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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
content / browser / preloading / prefetch / prefetch_match_resolver.h [blame]
// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CONTENT_BROWSER_PRELOADING_PREFETCH_PREFETCH_MATCH_RESOLVER_H_
#define CONTENT_BROWSER_PRELOADING_PREFETCH_PREFETCH_MATCH_RESOLVER_H_
#include <map>
#include "base/memory/weak_ptr.h"
#include "content/browser/preloading/prefetch/no_vary_search_helper.h"
#include "content/browser/preloading/prefetch/prefetch_container.h"
#include "content/browser/preloading/prefetch/prefetch_params.h"
#include "content/common/content_export.h"
#include "content/public/browser/global_routing_id.h"
#include "content/public/browser/navigation_handle_user_data.h"
namespace content {
class PrefetchContainer;
// TODO(crbug.com/40274818): Problem: how do we inform this class of prefetches
// being started while we are waiting for existing in-progress prefetches ?
// PrefetchService should probably do it.
class CONTENT_EXPORT PrefetchMatchResolver
: public NavigationHandleUserData<PrefetchMatchResolver> {
public:
PrefetchMatchResolver(const PrefetchMatchResolver&) = delete;
PrefetchMatchResolver& operator=(const PrefetchMatchResolver&) = delete;
~PrefetchMatchResolver() override;
base::WeakPtr<PrefetchMatchResolver> GetWeakPtr();
using OnPrefetchToServeReady =
base::OnceCallback<void(PrefetchContainer::Reader prefetch_to_serve)>;
void SetOnPrefetchToServeReadyCallback(
OnPrefetchToServeReady on_prefetch_to_serve_ready);
// A prefetch can be served, so let the browser know that it can use the
// prefetch for the navigation.
void PrefetchServed(PrefetchContainer::Reader reader);
// The prefetch container / prefetch_url cannot be used. If there are no
// more potential prefetches to wait for, let the browser know to fallback
// to normal navigation.
void PrefetchNotUsable(const PrefetchContainer& prefetch_container);
void PrefetchNotUsable(const GURL& prefetch_url);
// A prefetch is not available so let the browser know to fallback to regular
// navigation instead.
void PrefetchNotAvailable();
// If Cookies have changed, then none of the matched prefetches can be served.
// Remove all of the prefetches from `in_progress_prefetch_matches_` and let
// the browser know to fallback to regular navigation instead.
void FallbackToRegularNavigationWhenMatchedPrefetchCookiesChanged(
PrefetchContainer& prefetch_container,
const GURL& navigated_url);
void WaitForPrefetch(PrefetchContainer& prefetch_container);
void EndWaitForPrefetch(const GURL& prefetch_url);
// Check if we are waiting already for the head of this `prefetch_container`.
bool IsWaitingForPrefetch(const PrefetchContainer& prefetch_container) const;
bool IsWaitingForPrefetch(const GURL& prefetch_url) const;
private:
friend NavigationHandleUserData<PrefetchMatchResolver>;
explicit PrefetchMatchResolver(NavigationHandle& navigation_handle);
void MaybeFallbackToRegularNavigationWhenPrefetchNotUsable();
bool IsWaitingOnPrefetchHead() const;
OnPrefetchToServeReady ReleaseOnPrefetchToServeReadyCallback();
// Once the prefetch (if any) that can be used to serve a navigation to
// |url| is identified, this callback is called with that
// prefetch.
OnPrefetchToServeReady on_prefetch_to_serve_ready_callback_;
// Keep track of all prefetches that we are waiting for head on.
std::map<GURL, base::WeakPtr<PrefetchContainer>>
in_progress_prefetch_matches_;
base::WeakPtrFactory<PrefetchMatchResolver> weak_ptr_factory_{this};
// For debug logs.
CONTENT_EXPORT friend std::ostream& operator<<(
std::ostream& ostream,
const PrefetchMatchResolver& prefetch_match_resolver);
friend NavigationHandleUserData;
NAVIGATION_HANDLE_USER_DATA_KEY_DECL();
};
// Manages matching process of prefetch
// https://wicg.github.io/nav-speculation/prefetch.html#wait-for-a-matching-prefetch-record
//
// This class is created per call of
// `PrefetchURLLoaderInterceptor::MaybeCreateLoader()` except redirects for
// already matched prefetch and still servable ones, i.e. a prefetch was matched
// by prior call of `PrefetchMatchResolver2::FindPrefetch()`.
