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