base/prefs/json_pref_store.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 "base/prefs/json_pref_store.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/bind.h"
  10 #include "base/callback.h"
  11 #include "base/files/file_path.h"
  12 #include "base/files/file_util.h"
  13 #include "base/json/json_file_value_serializer.h"
  14 #include "base/json/json_string_value_serializer.h"
  15 #include "base/memory/ref_counted.h"
  16 #include "base/metrics/histogram.h"
  17 #include "base/prefs/pref_filter.h"
  18 #include "base/sequenced_task_runner.h"
  19 #include "base/strings/string_number_conversions.h"
  20 #include "base/strings/string_util.h"
  21 #include "base/task_runner_util.h"
  22 #include "base/threading/sequenced_worker_pool.h"
  23 #include "base/time/default_clock.h"
  24 #include "base/values.h"
  25
  26 // Result returned from internal read tasks.
  27 struct JsonPrefStore::ReadResult {
  28  public:
  29   ReadResult();
  30   ~ReadResult();
  31
  32   scoped_ptr<base::Value> value;
  33   PrefReadError error;
  34   bool no_dir;
  35
  36  private:
  37   DISALLOW_COPY_AND_ASSIGN(ReadResult);
  38 };
  39
  40 JsonPrefStore::ReadResult::ReadResult()
  41     : error(PersistentPrefStore::PREF_READ_ERROR_NONE), no_dir(false) {
  42 }
  43
  44 JsonPrefStore::ReadResult::~ReadResult() {
  45 }
  46
  47 namespace {
  48
  49 // Some extensions we'll tack on to copies of the Preferences files.
  50 const base::FilePath::CharType kBadExtension[] = FILE_PATH_LITERAL("bad");
  51
  52 PersistentPrefStore::PrefReadError HandleReadErrors(
  53     const base::Value* value,
  54     const base::FilePath& path,
  55     int error_code,
  56     const std::string& error_msg) {
  57   if (!value) {
  58     DVLOG(1) << "Error while loading JSON file: " << error_msg
  59              << ", file: " << path.value();
  60     switch (error_code) {
  61       case JSONFileValueDeserializer::JSON_ACCESS_DENIED:
  62         return PersistentPrefStore::PREF_READ_ERROR_ACCESS_DENIED;
  63         break;
  64       case JSONFileValueDeserializer::JSON_CANNOT_READ_FILE:
  65         return PersistentPrefStore::PREF_READ_ERROR_FILE_OTHER;
  66         break;
  67       case JSONFileValueDeserializer::JSON_FILE_LOCKED:
  68         return PersistentPrefStore::PREF_READ_ERROR_FILE_LOCKED;
  69         break;
  70       case JSONFileValueDeserializer::JSON_NO_SUCH_FILE:
  71         return PersistentPrefStore::PREF_READ_ERROR_NO_FILE;
  72         break;
  73       default:
  74         // JSON errors indicate file corruption of some sort.
  75         // Since the file is corrupt, move it to the side and continue with
  76         // empty preferences.  This will result in them losing their settings.
  77         // We keep the old file for possible support and debugging assistance
  78         // as well as to detect if they're seeing these errors repeatedly.
  79         // TODO(erikkay) Instead, use the last known good file.
  80         base::FilePath bad = path.ReplaceExtension(kBadExtension);
  81
  82         // If they've ever had a parse error before, put them in another bucket.
  83         // TODO(erikkay) if we keep this error checking for very long, we may
  84         // want to differentiate between recent and long ago errors.
  85         bool bad_existed = base::PathExists(bad);
  86         base::Move(path, bad);
  87         return bad_existed ? PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT
  88                            : PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
  89     }
  90   } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
  91     return PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
  92   }
  93   return PersistentPrefStore::PREF_READ_ERROR_NONE;
  94 }
  95
  96 // Records a sample for |size| in the Settings.JsonDataReadSizeKilobytes
  97 // histogram suffixed with the base name of the JSON file under |path|.