//
// Lifetime of this class is from the call of `FindPrefetch()` to calling
// `callback_`. This is owned by itself. See the comment on `self_`.
//
// Note about "2": This is the new implementation of the matching process
// of prefetch that is used when `UseNewWaitLoop()` returns true. The old
// implementation is `PrefetchMatchResolver`, so this is named "2".
// Differences are, for example:
//
// - `PrefetchMatchResolver2` has strict precondition/postcondition
// e.g. `CHECK_EQ(candidates_.size(), 0u);` when the matching process
// starts/ends.
// - `PrefetchMatchResolver` is `NavigationHandleUserData`
// and can be used multiple times for redirects, while
// `PrefetchMatchResolver2` forbids it in architecture level.
//
// That's the reason why we decided to implement the separate class.
//
// TODO(crbug.com/353490734): Remove the above `Note about "2"`.
class CONTENT_EXPORT PrefetchMatchResolver2 final
: public PrefetchContainer::Observer {
public:
using Callback = base::OnceCallback<void(PrefetchContainer::Reader reader)>;
~PrefetchMatchResolver2() override;
// Not movable nor copyable.
PrefetchMatchResolver2(PrefetchMatchResolver2&& other) = delete;
PrefetchMatchResolver2& operator=(PrefetchMatchResolver2&& other) = delete;
PrefetchMatchResolver2(const PrefetchMatchResolver2&) = delete;
PrefetchMatchResolver2& operator=(const PrefetchMatchResolver2&) = delete;
// PrefetchContainer::Observer implementation
void OnWillBeDestroyed(PrefetchContainer& prefetch_container) override;
void OnGotInitialEligibility(PrefetchContainer& prefetch_container,
PreloadingEligibility eligibility) override;
void OnDeterminedHead(PrefetchContainer& prefetch_container) override;
// Finds prefetch that matches to a navigation and is servable.
//
// Corresponds to
// https://wicg.github.io/nav-speculation/prefetch.html#wait-for-a-matching-prefetch-record
//
// This method is async. `callback` will be called when it is done.
// `bool(reader)` is true iff a matching servable prefetch is found.
static void FindPrefetch(PrefetchContainer::Key navigated_key,
bool is_nav_prerender,
PrefetchService& prefetch_service,
base::WeakPtr<PrefetchServingPageMetricsContainer>
serving_page_metrics_container,
Callback callback);
private:
struct CandidateData final {
CandidateData();
~CandidateData();
base::WeakPtr<PrefetchContainer> prefetch_container;
std::unique_ptr<base::OneShotTimer> timeout_timer;
};
explicit PrefetchMatchResolver2(PrefetchContainer::Key navigated_key,
base::WeakPtr<PrefetchService>,
Callback callback);
// Returns blocked duration. Returns null iff it's not blocked yet.
std::optional<base::TimeDelta> GetBlockedDuration() const;
// Helpers of `FindPrefetch()`.
//
// Control flow starts with `FindPrefetchInternal()` and ends with
// `UnblockInternal()`.
//
// Actually, it is different from
// https://wicg.github.io/nav-speculation/prefetch.html#wait-for-a-matching-prefetch-record
// Major ones:
//
// - This implementation has timeout: `CandidateData::timeout_timer`.
// - This implementation collects candidate prefetches first. So, it doesn't
// handle prefetches started after this method started.
void FindPrefetchInternal(bool is_nav_prerender,
PrefetchService& prefetch_service,
base::WeakPtr<PrefetchServingPageMetricsContainer>
serving_page_metrics_container);
// Each candidate `PrefetchContainer` proceeds to
//
// `RegisterCandidate()` (required)
// -> `StartWaitFor()` (optional, if servable state is
// `kShouldBlockUntilHead`)
// -> `UnregisterCandidate()` (required)
void RegisterCandidate(PrefetchContainer& prefetch_container);
void StartWaitFor(const PrefetchContainer::Key& prefetch_key,
PrefetchContainer::ServableState servable_state);
void UnregisterCandidate(const PrefetchContainer::Key& prefetch_key,
bool is_served);
void OnTimeout(PrefetchContainer::Key prefetch_key);
void UnblockForMatch(const PrefetchContainer::Key& prefetch_key);
void UnblockForNoCandidates();
// Unregisters unmatched prefetch and unblocks if there are no other waiting
// prefetches.
