Cluster configuration

The cluster configuration is specified in the YAML file passed in the --yaml-config parameter when the cluster nodes are run.

This article describes the main groups of configurable parameters in this file.

host_configs: Typical host configurations

A YDB cluster consists of multiple nodes, and one or more typical server configurations are usually used for their deployment. To avoid repeating its description for each node, there is a host_configs section in the configuration file that lists the used configurations and the assigned IDs.

Syntax

host_configs:
- host_config_id: 1
  drive:
  - path: <path_to_device>
    type: <type>
  - path: ...
- host_config_id: 2
  ...  

The host_config_id attribute specifies a numeric configuration ID. The drive attribute contains a collection of descriptions of connected drives. Each description consists of two attributes:

• path: Path to the mounted block device, for example, /dev/disk/by-partlabel/ydb_disk_ssd_01
• type: Type of the device's physical media: ssd, nvme, or rot (rotational - HDD)

Examples

One configuration with ID 1, one SSD disk accessible via /dev/disk/by-partlabel/ydb_disk_ssd_01:

host_configs:
- host_config_id: 1
  drive:
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_01
    type: SSD

Two configurations with IDs 1 (two SSD disks) and 2 (three SSD disks):

host_configs:
- host_config_id: 1
  drive:
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_01
    type: SSD
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_02
    type: SSD
- host_config_id: 2
  drive:
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_01
    type: SSD
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_02
    type: SSD
  - path: /dev/disk/by-partlabel/ydb_disk_ssd_03
    type: SSD

Kubernetes features

YDB Kubernetes operator mounts NBS disks for Storage nodes on the path /dev/kikimr_ssd_00. To use them, the following host_configs configuration must be specified:

host_configs:
- host_config_id: 1
  drive:
  - path: /dev/kikimr_ssd_00
    type: SSD

The configuration example files supplied as part of YDB Kubernetes operator contain such a section, and it does not need to be changed.

hosts: Static cluster nodes

This group lists the static cluster nodes on which the Storage processes run and specifies their main characteristics:

• Numeric node ID
• DNS host name and port that can be used to connect to a node on the IP network
• ID of the typical host configuration
• Placement in a specific availability zone, rack
• Server serial number (optional)

Syntax

hosts:
- host: <DNS host name>
  host_config_id: <numeric ID of the typical host configuration>
  port: <port> # 19001 by default
  location:
    unit: <string with the server serial number>
    data_center: <string with the availability zone ID>
    rack: <string with the rack ID>
- host: <DNS host name>
  ...

Examples

hosts:
- host: hostname1
  host_config_id: 1
  node_id: 1
  port: 19001
  location:
    unit: '1'
    data_center: '1'
    rack: '1'
- host: hostname2
  host_config_id: 1
  node_id: 2
  port: 19001
  location:
    unit: '1'
    data_center: '1'
    rack: '1'

Kubernetes features

When deploying YDB with a Kubernetes operator, the entire hosts section is generated automatically, replacing any user-specified content in the configuration passed to the operator. All Storage nodes use host_config_id = 1, for which the correct configuration must be specified.

domains_config: Cluster domain

This section contains the configuration of the YDB cluster root domain, including the Blob Storage (binary object storage), State Storage, and authentication configurations.

Syntax

domains_config:
  domain:
  - name: <root domain name>
    storage_pool_types: <Blob Storage configuration>
  state_storage: <State Storage configuration>
  security_config: <authentication configuration>

Blob Storage configuration

This section defines one or more types of storage pools available in the cluster for the data in the databases with the following configuration options:

• Storage pool name
• Device properties (for example, disk type)
• Data encryption (on/off)
• Fault tolerance mode

The following fault tolerance modes are available:

Syntax

  storage_pool_types:
  - kind: <storage pool name>
    pool_config:
      box_id: 1
      encryption: <optional, specify 1 to encrypt data on the disc>
      erasure_species: <fault tolerance mode name - none, block-4-2, or mirror-3-dc>
      kind: <storage pool name - specify the same value as above>
      pdisk_filter:
      - property:
        - type: <device type to be compared with the one specified in host_configs.drive.type>
      vdisk_kind: Default
  - kind: <storage pool name>
  ...

Each database in the cluster is assigned at least one of the available storage pools selected in the database creation operation. The names of storage pools among those assigned can be used in the DATA attribute when defining column groups in YQL operators CREATE TABLE/ALTER TABLE.

State Storage configuration

State Storage is an independent in-memory storage for modifiable data that supports internal YDB processes. It stores data replicas on multiple assigned nodes.

State Storage usually does not need scaling for better performance, so the number of nodes in it must be kept as small as possible taking into account the required level of fault tolerance.

State Storage availability is key for a YDB cluster because it affects all databases, regardless of which storage pools they use. To ensure fault tolerance of State Storage, its nodes must be selected in such a way as to guarantee a working majority in case of expected failures.

