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| 1 // Copyright (c) 2006-2010 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 "chrome/browser/net/dns_global.h" | |
| 6 | |
| 7 #include <map> | |
| 8 #include <string> | |
| 9 | |
| 10 #include "base/singleton.h" | |
| 11 #include "base/stats_counters.h" | |
| 12 #include "base/stl_util-inl.h" | |
| 13 #include "base/string_util.h" | |
| 14 #include "base/thread.h" | |
| 15 #include "base/waitable_event.h" | |
| 16 #include "base/values.h" | |
| 17 #include "chrome/browser/browser.h" | |
| 18 #include "chrome/browser/browser_process.h" | |
| 19 #include "chrome/browser/chrome_thread.h" | |
| 20 #include "chrome/browser/io_thread.h" | |
| 21 #include "chrome/browser/net/dns_host_info.h" | |
| 22 #include "chrome/browser/net/preconnect.h" | |
| 23 #include "chrome/browser/net/referrer.h" | |
| 24 #include "chrome/browser/pref_service.h" | |
| 25 #include "chrome/browser/profile.h" | |
| 26 #include "chrome/browser/session_startup_pref.h" | |
| 27 #include "chrome/common/notification_registrar.h" | |
| 28 #include "chrome/common/notification_service.h" | |
| 29 #include "chrome/common/pref_names.h" | |
| 30 #include "net/base/host_resolver.h" | |
| 31 #include "net/base/host_resolver_impl.h" | |
| 32 | |
| 33 using base::Time; | |
| 34 using base::TimeDelta; | |
| 35 | |
| 36 namespace chrome_browser_net { | |
| 37 | |
| 38 static void DnsMotivatedPrefetch(const GURL& url, | |
| 39 UrlInfo::ResolutionMotivation motivation); | |
| 40 | |
| 41 static void DnsPrefetchMotivatedList(const UrlList& urls, | |
| 42 UrlInfo::ResolutionMotivation motivation); | |
| 43 | |
| 44 static UrlList GetPredictedUrlListAtStartup( | |
| 45 PrefService* user_prefs, PrefService* local_state); | |
| 46 | |
| 47 // static | |
| 48 const size_t PredictorInit::kMaxPrefetchConcurrentLookups = 8; | |
| 49 | |
| 50 // static | |
| 51 const int PredictorInit::kMaxPrefetchQueueingDelayMs = 500; | |
| 52 | |
| 53 // A version number for prefs that are saved. This should be incremented when | |
| 54 // we change the format so that we discard old data. | |
| 55 static const int kPredictorStartupFormatVersion = 1; | |
| 56 | |
| 57 //------------------------------------------------------------------------------ | |
| 58 // Static helper functions | |
| 59 //------------------------------------------------------------------------------ | |
| 60 | |
| 61 // Put URL in canonical form, including a scheme, host, and port. | |
| 62 // Returns GURL::EmptyGURL() if the scheme is not http/https or if the url | |
| 63 // cannot be otherwise canonicalized. | |
| 64 static GURL CanonicalizeUrl(const GURL& url) { | |
| 65 if (!url.has_host()) | |
| 66 return GURL::EmptyGURL(); | |
| 67 | |
| 68 std::string scheme; | |
| 69 if (url.has_scheme()) { | |
| 70 scheme = url.scheme(); | |
| 71 if (scheme != "http" && scheme != "https") | |
| 72 return GURL::EmptyGURL(); | |
| 73 if (url.has_port()) | |
| 74 return url.GetWithEmptyPath(); | |
| 75 } else { | |
| 76 scheme = "http"; | |
| 77 } | |
| 78 | |
| 79 // If we omit a port, it will default to 80 or 443 as appropriate. | |
| 80 std::string colon_plus_port; | |
| 81 if (url.has_port()) | |
| 82 colon_plus_port = ":" + url.port(); | |
| 83 | |
| 84 return GURL(scheme + "://" + url.host() + colon_plus_port); | |
| 85 } | |
| 86 | |
| 87 //------------------------------------------------------------------------------ | |
| 88 // This section contains all the globally accessable API entry points for the | |
| 89 // DNS Prefetching feature. | |
| 90 //------------------------------------------------------------------------------ | |
| 91 | |
| 92 // Status of prefetch feature, controlling whether any prefetching is done. | |
| 93 static bool dns_prefetch_enabled = true; | |
| 94 | |
| 95 // Cached inverted copy of the off_the_record pref. | |
| 96 static bool on_the_record_switch = true; | |
| 97 | |
| 98 // Enable/disable Dns prefetch activity (either via command line, or via pref). | |
| 99 void EnablePredictor(bool enable) { | |
| 100 // NOTE: this is invoked on the UI thread. | |