void MaybeUnblockForUnmatch(const PrefetchContainer::Key& prefetch_key);
void UnblockForCookiesChanged();
void UnblockInternal(PrefetchContainer::Reader reader);
// Lifetime of this class is from the call of `FindPrefetch()` to calling
// `callback_`. Note that
//
// - `FindPrefetchInternal()` consumes this class. We don't want to use this
// class twice.
// - `NavigationLoaderInterceptor::MaybeCreateLoader()` can be called multiple
// times, e.g. redirect.
//
// So, we don't believe that `NavigationHandleUserData` is an appropriate
// choice to manage lifetime. Possible choices are:
//
// A. This way.
// B. Have another class that inherits `NavigationHandleUserData` and manages
// this class for each `NavigationLoaderInterceptor::MaybeCreateLoader()`
// call.
//
// Note that `NavigationLoaderInterceptor::MaybeCreateLoader()` requires that
// `callback_` is eventually called. So, we don't need to care about memory
// leak.
//
// A would be enough.
std::unique_ptr<PrefetchMatchResolver2> self_;
const PrefetchContainer::Key navigated_key_;
base::WeakPtr<PrefetchService> prefetch_service_;
Callback callback_;
std::map<PrefetchContainer::Key, std::unique_ptr<CandidateData>> candidates_;
std::optional<base::TimeTicks> wait_started_at_ = std::nullopt;
};
// Abstracts required operations for `PrefetchContainer` that is used to collect
// match candidates in the first phase of
// `PrefetchMatchResolver2::FindPrefetch()`. Used for unit testing.
template <class T>
concept MatchCandidate =
requires(T& t,
const GURL& url,
base::TimeDelta cacheable_duration,
base::WeakPtr<PrefetchServingPageMetricsContainer>
serving_page_metrics_container,
std::ostream& ostream) {
t.key();
t.GetURL();
t.GetServableState(cacheable_duration);
t.GetNoVarySearchHint();
t.IsNoVarySearchHeaderMatch(url);
t.ShouldWaitForNoVarySearchHeader(url);
t.HasPrefetchStatus();
t.GetPrefetchStatus();
t.HasPrefetchBeenConsideredToServe();
t.IsDecoy();
t.SetServingPageMetrics(serving_page_metrics_container);
t.UpdateServingPageMetrics();
ostream << t;
};
// Do not use it outside of this header.
//
// Collects "potentially matching" `PrefetchContainer`s.
//
// "potentially matching" is either:
//
// - Exact match
// - No-Vary-Search header match.
// - No-Vary-Search hint match and non redirect header is not still arrived.
template <class T>
requires MatchCandidate<T>
std::vector<T*> CollectPotentialMatchPrefetchContainers(
const std::map<PrefetchContainer::Key, std::unique_ptr<T>>& prefetches,
const PrefetchContainer::Key& navigated_key) {
std::vector<T*> result;
// Note that exact match one is at the head if exists by the property of
// `IterateCandidates()`.
no_vary_search::IterateCandidates(
navigated_key, prefetches,
base::BindRepeating(
[](const PrefetchContainer::Key& navigated_key,
std::vector<T*>* result,
const std::unique_ptr<T>& prefetch_container,
no_vary_search::MatchType match_type) {
switch (match_type) {
case no_vary_search::MatchType::kExact:
case no_vary_search::MatchType::kNoVarySearchHeader:
case no_vary_search::MatchType::kNoVarySearchHint:
result->push_back(prefetch_container.get());
break;
case no_vary_search::MatchType::kOther:
break;
}
return no_vary_search::IterateCandidateResult::kContinue;
},
navigated_key, base::Unretained(&result)));
return result;
}
// Do not use it outside of this header.
//
// Returns "availability" of a `PrefetchContainer`.
