content/browser/histogram_synchronizer.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 "content/browser/histogram_synchronizer.h"
   6
   7 #include "base/bind.h"
   8 #include "base/lazy_instance.h"
   9 #include "base/logging.h"
  10 #include "base/metrics/histogram.h"
  11 #include "base/pickle.h"
  12 #include "base/threading/thread.h"
  13 #include "base/threading/thread_restrictions.h"
  14 #include "content/browser/histogram_controller.h"
  15 #include "content/public/browser/browser_thread.h"
  16 #include "content/public/browser/histogram_fetcher.h"
  17 #include "content/public/common/content_constants.h"
  18
  19 using base::Time;
  20 using base::TimeDelta;
  21 using base::TimeTicks;
  22
  23 namespace {
  24
  25 // Negative numbers are never used as sequence numbers.  We explicitly pick a
  26 // negative number that is "so negative" that even when we add one (as is done
  27 // when we generated the next sequence number) that it will still be negative.
  28 // We have code that handles wrapping around on an overflow into negative
  29 // territory.
  30 static const int kNeverUsableSequenceNumber = -2;
  31
  32 }  // anonymous namespace
  33
  34 namespace content {
  35
  36 // The "RequestContext" structure describes an individual request received from
  37 // the UI. All methods are accessible on UI thread.
  38 class HistogramSynchronizer::RequestContext {
  39  public:
  40   // A map from sequence_number_ to the actual RequestContexts.
  41   typedef std::map<int, RequestContext*> RequestContextMap;
  42
  43   RequestContext(const base::Closure& callback, int sequence_number)
  44       : callback_(callback),
  45         sequence_number_(sequence_number),
  46         received_process_group_count_(0),
  47         processes_pending_(0) {
  48   }
  49   ~RequestContext() {}
  50
  51   void SetReceivedProcessGroupCount(bool done) {
  52     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  53     received_process_group_count_ = done;
  54   }
  55
  56   // Methods for book keeping of processes_pending_.
  57   void AddProcessesPending(int processes_pending) {
  58     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  59     processes_pending_ += processes_pending;
  60   }
  61
  62   void DecrementProcessesPending() {
  63     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  64     --processes_pending_;
  65   }
  66
  67   // Records that we are waiting for one less histogram data from a process for
  68   // the given sequence number. If |received_process_group_count_| and
  69   // |processes_pending_| are zero, then delete the current object by calling
  70   // Unregister.
  71   void DeleteIfAllDone() {
  72     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  73
  74     if (processes_pending_ <= 0 && received_process_group_count_)
  75       RequestContext::Unregister(sequence_number_);
  76   }
  77
  78   // Register |callback| in |outstanding_requests_| map for the given
  79   // |sequence_number|.
  80   static void Register(const base::Closure& callback, int sequence_number) {
  81     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  82
  83     RequestContext* request = new RequestContext(callback, sequence_number);
  84     outstanding_requests_.Get()[sequence_number] = request;
  85   }
  86
  87   // Find the |RequestContext| in |outstanding_requests_| map for the given
  88   // |sequence_number|.
  89   static RequestContext* GetRequestContext(int sequence_number) {
  90     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
  91
  92     RequestContextMap::iterator it =
  93         outstanding_requests_.Get().find(sequence_number);
  94     if (it == outstanding_requests_.Get().end())
  95       return NULL;
  96
  97     RequestContext* request = it->second;
  98     DCHECK_EQ(sequence_number, request->sequence_number_);
  99     return request;
 100   }
 101
 102   // Delete the entry for the given |sequence_number| from
 103   // |outstanding_requests_| map. This method is called when all changes have
 104   // been acquired, or when the wait time expires (whichever is sooner).
 105   static void Unregister(int sequence_number) {
 106     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 107
 108     RequestContextMap::iterator it =
 109         outstanding_requests_.Get().find(sequence_number);
 110     if (it == outstanding_requests_.Get().end())
 111       return;
 112
 113     RequestContext* request = it->second;
 114     DCHECK_EQ(sequence_number, request->sequence_number_);
 115     bool received_process_group_count = request->received_process_group_count_;
 116     int unresponsive_processes = request->processes_pending_;
 117
 118     request->callback_.Run();
 119
 120     delete request;
 121     outstanding_requests_.Get().erase(it);
 122
 123     UMA_HISTOGRAM_BOOLEAN("Histogram.ReceivedProcessGroupCount",
 124                           received_process_group_count);
 125     UMA_HISTOGRAM_COUNTS("Histogram.PendingProcessNotResponding",
 126                          unresponsive_processes);
 127   }
 128
 129   // Delete all the entries in |outstanding_requests_| map.
