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 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 and 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

The YDB Kubernetes operator mounts NBS disks for Storage nodes at 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 example configuration files provided with the YDB Kubernetes operator contain this 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 standard host configuration
  • Placement in a specific availability zone, rack
  • Server inventory number (optional)

Syntax

hosts:
- host: <DNS host name>
  host_config_id: <numeric ID of the standard 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:

Mode Description
none There is no redundancy. Applies for testing.
block-4-2 Redundancy factor of 1.5, applies to single data center clusters.
mirror-3-dc Redundancy factor of 3, applies to multi-data center clusters.
mirror-3dc-3-nodes Redundancy factor of 3. Applies for testing.

Syntax

  storage_pool_types:
  - kind: <storage pool name>
    pool_config:
      box_id: 1
      encryption: <optional, specify 1 to encrypt data on the disk>
      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 variable 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 to guarantee a working majority in case of expected failures.

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

Cluster type Min number of
nodes		 Selection guidelines
Without fault tolerance 1 Select one random node.
Within a single availability zone 5 Select five nodes in different block-4-2 storage pool failure domains to ensure that a majority of 3 working nodes (out of 5) remain when two domains fail.
Geo-distributed 9 Select three nodes in different failure domains within each of the three mirror-3-dc storage pool availability zones to ensure that a majority of 5 working nodes (out of 9) remain when the availability zone + failure domain fail.

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 to 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
  ...
Key Description
enforce_user_token_requirement Require a user token.
Acceptable values:
  • false: Anonymous authentication mode, no token needed (used by default if the parameter is omitted).
  • true: Username/password authentication mode. A valid user token is needed for authentication.

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: 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
  security_config:
    enforce_user_token_requirement: true



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

The CPU resources are mainly used by the actor system. Depending on the type, all actors run in one of the pools (the name parameter). Configuring is allocating a node's CPU cores across the actor system pools. When allocating them, please keep in mind that PDisks and the gRPC API run outside the actor system and require separate resources.

You can set up your actor system either automatically or manually. In the actor_system_config section, specify:

  • Node type and the number of CPU cores allocated to the ydbd process by automatic configuring.
  • Number of CPU cores for each YDB cluster subsystem in the case of manual configuring.

Automatic configuring adapts to the current system workload. It is recommended in most cases.

You might opt for manual configuring when a certain pool in your actor system is overwhelmed and undermines the overall database performance. You can track the workload on your pools on the Embedded UI monitoring page.

Automatic configuring

Example of the actor_system_config section for automatic configuring of the actor system:

actor_system_config:
  use_auto_config: true
  node_type: STORAGE
  cpu_count: 10
Parameter Description
use_auto_config Enabling automatic configuring of the actor system.
node_type Node type. Determines the expected workload and vCPU ratio between the pools. Possible values:
  • STORAGE: The node interacts with network block store volumes and is responsible for managing the Distributed Storage.
  • COMPUTE: The node processes the workload generated by users.
  • HYBRID: The node is used for hybrid load or the usage of System, User, and IC for the node under load is about the same.
cpu_count Number of vCPUs allocated to the node.

Manual configuring

Example of the actor_system_config section for manual configuring of the actor 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
Parameter Description
executor Pool configuration.
You should only change the number of CPU cores (the threads parameter) in the pool configs.
name Pool name that indicates its purpose. Possible values:
  • System: A pool that is designed for running quick internal operations in YDB (it serves system tablets, state storage, distributed storage I/O, and erasure coding).
  • User: A pool that serves the user load (user tablets, queries run in the Query Processor).
  • Batch: A pool that serves tasks with no strict limit on the execution time, background operations like garbage collection and heavy queries run in the Query Processor.
  • IO: A pool responsible for performing any tasks with blocking operations (such as authentication or writing logs to a file).
  • IC: Interconnect, it serves the load related to internode communication (system calls to wait for sending and send data across the network, data serialization, as well as message splits and merges).
spin_threshold The number of CPU cycles before going to sleep if there are no messages. In sleep mode, there is less power consumption, but it may increase request latency under low loads.
threads The number of CPU cores allocated per pool.
Make sure the total number of cores assigned to the System, User, Batch, and IC pools does not exceed the number of available system cores.
max_threads Maximum vCPU that can be allocated to the pool from idle cores of other pools. When you set this parameter, the system enables the mechanism of expanding the pool at full utilization, provided that idle vCPUs are available.
The system checks the current utilization and reallocates vCPUs once per second.
max_avg_ping_deviation Additional condition to expand the pool's vCPU. When more than 90% of vCPUs allocated to the pool are utilized, you need to worsen SelfPing by more than max_avg_ping_deviation microseconds from 10 milliseconds expected.
time_per_mailbox_micro_secs The number of messages per actor to be handled before switching to a different actor.
type Pool type. Possible values:
  • IO should be set for IO pools.
  • BASIC should be set for any other pool.
scheduler Scheduler configuration. The actor system scheduler is responsible for the delivery of deferred messages exchanged by actors.
We do not recommend changing the default scheduler parameters.
progress_threshold The actor system supports requesting message sending scheduled for a later point in time. The system might fail to send all scheduled messages at some point. In this case, it starts sending them in "virtual time" by handling message sending in each loop over a period that doesn't exceed the progress_threshold value in microseconds and shifting the virtual time by the progress_threshold value until it reaches real time.
resolution When making a schedule for sending messages, discrete time slots are used. The slot duration is set by the resolution parameter in microseconds.

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.

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