  98 void RecordJsonDataSizeHistogram(const base::FilePath& path, size_t size) {
  99   std::string spaceless_basename;
 100   base::ReplaceChars(path.BaseName().MaybeAsASCII(), " ", "_",
 101                      &spaceless_basename);
 102
 103   // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
 104   // macro adapted to allow for a dynamically suffixed histogram name.
 105   // Note: The factory creates and owns the histogram.
 106   base::HistogramBase* histogram = base::Histogram::FactoryGet(
 107       "Settings.JsonDataReadSizeKilobytes." + spaceless_basename, 1, 10000, 50,
 108       base::HistogramBase::kUmaTargetedHistogramFlag);
 109   histogram->Add(static_cast<int>(size) / 1024);
 110 }
 111
 112 scoped_ptr<JsonPrefStore::ReadResult> ReadPrefsFromDisk(
 113     const base::FilePath& path,
 114     const base::FilePath& alternate_path) {
 115   if (!base::PathExists(path) && !alternate_path.empty() &&
 116       base::PathExists(alternate_path)) {
 117     base::Move(alternate_path, path);
 118   }
 119
 120   int error_code;
 121   std::string error_msg;
 122   scoped_ptr<JsonPrefStore::ReadResult> read_result(
 123       new JsonPrefStore::ReadResult);
 124   JSONFileValueDeserializer deserializer(path);
 125   read_result->value.reset(deserializer.Deserialize(&error_code, &error_msg));
 126   read_result->error =
 127       HandleReadErrors(read_result->value.get(), path, error_code, error_msg);
 128   read_result->no_dir = !base::PathExists(path.DirName());
 129
 130   if (read_result->error == PersistentPrefStore::PREF_READ_ERROR_NONE)
 131     RecordJsonDataSizeHistogram(path, deserializer.get_last_read_size());
 132
 133   return read_result.Pass();
 134 }
 135
 136 }  // namespace
 137
 138 // static
 139 scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
 140     const base::FilePath& filename,
 141     base::SequencedWorkerPool* worker_pool) {
 142   std::string token("json_pref_store-");
 143   token.append(filename.AsUTF8Unsafe());
 144   return worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
 145       worker_pool->GetNamedSequenceToken(token),
 146       base::SequencedWorkerPool::BLOCK_SHUTDOWN);
 147 }
 148
 149 JsonPrefStore::JsonPrefStore(
 150     const base::FilePath& filename,
 151     const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
 152     scoped_ptr<PrefFilter> pref_filter)
 153     : JsonPrefStore(filename,
 154                     base::FilePath(),
 155                     sequenced_task_runner,
 156                     pref_filter.Pass()) {
 157 }
 158
 159 JsonPrefStore::JsonPrefStore(
 160     const base::FilePath& filename,
 161     const base::FilePath& alternate_filename,
 162     const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
 163     scoped_ptr<PrefFilter> pref_filter)
 164     : path_(filename),
 165       alternate_path_(alternate_filename),
 166       sequenced_task_runner_(sequenced_task_runner),
 167       prefs_(new base::DictionaryValue()),
 168       read_only_(false),
 169       writer_(filename, sequenced_task_runner),
 170       pref_filter_(pref_filter.Pass()),
 171       initialized_(false),
 172       filtering_in_progress_(false),
 173       pending_lossy_write_(false),
 174       read_error_(PREF_READ_ERROR_NONE),
 175       write_count_histogram_(writer_.commit_interval(), path_) {
 176   DCHECK(!path_.empty());
 177 }
 178
 179 bool JsonPrefStore::GetValue(const std::string& key,
 180                              const base::Value** result) const {
 181   DCHECK(CalledOnValidThread());
 182
 183   base::Value* tmp = NULL;
 184   if (!prefs_->Get(key, &tmp))