 130   static void OnShutdown() {
 131     // Just in case we have any pending tasks, clear them out.
 132     while (!outstanding_requests_.Get().empty()) {
 133       RequestContextMap::iterator it = outstanding_requests_.Get().begin();
 134       delete it->second;
 135       outstanding_requests_.Get().erase(it);
 136     }
 137   }
 138
 139   // Requests are made to asynchronously send data to the |callback_|.
 140   base::Closure callback_;
 141
 142   // The sequence number used by the most recent update request to contact all
 143   // processes.
 144   int sequence_number_;
 145
 146   // Indicates if we have received all pending processes count.
 147   bool received_process_group_count_;
 148
 149   // The number of pending processes (all renderer processes and browser child
 150   // processes) that have not yet responded to requests.
 151   int processes_pending_;
 152
 153   // Map of all outstanding RequestContexts, from sequence_number_ to
 154   // RequestContext.
 155   static base::LazyInstance<RequestContextMap>::Leaky outstanding_requests_;
 156 };
 157
 158 // static
 159 base::LazyInstance
 160     <HistogramSynchronizer::RequestContext::RequestContextMap>::Leaky
 161         HistogramSynchronizer::RequestContext::outstanding_requests_ =
 162             LAZY_INSTANCE_INITIALIZER;
 163
 164 HistogramSynchronizer::HistogramSynchronizer()
 165     : lock_(),
 166       callback_thread_(NULL),
 167       last_used_sequence_number_(kNeverUsableSequenceNumber),
 168       async_sequence_number_(kNeverUsableSequenceNumber) {
 169   HistogramController::GetInstance()->Register(this);
 170 }
 171
 172 HistogramSynchronizer::~HistogramSynchronizer() {
 173   RequestContext::OnShutdown();
 174
 175   // Just in case we have any pending tasks, clear them out.
 176   SetCallbackTaskAndThread(NULL, base::Closure());
 177 }
 178
 179 HistogramSynchronizer* HistogramSynchronizer::GetInstance() {
 180   return Singleton<HistogramSynchronizer,
 181       LeakySingletonTraits<HistogramSynchronizer> >::get();
 182 }
 183
 184 // static
 185 void HistogramSynchronizer::FetchHistograms() {
 186   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
 187     BrowserThread::PostTask(
 188         BrowserThread::UI, FROM_HERE,
 189         base::Bind(&HistogramSynchronizer::FetchHistograms));
 190     return;
 191   }
 192   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 193
 194   HistogramSynchronizer* current_synchronizer =
 195       HistogramSynchronizer::GetInstance();
 196   if (current_synchronizer == NULL)
 197     return;
 198
 199   current_synchronizer->RegisterAndNotifyAllProcesses(
 200       HistogramSynchronizer::UNKNOWN,
 201       base::TimeDelta::FromMinutes(1));
 202 }
 203
 204 void FetchHistogramsAsynchronously(MessageLoop* callback_thread,
 205                                    const base::Closure& callback,
 206                                    base::TimeDelta wait_time) {
 207   HistogramSynchronizer::FetchHistogramsAsynchronously(
 208       callback_thread, callback, wait_time);
 209 }
 210
 211 // static
 212 void HistogramSynchronizer::FetchHistogramsAsynchronously(
 213     MessageLoop* callback_thread,
 214     const base::Closure& callback,
 215     base::TimeDelta wait_time) {
 216   DCHECK(callback_thread != NULL);
 217   DCHECK(!callback.is_null());
 218
 219   HistogramSynchronizer* current_synchronizer =
 220       HistogramSynchronizer::GetInstance();
 221   current_synchronizer->SetCallbackTaskAndThread(
 222       callback_thread, callback);
 223
 224   current_synchronizer->RegisterAndNotifyAllProcesses(
 225       HistogramSynchronizer::ASYNC_HISTOGRAMS, wait_time);
 226 }
 227
 228 void HistogramSynchronizer::RegisterAndNotifyAllProcesses(
 229     ProcessHistogramRequester requester,
 230     base::TimeDelta wait_time) {
 231   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 232
 233   int sequence_number = GetNextAvailableSequenceNumber(requester);
 234
 235   base::Closure callback = base::Bind(
 236       &HistogramSynchronizer::ForceHistogramSynchronizationDoneCallback,
 237       base::Unretained(this),
 238       sequence_number);
 239
 240   RequestContext::Register(callback, sequence_number);
 241
 242   // Get histogram data from renderer and browser child processes.
