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