chrome/service/cloud_print/cloud_print_proxy_backend.cc

   1 // Copyright (c) 2012 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/service/cloud_print/cloud_print_proxy_backend.h"
   6
   7 #include <map>
   8 #include <vector>
   9
  10 #include "base/bind.h"
  11 #include "base/command_line.h"
  12 #include "base/compiler_specific.h"
  13 #include "base/location.h"
  14 #include "base/metrics/histogram.h"
  15 #include "base/rand_util.h"
  16 #include "base/single_thread_task_runner.h"
  17 #include "base/strings/string_util.h"
  18 #include "base/thread_task_runner_handle.h"
  19 #include "base/values.h"
  20 #include "chrome/common/cloud_print/cloud_print_constants.h"
  21 #include "chrome/service/cloud_print/cloud_print_auth.h"
  22 #include "chrome/service/cloud_print/cloud_print_connector.h"
  23 #include "chrome/service/cloud_print/cloud_print_service_helpers.h"
  24 #include "chrome/service/cloud_print/cloud_print_token_store.h"
  25 #include "chrome/service/cloud_print/connector_settings.h"
  26 #include "chrome/service/net/service_url_request_context_getter.h"
  27 #include "chrome/service/service_process.h"
  28 #include "components/cloud_devices/common/cloud_devices_switches.h"
  29 #include "google_apis/gaia/gaia_oauth_client.h"
  30 #include "google_apis/gaia/gaia_urls.h"
  31 #include "jingle/notifier/base/notifier_options.h"
  32 #include "jingle/notifier/listener/push_client.h"
  33 #include "jingle/notifier/listener/push_client_observer.h"
  34 #include "url/gurl.h"
  35
  36 namespace cloud_print {
  37
  38 // The real guts of CloudPrintProxyBackend, to keep the public client API clean.
  39 class CloudPrintProxyBackend::Core
  40     : public base::RefCountedThreadSafe<CloudPrintProxyBackend::Core>,
  41       public CloudPrintAuth::Client,
  42       public CloudPrintConnector::Client,
  43       public notifier::PushClientObserver {
  44  public:
  45   // It is OK for print_server_url to be empty. In this case system should
  46   // use system default (local) print server.
  47   Core(CloudPrintProxyBackend* backend,
  48        const ConnectorSettings& settings,
  49        const gaia::OAuthClientInfo& oauth_client_info,
  50        bool enable_job_poll);
  51
  52   // Note:
  53   //
  54   // The Do* methods are the various entry points from CloudPrintProxyBackend
  55   // It calls us on a dedicated thread to actually perform synchronous
  56   // (and potentially blocking) operations.
  57   void DoInitializeWithToken(const std::string& cloud_print_token);
  58   void DoInitializeWithRobotToken(const std::string& robot_oauth_refresh_token,
  59                                   const std::string& robot_email);
  60   void DoInitializeWithRobotAuthCode(const std::string& robot_oauth_auth_code,
  61                                      const std::string& robot_email);
  62
  63   // Called on the CloudPrintProxyBackend core_thread_ to perform
  64   // shutdown.
  65   void DoShutdown();
  66   void DoRegisterSelectedPrinters(
  67       const printing::PrinterList& printer_list);
  68   void DoUnregisterPrinters();
  69
  70   // CloudPrintAuth::Client implementation.
  71   void OnAuthenticationComplete(const std::string& access_token,
  72                                 const std::string& robot_oauth_refresh_token,
  73                                 const std::string& robot_email,
  74                                 const std::string& user_email) override;
  75   void OnInvalidCredentials() override;
  76
  77   // CloudPrintConnector::Client implementation.
  78   void OnAuthFailed() override;
  79   void OnXmppPingUpdated(int ping_timeout) override;
  80
  81   // notifier::PushClientObserver implementation.
  82   void OnNotificationsEnabled() override;
  83   void OnNotificationsDisabled(
  84       notifier::NotificationsDisabledReason reason) override;
  85   void OnIncomingNotification(
  86       const notifier::Notification& notification) override;
  87   void OnPingResponse() override;
  88
  89  private:
  90   friend class base::RefCountedThreadSafe<Core>;
  91
  92   ~Core() override {}
  93
  94   void CreateAuthAndConnector();
  95   void DestroyAuthAndConnector();
  96
  97   // NotifyXXX is how the Core communicates with the frontend across
  98   // threads.
