rocksdb/db
Peter Dillinger 879357fdb0 Make backups openable as read-only DBs (#8142)
Summary:
A current limitation of backups is that you don't know the
exact database state of when the backup was taken. With this new
feature, you can at least inspect the backup's DB state without
restoring it by opening it as a read-only DB.

Rather than add something like OpenAsReadOnlyDB to the BackupEngine API,
which would inhibit opening stackable DB implementations read-only
(if/when their APIs support it), we instead provide a DB name and Env
that can be used to open as a read-only DB.

Possible follow-up work:

* Add a version of GetBackupInfo for a single backup.
* Let CreateNewBackup return the BackupID of the newly-created backup.

Implementation details:

Refactored ChrootFileSystem to split off new base class RemapFileSystem,
which allows more general remapping of files. We use this base class to
implement BackupEngineImpl::RemapSharedFileSystem.

To minimize API impact, I decided to just add these fields `name_for_open`
and `env_for_open` to those set by GetBackupInfo when
include_file_details=true. Creating the RemapSharedFileSystem adds a bit
to the memory consumption, perhaps unnecessarily in some cases, but this
has been mitigated by (a) only initialize the RemapSharedFileSystem
lazily when GetBackupInfo with include_file_details=true is called, and
(b) using the existing `shared_ptr<FileInfo>` objects to hold most of the
mapping data.

To enhance API safety, RemapSharedFileSystem is wrapped by new
ReadOnlyFileSystem which rejects any attempts to write. This uncovered a
couple of places in which DB::OpenForReadOnly would write to the
filesystem, so I fixed these. Added a release note because this affects
logging.

Additional minor refactoring in backupable_db.cc to support the new
functionality.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8142

Test Plan:
new test (run with ASAN and UBSAN), added to stress test and
ran it for a while with amplified backup_one_in