| 101 dns_prefetch_enabled = enable; | |
| 102 } | |
| 103 | |
| 104 void OnTheRecord(bool enable) { | |
| 105 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 106 if (on_the_record_switch == enable) | |
| 107 return; | |
| 108 on_the_record_switch = enable; | |
| 109 if (on_the_record_switch) | |
| 110 g_browser_process->io_thread()->ChangedToOnTheRecord(); | |
| 111 } | |
| 112 | |
| 113 void RegisterPrefs(PrefService* local_state) { | |
| 114 local_state->RegisterListPref(prefs::kDnsStartupPrefetchList); | |
| 115 local_state->RegisterListPref(prefs::kDnsHostReferralList); | |
| 116 } | |
| 117 | |
| 118 void RegisterUserPrefs(PrefService* user_prefs) { | |
| 119 user_prefs->RegisterBooleanPref(prefs::kDnsPrefetchingEnabled, true); | |
| 120 } | |
| 121 | |
| 122 // When enabled, we use the following instance to service all requests in the | |
| 123 // browser process. | |
| 124 // TODO(willchan): Look at killing this. | |
| 125 static Predictor* predictor = NULL; | |
| 126 | |
| 127 // This API is only used in the browser process. | |
| 128 // It is called from an IPC message originating in the renderer. It currently | |
| 129 // includes both Page-Scan, and Link-Hover prefetching. | |
| 130 // TODO(jar): Separate out link-hover prefetching, and page-scan results. | |
| 131 void DnsPrefetchList(const NameList& hostnames) { | |
| 132 // TODO(jar): Push GURL transport further back into renderer. | |
| 133 UrlList urls; | |
| 134 for (NameList::const_iterator it = hostnames.begin(); | |
| 135 it < hostnames.end(); | |
| 136 ++it) { | |
| 137 urls.push_back(GURL("http://" + *it + ":80")); | |
| 138 } | |
| 139 | |
| 140 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 141 DnsPrefetchMotivatedList(urls, UrlInfo::PAGE_SCAN_MOTIVATED); | |
| 142 } | |
| 143 | |
| 144 static void DnsPrefetchMotivatedList( | |
| 145 const UrlList& urls, | |
| 146 UrlInfo::ResolutionMotivation motivation) { | |
| 147 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI) || | |
| 148 ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 149 if (!dns_prefetch_enabled || NULL == predictor) | |
| 150 return; | |
| 151 | |
| 152 if (ChromeThread::CurrentlyOn(ChromeThread::IO)) { | |
| 153 predictor->ResolveList(urls, motivation); | |
| 154 } else { | |
| 155 ChromeThread::PostTask( | |
| 156 ChromeThread::IO, | |
| 157 FROM_HERE, | |
| 158 NewRunnableMethod(predictor, | |
| 159 &Predictor::ResolveList, urls, motivation)); | |
| 160 } | |
| 161 } | |
| 162 | |
| 163 // This API is used by the autocomplete popup box (where URLs are typed). | |
| 164 void AnticipateUrl(const GURL& url, bool preconnectable) { | |
| 165 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 166 if (!dns_prefetch_enabled || NULL == predictor) | |
| 167 return; | |
| 168 if (!url.is_valid()) | |
| 169 return; | |
| 170 | |
| 171 static std::string last_host; | |
| 172 std::string host = url.HostNoBrackets(); | |
| 173 bool is_new_host_request = (host != last_host); | |
| 174 last_host = host; | |
| 175 | |
| 176 // Omnibox tends to call in pairs (just a few milliseconds apart), and we | |
| 177 // really don't need to keep resolving a name that often. | |
| 178 // TODO(jar): A/B tests could check for perf impact of the early returns. | |
| 179 static base::TimeTicks last_prefetch_for_host; | |
| 180 base::TimeTicks now = base::TimeTicks::Now(); | |
| 181 if (!is_new_host_request) { | |
| 182 const int kMinPreresolveSeconds(10); | |
| 183 if (kMinPreresolveSeconds > (now - last_prefetch_for_host).InSeconds()) | |
| 184 return; | |
| 185 } | |
| 186 last_prefetch_for_host = now; | |
| 187 | |
| 188 GURL canonical_url(CanonicalizeUrl(url)); | |
| 189 | |
| 190 if (predictor->preconnect_enabled() && preconnectable) { | |
| 191 static base::TimeTicks last_keepalive; | |
| 192 // TODO(jar): The wild guess of 30 seconds could be tuned/tested, but it | |
| 193 // currently is just a guess that most sockets will remain open for at least | |
| 194 // 30 seconds. | |
| 195 const int kMaxSearchKeepaliveSeconds(30); | |
| 196 if ((now - last_keepalive).InSeconds() < kMaxSearchKeepaliveSeconds) | |
| 197 return; | |
