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                              base::Value* value,
 225                              uint32 flags) {
 226   DCHECK(CalledOnValidThread());
 227
 228   DCHECK(value);
 229   scoped_ptr<base::Value> new_value(value);
 230   base::Value* old_value = NULL;
 231   prefs_->Get(key, &old_value);
 232   if (!old_value || !value->Equals(old_value)) {
 233     prefs_->Set(key, new_value.Pass());
 234     ReportValueChanged(key, flags);
 235   }
 236 }
 237
 238 void JsonPrefStore::SetValueSilently(const std::string& key,
 239                                      base::Value* value,
 240                                      uint32 flags) {
 241   DCHECK(CalledOnValidThread());
 242
 243   DCHECK(value);
 244   scoped_ptr<base::Value> new_value(value);
 245   base::Value* old_value = NULL;
 246   prefs_->Get(key, &old_value);
 247   if (!old_value || !value->Equals(old_value)) {
 248     prefs_->Set(key, new_value.Pass());
 249     ScheduleWrite(flags);
 250   }
 251 }
 252
 253 void JsonPrefStore::RemoveValue(const std::string& key, uint32 flags) {
 254   DCHECK(CalledOnValidThread());
 255
 256   if (prefs_->RemovePath(key, NULL))
 257     ReportValueChanged(key, flags);
 258 }
 259
 260 void JsonPrefStore::RemoveValueSilently(const std::string& key, uint32 flags) {
 261   DCHECK(CalledOnValidThread());
 262
 263   prefs_->RemovePath(key, NULL);
 264   ScheduleWrite(flags);
 265 }
 266
 267 bool JsonPrefStore::ReadOnly() const {
 268   DCHECK(CalledOnValidThread());
 269
 270   return read_only_;
 271 }
 272
 273 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 274   DCHECK(CalledOnValidThread());
 275
 276   return read_error_;
 277 }
 278
 279 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 280   DCHECK(CalledOnValidThread());
 281
 282   OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
 283   return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
 284                                 : read_error_;
 285 }
 286
 287 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
 288   DCHECK(CalledOnValidThread());
 289
 290   initialized_ = false;
 291   error_delegate_.reset(error_delegate);
 292
 293   // Weakly binds the read task so that it doesn't kick in during shutdown.
 294   base::PostTaskAndReplyWithResult(
 295       sequenced_task_runner_.get(),
 296       FROM_HERE,
 297       base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
 298       base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
 299 }
 300
 301 void JsonPrefStore::CommitPendingWrite() {
 302   DCHECK(CalledOnValidThread());
 303
 304   // Schedule a write for any lossy writes that are outstanding to ensure that
 305   // they get flushed when this function is called.
 306   if (pending_lossy_write_)
 307     writer_.ScheduleWrite(this);
 308
 309   if (writer_.HasPendingWrite() && !read_only_)
 310     writer_.DoScheduledWrite();
 311 }
 312
 313 void JsonPrefStore::ReportValueChanged(const std::string& key, uint32 flags) {
 314   DCHECK(CalledOnValidThread());
 315
 316   if (pref_filter_)
 317     pref_filter_->FilterUpdate(key);
 318
 319   FOR_EACH_OBSERVER(PrefStore::Observer, observers_, OnPrefValueChanged(key));
 320
 321   ScheduleWrite(flags);
 322 }
 323
 324 void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
 325     const base::Closure& on_next_successful_write) {
 326   DCHECK(CalledOnValidThread());
 327
 328   writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
 329 }
 330
 331 void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
 332   DCHECK(CalledOnValidThread());
 333
 334   DCHECK(read_result);
 335
 336   scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
 337
 338   read_error_ = read_result->error;
 339
 340   bool initialization_successful = !read_result->no_dir;
 341
 342   if (initialization_successful) {
 343     switch (read_error_) {
 344       case PREF_READ_ERROR_ACCESS_DENIED:
 345       case PREF_READ_ERROR_FILE_OTHER:
 346       case PREF_READ_ERROR_FILE_LOCKED:
 347       case PREF_READ_ERROR_JSON_TYPE:
 348       case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 349         read_only_ = true;
 350         break;
 351       case PREF_READ_ERROR_NONE:
 352         DCHECK(read_result->value.get());
 353         unfiltered_prefs.reset(
 354             static_cast<base::DictionaryValue*>(read_result->value.release()));
 355         break;
 356       case PREF_READ_ERROR_NO_FILE:
 357         // If the file just doesn't exist, maybe this is first run.  In any case
 358         // there's no harm in writing out default prefs in this case.
 359         break;
 360       case PREF_READ_ERROR_JSON_PARSE:
 361       case PREF_READ_ERROR_JSON_REPEAT:
 362         break;
 363       case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
 364         // This is a special error code to be returned by ReadPrefs when it
 365         // can't complete synchronously, it should never be returned by the read
 366         // operation itself.
 367         NOTREACHED();
 368         break;
 369       case PREF_READ_ERROR_LEVELDB_IO:
 370       case PREF_READ_ERROR_LEVELDB_CORRUPTION_READ_ONLY:
 371       case PREF_READ_ERROR_LEVELDB_CORRUPTION:
 372         // These are specific to LevelDBPrefStore.