 185     return false;
 186
 187   if (result)
 188     *result = tmp;
 189   return true;
 190 }
 191
 192 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 193   DCHECK(CalledOnValidThread());
 194
 195   observers_.AddObserver(observer);
 196 }
 197
 198 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 199   DCHECK(CalledOnValidThread());
 200
 201   observers_.RemoveObserver(observer);
 202 }
 203
 204 bool JsonPrefStore::HasObservers() const {
 205   DCHECK(CalledOnValidThread());
 206
 207   return observers_.might_have_observers();
 208 }
 209
 210 bool JsonPrefStore::IsInitializationComplete() const {
 211   DCHECK(CalledOnValidThread());
 212
 213   return initialized_;
 214 }
 215
 216 bool JsonPrefStore::GetMutableValue(const std::string& key,
 217                                     base::Value** result) {
 218   DCHECK(CalledOnValidThread());
 219
 220   return prefs_->Get(key, result);
 221 }
 222
 223 void JsonPrefStore::SetValue(const std::string& key,
 224                              scoped_ptr<base::Value> value,
 225                              uint32 flags) {
 226   DCHECK(CalledOnValidThread());
 227
 228   DCHECK(value);
 229   base::Value* old_value = NULL;
 230   prefs_->Get(key, &old_value);
 231   if (!old_value || !value->Equals(old_value)) {
 232     prefs_->Set(key, value.Pass());
 233     ReportValueChanged(key, flags);
 234   }
 235 }
 236
 237 void JsonPrefStore::SetValueSilently(const std::string& key,
 238                                      scoped_ptr<base::Value> value,
 239                                      uint32 flags) {
 240   DCHECK(CalledOnValidThread());
 241
 242   DCHECK(value);
 243   base::Value* old_value = NULL;
 244   prefs_->Get(key, &old_value);
 245   if (!old_value || !value->Equals(old_value)) {
 246     prefs_->Set(key, value.Pass());
 247     ScheduleWrite(flags);
 248   }
 249 }
 250
 251 void JsonPrefStore::RemoveValue(const std::string& key, uint32 flags) {
 252   DCHECK(CalledOnValidThread());
 253
 254   if (prefs_->RemovePath(key, NULL))
 255     ReportValueChanged(key, flags);
 256 }
 257
 258 void JsonPrefStore::RemoveValueSilently(const std::string& key, uint32 flags) {
 259   DCHECK(CalledOnValidThread());
 260
 261   prefs_->RemovePath(key, NULL);
 262   ScheduleWrite(flags);
 263 }
 264
 265 bool JsonPrefStore::ReadOnly() const {
 266   DCHECK(CalledOnValidThread());
 267
 268   return read_only_;
 269 }
 270
 271 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 272   DCHECK(CalledOnValidThread());
 273
 274   return read_error_;
 275 }
 276
 277 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 278   DCHECK(CalledOnValidThread());
 279
 280   OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
 281   return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
 282                                 : read_error_;
 283 }
 284
 285 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
 286   DCHECK(CalledOnValidThread());
 287
 288   initialized_ = false;
 289   error_delegate_.reset(error_delegate);
 290
 291   // Weakly binds the read task so that it doesn't kick in during shutdown.
 292   base::PostTaskAndReplyWithResult(
 293       sequenced_task_runner_.get(),
 294       FROM_HERE,
 295       base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
 296       base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
 297 }
 298
 299 void JsonPrefStore::CommitPendingWrite() {
 300   DCHECK(CalledOnValidThread());
 301
 302   // Schedule a write for any lossy writes that are outstanding to ensure that
 303   // they get flushed when this function is called.
