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     : path_(filename),
 154       sequenced_task_runner_(sequenced_task_runner),
 155       prefs_(new base::DictionaryValue()),
 156       read_only_(false),
 157       writer_(filename, sequenced_task_runner),
 158       pref_filter_(pref_filter.Pass()),
 159       initialized_(false),
 160       filtering_in_progress_(false),
 161       read_error_(PREF_READ_ERROR_NONE),
 162       write_count_histogram_(writer_.commit_interval(), path_) {
 163   DCHECK(!path_.empty());
 164 }
 165
 166 JsonPrefStore::JsonPrefStore(
 167     const base::FilePath& filename,
 168     const base::FilePath& alternate_filename,
 169     const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
 170     scoped_ptr<PrefFilter> pref_filter)
 171     : path_(filename),
 172       alternate_path_(alternate_filename),
 173       sequenced_task_runner_(sequenced_task_runner),
 174       prefs_(new base::DictionaryValue()),
 175       read_only_(false),
 176       writer_(filename, sequenced_task_runner),
 177       pref_filter_(pref_filter.Pass()),
 178       initialized_(false),
 179       filtering_in_progress_(false),
 180       read_error_(PREF_READ_ERROR_NONE),
 181       write_count_histogram_(writer_.commit_interval(), path_) {
 182   DCHECK(!path_.empty());
 183 }
 184
 185 bool JsonPrefStore::GetValue(const std::string& key,
 186                              const base::Value** result) const {
 187   DCHECK(CalledOnValidThread());
 188
 189   base::Value* tmp = NULL;
 190   if (!prefs_->Get(key, &tmp))
 191     return false;
 192
 193   if (result)
 194     *result = tmp;
 195   return true;
 196 }
 197
 198 void JsonPrefStore::AddObserver(PrefStore::Observer* observer) {
 199   DCHECK(CalledOnValidThread());
 200
 201   observers_.AddObserver(observer);
 202 }
 203
 204 void JsonPrefStore::RemoveObserver(PrefStore::Observer* observer) {
 205   DCHECK(CalledOnValidThread());
 206
 207   observers_.RemoveObserver(observer);
 208 }
 209
 210 bool JsonPrefStore::HasObservers() const {
 211   DCHECK(CalledOnValidThread());
 212
 213   return observers_.might_have_observers();
 214 }
 215
 216 bool JsonPrefStore::IsInitializationComplete() const {
 217   DCHECK(CalledOnValidThread());
 218
 219   return initialized_;
 220 }
 221
 222 bool JsonPrefStore::GetMutableValue(const std::string& key,
 223                                     base::Value** result) {
 224   DCHECK(CalledOnValidThread());
 225
 226   return prefs_->Get(key, result);
 227 }
 228
 229 void JsonPrefStore::SetValue(const std::string& key, base::Value* value) {
 230   DCHECK(CalledOnValidThread());
 231
 232   DCHECK(value);
 233   scoped_ptr<base::Value> new_value(value);
 234   base::Value* old_value = NULL;
 235   prefs_->Get(key, &old_value);
 236   if (!old_value || !value->Equals(old_value)) {
 237     prefs_->Set(key, new_value.release());
 238     ReportValueChanged(key);
 239   }
 240 }
 241
 242 void JsonPrefStore::SetValueSilently(const std::string& key,
 243                                      base::Value* value) {
 244   DCHECK(CalledOnValidThread());
 245
 246   DCHECK(value);
 247   scoped_ptr<base::Value> new_value(value);
 248   base::Value* old_value = NULL;
 249   prefs_->Get(key, &old_value);
 250   if (!old_value || !value->Equals(old_value)) {
 251     prefs_->Set(key, new_value.release());
 252     if (!read_only_)
 253       writer_.ScheduleWrite(this);
 254   }
 255 }
 256
 257 void JsonPrefStore::RemoveValue(const std::string& key) {
 258   DCHECK(CalledOnValidThread());
 259
 260   if (prefs_->RemovePath(key, NULL))
 261     ReportValueChanged(key);
 262 }
 263
 264 void JsonPrefStore::RemoveValueSilently(const std::string& key) {
 265   DCHECK(CalledOnValidThread());
 266
 267   prefs_->RemovePath(key, NULL);
 268   if (!read_only_)
 269     writer_.ScheduleWrite(this);
 270 }
 271
 272 bool JsonPrefStore::ReadOnly() const {
 273   DCHECK(CalledOnValidThread());
 274
 275   return read_only_;
 276 }
 277
 278 PersistentPrefStore::PrefReadError JsonPrefStore::GetReadError() const {
 279   DCHECK(CalledOnValidThread());
 280
 281   return read_error_;
 282 }
 283
 284 PersistentPrefStore::PrefReadError JsonPrefStore::ReadPrefs() {
 285   DCHECK(CalledOnValidThread());
 286
 287   OnFileRead(ReadPrefsFromDisk(path_, alternate_path_));
 288   return filtering_in_progress_ ? PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE
 289                                 : read_error_;
 290 }
 291
 292 void JsonPrefStore::ReadPrefsAsync(ReadErrorDelegate* error_delegate) {
 293   DCHECK(CalledOnValidThread());
 294
 295   initialized_ = false;
 296   error_delegate_.reset(error_delegate);
 297
 298   // Weakly binds the read task so that it doesn't kick in during shutdown.
