Iterator gets verification errors

[ofriedma]

After long running of blackbox_crash_test with allow_wbm_stalls = false, at some point there will be an error from the db_stress command such as:

stderr:
WARNING: prefix_size is non-zero but memtablerep != prefix_hash
WARNING: ~ExpectedStateTraceRecordHandler - num_write_ops_: 3755823 max_write_ops_: 3755826
Verification failed for column family 0 key 0000000000034874787878787878 (421446): value_from_db: 010000000504070609080B0A0D0C0F0E111013121514171619181B1A1D1C1F1E212023222524272629282B2A2D2C2F2E313033323534373639383B3A3D3C3F3E, value_from_expected: , msg: MultiGetEntity verification: Unexpected value found
Crash-recovery verification failed :(
No writes or ops?
Verification failed :(

./db_stress --acquire_snapshot_one_in=10000 --adaptive_readahead=1 --allow_concurrent_memtable_write=0 --allow_data_in_errors=True --allow_setting_blob_options_dynamically=1 --allow_wbm_stalls=0 --async_io=0 --atomic_flush=1 --avoid_flush_during_recovery=0 --avoid_unnecessary_blocking_io=0 --backup_max_size=104857600 --backup_one_in=100000 --batch_protection_bytes_per_key=0 --blob_cache_size=4194304 --blob_compaction_readahead_size=1048576 --blob_compression_type=snappy --blob_file_size=16777216 --blob_file_starting_level=1 --blob_garbage_collection_age_cutoff=0.25 --blob_garbage_collection_force_threshold=1.0 --block_protection_bytes_per_key=2 --block_size=16384 --bloom_bits=14 --bottommost_compression_type=disable --bottommost_file_compaction_delay=0 --bytes_per_sync=0 --cache_index_and_filter_blocks=1 --cache_size=8388608 --cache_type=fixed_hyper_clock_cache --charge_compression_dictionary_building_buffer=0 --charge_file_metadata=0 --charge_filter_construction=1 --charge_table_reader=1 --checkpoint_one_in=1000000 --checksum_type=kxxHash64 --clear_column_family_one_in=0 --column_families=1 --compact_files_one_in=1000000 --compact_range_one_in=1000000 --compaction_pri=2 --compaction_ttl=2 --compare_full_db_state_snapshot=1 --compression_checksum=0 --compression_max_dict_buffer_bytes=0 --compression_max_dict_bytes=0 --compression_parallel_threads=1 --compression_type=xpress --compression_use_zstd_dict_trainer=0 --compression_zstd_max_train_bytes=0 --continuous_verification_interval=0 --crash_test=1 --customopspercent=0 --data_block_index_type=0 --db=/tmp/rocksdb_crashtest_blackboxnaxjzguh --db_write_buffer_size=0 --delpercent=18 --delrangepercent=4 --destroy_db_initially=0 --detect_filter_construct_corruption=0 --disable_wal=1 --enable_blob_files=1 --enable_blob_garbage_collection=1 --enable_compaction_filter=0 --enable_pipelined_write=0 --enable_speedb_features=0 --enable_thread_tracking=1 --expected_values_dir=/tmp/rocksdb_crashtest_expected_m6qm99fd --fail_if_options_file_error=1 --fifo_allow_compaction=0 --file_checksum_impl=crc32c --flush_one_in=1000000 --format_version=5 --get_current_wal_file_one_in=0 --get_live_files_one_in=100000 --get_property_one_in=1000000 --get_sorted_wal_files_one_in=0 --index_block_restart_interval=9 --index_type=2 --ingest_external_file_one_in=0 --initial_auto_readahead_size=16384 --initiate_wbm_flushes=0 --iterpercent=24 --key_len_percent_dist=51,11,38 --level_compaction_dynamic_level_bytes=1 --lock_wal_one_in=1000000 --long_running_snapshots=1 --manual_wal_flush_one_in=0 --mark_for_compaction_one_file_in=10 --max_auto_readahead_size=0 --max_background_compactions=1 --max_background_jobs=4 --max_bytes_for_level_base=67108864 --max_key=10485760 --max_key_len=3 --max_manifest_file_size=1073741824 --max_write_batch_group_size_bytes=64 --max_write_buffer_number=3 --max_write_buffer_size_to_maintain=0 --memtable_max_range_deletions=0 --memtable_prefix_bloom_size_ratio=0.5 --memtable_protection_bytes_per_key=4 --memtable_whole_key_filtering=1 --memtablerep=skip_list --min_blob_size=8 --min_write_buffer_number_to_merge=1 --mmap_read=1 --mock_direct_io=False --nooverwritepercent=40 --num_file_reads_for_auto_readahead=1 --num_iterations=86 --open_files=-1 --open_metadata_write_fault_one_in=8 --open_read_fault_one_in=0 --open_write_fault_one_in=0 --ops_per_thread=100000000 --optimize_filters_for_memory=1 --paranoid_file_checks=1 --partition_filters=0 --partition_pinning=0 --pause_background_one_in=1000000 --periodic_compaction_seconds=0 --pinning_policy=default --prefix_size=8 --prefixpercent=8 --prepopulate_blob_cache=0 --prepopulate_block_cache=0 --preserve_internal_time_seconds=36000 --progress_reports=0 --read_fault_one_in=0 --readahead_size=524288 --readpercent=11 --recycle_log_file_num=0 --reopen=0 --ribbon_starting_level=999 --secondary_cache_fault_one_in=0 --secondary_cache_uri= --seed=235928445 --set_options_one_in=0 --snapshot_hold_ops=100000 --sst_file_manager_bytes_per_sec=104857600 --sst_file_manager_bytes_per_truncate=1048576 --start_delay_percent=35 --stats_dump_period_sec=0 --subcompactions=4 --sync=0 --sync_fault_injection=1 --sync_wal_one_in=100000 --target_file_size_base=16777216 --target_file_size_multiplier=1 --test_batches_snapshots=0 --top_level_index_pinning=3 --total_ram_size=536870912 --unpartitioned_pinning=3 --use_blob_cache=1 --use_direct_io_for_flush_and_compaction=0 --use_direct_reads=0 --use_dynamic_delay=1 --use_full_merge_v1=False --use_get_entity=0 --use_merge=0 --use_multi_get_entity=0 --use_multiget=0 --use_put_entity_one_in=0 --use_shared_block_and_blob_cache=0 --user_timestamp_size=0 --value_size_mult=32 --verify_before_write=False --verify_checksum=1 --verify_checksum_one_in=1000000 --verify_db_one_in=100000 --verify_file_checksums_one_in=1000000 --verify_iterator_with_expected_state_one_in=5 --verify_sst_unique_id_in_manifest=1 --wal_bytes_per_sync=524288 --wal_compression=zstd --write_buffer_size=33554432 --write_dbid_to_manifest=0 --write_fault_one_in=0 --writepercent=35