| 198 last_keepalive = now; | |
| 199 | |
| 200 if (Preconnect::PreconnectOnUIThread(canonical_url)) | |
| 201 return; // Skip pre-resolution, since we'll open a connection. | |
| 202 } | |
| 203 | |
| 204 // Perform at least DNS pre-resolution. | |
| 205 DnsMotivatedPrefetch(canonical_url, UrlInfo::OMNIBOX_MOTIVATED); | |
| 206 } | |
| 207 | |
| 208 static void DnsMotivatedPrefetch(const GURL& url, | |
| 209 UrlInfo::ResolutionMotivation motivation) { | |
| 210 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 211 if (!dns_prefetch_enabled || NULL == predictor || !url.has_host()) | |
| 212 return; | |
| 213 | |
| 214 ChromeThread::PostTask( | |
| 215 ChromeThread::IO, | |
| 216 FROM_HERE, | |
| 217 NewRunnableMethod(predictor, | |
| 218 &Predictor::Resolve, url, motivation)); | |
| 219 } | |
| 220 | |
| 221 //------------------------------------------------------------------------------ | |
| 222 // This section intermingles prefetch results with actual browser HTTP | |
| 223 // network activity. It supports calculating of the benefit of a prefetch, as | |
| 224 // well as recording what prefetched hostname resolutions might be potentially | |
| 225 // helpful during the next chrome-startup. | |
| 226 //------------------------------------------------------------------------------ | |
| 227 | |
| 228 // This function determines if there was a saving by prefetching the hostname | |
| 229 // for which the navigation_info is supplied. | |
| 230 static bool AccruePrefetchBenefits(const GURL& referrer_url, | |
| 231 UrlInfo* navigation_info) { | |
| 232 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 233 if (!dns_prefetch_enabled || NULL == predictor) | |
| 234 return false; | |
| 235 DCHECK(referrer_url == referrer_url.GetWithEmptyPath()); | |
| 236 return predictor->AccruePrefetchBenefits(referrer_url, navigation_info); | |
| 237 } | |
| 238 | |
| 239 void PredictSubresources(const GURL& url) { | |
| 240 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 241 if (!dns_prefetch_enabled || NULL == predictor) | |
| 242 return; | |
| 243 predictor->PredictSubresources(url); | |
| 244 } | |
| 245 | |
| 246 void PredictFrameSubresources(const GURL& url) { | |
| 247 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 248 if (!dns_prefetch_enabled || NULL == predictor) | |
| 249 return; | |
| 250 predictor->PredictFrameSubresources(url); | |
| 251 } | |
| 252 | |
| 253 void LearnFromNavigation(const GURL& referring_url, const GURL& target_url) { | |
| 254 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 255 if (!dns_prefetch_enabled || NULL == predictor) | |
| 256 return; | |
| 257 predictor->LearnFromNavigation(referring_url, target_url); | |
| 258 } | |
| 259 | |
| 260 // The observer class needs to connect starts and finishes of HTTP network | |
| 261 // resolutions. We use the following type for that map. | |
| 262 typedef std::map<int, UrlInfo> ObservedResolutionMap; | |
| 263 | |
| 264 // There will only be one instance ever created of the following Observer | |
| 265 // class. The PrefetchObserver lives on the IO thread, and intercepts DNS | |
| 266 // resolutions made by the network stack. | |
| 267 class PrefetchObserver : public net::HostResolver::Observer { | |
| 268 public: | |
| 269 typedef std::map<GURL, UrlInfo> FirstResolutionMap; | |
| 270 | |
| 271 // net::HostResolver::Observer implementation: | |
| 272 virtual void OnStartResolution( | |
| 273 int request_id, | |
| 274 const net::HostResolver::RequestInfo& request_info); | |
| 275 virtual void OnFinishResolutionWithStatus( | |
| 276 int request_id, | |
| 277 bool was_resolved, | |
| 278 const net::HostResolver::RequestInfo& request_info); | |
| 279 virtual void OnCancelResolution( | |
| 280 int request_id, | |
| 281 const net::HostResolver::RequestInfo& request_info); | |
| 282 | |
| 283 void DnsGetFirstResolutionsHtml(std::string* output); | |
| 284 void GetInitialDnsResolutionList(ListValue* startup_list); | |
| 285 | |
| 286 private: | |
| 287 void StartupListAppend(const UrlInfo& navigation_info); | |
| 288 | |
| 289 // Map of pending resolutions seen by observer. | |