  99   void NotifyPrinterListAvailable(
 100       const printing::PrinterList& printer_list);
 101   void NotifyAuthenticated(
 102     const std::string& robot_oauth_refresh_token,
 103     const std::string& robot_email,
 104     const std::string& user_email);
 105   void NotifyAuthenticationFailed();
 106   void NotifyPrintSystemUnavailable();
 107   void NotifyUnregisterPrinters(const std::string& auth_token,
 108                                 const std::list<std::string>& printer_ids);
 109   void NotifyXmppPingUpdated(int ping_timeout);
 110
 111   // Init XMPP channel
 112   void InitNotifications(const std::string& robot_email,
 113                          const std::string& access_token);
 114
 115   void HandlePrinterNotification(const std::string& notification);
 116   void PollForJobs();
 117   // Schedules a task to poll for jobs. Does nothing if a task is already
 118   // scheduled.
 119   void ScheduleJobPoll();
 120   void PingXmppServer();
 121   void ScheduleXmppPing();
 122   void CheckXmppPingStatus();
 123
 124   CloudPrintTokenStore* GetTokenStore();
 125
 126   // Our parent CloudPrintProxyBackend
 127   CloudPrintProxyBackend* backend_;
 128
 129   // Cloud Print authenticator.
 130   scoped_refptr<CloudPrintAuth> auth_;
 131
 132   // Cloud Print connector.
 133   scoped_refptr<CloudPrintConnector> connector_;
 134
 135   // OAuth client info.
 136   gaia::OAuthClientInfo oauth_client_info_;
 137   // Notification (xmpp) handler.
 138   scoped_ptr<notifier::PushClient> push_client_;
 139   // Indicates whether XMPP notifications are currently enabled.
 140   bool notifications_enabled_;
 141   // The time when notifications were enabled. Valid only when
 142   // notifications_enabled_ is true.
 143   base::TimeTicks notifications_enabled_since_;
 144   // Indicates whether a task to poll for jobs has been scheduled.
 145   bool job_poll_scheduled_;
 146   // Indicates whether we should poll for jobs when we lose XMPP connection.
 147   bool enable_job_poll_;
 148   // Indicates whether a task to ping xmpp server has been scheduled.
 149   bool xmpp_ping_scheduled_;
 150   // Number of XMPP pings pending reply from the server.
 151   int pending_xmpp_pings_;
 152   // Connector settings.
 153   ConnectorSettings settings_;
 154   std::string robot_email_;
 155   scoped_ptr<CloudPrintTokenStore> token_store_;
 156
 157   DISALLOW_COPY_AND_ASSIGN(Core);
 158 };
 159
 160 CloudPrintProxyBackend::CloudPrintProxyBackend(
 161     CloudPrintProxyFrontend* frontend,
 162     const ConnectorSettings& settings,
 163     const gaia::OAuthClientInfo& oauth_client_info,
 164     bool enable_job_poll)
 165     : core_thread_("Chrome_CloudPrintProxyCoreThread"),
 166       frontend_loop_(base::MessageLoop::current()),
 167       frontend_(frontend) {
 168   DCHECK(frontend_);
 169   core_ = new Core(this, settings, oauth_client_info, enable_job_poll);
 170 }
 171
 172 CloudPrintProxyBackend::~CloudPrintProxyBackend() { DCHECK(!core_.get()); }
 173
 174 bool CloudPrintProxyBackend::InitializeWithToken(
 175     const std::string& cloud_print_token) {
 176   if (!core_thread_.Start())
 177     return false;
 178   core_thread_.task_runner()->PostTask(
 179       FROM_HERE,
 180       base::Bind(&CloudPrintProxyBackend::Core::DoInitializeWithToken,
 181                  core_.get(), cloud_print_token));
 182   return true;
 183 }
 184
 185 bool CloudPrintProxyBackend::InitializeWithRobotToken(
 186     const std::string& robot_oauth_refresh_token,
 187     const std::string& robot_email) {
 188   if (!core_thread_.Start())
 189     return false;
 190   core_thread_.task_runner()->PostTask(
 191       FROM_HERE,
 192       base::Bind(&CloudPrintProxyBackend::Core::DoInitializeWithRobotToken,
 193                  core_.get(), robot_oauth_refresh_token, robot_email));
 194   return true;
 195 }
 196
 197 bool CloudPrintProxyBackend::InitializeWithRobotAuthCode(
 198     const std::string& robot_oauth_auth_code,
 199     const std::string& robot_email) {
 200   if (!core_thread_.Start())
 201     return false;
 202   core_thread_.task_runner()->PostTask(
 203       FROM_HERE,
 204       base::Bind(&CloudPrintProxyBackend::Core::DoInitializeWithRobotAuthCode,
 205                  core_.get(), robot_oauth_auth_code, robot_email));
 206   return true;
 207 }
 208
 209 void CloudPrintProxyBackend::Shutdown() {
 210   core_thread_.task_runner()->PostTask(
 211       FROM_HERE,
 212       base::Bind(&CloudPrintProxyBackend::Core::DoShutdown, core_.get()));
 213   core_thread_.Stop();
 214   core_ = NULL;  // Releases reference to core_.