Reviewed By: ajkr

Differential Revision: D27535408

Pulled By: pdillinger

fbshipit-source-id: 04666d310aa0261ef6b2385c43ca793ce1dfd148
2021-04-06 14:37:53 -07:00
..
blob Add request_id in IODebugContext. (#8045) 2021-04-01 13:14:51 -07:00
compaction Compaction should not move data to up level (#8116) 2021-03-29 17:10:42 -07:00
db_impl Make backups openable as read-only DBs (#8142) 2021-04-06 14:37:53 -07:00
arena_wrapped_db_iter.cc Add blob support to DBIter (#7731) 2020-12-04 21:29:38 -08:00
arena_wrapped_db_iter.h Add blob support to DBIter (#7731) 2020-12-04 21:29:38 -08:00
builder.cc Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
builder.h Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
c_test.c make:Fix c header prototypes (#7994) 2021-03-09 20:44:23 -08:00
c.cc Use malloc in rocksdb_transaction_get_snapshot (#8114) 2021-03-26 15:51:34 -07:00
column_family_test.cc Using emplace_back replace push_back (#7568) 2021-01-15 16:56:41 -08:00
column_family.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
column_family.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
compact_files_test.cc Compaction should not move data to up level (#8116) 2021-03-29 17:10:42 -07:00
comparator_db_test.cc Remove unused includes (#7604) 2020-10-28 23:22:27 -07:00
convenience.cc sst_dump to reduce number of file reads (#6836) 2020-05-12 18:23:33 -07:00
corruption_test.cc Extend VerifyFileChecksums API for blob files (#7979) 2021-02-22 22:09:22 -08:00
cuckoo_table_db_test.cc Revert "Turn on memtable bloom filter by default. (#6584)" (#7939) 2021-02-06 22:34:30 -08:00
db_basic_test.cc Create a CustomEnv class; Add WinFileSystem; Make LegacyFileSystemWrapper private (#7703) 2021-01-06 10:49:32 -08:00
db_block_cache_test.cc Add further tests to ASSERT_STATUS_CHECKED (2) (#7698) 2020-12-09 21:21:16 -08:00
db_bloom_filter_test.cc Fix a bug for SeekForPrev with partitioned filter and prefix (#8137) 2021-04-06 12:14:08 -07:00
db_compaction_filter_test.cc Add more tests to ASSERT_STATUS_CHECKED (3), API change (#7715) 2021-01-06 14:15:02 -08:00
db_compaction_test.cc Use SST file manager to track blob files as well (#8037) 2021-03-17 20:44:49 -07:00
db_dynamic_level_test.cc Add a SystemClock class to capture the time functions of an Env (#7858) 2021-01-25 22:09:11 -08:00
db_encryption_test.cc Improvements to Env::GetChildren (#7819) 2021-01-09 09:44:34 -08:00
db_filesnapshot.cc Fix checkpoint file deletion race with avoid_unnecessary_blocking_io (#7369) 2020-09-10 22:35:25 -07:00
db_flush_test.cc Fix possible hang issue in ~DBImpl() when flush is scheduled in LOW pool (#8125) 2021-03-30 18:35:20 -07:00
db_info_dumper.cc Fix write-ahead log file size overflow (#7870) 2021-01-19 13:47:48 -08:00
db_info_dumper.h Add a DB Session ID (#6959) 2020-06-15 10:47:02 -07:00
db_inplace_update_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_io_failure_test.cc Add more tests to ASSERT_STATUS_CHECKED (3), API change (#7715) 2021-01-06 14:15:02 -08:00
db_iter_stress_test.cc Add blob support to DBIter (#7731) 2020-12-04 21:29:38 -08:00
db_iter_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
db_iter.cc Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
db_iter.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
db_iterator_test.cc Instantiate tests DBIteratorTestForPinnedData (#8051) 2021-03-12 12:31:29 -08:00
db_kv_checksum_test.cc Integrity protection for live updates to WriteBatch (#7748) 2021-01-29 12:18:58 -08:00
db_log_iter_test.cc Add a SystemClock class to capture the time functions of an Env (#7858) 2021-01-25 22:09:11 -08:00
db_logical_block_size_cache_test.cc Add further tests to ASSERT_STATUS_CHECKED (2) (#7698) 2020-12-09 21:21:16 -08:00
db_memtable_test.cc Integrity protection for live updates to WriteBatch (#7748) 2021-01-29 12:18:58 -08:00
db_merge_operand_test.cc Add further tests to ASSERT_STATUS_CHECKED (1) (#7679) 2020-12-08 15:55:04 -08:00
db_merge_operator_test.cc Add further tests to ASSERT_STATUS_CHECKED (1) (#7679) 2020-12-08 15:55:04 -08:00
db_options_test.cc Fix handling of Mutable options; Allow DB::SetOptions to update mutable TableFactory Options (#7936) 2021-02-19 10:29:02 -08:00
db_properties_test.cc Add sample_for_compression results to table properties (#8139) 2021-03-31 18:21:50 -07:00
db_range_del_test.cc Fix compression dictionary sampling with dedicated range tombstone SSTs (#8141) 2021-04-01 05:08:17 -07:00
db_secondary_test.cc Move a test file to a better location (#8054) 2021-03-15 15:03:27 -07:00
db_sst_test.cc Use separate db dir for different tests hoping to remove flakiness (#8147) 2021-04-03 11:48:56 -07:00
db_statistics_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
db_table_properties_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
db_tailing_iter_test.cc Add more tests to ASSERT_STATUS_CHECKED (3), API change (#7715) 2021-01-06 14:15:02 -08:00
db_test2.cc Fix db_test2 parallelism (#8145) 2021-04-02 13:38:04 -07:00
db_test_util.cc Use SST file manager to track blob files as well (#8037) 2021-03-17 20:44:49 -07:00
db_test_util.h Add new Append API with DataVerificationInfo to Env WritableFile (#8071) 2021-03-19 11:44:13 -07:00
db_test.cc Revamp WriteController (#8064) 2021-03-18 09:47:31 -07:00
db_universal_compaction_test.cc Revert "Turn on memtable bloom filter by default. (#6584)" (#7939) 2021-02-06 22:34:30 -08:00
db_wal_test.cc Always truncate the latest WAL file on DB Open (#8122) 2021-03-28 10:00:08 -07:00