| 290 ObservedResolutionMap resolutions_; | |
| 291 // List of the first N hostname resolutions observed in this run. | |
| 292 FirstResolutionMap first_resolutions_; | |
| 293 // The number of hostnames we'll save for prefetching at next startup. | |
| 294 static const size_t kStartupResolutionCount = 10; | |
| 295 }; | |
| 296 | |
| 297 // TODO(willchan): Look at killing this global. | |
| 298 static PrefetchObserver* g_prefetch_observer = NULL; | |
| 299 | |
| 300 //------------------------------------------------------------------------------ | |
| 301 // Member definitions for above Observer class. | |
| 302 | |
| 303 void PrefetchObserver::OnStartResolution( | |
| 304 int request_id, | |
| 305 const net::HostResolver::RequestInfo& request_info) { | |
| 306 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 307 if (request_info.is_speculative()) | |
| 308 return; // One of our own requests. | |
| 309 if (!request_info.hostname().length()) | |
| 310 return; // PAC scripts may create queries without a hostname. | |
| 311 | |
| 312 UrlInfo navigation_info; | |
| 313 // TODO(jar): Remove hack which guestimates ssl via port number, and perhaps | |
| 314 // have actual URL passed down in request_info instead. | |
| 315 bool is_ssl(443 == request_info.port()); | |
| 316 std::string url_spec = is_ssl ? "https://" : "http://"; | |
| 317 url_spec += request_info.hostname(); | |
| 318 url_spec += ":"; | |
| 319 url_spec += IntToString(request_info.port()); | |
| 320 navigation_info.SetUrl(GURL(url_spec)); | |
| 321 navigation_info.SetStartedState(); | |
| 322 | |
| 323 // This entry will be deleted either by OnFinishResolutionWithStatus(), or | |
| 324 // by OnCancelResolution(). | |
| 325 resolutions_[request_id] = navigation_info; | |
| 326 } | |
| 327 | |
| 328 void PrefetchObserver::OnFinishResolutionWithStatus( | |
| 329 int request_id, | |
| 330 bool was_resolved, | |
| 331 const net::HostResolver::RequestInfo& request_info) { | |
| 332 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 333 if (request_info.is_speculative()) | |
| 334 return; // One of our own requests. | |
| 335 if (!request_info.hostname().length()) | |
| 336 return; // PAC scripts may create queries without a hostname. | |
| 337 UrlInfo navigation_info; | |
| 338 size_t startup_count = 0; | |
| 339 { | |
| 340 ObservedResolutionMap::iterator it = resolutions_.find(request_id); | |
| 341 if (resolutions_.end() == it) { | |
| 342 NOTREACHED(); | |
| 343 return; | |
| 344 } | |
| 345 navigation_info = it->second; | |
| 346 resolutions_.erase(it); | |
| 347 startup_count = first_resolutions_.size(); | |
| 348 } | |
| 349 | |
| 350 navigation_info.SetFinishedState(was_resolved); // Get timing info | |
| 351 AccruePrefetchBenefits(CanonicalizeUrl(request_info.referrer()), | |
| 352 &navigation_info); | |
| 353 | |
| 354 // Handle sub-resource resolutions now that the critical navigational | |
| 355 // resolution has completed. This prevents us from in any way delaying that | |
| 356 // navigational resolution. | |
| 357 std::string url_spec; | |
| 358 StringAppendF(&url_spec, "http%s://%s:%d", "", | |
| 359 request_info.hostname().c_str(), request_info.port()); | |
| 360 PredictSubresources(GURL(url_spec)); | |
| 361 | |
| 362 if (kStartupResolutionCount <= startup_count || !was_resolved) | |
| 363 return; | |
| 364 // TODO(jar): Don't add host to our list if it is a non-linked lookup, and | |
| 365 // instead rely on Referrers to pull this in automatically with the enclosing | |
| 366 // page load (once we start to persist elements of our referrer tree). | |
| 367 StartupListAppend(navigation_info); | |
| 368 } | |
| 369 | |
| 370 void PrefetchObserver::OnCancelResolution( | |
| 371 int request_id, | |
| 372 const net::HostResolver::RequestInfo& request_info) { | |
| 373 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 374 if (request_info.is_speculative()) | |
| 375 return; // One of our own requests. | |
| 376 if (!request_info.hostname().length()) | |
| 377 return; // PAC scripts may create queries without a hostname. | |
| 378 | |
| 379 // Remove the entry from |resolutions| that was added by OnStartResolution(). | |