The following guidelines can be used to select State Storage nodes:

When deploying State Storage on clusters that use multiple storage pools with a possible combination of fault tolerance modes, consider increasing the number of nodes and spreading them across different storage pools because unavailability of State Storage results in unavailability of the entire cluster.

Syntax

state_storage:
- ring:
    node: <StateStorage node array>
    nto_select: <number of data replicas in StateStorage>
  ssid: 1

Each State Storage client (for example, DataShard tablet) uses nto_select nodes to write copies of its data to State Storage. If State Storage consists of more than nto_select nodes, different nodes can be used for different clients, so you must ensure that any subset of nto_select nodes within State Storage meets the fault tolerance criteria.

Odd numbers must be used for nto_select because using even numbers does not improve fault tolerance in comparison with the nearest smaller odd number.

Authentication configuration

The authentication mode in the YDB cluster is created in the domains_config.security_config section.

Syntax:

domains_config:
  ...
  security_config:
    enforce_user_token_requirement: Bool
  ...

Examples

domains_config:
  domain:
  - name: Root
    storage_pool_types:
    - kind: ssd
      pool_config:
        box_id: 1
        erasure_species: block-4-2
        kind: ssd
        pdisk_filter:
        - property:
          - type: SSD
        vdisk_kind: Default
  state_storage:
  - ring:
      node: [1, 2, 3, 4, 5, 6, 7, 8]
      nto_select: 5
    ssid: 1

domains_config:
  domain:
  - name: global
    storage_pool_types:
    - kind: ssd
      pool_config:
        box_id: 1
        erasure_species: mirror-3-dc
        kind: ssd
        pdisk_filter:
        - property:
          - type: SSD
        vdisk_kind: Default
  state_storage:
  - ring:
      node: [1, 2, 3, 4, 5, 6, 7, 8, 9]
      nto_select: 9
    ssid: 1

domains_config:
  domain:
  - name: Root
    storage_pool_types:
    - kind: ssd
      pool_config:
        box_id: 1
        erasure_species: none
        kind: ssd
        pdisk_filter:
        - property:
          - type: SSD
        vdisk_kind: Default
  state_storage:
  - ring:
      node:
      - 1
      nto_select: 1
    ssid: 1

domains_config:
  domain:
  - name: Root
    storage_pool_types:
    - kind: ssd
      pool_config:
        box_id: '1'
        erasure_species: block-4-2
        kind: ssd
        pdisk_filter:
        - property:
          - {type: SSD}
        vdisk_kind: Default
    - kind: rot
      pool_config:
        box_id: '1'
        erasure_species: block-4-2
        kind: rot
        pdisk_filter:
        - property:
          - {type: ROT}
        vdisk_kind: Default
    - kind: rotencrypted
      pool_config:
        box_id: '1'
        encryption_mode: 1
        erasure_species: block-4-2
        kind: rotencrypted
        pdisk_filter:
        - property:
          - {type: ROT}
        vdisk_kind: Default
    - kind: ssdencrypted
      pool_config:
        box_id: '1'
        encryption_mode: 1
        erasure_species: block-4-2
        kind: ssdencrypted
        pdisk_filter:
        - property:
          - {type: SSD}
        vdisk_kind: Default
  state_storage:
  - ring:
      node: [1, 16, 31, 46, 61, 76, 91, 106]
      nto_select: 5
    ssid: 1

actor_system_config: Actor system

Create an actor system configuration. Specify how processor cores will be distributed across the pools of cores available in the system.

actor_system_config:
  executor:
  - name: System
    spin_threshold: 0
    threads: 2
    type: BASIC
  - name: User
    spin_threshold: 0
    threads: 3
    type: BASIC
  - name: Batch
    spin_threshold: 0
    threads: 2
    type: BASIC
  - name: IO
    threads: 1
    time_per_mailbox_micro_secs: 100
    type: IO
  - name: IC
    spin_threshold: 10
    threads: 1
    time_per_mailbox_micro_secs: 100
    type: BASIC
  scheduler:
    progress_threshold: 10000
    resolution: 256
    spin_threshold: 0

blob_storage_config: Static cluster group

Specify a static cluster group's configuration. A static group is necessary for the operation of the basic cluster tablets, including Hive, SchemeShard, and BlobstorageContoller.
As a rule, these tablets do not store a lot of data, so we don't recommend creating more than one static group.

For a static group, specify the disks and nodes that the static group will be placed on. For example, a configuration for the erasure: none model can be as follows:

blob_storage_config:
  service_set:
    groups:
    - erasure_species: none
      rings:
      - fail_domains:
        - vdisk_locations:
          - node_id: 1
            path: /dev/disk/by-partlabel/ydb_disk_ssd_02
            pdisk_category: SSD
....

For a configuration located in 3 availability zones, specify 3 rings. For a configuration within a single availability zone, specify exactly one ring.

Sample cluster configurations

You can find model cluster configurations for deployment in the repository. Check them out before deploying a cluster.