Configuring Multiple Pools¶

Administrators can group DNS namespace servers into multiple pools to help them manage their DNS environments. See DNS Server Pools to learn more about what pools are and how you can use them.

Configuring Designate to use multiple pools consists of:

Defining new pools and loading their definitions into the database.
Configuring the pool scheduler with filters that you have created or with filters provided by Designate.
Supplying the required pool information to users to specify when they create zones.

Defining New Pools¶

In Designate, you define a new pool in a pool definition file, and then load the definition into the Designate database by running the designate-manage command.

Add the pool to the pool definition file, by following the required key value pairs in YAML format that are documented under “Pool Definition File” in DNS Server Pools.

Here is an example of a pool definition file, pools.yaml, that configures two different pools. Each pool supports a different usage level, gold and standard, and each contains zones that reflect their respective usage levels.

The gold level provides 6 nameservers that users have access to. The standard level provides only 2 nameservers. Both pools have one target that is written to.

---

- name: golden_pool
  description: The golden pool!

  attributes:
    service_tier: gold

  ns_records:
    - hostname: ns1-gold.example.org
      priority: 1

    - hostname: ns2-gold.example.org
      priority: 2

    - hostname: ns3-gold.example.net
      priority: 3

    - hostname: ns4-gold.example.net
      priority: 4

    - hostname: ns5-gold.example.net
      priority: 5

    - hostname: ns6-gold.example.net
      priority: 6

  nameservers:
    - host: ns1-gold.example.net
      port: 53

    - host: ns2-gold.example.net
      port: 53

    - host: ns3-gold.example.net
      port: 53

    - host: ns4-gold.example.net
      port: 53

    - host: ns5-gold.example.net
      port: 53

    - host: ns6-gold.example.net
      port: 53

  targets:
    - type: bind9
      description: bind9 golden master

      masters:
        - host: mdns.designate.example.com
          port: 5354

      options:
        host: ns-master-gold.example.org
        port: 53
        rndc_host: ns-master-gold.example.org
        rndc_port: 953
        rndc_key_file: /etc/designate.rndc.key


- name: standard_pool
  description: The standard pool

  attributes:
    service_tier: standard

  ns_records:
    - hostname: ns1-std.example.org
      priority: 1

    - hostname: ns2-std.example.org
      priority: 2

  nameservers:
    - host: ns1-std.example.net
      port: 53

    - host: ns2-std.example.net
      port: 53

  targets:
    - type: bind9
      description: bind9 golden master

      masters:
        - host: mdns.designate.example.com
          port: 5354

      options:
        host: ns-master-std.example.org
        port: 53
        rndc_host: ns-master-std.example.org
        rndc_port: 953
        rndc_key_file: /etc/designate.rndc.key

Load the definitions into the Designate database using the designate-manage pool update command:
```
# Do a dry run
$ designate-manage pool update --file pools.yaml --dry-run
$ designate-manage pool update --file pools.yaml
```
Designate now has two pools to work with. The next step is to configure the pool scheduler to use the attributes–provided through filters–when choosing the pool to store the zone on.

Showing the configured pools¶

In Designate, you can show the current configured default pool by running the designate-manage pool show_config command. You can either see a different pool by adding –pool_id <POOL_ID>, or you can see all the configured pools by adding --all_pools or just --all.

Configuring the Pool Scheduler¶

When a user creates a zone, the pool scheduler uses filters to assign the zone to a particular DNS server pool. As the administrator, you choose an ordered list of filters that runs on each zone create API request. You configure the scheduler to use filters that are provided with Designate or create your own.

Do one of the following:
- Write one or more custom filters.
  
  See Pool Scheduler Filters.
- Choose one or more of the filters that Designate provides:
  - attribute–assigns the zone to the pool whose attribute is specified.
  - pool_id_attribute–if the user is a member of the specified role assigns the zone to the pool whose ID is specified.
  - default_pool–assigns the zone to the default pool specified in the Designate configuration file.
  - fallback–if there are no pools available, assigns the zone to the default pool.
  - random–if multiple pools have been specified, randomly assigns the zone to a pool.
  - in_doubt_default_pool–if none of the specified pools are available, and the default pool has not been specified, assigns the zone to the default pool.
Add the filters that you want the scheduler to use in the service:central section of the designate.conf file. See Pool Scheduler Filters for more information.

Schedule by Pool ID Example¶

For example, to allow a user to select a pool by specifying an ID or fallback to using a default, you could use the following configuration:

[service:central]
default_pool_id = 794ccc2c-d751-44fe-b57f-8894c9f5c842
scheduler_filters = pool_id_attribute, fallback

The pool scheduler applies filters from left to right. If the zone body doesn’t contain an attributes object with a pool_id set to a valid pool ID, the fallback filter is then called, returning the default pool as the scheduled pool for that zone.

Schedule by Tier Example¶

In this tier example, the attribute filter is used to select the correct pool.

[service:central]
default_pool_id = 794ccc2c-d751-44fe-b57f-8894c9f5c842  # the std pool
scheduler_filters = attribute, fallback

When a user wants to assign a zone to the gold pool, the user must provide the appropriate attribute in the zone.

POST /v2/zones HTTP/1.1
Accept: application/json
Content-Type: application/json

{
    "attributes": {
        "service_tier": "gold"
    },
    "email": "user@example.com",
    "name": "example.net."
}

In this example, the user defines which pool is scheduled. If the zone should be scheduled based on the tenant, a custom filter could be written that looks up the appropriate group and adds the appropriate pool.

Configuring Multiple Pools