 215 }
 216
 217 void CloudPrintProxyBackend::UnregisterPrinters() {
 218   core_thread_.task_runner()->PostTask(
 219       FROM_HERE, base::Bind(&CloudPrintProxyBackend::Core::DoUnregisterPrinters,
 220                             core_.get()));
 221 }
 222
 223 CloudPrintProxyBackend::Core::Core(
 224     CloudPrintProxyBackend* backend,
 225     const ConnectorSettings& settings,
 226     const gaia::OAuthClientInfo& oauth_client_info,
 227     bool enable_job_poll)
 228       : backend_(backend),
 229         oauth_client_info_(oauth_client_info),
 230         notifications_enabled_(false),
 231         job_poll_scheduled_(false),
 232         enable_job_poll_(enable_job_poll),
 233         xmpp_ping_scheduled_(false),
 234         pending_xmpp_pings_(0) {
 235   settings_.CopyFrom(settings);
 236 }
 237
 238 void CloudPrintProxyBackend::Core::CreateAuthAndConnector() {
 239   if (!auth_.get()) {
 240     auth_ = new CloudPrintAuth(this, settings_.server_url(), oauth_client_info_,
 241                                settings_.proxy_id());
 242   }
 243
 244   if (!connector_.get()) {
 245     connector_ = new CloudPrintConnector(this, settings_);
 246   }
 247 }
 248
 249 void CloudPrintProxyBackend::Core::DestroyAuthAndConnector() {
 250   auth_ = NULL;
 251   connector_ = NULL;
 252 }
 253
 254 void CloudPrintProxyBackend::Core::DoInitializeWithToken(
 255     const std::string& cloud_print_token) {
 256   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 257   CreateAuthAndConnector();
 258   auth_->AuthenticateWithToken(cloud_print_token);
 259 }
 260
 261 void CloudPrintProxyBackend::Core::DoInitializeWithRobotToken(
 262     const std::string& robot_oauth_refresh_token,
 263     const std::string& robot_email) {
 264   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 265   CreateAuthAndConnector();
 266   auth_->AuthenticateWithRobotToken(robot_oauth_refresh_token, robot_email);
 267 }
 268
 269 void CloudPrintProxyBackend::Core::DoInitializeWithRobotAuthCode(
 270     const std::string& robot_oauth_auth_code,
 271     const std::string& robot_email) {
 272   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 273   CreateAuthAndConnector();
 274   auth_->AuthenticateWithRobotAuthCode(robot_oauth_auth_code, robot_email);
 275 }
 276
 277 void CloudPrintProxyBackend::Core::OnAuthenticationComplete(
 278     const std::string& access_token,
 279     const std::string& robot_oauth_refresh_token,
 280     const std::string& robot_email,
 281     const std::string& user_email) {
 282   CloudPrintTokenStore* token_store  = GetTokenStore();
 283   bool first_time = token_store->token().empty();
 284   token_store->SetToken(access_token);
 285   robot_email_ = robot_email;
 286   // Let the frontend know that we have authenticated.