 304   SchedulePendingLossyWrites();
 305
 306   if (writer_.HasPendingWrite() && !read_only_)
 307     writer_.DoScheduledWrite();
 308 }
 309
 310 void JsonPrefStore::SchedulePendingLossyWrites() {
 311   if (pending_lossy_write_)
 312     writer_.ScheduleWrite(this);
 313 }
 314
 315 void JsonPrefStore::ReportValueChanged(const std::string& key, uint32 flags) {
 316   DCHECK(CalledOnValidThread());
 317
 318   if (pref_filter_)
 319     pref_filter_->FilterUpdate(key);
 320
 321   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 322
 323   ScheduleWrite(flags);
 324 }
 325
 326 void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
 327     const base::Closure& on_next_successful_write) {
 328   DCHECK(CalledOnValidThread());
 329
 330   writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
 331 }
 332
 333 void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
 334   DCHECK(CalledOnValidThread());
 335
 336   DCHECK(read_result);
 337
 338   scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
 339
 340   read_error_ = read_result->error;
 341
 342   bool initialization_successful = !read_result->no_dir;
 343
 344   if (initialization_successful) {
 345     switch (read_error_) {
 346       case PREF_READ_ERROR_ACCESS_DENIED:
 347       case PREF_READ_ERROR_FILE_OTHER:
 348       case PREF_READ_ERROR_FILE_LOCKED:
 349       case PREF_READ_ERROR_JSON_TYPE:
 350       case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 351         read_only_ = true;
 352         break;
 353       case PREF_READ_ERROR_NONE:
 354         DCHECK(read_result->value.get());
 355         unfiltered_prefs.reset(
 356             static_cast<base::DictionaryValue*>(read_result->value.release()));
 357         break;
 358       case PREF_READ_ERROR_NO_FILE:
 359         // If the file just doesn't exist, maybe this is first run.  In any case
 360         // there's no harm in writing out default prefs in this case.
 361         break;
 362       case PREF_READ_ERROR_JSON_PARSE:
 363       case PREF_READ_ERROR_JSON_REPEAT:
 364         break;
 365       case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
 366         // This is a special error code to be returned by ReadPrefs when it
 367         // can't complete synchronously, it should never be returned by the read
 368         // operation itself.
 369         NOTREACHED();
 370         break;
 371       case PREF_READ_ERROR_MAX_ENUM:
 372         NOTREACHED();
 373         break;
 374     }
 375   }
 376
 377   if (pref_filter_) {
 378     filtering_in_progress_ = true;
 379     const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
 380         base::Bind(
 381             &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
 382             initialization_successful));
 383     pref_filter_->FilterOnLoad(post_filter_on_load_callback,
 384                                unfiltered_prefs.Pass());
 385   } else {
 386     FinalizeFileRead(initialization_successful, unfiltered_prefs.Pass(), false);
 387   }
 388 }
 389
 390 JsonPrefStore::~JsonPrefStore() {
 391   CommitPendingWrite();
 392 }
 393
 394 bool JsonPrefStore::SerializeData(std::string* output) {
 395   DCHECK(CalledOnValidThread());
 396
 397   pending_lossy_write_ = false;
 398
 399   write_count_histogram_.RecordWriteOccured();
 400
 401   if (pref_filter_)
 402     pref_filter_->FilterSerializeData(prefs_.get());
 403
 404   JSONStringValueSerializer serializer(output);
 405   // Not pretty-printing prefs shrinks pref file size by ~30%. To obtain
 406   // readable prefs for debugging purposes, you can dump your prefs into any
 407   // command-line or online JSON pretty printing tool.
 408   serializer.set_pretty_print(false);
 409   return serializer.Serialize(*prefs_);
 410 }
 411
 412 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
 413                                      scoped_ptr<base::DictionaryValue> prefs,
 414                                      bool schedule_write) {
 415   DCHECK(CalledOnValidThread());
 416
 417   filtering_in_progress_ = false;
 418
 419   if (!initialization_successful) {
 420     FOR_EACH_OBSERVER(PrefStore::Observer,
 421                       observers_,
 422                       OnInitializationCompleted(false));
 423     return;
 424   }
 425
 426   prefs_ = prefs.Pass();
 427
 428   initialized_ = true;
 429
 430   if (schedule_write)
 431     ScheduleWrite(DEFAULT_PREF_WRITE_FLAGS);
 432
 433   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
 434     error_delegate_->OnError(read_error_);
 435
 436   FOR_EACH_OBSERVER(PrefStore::Observer,
 437                     observers_,
 438                     OnInitializationCompleted(true));
 439
 440   return;
 441 }
 442
 443 void JsonPrefStore::ScheduleWrite(uint32 flags) {
 444   if (read_only_)
 445     return;
 446
 447   if (flags & LOSSY_PREF_WRITE_FLAG)
 448     pending_lossy_write_ = true;
 449   else
 450     writer_.ScheduleWrite(this);
 451 }
 452
 453 // NOTE: This value should NOT be changed without renaming the histogram
 454 // otherwise it will create incompatible buckets.
