1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
// 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/files/file_path.h"
#include "base/metrics/histogram.h"
#include "base/time/time.h"
#include "components/precache/core/precache_url_table.h"
#include "sql/connection.h"
#include "sql/transaction.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 int kPrecacheHistoryExpiryPeriodDays = 60;
} // namespace
namespace precache {
PrecacheDatabase::PrecacheDatabase()
: precache_url_table_(new PrecacheURLTable()) {
// A PrecacheDatabase can be constructed on any thread.
thread_checker_.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.
thread_checker_.DetachFromThread();
}
bool PrecacheDatabase::Init(const base::FilePath& db_path) {
DCHECK(thread_checker_.CalledOnValidThread());
DCHECK(!db_); // Init must only be called once.
db_.reset(new sql::Connection());
db_->set_histogram_tag("Precache");
if (!db_->Open(db_path)) {
// Don't initialize the URL table if unable to access
// the database.
return false;
}
if (!precache_url_table_->Init(db_.get())) {
// Raze and close the database connection to indicate that it's not usable,
// and so that the database will be created anew next time, in case it's
// corrupted.
db_->RazeAndClose();
return false;
}
return true;
}
void PrecacheDatabase::DeleteExpiredPrecacheHistory(
const base::Time& current_time) {
if (!IsDatabaseAccessible()) {
// Do nothing if unable to access the database.
return;
}
// Delete old precache history that has expired.
precache_url_table_->DeleteAllPrecachedBefore(
current_time -
base::TimeDelta::FromDays(kPrecacheHistoryExpiryPeriodDays));
}
void PrecacheDatabase::RecordURLPrecached(const GURL& url,
const base::Time& fetch_time,
int64 size, bool was_cached) {
if (!IsDatabaseAccessible()) {
// Don't track anything if unable to access the database.
return;
}
sql::Transaction transaction(db_.get());
if (!transaction.Begin()) {
// Do nothing if unable to begin a transaction.
return;
}
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.
UMA_HISTOGRAM_COUNTS("Precache.DownloadedPrecacheMotivated", size);
}
// 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);
transaction.Commit();
}
void PrecacheDatabase::RecordURLFetched(const GURL& url,
const base::Time& fetch_time,
int64 size, bool was_cached,
bool is_connection_cellular) {
if (!IsDatabaseAccessible()) {
// Don't track anything if unable to access the database.
return;
}
sql::Transaction transaction(db_.get());
if (!transaction.Begin()) {
// Do nothing if unable to begin a transaction.
return;
}
if (was_cached && !precache_url_table_->HasURL(url)) {
// Ignore cache hits that precache can't take credit for.
return;
}
if (!was_cached) {
// The fetch was served over the network during user browsing, so count it
// as downloaded non-precache bytes.
UMA_HISTOGRAM_COUNTS("Precache.DownloadedNonPrecache", size);
if (is_connection_cellular) {
UMA_HISTOGRAM_COUNTS("Precache.DownloadedNonPrecache.Cellular", size);
}
} else {
// 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.
UMA_HISTOGRAM_COUNTS("Precache.Saved", size);
if (is_connection_cellular) {
UMA_HISTOGRAM_COUNTS("Precache.Saved.Cellular", size);
}
}
// Since the resource has been fetched during user browsing, remove any record
// of that URL having been precached from the URL table, if any exists.
// The current fetch would have put this resource in the cache regardless of
// whether or not it was previously precached, so delete any record of that
// URL having been precached from the URL table.
precache_url_table_->DeleteURL(url);
transaction.Commit();
}
bool PrecacheDatabase::IsDatabaseAccessible() const {
DCHECK(thread_checker_.CalledOnValidThread());
DCHECK(db_);
return db_->is_open();
}
} // namespace precache
|