 287   backend_->frontend_loop_->task_runner()->PostTask(
 288       FROM_HERE,
 289       base::Bind(&Core::NotifyAuthenticated, this, robot_oauth_refresh_token,
 290                  robot_email, user_email));
 291   if (first_time) {
 292     InitNotifications(robot_email, access_token);
 293   } else {
 294     // If we are refreshing a token, update the XMPP token too.
 295     DCHECK(push_client_.get());
 296     push_client_->UpdateCredentials(robot_email, access_token);
 297   }
 298   // Start cloud print connector if needed.
 299   if (!connector_->IsRunning()) {
 300     if (!connector_->Start()) {
 301       // Let the frontend know that we do not have a print system.
 302       backend_->frontend_loop_->task_runner()->PostTask(
 303           FROM_HERE, base::Bind(&Core::NotifyPrintSystemUnavailable, this));
 304     }
 305   }
 306 }
 307
 308 void CloudPrintProxyBackend::Core::OnInvalidCredentials() {
 309   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 310   VLOG(1) << "CP_CONNECTOR: Auth Error";
 311   backend_->frontend_loop_->task_runner()->PostTask(
 312       FROM_HERE, base::Bind(&Core::NotifyAuthenticationFailed, this));
 313 }
 314
 315 void CloudPrintProxyBackend::Core::OnAuthFailed() {
 316   VLOG(1) << "CP_CONNECTOR: Authentication failed in connector.";
 317   // Let's stop connecter and refresh token. We'll restart connecter once
 318   // new token available.
 319   if (connector_->IsRunning())
 320     connector_->Stop();
 321
 322   // Refresh Auth token.
 323   auth_->RefreshAccessToken();
 324 }
 325
 326 void CloudPrintProxyBackend::Core::OnXmppPingUpdated(int ping_timeout) {
 327   settings_.SetXmppPingTimeoutSec(ping_timeout);
 328   backend_->frontend_loop_->task_runner()->PostTask(
 329       FROM_HERE, base::Bind(&Core::NotifyXmppPingUpdated, this, ping_timeout));
 330 }
 331
 332 void CloudPrintProxyBackend::Core::InitNotifications(
 333     const std::string& robot_email,
 334     const std::string& access_token) {
 335   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 336
 337   pending_xmpp_pings_ = 0;
 338   notifier::NotifierOptions notifier_options;
 339   notifier_options.request_context_getter =
 340       g_service_process->GetServiceURLRequestContextGetter();
 341   notifier_options.auth_mechanism = "X-OAUTH2";
 342   notifier_options.try_ssltcp_first = true;
 343   notifier_options.xmpp_host_port = net::HostPortPair::FromString(
 344       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
 345           switches::kCloudPrintXmppEndpoint));
 346   push_client_ = notifier::PushClient::CreateDefault(notifier_options);
 347   push_client_->AddObserver(this);
 348   notifier::Subscription subscription;
 349   subscription.channel = kCloudPrintPushNotificationsSource;
 350   subscription.from = kCloudPrintPushNotificationsSource;
 351   push_client_->UpdateSubscriptions(
 352       notifier::SubscriptionList(1, subscription));
 353   push_client_->UpdateCredentials(robot_email, access_token);
 354 }
 355
 356 void CloudPrintProxyBackend::Core::DoShutdown() {
 357   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 358   VLOG(1) << "CP_CONNECTOR: Shutdown connector, id: " << settings_.proxy_id();
 359
 360   if (connector_->IsRunning())
 361     connector_->Stop();
 362
 363   // Important to delete the PushClient on this thread.