 243   HistogramController::GetInstance()->GetHistogramData(sequence_number);
 244
 245   // Post a task that would be called after waiting for wait_time.  This acts
 246   // as a watchdog, to cancel the requests for non-responsive processes.
 247   BrowserThread::PostDelayedTask(
 248       BrowserThread::UI, FROM_HERE,
 249       base::Bind(&RequestContext::Unregister, sequence_number),
 250       wait_time);
 251 }
 252
 253 void HistogramSynchronizer::OnPendingProcesses(int sequence_number,
 254                                                int pending_processes,
 255                                                bool end) {
 256   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 257
 258   RequestContext* request = RequestContext::GetRequestContext(sequence_number);
 259   if (!request)
 260     return;
 261   request->AddProcessesPending(pending_processes);
 262   request->SetReceivedProcessGroupCount(end);
 263   request->DeleteIfAllDone();
 264 }
 265
 266 void HistogramSynchronizer::OnHistogramDataCollected(
 267     int sequence_number,
 268     const std::vector<std::string>& pickled_histograms) {
 269   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 270
 271   RequestContext* request = RequestContext::GetRequestContext(sequence_number);
 272
 273   for (std::vector<std::string>::const_iterator it = pickled_histograms.begin();
 274        it < pickled_histograms.end();
 275        ++it) {
 276     Pickle pickle(it->data(), it->size());
 277     PickleIterator iter(pickle);
 278     base::DeserializeHistogramAndAddSamples(&iter);
 279   }
 280
 281   if (!request)
 282     return;
 283
 284   // Delete request if we have heard back from all child processes.
 285   request->DecrementProcessesPending();
 286   request->DeleteIfAllDone();
 287 }
 288
 289 void HistogramSynchronizer::SetCallbackTaskAndThread(
 290     MessageLoop* callback_thread,
 291     const base::Closure& callback) {
 292   base::Closure old_callback;
 293   MessageLoop* old_thread = NULL;
 294   {
 295     base::AutoLock auto_lock(lock_);
 296     old_callback = callback_;
 297     callback_ = callback;
 298     old_thread = callback_thread_;
 299     callback_thread_ = callback_thread;
 300     // Prevent premature calling of our new callbacks.
 301     async_sequence_number_ = kNeverUsableSequenceNumber;
 302   }
 303   // Just in case there was a task pending....
 304   InternalPostTask(old_thread, old_callback);
 305 }
 306
 307 void HistogramSynchronizer::ForceHistogramSynchronizationDoneCallback(
 308     int sequence_number) {
 309   base::Closure callback;
 310   MessageLoop* thread = NULL;
 311   {
 312     base::AutoLock lock(lock_);
 313     if (sequence_number != async_sequence_number_)
 314       return;
 315     callback = callback_;
 316     thread = callback_thread_;
 317     callback_.Reset();
 318     callback_thread_ = NULL;
 319   }
 320   InternalPostTask(thread, callback);
 321 }
 322
 323 void HistogramSynchronizer::InternalPostTask(MessageLoop* thread,
 324                                              const base::Closure& callback) {
 325   if (callback.is_null() || !thread)
 326     return;
 327   thread->PostTask(FROM_HERE, callback);
 328 }
 329
 330 int HistogramSynchronizer::GetNextAvailableSequenceNumber(
 331     ProcessHistogramRequester requester) {
 332   base::AutoLock auto_lock(lock_);
 333   ++last_used_sequence_number_;
 334   // Watch out for wrapping to a negative number.
 335   if (last_used_sequence_number_ < 0) {
 336     // Bypass the reserved number, which is used when a renderer spontaneously
 337     // decides to send some histogram data.
 338     last_used_sequence_number_ =
 339         kHistogramSynchronizerReservedSequenceNumber + 1;
 340   }
 341   DCHECK_NE(last_used_sequence_number_,
 342             kHistogramSynchronizerReservedSequenceNumber);
 343   if (requester == ASYNC_HISTOGRAMS)
 344     async_sequence_number_ = last_used_sequence_number_;
 345   return last_used_sequence_number_;
 346 }
 347
 348 }  // namespace content