//
// "Available" here is not a technical term. It means that the
// `PrefetchContainer` is able to be used or has the possibility in the near
// future. See implementation for the detailed conditions.
template <class T>
requires MatchCandidate<T>
bool IsCandidateAvailable(const T& candidate,
PrefetchContainer::ServableState servable_state,
bool is_nav_prerender) {
if (candidate.HasPrefetchBeenConsideredToServe()) {
DVLOG(1) << "CollectMatchCandidatesGeneric: skipped because already "
"considered to serve: candidate = "
<< candidate;
return false;
}
switch (servable_state) {
case PrefetchContainer::ServableState::kNotServable:
DVLOG(1) << "CollectMatchCandidatesGeneric: skipped because not "
"servable: candidate = "
<< candidate;
return false;
case PrefetchContainer::ServableState::kShouldBlockUntilEligibilityGot:
case PrefetchContainer::ServableState::kShouldBlockUntilHeadReceived:
case PrefetchContainer::ServableState::kServable:
break;
}
switch (servable_state) {
case PrefetchContainer::ServableState::kShouldBlockUntilEligibilityGot:
if (!is_nav_prerender) {
DVLOG(1)
<< "CollectMatchCandidatesGeneric: skipped because it's checking "
"eligibility and the navigation is not a prerender: candidate = "
<< candidate;
return false;
}
break;
case PrefetchContainer::ServableState::kServable:
case PrefetchContainer::ServableState::kNotServable:
case PrefetchContainer::ServableState::kShouldBlockUntilHeadReceived:
break;
}
if (candidate.IsDecoy()) {
DVLOG(1) << "CollectMatchCandidatesGeneric: skipped because prefetch is a "
"decoy: candidate = "
<< candidate;
return false;
}
if (candidate.HasPrefetchStatus() &&
candidate.GetPrefetchStatus() ==
PrefetchStatus::kPrefetchNotUsedCookiesChanged) {
// Note: This codepath is only be reached in practice if we create a
// second NavigationRequest to this prefetch's URL. The first
// NavigationRequest would call GetPrefetch, which might set this
// PrefetchContainer's status to kPrefetchNotUsedCookiesChanged.
DVLOG(1) << "CollectMatchCandidatesGeneric: skipped because cookies for "
"url have changed since prefetch completed: candidate = "
<< candidate;
return false;
}
DVLOG(1) << "CollectMatchCandidatesGeneric: matched: candidate = "
<< candidate;
return true;
}
// Collects `PrefetchContainer`s that are expected to match to `navigated_key`.
//
// This is defined with the template for testing the first phase of
// `PrefetchMatchResolver2::FindPrefetch()` with mock `PrefetchContainer`.
template <class T>
requires MatchCandidate<T>
std::pair<
std::vector<T*>,
base::flat_map<PrefetchContainer::Key, PrefetchContainer::ServableState>>
CollectMatchCandidatesGeneric(
const std::map<PrefetchContainer::Key, std::unique_ptr<T>>& prefetches,
const PrefetchContainer::Key& navigated_key,
bool is_nav_prerender,
base::WeakPtr<PrefetchServingPageMetricsContainer>
serving_page_metrics_container) {
std::vector<T*> candidates =
CollectPotentialMatchPrefetchContainers(prefetches, navigated_key);
for (T* candidate : candidates) {
candidate->SetServingPageMetrics(serving_page_metrics_container);
candidate->UpdateServingPageMetrics();
}
std::vector<T*> candidates_available;
// See the comment of `PrefetchService::CollectMatchCandidates()`.
base::flat_map<PrefetchContainer::Key, PrefetchContainer::ServableState>
servable_states;
for (T* candidate : candidates) {
PrefetchContainer::ServableState servable_state =
candidate->GetServableState(PrefetchCacheableDuration());
if (IsCandidateAvailable(*candidate, servable_state, is_nav_prerender)) {
candidates_available.push_back(candidate);
servable_states.emplace(candidate->key(), servable_state);
}
}
return std::make_pair(std::move(candidates_available),
std::move(servable_states));
}
} // namespace content
#endif // CONTENT_BROWSER_PRELOADING_PREFETCH_PREFETCH_MATCH_RESOLVER_H_