 299   base::PostTaskAndReplyWithResult(
 300       sequenced_task_runner_.get(),
 301       FROM_HERE,
 302       base::Bind(&ReadPrefsFromDisk, path_, alternate_path_),
 303       base::Bind(&JsonPrefStore::OnFileRead, AsWeakPtr()));
 304 }
 305
 306 void JsonPrefStore::CommitPendingWrite() {
 307   DCHECK(CalledOnValidThread());
 308
 309   if (writer_.HasPendingWrite() && !read_only_)
 310     writer_.DoScheduledWrite();
 311 }
 312
 313 void JsonPrefStore::ReportValueChanged(const std::string& key) {
 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   if (!read_only_)
 322     writer_.ScheduleWrite(this);
 323 }
 324
 325 void JsonPrefStore::RegisterOnNextSuccessfulWriteCallback(
 326     const base::Closure& on_next_successful_write) {
 327   DCHECK(CalledOnValidThread());
 328
 329   writer_.RegisterOnNextSuccessfulWriteCallback(on_next_successful_write);
 330 }
 331
 332 void JsonPrefStore::OnFileRead(scoped_ptr<ReadResult> read_result) {
 333   DCHECK(CalledOnValidThread());
 334
 335   DCHECK(read_result);
 336
 337   scoped_ptr<base::DictionaryValue> unfiltered_prefs(new base::DictionaryValue);
 338
 339   read_error_ = read_result->error;
 340
 341   bool initialization_successful = !read_result->no_dir;
 342
 343   if (initialization_successful) {
 344     switch (read_error_) {
 345       case PREF_READ_ERROR_ACCESS_DENIED:
 346       case PREF_READ_ERROR_FILE_OTHER:
 347       case PREF_READ_ERROR_FILE_LOCKED:
 348       case PREF_READ_ERROR_JSON_TYPE:
 349       case PREF_READ_ERROR_FILE_NOT_SPECIFIED:
 350         read_only_ = true;
 351         break;
 352       case PREF_READ_ERROR_NONE:
 353         DCHECK(read_result->value.get());
 354         unfiltered_prefs.reset(
 355             static_cast<base::DictionaryValue*>(read_result->value.release()));
 356         break;
 357       case PREF_READ_ERROR_NO_FILE:
 358         // If the file just doesn't exist, maybe this is first run.  In any case
 359         // there's no harm in writing out default prefs in this case.
 360         break;
 361       case PREF_READ_ERROR_JSON_PARSE:
 362       case PREF_READ_ERROR_JSON_REPEAT:
 363         break;
 364       case PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE:
 365         // This is a special error code to be returned by ReadPrefs when it
 366         // can't complete synchronously, it should never be returned by the read
 367         // operation itself.
 368         NOTREACHED();
 369         break;
 370       case PREF_READ_ERROR_LEVELDB_IO:
 371       case PREF_READ_ERROR_LEVELDB_CORRUPTION_READ_ONLY:
 372       case PREF_READ_ERROR_LEVELDB_CORRUPTION:
 373         // These are specific to LevelDBPrefStore.
 374         NOTREACHED();
 375       case PREF_READ_ERROR_MAX_ENUM:
 376         NOTREACHED();
 377         break;
 378     }
 379   }
 380
 381   if (pref_filter_) {
 382     filtering_in_progress_ = true;
 383     const PrefFilter::PostFilterOnLoadCallback post_filter_on_load_callback(
 384         base::Bind(
 385             &JsonPrefStore::FinalizeFileRead, AsWeakPtr(),
 386             initialization_successful));
 387     pref_filter_->FilterOnLoad(post_filter_on_load_callback,
 388                                unfiltered_prefs.Pass());
 389   } else {
 390     FinalizeFileRead(initialization_successful, unfiltered_prefs.Pass(), false);
 391   }
 392 }
 393
 394 JsonPrefStore::~JsonPrefStore() {
 395   CommitPendingWrite();
 396 }
 397
 398 bool JsonPrefStore::SerializeData(std::string* output) {
 399   DCHECK(CalledOnValidThread());
 400
 401   write_count_histogram_.RecordWriteOccured();
 402
 403   if (pref_filter_)
 404     pref_filter_->FilterSerializeData(prefs_.get());
 405
 406   JSONStringValueSerializer serializer(output);
 407   // Not pretty-printing prefs shrinks pref file size by ~30%. To obtain
 408   // readable prefs for debugging purposes, you can dump your prefs into any
 409   // command-line or online JSON pretty printing tool.
