Merge "Blueprint: external-dns-ntp-support"
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specs/6.1/external-dns-ntp-support.rst
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specs/6.1/external-dns-ntp-support.rst
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==========================================
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Support user-defined DNS and NTP
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==========================================
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https://blueprints.launchpad.net/fuel/+spec/external-dns-ntp-support
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Nodes that deployed by Fuel should support user-defined DNS and NTP settings.
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Problem description
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===================
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After deployment today we have hard-coded DNS and NTP fields on all nodes that
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referred to master node. So if master node will not have internet access to NTP
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servers that ships by default with ISO or if master node will disabled after
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deployment then all nodes can have wrong time. It's right for DNS also.
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Moreover, usually companies have internal NTP servers to sync over and internal
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DNS to work over, but now user can't provide them to Fuel for slave nodes.
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Proposed change
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===============
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Provide ability to change NTP and DNS servers for controllers through Fuel UI.
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We can do it relatively simply by adding appropriate fields for external
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DNS and NTP servers, then forward data from that fields to astute.yaml,
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transfer it to nodes and apply data on nodes.
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It is important to note that slave nodes /etc/resolve.conf files will be
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pointed to controller DNS and controllers will resolve all clients queries by
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next logic:
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#. All local queries will be forwarded to Fuel Master node.
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#. All external queries will be forwarded to external DNS servers.
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Scheme how it works today:
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::
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Fuel Master
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+----------+
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|NTP Client|
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Custom +----------+ Slave node
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^
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+----------+ +-----+----+ +----------+
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|NTP Server+---------->|NTP Server+---------->|NTP Client|
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+----------+ +----------+ +----------+
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+----------+ +----------+ +----------+
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|DNS server+---------->|DNS server+---------->|DNS Client|
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+----------+ +-----+----+ +----------+
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v
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+----------+
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|DNS Client|
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+----------+
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Scheme how it can work after:
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::
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Fuel Master
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+----------+
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|NTP Client|
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+----------+ Custom
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^
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+-----+----+ +----------+
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|NTP Server|<-----+NTP Server+--+
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+----------+ +----------+ | external queries
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+------------+
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+----------+ +----------+ | |
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+----|DNS server|<-----+DNS server+--+ |
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| +-----+----+ +----------+ |
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| v |
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| +----------+ |
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| |DNS Client| |
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| +----------+ |
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| |
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| Controllers |
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| +-----------+----------+-----v-----+
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| Slave node | |Controller| |
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| +----------+ | | | |
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| |NTP Client|<-+ | |NTP Server| |
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| +----------+ | |VIP-Router | | VIP-Router|
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| +-+Management | | Public |
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| +----------+ | | | | |
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| |DNS Client|<-+ | |DNS server| |
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| +----------+ | | | |
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| | | | |
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| +-----------+----------+-----------+
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| ^
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+--------------------------+
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local DNS queries
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Alternatives
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------------
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User can do all stuff about adding NTP and DNS records on all nodes
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himself (manually).
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Pros:
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* We don't need to change any code at all.
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Cons:
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* It inconvinient, can lead to typo errors and, as result, to
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delay in work of all system.
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* If customer's ntp server will N/A for long time, time synchronization
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between controllers and computes will be lost. After this Nova will
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mark nodes with different time as failed. Openstack env starts spoiling
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Data model impact
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-----------------
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Support to store external DNS and NTP fields in database required.
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REST API impact
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---------------
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None
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Upgrade impact
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--------------
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So as we don't have any implementation of major environments upgrade, we will
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not support upgrade from old environments where we hadn't vrouter [1] for
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external DNS and NTP to new environment where we have one. Downgrade also will
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not support.
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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Impact on fuel_health. If user define some external dns current ostf test
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for dns will fail.
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Performance Impact
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------------------
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All DNS and NTP queries may be addressed to external servers, so how long they
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will do right answer to that queries will depend from this servers settings.
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Other deployer impact
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---------------------
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None
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Developer impact
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----------------
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UI team will be affected, cause new UI options needed.
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Maybe nailgun-related team is going to be affected to correctly put new values
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from UI to database and from database to yaml
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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sbogatkin
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Work Items
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----------
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#. Sync upstream puppet-ntp module
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#. Adapt upstream module to Fuel
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#. Write puppet manifest to provide ability change NTP and DNS adresses on
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controllers
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#. Write puppet manifest to provide ability change NTP and DNS adresses on
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nodes
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#. Add changes to UI and database
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Dependencies
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============
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* https://blueprints.launchpad.net/fuel/+spec/virtual-router-for-env-nodes
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Testing
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=======
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#. We need to build new fuel ISO and test if deployment work as expected.
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#. We need to test how DNS&NTP will work with upstream external DNS&NTP
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servers.
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#. We need to test how NTP will work when upstream external NTP will disabled.
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Nodes should sync with controller NTP anyway in that case.
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Documentation Impact
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====================
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It should be described how to change DNS and NTP servers on controllers to
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external and what exactly will be changed by this settings.
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References
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==========
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[1] Virtual router blueprint: https://review.openstack.org/#/c/122123/
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