| 380 ObservedResolutionMap::iterator it = resolutions_.find(request_id); | |
| 381 if (resolutions_.end() == it) { | |
| 382 NOTREACHED(); | |
| 383 return; | |
| 384 } | |
| 385 resolutions_.erase(it); | |
| 386 } | |
| 387 | |
| 388 void PrefetchObserver::StartupListAppend(const UrlInfo& navigation_info) { | |
| 389 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 390 | |
| 391 if (!on_the_record_switch || NULL == predictor) | |
| 392 return; | |
| 393 if (kStartupResolutionCount <= first_resolutions_.size()) | |
| 394 return; // Someone just added the last item. | |
| 395 if (ContainsKey(first_resolutions_, navigation_info.url())) | |
| 396 return; // We already have this hostname listed. | |
| 397 first_resolutions_[navigation_info.url()] = navigation_info; | |
| 398 } | |
| 399 | |
| 400 void PrefetchObserver::GetInitialDnsResolutionList(ListValue* startup_list) { | |
| 401 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 402 DCHECK(startup_list); | |
| 403 startup_list->Clear(); | |
| 404 DCHECK_EQ(0u, startup_list->GetSize()); | |
| 405 startup_list->Append(new FundamentalValue(kPredictorStartupFormatVersion)); | |
| 406 for (FirstResolutionMap::iterator it = first_resolutions_.begin(); | |
| 407 it != first_resolutions_.end(); | |
| 408 ++it) { | |
| 409 DCHECK(it->first == CanonicalizeUrl(it->first)); | |
| 410 startup_list->Append(new StringValue(it->first.spec())); | |
| 411 } | |
| 412 } | |
| 413 | |
| 414 void PrefetchObserver::DnsGetFirstResolutionsHtml(std::string* output) { | |
| 415 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 416 | |
| 417 UrlInfo::DnsInfoTable resolution_list; | |
| 418 { | |
| 419 for (FirstResolutionMap::iterator it(first_resolutions_.begin()); | |
| 420 it != first_resolutions_.end(); | |
| 421 it++) { | |
| 422 resolution_list.push_back(it->second); | |
| 423 } | |
| 424 } | |
| 425 UrlInfo::GetHtmlTable(resolution_list, | |
| 426 "Future startups will prefetch DNS records for ", false, output); | |
| 427 } | |
| 428 | |
| 429 //------------------------------------------------------------------------------ | |
| 430 // Support observer to detect opening and closing of OffTheRecord windows. | |
| 431 // This object lives on the UI thread. | |
| 432 | |
| 433 class OffTheRecordObserver : public NotificationObserver { | |
| 434 public: | |
| 435 void Register() { | |
| 436 // TODO(pkasting): This test should not be necessary. See crbug.com/12475. | |
| 437 if (registrar_.IsEmpty()) { | |
| 438 registrar_.Add(this, NotificationType::BROWSER_CLOSED, | |
| 439 NotificationService::AllSources()); | |
| 440 registrar_.Add(this, NotificationType::BROWSER_OPENED, | |
| 441 NotificationService::AllSources()); | |
| 442 } | |
| 443 } | |
| 444 | |
| 445 void Observe(NotificationType type, const NotificationSource& source, | |
| 446 const NotificationDetails& details) { | |
| 447 switch (type.value) { | |
| 448 case NotificationType::BROWSER_OPENED: | |
| 449 if (!Source<Browser>(source)->profile()->IsOffTheRecord()) | |
| 450 break; | |
| 451 ++count_off_the_record_windows_; | |
| 452 OnTheRecord(false); | |
| 453 break; | |
| 454 | |
| 455 case NotificationType::BROWSER_CLOSED: | |
| 456 if (!Source<Browser>(source)->profile()->IsOffTheRecord()) | |
| 457 break; // Ignore ordinary windows. | |
| 458 DCHECK_LT(0, count_off_the_record_windows_); | |
| 459 if (0 >= count_off_the_record_windows_) // Defensive coding. | |
| 460 break; | |
| 461 if (--count_off_the_record_windows_) | |
| 462 break; // Still some windows are incognito. | |
| 463 OnTheRecord(true); | |
| 464 break; | |
| 465 | |
| 466 default: | |
| 467 break; | |
| 468 } | |
| 469 } | |
| 470 | |
| 471 private: | |
| 472 friend struct DefaultSingletonTraits<OffTheRecordObserver>; | |
| 473 OffTheRecordObserver() : count_off_the_record_windows_(0) {} | |
| 474 ~OffTheRecordObserver() {} | |
| 475 | |
| 476 NotificationRegistrar registrar_; | |
| 477 int count_off_the_record_windows_; | |
| 478 | |
| 479 DISALLOW_COPY_AND_ASSIGN(OffTheRecordObserver); | |
| 480 }; | |
| 481 | |
