Docs for working with multiple pools
These docs go through the process of setting up multiple pools and configuring the scheduler to use them automatically. Closes-Bug: #1602694 Change-Id: Id0398741fe8119313c142e305d2a060af57dad00
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Eric Larson
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Copyright 2016 Rackspace Hosting
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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=================================
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How To Configure Multiple Pools
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=================================
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Designate supports "pools" of nameservers. A pool is a collection of
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nameservers and targets that Designate will write to and read from to
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confirm changes are successfull. In some cases you might have multiple
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pools that you need to manage differently. For example, you might use
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separate pools to distribute tenants across some subset of your DNS
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infrastructure.
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Target vs. Nameserver
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=====================
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One thing that can be confusing about pools is the differentiation
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between a target and a nameserver. The target is where Designate will
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try to write the change, while a namserver is where Designate checks
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that the change exists.
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A great example of this is `bind's stealth master system
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<http://www.zytrax.com/books/dns/ch4/#stealth>`_. In this
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configuration, there could be a stealth master that you configure as
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your target and a set of slaves pointed to that master as your
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nameservers. Designate will write to the master and then look for the
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changes on the slaves before considering the change active.
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Another example would be where Designate uses an API backend such as
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DynDNS or even another Designate instance. In this situation, you will
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typically have a single target with a set of nameservers to test that
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meet your requirements.
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Yet another example is when using a Designate agent. In this scenario
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your agent instances are the targets and the nameservers the agent
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updates would be checked for the correct information.
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Pools Configuration
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===================
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Pools are configured by a `pools.yml` file. This file describes the
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pools and can be used to update Designate via `designate-manage`
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commands.
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Here is an example `pools.yml` that configures two different
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pools. The idea is that we'll configure our pools to support different
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usage levels. We'll define a `gold` and `standard` level and put zones
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in each based on the tenant.
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Our `gold` leve will provide 6 nameservers that users have access to
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where our `standard` will only provide 2. Both pools will have one
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master target we write to.
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.. code-block:: yaml
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---
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- name: golden_pool
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description: The golden pool!
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attributes:
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service_tier: gold
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ns_records:
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- hostname: ns1-gold.example.org
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priority: 1
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- hostname: ns2-gold.example.org
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priority: 2
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- hostname: ns3-gold.example.net
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priority: 3
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- hostname: ns4-gold.example.net
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priority: 4
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- hostname: ns5-gold.example.net
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priority: 5
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- hostname: ns6-gold.example.net
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priority: 6
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nameservers:
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- host: ns1-gold.example.net
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port: 53
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- host: ns2-gold.example.net
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port: 53
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- host: ns3-gold.example.net
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port: 53
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- host: ns4-gold.example.net
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port: 53
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- host: ns5-gold.example.net
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port: 53
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- host: ns6-gold.example.net
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port: 53
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targets:
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- type: bind9
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description: bind9 golden master
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masters:
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- host: mdns.designate.example.com
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port: 5354
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options:
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host: ns-master-gold.example.org
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port: 53
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rndc_host: ns-master-gold.example.org
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rndc_port: 953
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rndc_key_file: /etc/designate.rndc.key
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- name: standard_pool
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description: The standard pool
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attributes:
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service_tier: standard
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ns_records:
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- hostname: ns1-std.example.org
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priority: 1
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- hostname: ns2-std.example.org
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priority: 2
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nameservers:
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- host: ns1-std.example.net
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port: 53
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- host: ns2-std.example.net
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port: 53
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targets:
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- type: bind9
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description: bind9 golden master
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masters:
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- host: mdns.designate.example.com
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port: 5354
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options:
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host: ns-master-std.example.org
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port: 53
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rndc_host: ns-master-std.example.org
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rndc_port: 953
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rndc_key_file: /etc/designate.rndc.key
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With our configuration in place, we can then update Designate to use
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the pool configuration.
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.. code-block:: bash
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# Do a dry run
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$ designate-manage pool update --file pools.yml --dry_run
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$ designate-manage pool update --file pools.yml
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Designate now has two pools to work with. The next step will be to
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configure the scheduler to use the attributes when choosing what pool
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to store the zone on.
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Pool Scheduler
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==============
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The pool scheduler allows selecting a pool when a zone is
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created. Each scheduler acts as a filter, selecting or negating each
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pool based on some attributes. Designate comes with some simple
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schedulers to support common patterns:
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- default_pool
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- fallback
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- random
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- pool_id_attribute
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- attribute
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These are configured in the `service:central` section of the
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config.
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Schedule by Pool ID Example
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---------------------------
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For example, if we wanted to allow a user to select a specific pool by
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id or fallback to using a default, we could use the following
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configuration.
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.. code-block:: conf
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[service:central]
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default_pool_id = 794ccc2c-d751-44fe-b57f-8894c9f5c842
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scheduler_filters = pool_id_attribute, fallback
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The filters are applied from left to right. If the zone body doesn't
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contain an `attributes` object with a `pool_id` set to a valid pool
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id, the fallback filter is then called, returning the default pool as
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the scheduled pool for that zone.
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Schedule by Tier Example
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------------------------
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In our tiered example, we'll use the `attribute` filter to select the
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correct pool.
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.. code-block:: conf
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[service:central]
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default_pool_id = 794ccc2c-d751-44fe-b57f-8894c9f5c842 # the std pool
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scheduler_filters = attribute, fallback
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When a user needs the zone to go to the `gold` pool, the user needs to
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provide the appropriate attribute in the zone.
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.. code-block:: http
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POST /v2/zones HTTP/1.1
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Accept: application/json
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Content-Type: application/json
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{
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"attributes": {
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"service_tier": "gold"
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},
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"email": "user@example.com",
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"name": "example.net."
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}
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This ensures the zone ends up on the correct pool.
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In this example, we've allowed the user to define what pool should be
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scheduled. If we wanted to schedule the zone based on the tenant, we
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could write a custom filter that looked up the appropriate group and
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adds the appropriate pool.
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