/precache/core/precache_url_table.h"
+#include "sql/connection.h"
+#include "url/gurl.h"
+
+namespace {
+
+// The number of days old that an entry in the precache URL table can be before
+// it is considered "old" and is removed from the table.
+const int64 kPrecacheHistoryExpiryPeriodDays = 60;
+
+void RecordSingleDayPrecacheUMA(
+    const precache::PrecacheStatisticsTable::PrecacheStatistics& stats) {
+  UMA_HISTOGRAM_COUNTS("Precache.DailyPrecachedKB",
+                       stats.precached_bytes / 1024);
+  UMA_HISTOGRAM_COUNTS("Precache.DailyDownloadedKB",
+                       stats.downloaded_bytes / 1024);
+  UMA_HISTOGRAM_COUNTS("Precache.DailyDownloadedKB.Cellular",
+                       stats.downloaded_bytes_cellular / 1024);
+  UMA_HISTOGRAM_COUNTS("Precache.DailySavedKB", stats.saved_bytes / 1024);
+  UMA_HISTOGRAM_COUNTS("Precache.DailySavedKB.Cellular",
+                       stats.saved_bytes_cellular / 1024);
+
+  if (stats.saved_bytes + stats.downloaded_bytes > 0) {
+    UMA_HISTOGRAM_PERCENTAGE("Precache.DailySavingsPercentage",
+                             stats.saved_bytes * 100.0 /
+                                 (stats.saved_bytes + stats.downloaded_bytes));
+  }
+
+  if (stats.saved_bytes_cellular + stats.downloaded_bytes_cellular > 0) {
+    UMA_HISTOGRAM_PERCENTAGE(
+        "Precache.DailySavingsPercentage.Cellular",
+        stats.saved_bytes_cellular * 100.0 /
+            (stats.saved_bytes_cellular + stats.downloaded_bytes_cellular));
+  }
+}
+
+}  // namespace
+
+namespace precache {
+
+PrecacheDatabase::PrecacheDatabase()
+    : precache_url_table_(new PrecacheURLTable()),
+      precache_statistics_table_(new PrecacheStatisticsTable()) {
+  // A PrecacheDatabase can be constructed on any thread.
+  DetachFromThread();
+}
+
+PrecacheDatabase::~PrecacheDatabase() {
+  // Since the PrecacheDatabase is refcounted, it will only be deleted if there
+  // are no references remaining to it, meaning that it is not in use. Thus, it
+  // is safe to delete it, regardless of what thread we are on.
+  DetachFromThread();
+}
+
+void PrecacheDatabase::Init(scoped_ptr<sql::Connection> db) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(!db_);  // Init must only be called once.
+  DCHECK(db);    // |db| must not be NULL.
+
+  db_.reset(db.release());
+  if (!IsDatabaseAccessible()) {
+    // Don't initialize the URL table or statistics table if unable to access
+    // the database.
+    return;
+  }
+
+  precache_url_table_->Init(db_.get());
+  precache_statistics_table_->Init(db_.get());
+}
+
+void PrecacheDatabase::ReportAndDeleteOldStats(const base::Time& end_date) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(db_);
+
+  if (!IsDatabaseAccessible()) {
+    // Do nothing if unable to access the database.
+    return;
+  }
+
+  // Delete old precache history that has expired.
+  precache_url_table_->DeleteAllPrecachedBetween(
+      base::Time(),
+      end_date - base::TimeDelta::FromDays(kPrecacheHistoryExpiryPeriodDays));
+
+  PrecacheStatisticsTable::PrecacheStatisticsMap stats_map;
+  precache_statistics_table_->GetAllStatsBetween(base::Time(), end_date,
+                                                 &stats_map);
+
+  // Report UMA for every row of old statistics in the statistics table. There
+  // won't be any rows in the statistics table for days when nothing was fetched
+  // or precached.
+  for (PrecacheStatisticsTable::PrecacheStatisticsMap::const_iterator it =
+           stats_map.begin();
+       it != stats_map.end(); ++it) {
+    RecordSingleDayPrecacheUMA(it->second);
+  }
+
+  precache_statistics_table_->DeleteAllStatsBetween(base::Time(), end_date);
+}
+
+void PrecacheDatabase::RecordURLFetched(const GURL& url,
+                                        const base::Time& fetch_time,
+                                        int64 size, bool was_cached,
+                                        bool is_precache,
+                                        bool is_connection_cellular) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(db_);
+
+  if (!IsDatabaseAccessible()) {
+    // Don't track anything if unable to access the database.
+    return;
+  }
+
+  if (is_precache) {
+    if (was_cached && !precache_url_table_->HasURL(url)) {
+      // Since the precache came from the cache, and there's no entry in the
+      // URL table for the URL, this means that the resource was already in the
+      // cache because of user browsing. Thus, this precache had no effect, so
+      // ignore it.
+      return;
+    }
+
+    if (!was_cached) {
+      // The precache only counts as overhead if it was downloaded over the
+      // network.
+      PrecacheStatisticsTable::PrecacheStatistics stats;
+      stats.precached_bytes = size;
+      precache_statistics_table_->IncreaseDailyStats(fetch_time, stats);
+    }
+
+    // Use the URL table to keep track of URLs that are in the cache thanks to
+    // precaching. If a row for the URL already exists, than update the
+    // timestamp to |fetch_time|.
+    precache_url_table_->AddURL(url, fetch_time);
+    return;
+  }
+
+  if (!was_cached) {
+    // The fetch was served over the network during user browsing, so count it
+    // as downloaded bytes.
+    PrecacheStatisticsTable::PrecacheStatistics stats;
+    stats.downloaded_bytes = size;
+    if (is_connection_cellular) {
+      stats.downloaded_bytes_cellular = size;
+    }
+    precache_statistics_table_->IncreaseDailyStats(fetch_time, stats);
+
+    // Since the fetch was over the network during user browsing, delete any
+    // record of it having been precached from the URL table. If it had been
+    // precached, the resource must have expired.
+    precache_url_table_->DeleteURL(url);
+    return;
+  }
+
+  if (was_cached && precache_url_table_->HasURL(url)) {
+    // The fetch was served from the cache, and since there's an entry for this
+    // URL in the URL table, this means that the resource was served from the
+    // cache only because precaching put it there. Thus, precaching was helpful,
+    // so count the fetch as saved bytes.
+    PrecacheStatisticsTable::PrecacheStatistics stats;
+    stats.saved_bytes = size;
+    if (is_connection_cellular) {
+      stats.saved_bytes_cellular = size;
+    }
+    precache_statistics_table_->IncreaseDailyStats(fetch_time, stats);
+
+    precache_url_table_->DeleteURL(url);
+  }
+}
+
+bool PrecacheDatabase::IsDatabaseAccessible() const {
+  DCHECK(CalledOnValidThread());
+  DCHECK(db_);
+
+  return db_->is_open();
+}
+
+}  // namespace precache