Configuration 
-- get a list of all configuration and runtime variables
SHOW CONFIG
{
  "version": "0.0",
  "uuid": "867638f7-380e-f20f-029f-51df1ff5b9c5",
  "directory": "./storage",
  "log": true,
  "log_to_file": true,
  "log_to_stdout": false,
  "mm_page_size": 2097152,
  "mm_limit": false,
  "mm_limit_wm": 8589934592,
  "mm_limit_behaviour": "block",
  "mm_cache": 8589934592,
  "wal": true,
  "wal_rotate_wm": 104857600,
  "wal_sync_on_rotate": true,
  "wal_sync_on_write": false,
  "wal_crc": false,
  "serial": true,
  "interval": 3000000,
  "compression": "zstd",
  "compression_level": 0,
  "workers": 3,
  "workers_upload": 1,
  "ssn": 0,
  "lsn": 0
}

-- change partitioning interval
SET interval TO 3000000

-- change number of background workers
SET workers TO 4

-- disable WAL
SET wal TO false

Some essential configuration options must be considered after environment creation creation and before creating or openning a repository.

Please take a look at the SHOW CONFIG and SET commands.

Instance UUID #

  • uuid string

Set UUID.

By default, the UUID is generated upon creation. In some cases, it might be useful to set it to a predefined value.

UUID can be changed only before the first opening.

See also CREATE STORAGE.

Serial Mode #

  • serial bool

Serial mode allows the assignment of event IDs automatically when written in an auto-increment way.

It is enabled by default.

The current serial state is stored inside the ssn variable, which can be changed. Each new event id will be assigned as ssn + 1. The serial state is persistent.

The event ID must be set to UINT64_MAX on write.

Partitioning Interval #

  • interval int

Set partitioning interval value.

Each partition has inclusive min/max interval.

This metric sets the partition range per each new partition as: partition min + interval - 1.

It can be changed during runtime.

See also CREATE PARTITIONS.

Write-Ahead Log #

Options to control WAL behavior.

WAL significantly affects performance and write-amplification in exchange for the per-operation durability.

Disabling WAL and relying only on automatic (or manual) per-partition durability might be a reasonable option.

  • wal bool

  • wal_rotate_wm int

    The number of operations per WAL file. When the current WAL file reaches this value, a new file will be created.

  • wal_sync_on_rotate bool

    Sync the previous WAL file when a new one is created (enabled by default).

  • wal_sync_on_write bool

    Sync the current WAL file on each write (disabled by default).

  • wal_crc bool

    Calculate and validate crc for each transaction (disabled by default).

Default Compression #

  • compression string

    Default compression type for CREATE STORAGE and the main storage.

    Supported values are: none, zstd, lz4 ( set to zstd by default).

  • compression_level int

    Default compression level depending on the compression type.

Background Workers #

  • workers int

Set the number of background workers. It can be changed only before opening.

It can be set to zero for complete manual control and deterministic testing.

Workers share the workload.
  • workers_upload int

Set the number of background workers for upload only. It can be changed only before opening.

If set to zero, regular workers will do the upload.

Enabling upload workers to access the cloud is highly recommended.

Running separate upload workers might be necessary in case of a slow network or big partitions. Workers might stall, which would lead to excessive memory consumption.

If cloud is not used, can be set to zero.

Log file #

Log messages and errors.

  • log bool

  • log_to_file string

    Create and write a log file inside the base directory (enabled by default).

  • log_to_stdout bool

    Duplicate messages from the log file to stdout (disabled by default).

Memory Manager #

  • mm_limit bool

    Turn the memory limit on or off (disabled by default).

  • mm_limit_wm int

    Memory limit watermark value.

  • mm_limit_behaviour string

    Behavior for memory limit reach. Supported values are block, error.

  • mm_page_size int

    Size of a single memory page.

  • mm_cache int

    Size of a free page cache. Can be set to zero.

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