 373         NOTREACHED();
 374       case PREF_READ_ERROR_MAX_ENUM:
 375         NOTREACHED();
 376         break;
 377     }
 378   }
 379
 380   if (pref_filter_) {
 381     filtering_in_progress_ = true;
 382     const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
 383         base::Bind(
 384             &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
 385             initialization_successful));
 386     pref_filter_->FilterOnLoad(post_filter_on_load_callback,
 387                                unfiltered_prefs.Pass());
 388   } else {
 389     FinalizeFileRead(initialization_successful, unfiltered_prefs.Pass(), false);
 390   }
 391 }
 392
 393 JsonPrefStore::~JsonPrefStore() {
 394   CommitPendingWrite();
 395 }
 396
 397 bool JsonPrefStore::SerializeData(std::string* output) {
 398   DCHECK(CalledOnValidThread());
 399
 400   pending_lossy_write_ = false;
 401
 402   write_count_histogram_.RecordWriteOccured();
 403
 404   if (pref_filter_)
 405     pref_filter_->FilterSerializeData(prefs_.get());
 406
 407   JSONStringValueSerializer serializer(output);
 408   // Not pretty-printing prefs shrinks pref file size by ~30%. To obtain
 409   // readable prefs for debugging purposes, you can dump your prefs into any
 410   // command-line or online JSON pretty printing tool.
 411   serializer.set_pretty_print(false);
 412   return serializer.Serialize(*prefs_);
 413 }
 414
 415 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
 416                                      scoped_ptr<base::DictionaryValue> prefs,
 417                                      bool schedule_write) {
 418   DCHECK(CalledOnValidThread());
 419
 420   filtering_in_progress_ = false;
 421
 422   if (!initialization_successful) {
 423     FOR_EACH_OBSERVER(PrefStore::Observer,
 424                       observers_,
 425                       OnInitializationCompleted(false));
 426     return;
 427   }
 428
 429   prefs_ = prefs.Pass();
 430
 431   initialized_ = true;
 432
 433   if (schedule_write)
 434     ScheduleWrite(DEFAULT_PREF_WRITE_FLAGS);
 435
 436   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
 437     error_delegate_->OnError(read_error_);
 438
 439   FOR_EACH_OBSERVER(PrefStore::Observer,
 440                     observers_,
 441                     OnInitializationCompleted(true));
 442
 443   return;
 444 }
 445
 446 void JsonPrefStore::ScheduleWrite(uint32 flags) {
 447   if (read_only_)
 448     return;
 449
 450   if (flags & LOSSY_PREF_WRITE_FLAG)
 451     pending_lossy_write_ = true;
 452   else
 453     writer_.ScheduleWrite(this);
 454 }
 455
 456 // NOTE: This value should NOT be changed without renaming the histogram
 457 // otherwise it will create incompatible buckets.
 458 const int32_t
 459     JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins = 5;
 460
 461 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 462     const base::TimeDelta& commit_interval,
 463     const base::FilePath& path)
 464     : WriteCountHistogram(commit_interval,
 465                           path,
 466                           scoped_ptr<base::Clock>(new base::DefaultClock)) {
 467 }
 468
 469 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 470     const base::TimeDelta& commit_interval,
 471     const base::FilePath& path,
 472     scoped_ptr<base::Clock> clock)
 473     : commit_interval_(commit_interval),
 474       path_(path),
 475       clock_(clock.release()),
 476       report_interval_(
 477           base::TimeDelta::FromMinutes(kHistogramWriteReportIntervalMins)),
 478       last_report_time_(clock_->Now()),
 479       writes_since_last_report_(0) {
 480 }
 481
 482 JsonPrefStore::WriteCountHistogram::~WriteCountHistogram() {
 483   ReportOutstandingWrites();
 484 }
 485
 486 void JsonPrefStore::WriteCountHistogram::RecordWriteOccured() {
 487   ReportOutstandingWrites();
 488
 489   ++writes_since_last_report_;
 490 }
 491
 492 void JsonPrefStore::WriteCountHistogram::ReportOutstandingWrites() {
 493   base::Time current_time = clock_->Now();
 494   base::TimeDelta time_since_last_report = current_time - last_report_time_;
 495
 496   if (time_since_last_report <= report_interval_)
 497     return;
 498
 499   // If the time since the last report exceeds the report interval, report all
 500   // the writes since the last report. They must have all occurred in the same
 501   // report interval.
 502   base::HistogramBase* histogram = GetHistogram();
 503   histogram->Add(writes_since_last_report_);
 504
 505   // There may be several report intervals that elapsed that don't have any
 506   // writes in them. Report these too.
 507   int64 total_num_intervals_elapsed =
 508       (time_since_last_report / report_interval_);
 509   for (int64 i = 0; i < total_num_intervals_elapsed - 1; ++i)
 510     histogram->Add(0);
 511
 512   writes_since_last_report_ = 0;
 513   last_report_time_ += total_num_intervals_elapsed * report_interval_;
 514 }
 515
 516 base::HistogramBase* JsonPrefStore::WriteCountHistogram::GetHistogram() {
 517   std::string spaceless_basename;
 518   base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
 519                      &spaceless_basename);
 520   std::string histogram_name =
 521       "Settings.JsonDataWriteCount." + spaceless_basename;
 522
 523   // The min value for a histogram is 1. The max value is the maximum number of
 524   // writes that can occur in the window being recorded. The number of buckets
 525   // used is the max value (plus the underflow/overflow buckets).
 526   int32_t min_value = 1;
 527   int32_t max_value = report_interval_ / commit_interval_;
 528   int32_t num_buckets = max_value + 1;
 529
 530   // NOTE: These values should NOT be changed without renaming the histogram
 531   // otherwise it will create incompatible buckets.
 532   DCHECK_EQ(30, max_value);
 533   DCHECK_EQ(31, num_buckets);
 534
 535   // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
 536   // macro adapted to allow for a dynamically suffixed histogram name.
 537   // Note: The factory creates and owns the histogram.
 538   base::HistogramBase* histogram = base::Histogram::FactoryGet(
 539       histogram_name, min_value, max_value, num_buckets,
 540       base::HistogramBase::kUmaTargetedHistogramFlag);
 541   return histogram;
 542 }