 364   if (push_client_.get()) {
 365     push_client_->RemoveObserver(this);
 366   }
 367   push_client_.reset();
 368   notifications_enabled_ = false;
 369   notifications_enabled_since_ = base::TimeTicks();
 370   token_store_.reset();
 371
 372   DestroyAuthAndConnector();
 373 }
 374
 375 void CloudPrintProxyBackend::Core::DoUnregisterPrinters() {
 376   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 377
 378   std::string access_token = GetTokenStore()->token();
 379
 380   std::list<std::string> printer_ids;
 381   connector_->GetPrinterIds(&printer_ids);
 382
 383   backend_->frontend_loop_->task_runner()->PostTask(
 384       FROM_HERE, base::Bind(&Core::NotifyUnregisterPrinters, this, access_token,
 385                             printer_ids));
 386 }
 387
 388 void CloudPrintProxyBackend::Core::HandlePrinterNotification(
 389     const std::string& notification) {
 390   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 391
 392   size_t pos = notification.rfind(kNotificationUpdateSettings);
 393   if (pos == std::string::npos) {
 394     VLOG(1) << "CP_CONNECTOR: Handle printer notification, id: "
 395             << notification;
 396     connector_->CheckForJobs(kJobFetchReasonNotified, notification);
 397   } else {
 398     DCHECK(pos == notification.length() - strlen(kNotificationUpdateSettings));
 399     std::string printer_id = notification.substr(0, pos);
 400     VLOG(1) << "CP_CONNECTOR: Update printer settings, id: " << printer_id;
 401     connector_->UpdatePrinterSettings(printer_id);
 402   }
 403 }
 404
 405 void CloudPrintProxyBackend::Core::PollForJobs() {
 406   VLOG(1) << "CP_CONNECTOR: Polling for jobs.";
 407   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 408   // Check all printers for jobs.
 409   connector_->CheckForJobs(kJobFetchReasonPoll, std::string());
 410
 411   job_poll_scheduled_ = false;
 412   // If we don't have notifications and job polling is enabled, poll again
 413   // after a while.
 414   if (!notifications_enabled_ && enable_job_poll_)
 415     ScheduleJobPoll();
 416 }
 417
 418 void CloudPrintProxyBackend::Core::ScheduleJobPoll() {
 419   if (!job_poll_scheduled_) {
 420     base::TimeDelta interval = base::TimeDelta::FromSeconds(
 421         base::RandInt(kMinJobPollIntervalSecs, kMaxJobPollIntervalSecs));
 422     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
 423         FROM_HERE, base::Bind(&CloudPrintProxyBackend::Core::PollForJobs, this),
 424         interval);
 425     job_poll_scheduled_ = true;
 426   }
 427 }
 428
 429 void CloudPrintProxyBackend::Core::PingXmppServer() {
 430   xmpp_ping_scheduled_ = false;
 431
 432   if (!push_client_.get())
 433     return;
 434
 435   push_client_->SendPing();
 436
 437   pending_xmpp_pings_++;
 438   if (pending_xmpp_pings_ >= kMaxFailedXmppPings) {
 439     // Check ping status when we close to the limit.
 440     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
 441         FROM_HERE,
 442         base::Bind(&CloudPrintProxyBackend::Core::CheckXmppPingStatus, this),
 443         base::TimeDelta::FromSeconds(kXmppPingCheckIntervalSecs));
 444   }
 445
 446   // Schedule next ping if needed.
 447   if (notifications_enabled_)
 448     ScheduleXmppPing();
 449 }
 450
 451 void CloudPrintProxyBackend::Core::ScheduleXmppPing() {
 452   // settings_.xmpp_ping_enabled() is obsolete, we are now control
 453   // XMPP pings from Cloud Print server.
 454   if (!xmpp_ping_scheduled_) {
 455     base::TimeDelta interval = base::TimeDelta::FromSeconds(
 456       base::RandInt(settings_.xmpp_ping_timeout_sec() * 0.9,
 457                     settings_.xmpp_ping_timeout_sec() * 1.1));
 458     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
 459         FROM_HERE,
 460         base::Bind(&CloudPrintProxyBackend::Core::PingXmppServer, this),
 461         interval);
 462     xmpp_ping_scheduled_ = true;
 463   }
 464 }
 465
 466 void CloudPrintProxyBackend::Core::CheckXmppPingStatus() {
 467   if (pending_xmpp_pings_ >= kMaxFailedXmppPings) {
 468     UMA_HISTOGRAM_COUNTS_100("CloudPrint.XmppPingTry", 99);  // Max on fail.
 469     // Reconnect to XMPP.