 455 const int32_t
 456     JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins = 5;
 457
 458 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 459     const base::TimeDelta& commit_interval,
 460     const base::FilePath& path)
 461     : WriteCountHistogram(commit_interval,
 462                           path,
 463                           scoped_ptr<base::Clock>(new base::DefaultClock)) {
 464 }
 465
 466 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 467     const base::TimeDelta& commit_interval,
 468     const base::FilePath& path,
 469     scoped_ptr<base::Clock> clock)
 470     : commit_interval_(commit_interval),
 471       path_(path),
 472       clock_(clock.release()),
 473       report_interval_(
 474           base::TimeDelta::FromMinutes(kHistogramWriteReportIntervalMins)),
 475       last_report_time_(clock_->Now()),
 476       writes_since_last_report_(0) {
 477 }
 478
 479 JsonPrefStore::WriteCountHistogram::~WriteCountHistogram() {
 480   ReportOutstandingWrites();
 481 }
 482
 483 void JsonPrefStore::WriteCountHistogram::RecordWriteOccured() {
 484   ReportOutstandingWrites();
 485
 486   ++writes_since_last_report_;
 487 }
 488
 489 void JsonPrefStore::WriteCountHistogram::ReportOutstandingWrites() {
 490   base::Time current_time = clock_->Now();
 491   base::TimeDelta time_since_last_report = current_time - last_report_time_;
 492
 493   if (time_since_last_report <= report_interval_)
 494     return;
 495
 496   // If the time since the last report exceeds the report interval, report all
 497   // the writes since the last report. They must have all occurred in the same
 498   // report interval.
 499   base::HistogramBase* histogram = GetHistogram();
 500   histogram->Add(writes_since_last_report_);
 501
 502   // There may be several report intervals that elapsed that don't have any
 503   // writes in them. Report these too.
 504   int64 total_num_intervals_elapsed =
 505       (time_since_last_report / report_interval_);
 506   for (int64 i = 0; i < total_num_intervals_elapsed - 1; ++i)
 507     histogram->Add(0);
 508
 509   writes_since_last_report_ = 0;
 510   last_report_time_ += total_num_intervals_elapsed * report_interval_;
 511 }
 512
 513 base::HistogramBase* JsonPrefStore::WriteCountHistogram::GetHistogram() {
 514   std::string spaceless_basename;
 515   base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
 516                      &spaceless_basename);
 517   std::string histogram_name =
 518       "Settings.JsonDataWriteCount." + spaceless_basename;
 519
 520   // The min value for a histogram is 1. The max value is the maximum number of
 521   // writes that can occur in the window being recorded. The number of buckets
 522   // used is the max value (plus the underflow/overflow buckets).
 523   int32_t min_value = 1;
 524   int32_t max_value = report_interval_ / commit_interval_;
 525   int32_t num_buckets = max_value + 1;
 526
 527   // NOTE: These values should NOT be changed without renaming the histogram
 528   // otherwise it will create incompatible buckets.
 529   DCHECK_EQ(30, max_value);
 530   DCHECK_EQ(31, num_buckets);
 531
 532   // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
 533   // macro adapted to allow for a dynamically suffixed histogram name.
 534   // Note: The factory creates and owns the histogram.
 535   base::HistogramBase* histogram = base::Histogram::FactoryGet(
 536       histogram_name, min_value, max_value, num_buckets,
 537       base::HistogramBase::kUmaTargetedHistogramFlag);
 538   return histogram;
 539 }