Storage Configurations¶

This document introduces the storaged configuration file. The default directory is /usr/local/nebula/etc/. If you have customized your Nebula Graph installation directory, your configuration file path is $pwd/nebula/etc/.

• The *.default files are used for daily debugging. When you start the services, they are the default configuration files.
• The *.production files are used for the recommended production. When they are used for production, the .production suffix must be removed.

Basic Configurations¶

Logging Configurations¶

For example, change the storage log level to v=1 with the following command.

nebula> UPDATE CONFIGS storage:v=1;

Networking Configurations¶

NOTE: We recommend you using the actual IP in the meta_server_addrs parameter because sometimes 127.0.0.1 will not be parsed correctly.

Data persistence setting for storage¶

Separate directories when using multiple hard disks. Each directory corresponds to a RocksDB instance for better concurrency. For example:

--data_path=/disk1/storage/,/disk2/storage/,/disk3/storage/

RocksDB Options¶

rocksdb_db_options¶

max_total_wal_size
delete_obsolete_files_period_micros
max_background_jobs
stats_dump_period_sec
compaction_readahead_size
writable_file_max_buffer_size
bytes_per_sync
wal_bytes_per_sync
delayed_write_rate
avoid_flush_during_shutdown
max_open_files
stats_persist_period_sec
stats_history_buffer_size
strict_bytes_per_sync
enable_rocksdb_prefix_filtering
enable_rocksdb_whole_key_filtering
rocksdb_filtering_prefix_length
num_compaction_threads
rate_limit

The parameters above can either be dynamically modified by the UPDATE CONFIGS syntax, or written in the local configuration file. Please refer to the RocksDB manual for specific functions and whether restarting is needed.

rocksdb_column_family_options¶

write_buffer_size
max_write_buffer_number
level0_file_num_compaction_trigger
level0_slowdown_writes_trigger
level0_stop_writes_trigger
target_file_size_base
target_file_size_multiplier
max_bytes_for_level_base
max_bytes_for_level_multiplier
disable_auto_compactions       -- Compact automatically when writing data is stopped, default value is false. Dynamic modification takes effect immediately.

The preceding parameters can either be dynamically modified by UPDATE CONFIGS syntax, or written in the local configuration file. Please refer to the RocksDB manual for specific functions and whether restarting is needed.

The preceding parameters can be set via the command line as follows:

nebula> UPDATE CONFIGS storage:rocksdb_column_family_options = \
        { disable_auto_compactions = false, level0_file_num_compaction_trigger = 10 };
        -- The command overwrites rocksdb_column_family_options. Please note whether other sub-items will be overwritten

nebula> UPDATE CONFIGS storage:rocksdb_db_options  = \
        { max_subcompactions = 10, max_background_jobs = 10};
nebula> UPDATE CONFIGS storage:max_edge_returned_per_vertex = 10; -- The parameter is explained below

We recommend the following configuration:

    rocksdb_db_options = {"stats_dump_period_sec":"200", "write_thread_max_yield_usec":"600"}
    rocksdb_column_family_options = {"max_write_buffer_number":"4", "min_write_buffer_number_to_merge":"2", "max_write_buffer_number_to_maintain":"1"}
    rocksdb_block_based_table_options = {"block_restart_interval":"2"}

Description on Super-Large Vertices¶

For super vertex with a large number of edges, currently there are two truncation strategies:

1. Truncate directly. Set the enable_reservoir_sampling parameter to false. A certain number of edges specified in the Max_edge_returned_per_vertex parameter are truncated by default.

2. Truncate with the reservoir sampling algorithm. Based on the algorithm, a certain number of edges specified in the Max_edge_returned_per_vertex parameter are truncated with equal probability from the total n edges. Equal probability sampling is useful in some business scenarios. However, the performance is effected compared to direct truncation due to the probability calculation.

For example:

nebula> UPDATE CONFIGS storage:enable_reservoir_sampling = false;

Truncating Directly¶

Reservoir Sampling Truncation¶

Storage Configuration When You Have a Lot of Data¶

If you have a lot of data (in the RocksDB directory) and your memory is tight, we recommend you setting the enable_partitioned_index_filter parameter in the storage configuration to true. For example, 100 vertices + 100 edges occupies 300 keys. Each key is 10bit or 3k. Then you can calculate your own data storage.