db_with_timestamp_basic_test.cc Fix a bug in key comparison when index type is kBinarySearchWithFirstKey (#8062) 2021-03-15 17:44:52 -07:00
db_with_timestamp_compaction_test.cc Whole DBTest to skip fsync (#7274) 2020-08-17 18:42:25 -07:00
db_write_test.cc Add more tests to ASSERT_STATUS_CHECKED (4) (#7718) 2020-12-22 15:09:39 -08:00
dbformat_test.cc Remove unused includes (#7604) 2020-10-28 23:22:27 -07:00
dbformat.cc Make CompactRange and GetApproximateSizes work with timestamp (#7684) 2020-12-02 13:00:53 -08:00
dbformat.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
deletefile_test.cc Add more tests to ASSERT_STATUS_CHECKED (4) (#7718) 2020-12-22 15:09:39 -08:00
error_handler_fs_test.cc Fix error_handler_fs_test failure due to statistics (#8136) 2021-03-30 21:44:44 -07:00
error_handler.cc Add the statistics and info log for Error handler (#8050) 2021-03-17 22:38:13 -07:00
error_handler.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
event_helpers.cc Add sample_for_compression results to table properties (#8139) 2021-03-31 18:21:50 -07:00
event_helpers.h Pass SST file checksum information through OnTableFileCreated (#7108) 2020-08-25 10:46:11 -07:00
experimental.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
external_sst_file_basic_test.cc Add further tests to ASSERT_STATUS_CHECKED (2) (#7698) 2020-12-09 21:21:16 -08:00
external_sst_file_ingestion_job.cc Merge checks into one (#8138) 2021-03-31 19:13:10 -07:00
external_sst_file_ingestion_job.h Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
external_sst_file_test.cc Introduce a ThreadGuard class and use it in ExternalSSTFileTest.PickedLevelBug (#8112) 2021-03-25 22:08:58 -07:00
fault_injection_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
file_indexer_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
file_indexer.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
file_indexer.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
filename_test.cc Remove unused includes (#7604) 2020-10-28 23:22:27 -07:00
flush_job_test.cc Fix testcase failures on windows (#7992) 2021-02-23 14:35:06 -08:00
flush_job.cc Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
flush_job.h Use SST file manager to track blob files as well (#8037) 2021-03-17 20:44:49 -07:00
flush_scheduler.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
flush_scheduler.h Include C++ standard library headers instead of C compatibility headers (#8068) 2021-03-19 12:09:47 -07:00
forward_iterator_bench.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
forward_iterator.cc Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
forward_iterator.h Properly report IO errors when IndexType::kBinarySearchWithFirstKey is used (#6621) 2020-04-15 17:40:44 -07:00
import_column_family_job.cc Add a SystemClock class to capture the time functions of an Env (#7858) 2021-01-25 22:09:11 -08:00
import_column_family_job.h Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
import_column_family_test.cc No elide constructors (#7798) 2020-12-23 16:55:53 -08:00
internal_stats.cc Update compaction statistics to include the amount of data read from blob files (#8022) 2021-03-04 00:43:48 -08:00
internal_stats.h Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
job_context.h Expose the set of live blob files from Version/VersionSet (#6785) 2020-05-04 15:08:13 -07:00
kv_checksum.h Integrity protection for live updates to WriteBatch (#7748) 2021-01-29 12:18:58 -08:00
listener_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
log_format.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
log_reader.cc Fix kPointInTimeRecovery handling of truncated WAL (#7701) 2020-11-30 18:11:38 -08:00
log_reader.h Real fix for race in backup custom checksum checking (#7309) 2020-08-26 10:39:20 -07:00
log_test.cc Make StringEnv, StringSink, StringSource use FS classes (#7786) 2021-01-04 16:01:01 -08:00
log_writer.cc No elide constructors (#7798) 2020-12-23 16:55:53 -08:00
log_writer.h Include C++ standard library headers instead of C compatibility headers (#8068) 2021-03-19 12:09:47 -07:00
logs_with_prep_tracker.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
logs_with_prep_tracker.h Include C++ standard library headers instead of C compatibility headers (#8068) 2021-03-19 12:09:47 -07:00
lookup_key.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
malloc_stats.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
malloc_stats.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
manual_compaction_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
memtable_list_test.cc Revert "Turn on memtable bloom filter by default. (#6584)" (#7939) 2021-02-06 22:34:30 -08:00
memtable_list.cc Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
memtable_list.h Add initial blob support to batched MultiGet (#7766) 2020-12-14 13:48:22 -08:00
memtable.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
memtable.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
merge_context.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_helper_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_helper.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
merge_helper.h Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
merge_operator.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
merge_test.cc MergeHelper::FilterMerge() calling ElapsedNanosSafe() upon exit even … (#7867) 2021-01-21 13:13:02 -08:00