| 482 //------------------------------------------------------------------------------ | |
| 483 // This section supports the about:dns page. | |
| 484 //------------------------------------------------------------------------------ | |
| 485 | |
| 486 // Provide global support for the about:dns page. | |
| 487 void PredictorGetHtmlInfo(std::string* output) { | |
| 488 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 489 | |
| 490 output->append("<html><head><title>About DNS</title>" | |
| 491 // We'd like the following no-cache... but it doesn't work. | |
| 492 // "<META HTTP-EQUIV=\"Pragma\" CONTENT=\"no-cache\">" | |
| 493 "</head><body>"); | |
| 494 if (!dns_prefetch_enabled || NULL == predictor) { | |
| 495 output->append("Dns Prefetching is disabled."); | |
| 496 } else { | |
| 497 if (!on_the_record_switch) { | |
| 498 output->append("Incognito mode is active in a window."); | |
| 499 } else { | |
| 500 predictor->GetHtmlInfo(output); | |
| 501 if (g_prefetch_observer) | |
| 502 g_prefetch_observer->DnsGetFirstResolutionsHtml(output); | |
| 503 predictor->GetHtmlReferrerLists(output); | |
| 504 } | |
| 505 } | |
| 506 output->append("</body></html>"); | |
| 507 } | |
| 508 | |
| 509 //------------------------------------------------------------------------------ | |
| 510 // This section intializes global DNS prefetch services. | |
| 511 //------------------------------------------------------------------------------ | |
| 512 | |
| 513 static void InitNetworkPredictor(TimeDelta max_dns_queue_delay, | |
| 514 size_t max_concurrent, PrefService* user_prefs, PrefService* local_state, | |
| 515 bool preconnect_enabled) { | |
| 516 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 517 | |
| 518 bool prefetching_enabled = | |
| 519 user_prefs->GetBoolean(prefs::kDnsPrefetchingEnabled); | |
| 520 | |
| 521 // Gather the list of hostnames to prefetch on startup. | |
| 522 UrlList urls = | |
| 523 GetPredictedUrlListAtStartup(user_prefs, local_state); | |
| 524 | |
| 525 ListValue* referral_list = | |
| 526 static_cast<ListValue*>( | |
| 527 local_state->GetMutableList(prefs::kDnsHostReferralList)->DeepCopy()); | |
| 528 | |
| 529 g_browser_process->io_thread()->InitNetworkPredictor( | |
| 530 prefetching_enabled, max_dns_queue_delay, max_concurrent, urls, | |
| 531 referral_list, preconnect_enabled); | |
| 532 } | |
| 533 | |
| 534 void FinalizePredictorInitialization( | |
| 535 Predictor* global_predictor, | |
| 536 net::HostResolver::Observer* global_prefetch_observer, | |
| 537 const UrlList& startup_urls, | |
| 538 ListValue* referral_list) { | |
| 539 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 540 predictor = global_predictor; | |
| 541 g_prefetch_observer = | |
| 542 static_cast<PrefetchObserver*>(global_prefetch_observer); | |
| 543 | |
| 544 DLOG(INFO) << "DNS Prefetch service started"; | |
| 545 | |
| 546 // Prefetch these hostnames on startup. | |
| 547 DnsPrefetchMotivatedList(startup_urls, | |
| 548 UrlInfo::STARTUP_LIST_MOTIVATED); | |
| 549 predictor->DeserializeReferrersThenDelete(referral_list); | |
| 550 } | |
| 551 | |
| 552 void FreePredictorResources() { | |
| 553 predictor = NULL; | |
| 554 g_prefetch_observer = NULL; | |
| 555 } | |
| 556 | |
| 557 //------------------------------------------------------------------------------ | |
| 558 | |
| 559 net::HostResolver::Observer* CreateResolverObserver() { | |
| 560 return new PrefetchObserver(); | |
| 561 } | |
| 562 | |
| 563 //------------------------------------------------------------------------------ | |
| 564 // Functions to handle saving of hostnames from one session to the next, to | |
| 565 // expedite startup times. | |
| 566 | |
| 567 static void SaveDnsPrefetchStateForNextStartupAndTrimOnIOThread( | |
| 568 ListValue* startup_list, | |
| 569 ListValue* referral_list, | |
| 570 base::WaitableEvent* completion) { | |
| 571 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::IO)); | |
| 572 | |
| 573 if (NULL == predictor) { | |
| 574 completion->Signal(); | |
| 575 return; | |
| 576 } | |
| 577 | |
| 578 if (g_prefetch_observer) | |
| 579 g_prefetch_observer->GetInitialDnsResolutionList(startup_list); | |
