Centralized configuration storages

Tarantool-based storage

To make a replica set act as a configuration storage, use the built-in config.storage role.

credentials:
  users:
    sampleuser:
      password: '123456'
      privileges:
      - permissions: [ read, write ]
        spaces: [ config_storage, config_storage_meta ]
      - permissions: [ execute ]
        universe: true
    replicator:
      password: 'topsecret'
      roles: [ replication ]

iproto:
  advertise:
    peer:
      login: replicator

replication:
  failover: election

database:
  use_mvcc_engine: true

groups:
  group001:
    replicasets:
      replicaset001:
        roles: [ config.storage ]
        roles_cfg:
          config.storage:
            status_check_interval: 3
        instances:
          instance001:
            iproto:
              listen:
              - uri: '127.0.0.1:4401'
          instance002:
            iproto:
              listen:
              - uri: '127.0.0.1:4402'
          instance003:
            iproto:
              listen:
              - uri: '127.0.0.1:4403'

$ tt start tarantool_config_storage

etcd-based storage

To learn how to set up an etcd-based configuration storage, consult the etcd documentation.

The example script below demonstrates how to use the etcdctl utility to create a user that has read and write access to configurations stored by the /myapp/ prefix:

etcdctl user add root:topsecret
etcdctl role add myapp_config_manager
etcdctl role grant-permission myapp_config_manager --prefix=true readwrite /myapp/
etcdctl user add sampleuser:123456
etcdctl user grant-role sampleuser myapp_config_manager
etcdctl auth enable

The credentials of this user should be specified when configuring a connection to the etcd cluster.

Publishing configuration using the tt utility

The tt utility provides the tt cluster command for managing centralized cluster configurations. The tt cluster publish command can be used to publish a cluster’s configuration to both Tarantool and etcd-based storages.

The example below shows how a tt environment and a layout of the application called myapp might look:

├── tt.yaml
├── source.yaml
└── instances.enabled
    └── myapp
        ├── config.yaml
        └── instances.yml

• tt.yaml: a tt configuration file.
• source.yaml contains a cluster’s configuration to be published.
• config.yaml contains a local configuration used to connect to the centralized storage.
• instances.yml specifies instances to run in the current environment. The configured instances are used by tt when starting a cluster. tt cluster publish ignores this configuration file.

To publish a cluster’s configuration (source.yaml) to a centralized storage, execute tt cluster publish as follows:

$ tt cluster publish "http://sampleuser:123456@localhost:2379/myapp" source.yaml

Executing this command publishes a cluster configuration by the /myapp/config/all path.

Publishing configuration using the „config“ module

The config module provides the API for interacting with a Tarantool-based configuration storage. The example below shows how to read a configuration stored in the source.yaml file using the fio module API and put this configuration by the /myapp/config/all path:

local fio = require('fio')
local cluster_config_handle = fio.open('../../source.yaml')
local cluster_config = cluster_config_handle:read()
local response = config.storage.put('/myapp/config/all', cluster_config)
cluster_config_handle:close()

Learn more from the config.storage API section.

Publishing configuration using etcdctl

To publish a cluster’s configuration to etcd using the etcdctl utility, use the put command:

$ etcdctl put /myapp/config/all < source.yaml

Configuring connection to a Tarantool storage

Connection options for a Tarantool-based storage should be specified in the config.storage section of the configuration file. In the example below, the following options are specified:

config:
  storage:
    endpoints:
      - uri: '127.0.0.1:4401'
        login: sampleuser
        password: '123456'
      - uri: '127.0.0.1:4402'
        login: sampleuser
        password: '123456'
      - uri: '127.0.0.1:4403'
        login: sampleuser
        password: '123456'
    prefix: /myapp
    timeout: 3
    reconnect_after: 5

• endpoints specifies the list of configuration storage endpoints.
• prefix sets a key prefix used to search a configuration. Tarantool searches keys by the following path: <prefix>/config/*. Note that <prefix> should start with a slash (/).
• timeout specifies the interval (in seconds) to perform the status check of a configuration storage.
• reconnect_after specifies how much time to wait (in seconds) before reconnecting to a configuration storage.

You can find the full example here: config_storage.

Configuring connection to an etcd storage

Connection options for etcd should be specified in the config.etcd section of the configuration file. In the example below, the following options are specified:

config:
  etcd:
    endpoints:
    - http://localhost:2379
    prefix: /myapp
    username: sampleuser
    password: '123456'
    http:
      request:
        timeout: 3

• endpoints specifies the list of etcd endpoints.
• prefix sets a key prefix used to search a configuration. Tarantool searches keys by the following path: <prefix>/config/*. Note that <prefix> should start with a slash (/).
• username and password specify credentials used for authentication.
• http.request.timeout configures a request timeout for an etcd server.

You can find the full example here: config_etcd.