obsolete_files_test.cc Fix a harmless data race affecting two test cases (#8055) 2021-03-12 16:44:35 -08:00
options_file_test.cc No elide constructors (#7798) 2020-12-23 16:55:53 -08:00
output_validator.cc Use NPHash64 in more places (#7632) 2020-11-10 23:42:13 -08:00
output_validator.h Use NPHash64 in more places (#7632) 2020-11-10 23:42:13 -08:00
perf_context_test.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
periodic_work_scheduler_test.cc Add a SystemClock class to capture the time functions of an Env (#7858) 2021-01-25 22:09:11 -08:00
periodic_work_scheduler.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
periodic_work_scheduler.h Add a SystemClock class to capture the time functions of an Env (#7858) 2021-01-25 22:09:11 -08:00
pinned_iterators_manager.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
plain_table_db_test.cc Make StringEnv, StringSink, StringSource use FS classes (#7786) 2021-01-04 16:01:01 -08:00
pre_release_callback.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
prefix_test.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
range_del_aggregator_bench.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
range_del_aggregator_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_del_aggregator.cc In ParseInternalKey(), include corrupt key info in Status (#7515) 2020-10-28 10:12:58 -07:00
range_del_aggregator.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
range_tombstone_fragmenter_test.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
range_tombstone_fragmenter.cc Include C++ standard library headers instead of C compatibility headers (#8068) 2021-03-19 12:09:47 -07:00
range_tombstone_fragmenter.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
read_callback.h Get() with timestamp should respect snapshot (#7227) 2020-08-14 19:20:58 -07:00
repair_test.cc Use SST file manager to track blob files as well (#8037) 2021-03-17 20:44:49 -07:00
repair.cc Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
snapshot_checker.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
snapshot_impl.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
snapshot_impl.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
table_cache.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
table_cache.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
table_properties_collector_test.cc Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
table_properties_collector.cc Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
table_properties_collector.h Apply sample_for_compression to all block-based tables (#8105) 2021-03-25 15:00:45 -07:00
transaction_log_impl.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
transaction_log_impl.h Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
trim_history_scheduler.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
trim_history_scheduler.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
version_builder_test.cc Remove unused includes (#7604) 2020-10-28 23:22:27 -07:00
version_builder.cc Log sst number in Corruption status (#7767) 2020-12-14 14:07:52 -08:00
version_builder.h make L0 index/filter pinned memory usage predictable (#6911) 2020-06-09 16:51:23 -07:00
version_edit_handler.cc Make secondary instance use ManifestTailer (#7998) 2021-03-10 10:59:44 -08:00
version_edit_handler.h Make secondary instance use ManifestTailer (#7998) 2021-03-10 10:59:44 -08:00
version_edit_test.cc Make it able to ignore WAL related VersionEdits in older versions (#7873) 2021-01-19 19:27:53 -08:00
version_edit.cc Make blob related VersionEdit tags unignorable (#7886) 2021-01-20 20:29:04 -08:00
version_edit.h Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
version_set_test.cc version_set_test.cc: remove a redundent obj copy (#7880) 2021-04-01 11:28:54 -07:00
version_set.cc Fix some typos in comments (#8066) 2021-03-25 21:18:08 -07:00
version_set.h Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
wal_edit_test.cc Always track WAL obsoletion (#7759) 2020-12-09 16:02:12 -08:00
wal_edit.cc Always track WAL obsoletion (#7759) 2020-12-09 16:02:12 -08:00
wal_edit.h Always track WAL obsoletion (#7759) 2020-12-09 16:02:12 -08:00
wal_manager_test.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
wal_manager.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
wal_manager.h Store FileSystemPtr object that contains FileSystem ptr (#7180) 2020-08-12 17:31:23 -07:00
write_batch_base.cc Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_batch_internal.h Integrity protection for live updates to WriteBatch (#7748) 2021-01-29 12:18:58 -08:00
write_batch_test.cc Add further tests to ASSERT_STATUS_CHECKED (1) (#7679) 2020-12-08 15:55:04 -08:00
write_batch.cc Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033) 2021-03-15 04:34:11 -07:00
write_callback_test.cc Add more tests for assert status checked (#7524) 2020-12-22 23:45:58 -08:00
write_callback.h Replace namespace name "rocksdb" with ROCKSDB_NAMESPACE (#6433) 2020-02-20 12:09:57 -08:00
write_controller_test.cc Revamp WriteController (#8064) 2021-03-18 09:47:31 -07:00
write_controller.cc Revamp WriteController (#8064) 2021-03-18 09:47:31 -07:00
write_controller.h Revamp WriteController (#8064) 2021-03-18 09:47:31 -07:00
write_thread.cc Integrity protection for live updates to WriteBatch (#7748) 2021-01-29 12:18:58 -08:00
write_thread.h Include C++ standard library headers instead of C compatibility headers (#8068) 2021-03-19 12:09:47 -07:00