| 580 | |
| 581 // TODO(jar): Trimming should be done more regularly, such as every 48 hours | |
| 582 // of physical time, or perhaps after 48 hours of running (excluding time | |
| 583 // between sessions possibly). | |
| 584 // For now, we'll just trim at shutdown. | |
| 585 predictor->TrimReferrers(); | |
| 586 predictor->SerializeReferrers(referral_list); | |
| 587 | |
| 588 completion->Signal(); | |
| 589 } | |
| 590 | |
| 591 void SavePredictorStateForNextStartupAndTrim(PrefService* prefs) { | |
| 592 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 593 | |
| 594 if (!dns_prefetch_enabled || predictor == NULL) | |
| 595 return; | |
| 596 | |
| 597 base::WaitableEvent completion(true, false); | |
| 598 | |
| 599 bool posted = ChromeThread::PostTask( | |
| 600 ChromeThread::IO, | |
| 601 FROM_HERE, | |
| 602 NewRunnableFunction(SaveDnsPrefetchStateForNextStartupAndTrimOnIOThread, | |
| 603 prefs->GetMutableList(prefs::kDnsStartupPrefetchList), | |
| 604 prefs->GetMutableList(prefs::kDnsHostReferralList), | |
| 605 &completion)); | |
| 606 | |
| 607 DCHECK(posted); | |
| 608 if (posted) | |
| 609 completion.Wait(); | |
| 610 } | |
| 611 | |
| 612 static UrlList GetPredictedUrlListAtStartup(PrefService* user_prefs, | |
| 613 PrefService* local_state) { | |
| 614 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 615 UrlList urls; | |
| 616 // Recall list of URLs we learned about during last session. | |
| 617 // This may catch secondary hostnames, pulled in by the homepages. It will | |
| 618 // also catch more of the "primary" home pages, since that was (presumably) | |
| 619 // rendered first (and will be rendered first this time too). | |
| 620 ListValue* startup_list = | |
| 621 local_state->GetMutableList(prefs::kDnsStartupPrefetchList); | |
| 622 if (startup_list) { | |
| 623 ListValue::iterator it = startup_list->begin(); | |
| 624 int format_version = -1; | |
| 625 if (it != startup_list->end() && | |
| 626 (*it)->GetAsInteger(&format_version) && | |
| 627 format_version == kPredictorStartupFormatVersion) { | |
| 628 ++it; | |
| 629 for (; it != startup_list->end(); ++it) { | |
| 630 std::string url_spec; | |
| 631 if (!(*it)->GetAsString(&url_spec)) { | |
| 632 LOG(DFATAL); | |
| 633 break; // Format incompatibility. | |
| 634 } | |
| 635 GURL url(url_spec); | |
| 636 if (!url.has_host() || !url.has_scheme()) { | |
| 637 LOG(DFATAL); | |
| 638 break; // Format incompatibility. | |
| 639 } | |
| 640 | |
| 641 urls.push_back(url); | |
| 642 } | |
| 643 } | |
| 644 } | |
| 645 | |
| 646 // Prepare for any static home page(s) the user has in prefs. The user may | |
| 647 // have a LOT of tab's specified, so we may as well try to warm them all. | |
| 648 SessionStartupPref tab_start_pref = | |
| 649 SessionStartupPref::GetStartupPref(user_prefs); | |
| 650 if (SessionStartupPref::URLS == tab_start_pref.type) { | |
| 651 for (size_t i = 0; i < tab_start_pref.urls.size(); i++) { | |
| 652 GURL gurl = tab_start_pref.urls[i]; | |
| 653 if (!gurl.is_valid() || gurl.SchemeIsFile() || gurl.host().empty()) | |
| 654 continue; | |
| 655 if (gurl.SchemeIs("http") || gurl.SchemeIs("https")) | |
| 656 urls.push_back(gurl.GetWithEmptyPath()); | |
| 657 } | |
| 658 } | |
| 659 | |
| 660 if (urls.empty()) | |
| 661 urls.push_back(GURL("http://www.google.com:80")); | |
| 662 | |
| 663 return urls; | |
| 664 } | |
| 665 | |
| 666 //------------------------------------------------------------------------------ | |
| 667 // Methods for the helper class that is used to startup and teardown the whole | |
| 668 // predictor system (both DNS pre-resolution and TCP/IP connection prewarming). | |
| 669 | |
| 670 PredictorInit::PredictorInit(PrefService* user_prefs, | |
| 671 PrefService* local_state, | |
| 672 bool preconnect_enabled) { | |
| 673 DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI)); | |
| 674 // Set up a field trial to see what disabling DNS pre-resolution does to | |
| 675 // latency of page loads. | |
| 676 FieldTrial::Probability kDivisor = 1000; | |
| 677 // For each option (i.e., non-default), we have a fixed probability. | |