 470     pending_xmpp_pings_ = 0;
 471     push_client_.reset();
 472     InitNotifications(robot_email_, GetTokenStore()->token());
 473   }
 474 }
 475
 476 CloudPrintTokenStore* CloudPrintProxyBackend::Core::GetTokenStore() {
 477   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 478   if (!token_store_.get())
 479     token_store_.reset(new CloudPrintTokenStore);
 480   return token_store_.get();
 481 }
 482
 483 void CloudPrintProxyBackend::Core::NotifyAuthenticated(
 484     const std::string& robot_oauth_refresh_token,
 485     const std::string& robot_email,
 486     const std::string& user_email) {
 487   DCHECK(base::MessageLoop::current() == backend_->frontend_loop_);
 488   backend_->frontend_
 489       ->OnAuthenticated(robot_oauth_refresh_token, robot_email, user_email);
 490 }
 491
 492 void CloudPrintProxyBackend::Core::NotifyAuthenticationFailed() {
 493   DCHECK(base::MessageLoop::current() == backend_->frontend_loop_);
 494   backend_->frontend_->OnAuthenticationFailed();
 495 }
 496
 497 void CloudPrintProxyBackend::Core::NotifyPrintSystemUnavailable() {
 498   DCHECK(base::MessageLoop::current() == backend_->frontend_loop_);
 499   backend_->frontend_->OnPrintSystemUnavailable();
 500 }
 501
 502 void CloudPrintProxyBackend::Core::NotifyUnregisterPrinters(
 503     const std::string& auth_token,
 504     const std::list<std::string>& printer_ids) {
 505   DCHECK(base::MessageLoop::current() == backend_->frontend_loop_);
 506   backend_->frontend_->OnUnregisterPrinters(auth_token, printer_ids);
 507 }
 508
 509 void CloudPrintProxyBackend::Core::NotifyXmppPingUpdated(int ping_timeout) {
 510   DCHECK(base::MessageLoop::current() == backend_->frontend_loop_);
 511   backend_->frontend_->OnXmppPingUpdated(ping_timeout);
 512 }
 513
 514 void CloudPrintProxyBackend::Core::OnNotificationsEnabled() {
 515   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 516   notifications_enabled_ = true;
 517   notifications_enabled_since_ = base::TimeTicks::Now();
 518   VLOG(1) << "Notifications for connector " << settings_.proxy_id()
 519           << " were enabled at "
 520           << notifications_enabled_since_.ToInternalValue();
 521   // Notifications just got re-enabled. In this case we want to schedule
 522   // a poll once for jobs we might have missed when we were dark.
 523   // Note that ScheduleJobPoll will not schedule again if a job poll task is
 524   // already scheduled.
 525   ScheduleJobPoll();
 526
 527   // Schedule periodic ping for XMPP notification channel.
 528   ScheduleXmppPing();
 529 }
 530
 531 void CloudPrintProxyBackend::Core::OnNotificationsDisabled(
 532     notifier::NotificationsDisabledReason reason) {
 533   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 534   notifications_enabled_ = false;
 535   LOG(ERROR) << "Notifications for connector " << settings_.proxy_id()
 536              << " disabled.";
 537   notifications_enabled_since_ = base::TimeTicks();
 538   // We just lost notifications. This this case we want to schedule a
 539   // job poll if enable_job_poll_ is true.
 540   if (enable_job_poll_)
 541     ScheduleJobPoll();
 542 }
 543
 544
 545 void CloudPrintProxyBackend::Core::OnIncomingNotification(
 546     const notifier::Notification& notification) {
 547   // Since we got some notification from the server,
 548   // reset pending ping counter to 0.
 549   pending_xmpp_pings_ = 0;
 550
 551   DCHECK(base::MessageLoop::current() == backend_->core_thread_.message_loop());
 552   VLOG(1) << "CP_CONNECTOR: Incoming notification.";
 553   if (0 == base::strcasecmp(kCloudPrintPushNotificationsSource,
 554                             notification.channel.c_str()))
 555     HandlePrinterNotification(notification.data);
 556 }
 557
 558 void CloudPrintProxyBackend::Core::OnPingResponse() {
 559   UMA_HISTOGRAM_COUNTS_100("CloudPrint.XmppPingTry", pending_xmpp_pings_);
 560   pending_xmpp_pings_ = 0;
 561   VLOG(1) << "CP_CONNECTOR: Ping response received.";
 562 }
 563
 564 }  // namespace cloud_print