 410   serializer.set_pretty_print(false);
 411   return serializer.Serialize(*prefs_);
 412 }
 413
 414 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
 415                                      scoped_ptr<base::DictionaryValue> prefs,
 416                                      bool schedule_write) {
 417   DCHECK(CalledOnValidThread());
 418
 419   filtering_in_progress_ = false;
 420
 421   if (!initialization_successful) {
 422     FOR_EACH_OBSERVER(PrefStore::Observer,
 423                       observers_,
 424                       OnInitializationCompleted(false));
 425     return;
 426   }
 427
 428   prefs_ = prefs.Pass();
 429
 430   initialized_ = true;
 431
 432   if (schedule_write && !read_only_)
 433     writer_.ScheduleWrite(this);
 434
 435   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
 436     error_delegate_->OnError(read_error_);
 437
 438   FOR_EACH_OBSERVER(PrefStore::Observer,
 439                     observers_,
 440                     OnInitializationCompleted(true));
 441
 442   return;
 443 }
 444
 445 // NOTE: This value should NOT be changed without renaming the histogram
 446 // otherwise it will create incompatible buckets.
 447 const int32_t
 448     JsonPrefStore::WriteCountHistogram::kHistogramWriteReportIntervalMins = 5;
 449
 450 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 451     const base::TimeDelta& commit_interval,
 452     const base::FilePath& path)
 453     : WriteCountHistogram(commit_interval,
 454                           path,
 455                           scoped_ptr<base::Clock>(new base::DefaultClock)) {
 456 }
 457
 458 JsonPrefStore::WriteCountHistogram::WriteCountHistogram(
 459     const base::TimeDelta& commit_interval,
 460     const base::FilePath& path,
 461     scoped_ptr<base::Clock> clock)
 462     : commit_interval_(commit_interval),
 463       path_(path),
 464       clock_(clock.release()),
 465       report_interval_(
 466           base::TimeDelta::FromMinutes(kHistogramWriteReportIntervalMins)),
 467       last_report_time_(clock_->Now()),
 468       writes_since_last_report_(0) {
 469 }
 470
 471 JsonPrefStore::WriteCountHistogram::~WriteCountHistogram() {
 472   ReportOutstandingWrites();
 473 }
 474
 475 void JsonPrefStore::WriteCountHistogram::RecordWriteOccured() {
 476   ReportOutstandingWrites();
 477
 478   ++writes_since_last_report_;
 479 }
 480
 481 void JsonPrefStore::WriteCountHistogram::ReportOutstandingWrites() {
 482   base::Time current_time = clock_->Now();
 483   base::TimeDelta time_since_last_report = current_time - last_report_time_;
 484
 485   if (time_since_last_report <= report_interval_)
 486     return;
 487
 488   // If the time since the last report exceeds the report interval, report all
 489   // the writes since the last report. They must have all occurred in the same
 490   // report interval.
 491   base::HistogramBase* histogram = GetHistogram();
 492   histogram->Add(writes_since_last_report_);
 493
 494   // There may be several report intervals that elapsed that don't have any
 495   // writes in them. Report these too.
 496   int64 total_num_intervals_elapsed =
 497       (time_since_last_report / report_interval_);
 498   for (int64 i = 0; i < total_num_intervals_elapsed - 1; ++i)
 499     histogram->Add(0);
 500
 501   writes_since_last_report_ = 0;
 502   last_report_time_ += total_num_intervals_elapsed * report_interval_;
 503 }
 504
 505 base::HistogramBase* JsonPrefStore::WriteCountHistogram::GetHistogram() {
 506   std::string spaceless_basename;
 507   base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
 508                      &spaceless_basename);
 509   std::string histogram_name =
 510       "Settings.JsonDataWriteCount." + spaceless_basename;
 511
 512   // The min value for a histogram is 1. The max value is the maximum number of
 513   // writes that can occur in the window being recorded. The number of buckets
 514   // used is the max value (plus the underflow/overflow buckets).
 515   int32_t min_value = 1;
 516   int32_t max_value = report_interval_ / commit_interval_;
 517   int32_t num_buckets = max_value + 1;
 518
 519   // NOTE: These values should NOT be changed without renaming the histogram
 520   // otherwise it will create incompatible buckets.
 521   DCHECK_EQ(30, max_value);
 522   DCHECK_EQ(31, num_buckets);
 523
 524   // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
 525   // macro adapted to allow for a dynamically suffixed histogram name.
 526   // Note: The factory creates and owns the histogram.
 527   base::HistogramBase* histogram = base::Histogram::FactoryGet(
 528       histogram_name, min_value, max_value, num_buckets,
 529       base::HistogramBase::kUmaTargetedHistogramFlag);
 530   return histogram;
 531 }