| 678 FieldTrial::Probability kProbabilityPerGroup = 1; // 0.1% probability. | |
| 679 | |
| 680 trial_ = new FieldTrial("DnsImpact", kDivisor); | |
| 681 | |
| 682 // First option is to disable prefetching completely. | |
| 683 int disabled_prefetch = trial_->AppendGroup("_disabled_prefetch", | |
| 684 kProbabilityPerGroup); | |
| 685 | |
| 686 | |
| 687 // We're running two experiments at the same time. The first set of trials | |
| 688 // modulates the delay-time until we declare a congestion event (and purge | |
| 689 // our queue). The second modulates the number of concurrent resolutions | |
| 690 // we do at any time. Users are in exactly one trial (or the default) during | |
| 691 // any one run, and hence only one experiment at a time. | |
| 692 // Experiment 1: | |
| 693 // Set congestion detection at 250, 500, or 750ms, rather than the 1 second | |
| 694 // default. | |
| 695 int max_250ms_prefetch = trial_->AppendGroup("_max_250ms_queue_prefetch", | |
| 696 kProbabilityPerGroup); | |
| 697 int max_500ms_prefetch = trial_->AppendGroup("_max_500ms_queue_prefetch", | |
| 698 kProbabilityPerGroup); | |
| 699 int max_750ms_prefetch = trial_->AppendGroup("_max_750ms_queue_prefetch", | |
| 700 kProbabilityPerGroup); | |
| 701 // Set congestion detection at 2 seconds instead of the 1 second default. | |
| 702 int max_2s_prefetch = trial_->AppendGroup("_max_2s_queue_prefetch", | |
| 703 kProbabilityPerGroup); | |
| 704 // Experiment 2: | |
| 705 // Set max simultaneous resoultions to 2, 4, or 6, and scale the congestion | |
| 706 // limit proportionally (so we don't impact average probability of asserting | |
| 707 // congesion very much). | |
| 708 int max_2_concurrent_prefetch = trial_->AppendGroup( | |
| 709 "_max_2 concurrent_prefetch", kProbabilityPerGroup); | |
| 710 int max_4_concurrent_prefetch = trial_->AppendGroup( | |
| 711 "_max_4 concurrent_prefetch", kProbabilityPerGroup); | |
| 712 int max_6_concurrent_prefetch = trial_->AppendGroup( | |
| 713 "_max_6 concurrent_prefetch", kProbabilityPerGroup); | |
| 714 | |
| 715 trial_->AppendGroup("_default_enabled_prefetch", | |
| 716 FieldTrial::kAllRemainingProbability); | |
| 717 | |
| 718 // We will register the incognito observer regardless of whether prefetching | |
| 719 // is enabled, as it is also used to clear the host cache. | |
| 720 Singleton<OffTheRecordObserver>::get()->Register(); | |
| 721 | |
| 722 if (trial_->group() != disabled_prefetch) { | |
| 723 // Initialize the DNS prefetch system. | |
| 724 size_t max_concurrent = kMaxPrefetchConcurrentLookups; | |
| 725 int max_queueing_delay_ms = kMaxPrefetchQueueingDelayMs; | |
| 726 | |
| 727 if (trial_->group() == max_250ms_prefetch) | |
| 728 max_queueing_delay_ms = 250; | |
| 729 else if (trial_->group() == max_500ms_prefetch) | |
| 730 max_queueing_delay_ms = 500; | |
| 731 else if (trial_->group() == max_750ms_prefetch) | |
| 732 max_queueing_delay_ms = 750; | |
| 733 else if (trial_->group() == max_2s_prefetch) | |
| 734 max_queueing_delay_ms = 2000; | |
| 735 if (trial_->group() == max_2_concurrent_prefetch) | |
| 736 max_concurrent = 2; | |
| 737 else if (trial_->group() == max_4_concurrent_prefetch) | |
| 738 max_concurrent = 4; | |
| 739 else if (trial_->group() == max_6_concurrent_prefetch) | |
| 740 max_concurrent = 6; | |
| 741 // Scale acceptable delay so we don't cause congestion limits to fire as | |
| 742 // we modulate max_concurrent (*if* we are modulating it at all). | |
| 743 max_queueing_delay_ms = (kMaxPrefetchQueueingDelayMs * | |
| 744 kMaxPrefetchConcurrentLookups) / max_concurrent; | |
| 745 | |
| 746 TimeDelta max_queueing_delay( | |
| 747 TimeDelta::FromMilliseconds(max_queueing_delay_ms)); | |
| 748 | |
| 749 DCHECK(!predictor); | |
| 750 InitNetworkPredictor(max_queueing_delay, max_concurrent, user_prefs, | |
| 751 local_state, preconnect_enabled); | |
| 752 } | |
| 753 } | |
| 754 | |
| 755 | |
| 756 } // namespace chrome_browser_net | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2866026:
Rename Dns prefetching files to Predictor files... (Closed)
Base URL: svn://chrome-svn/chrome/trunk/src/