Ansible multi-node specification
This specification outlines some of the design goals and practices to be used to implement an Ansible multi-node deployment tool. The goals of this work are simplicity, optimizing deployment time, and Operator flexibility. The long term objective is for Kolla to become the de-facto solution for deploying OpenStack in containers. Partially Implements: blueprint ansible-multi Co-Authored-By: Sam Yaple <sam@yaple.net> Change-Id: I8c5d8b7e69c4ed54624061428e2fbde6af6a1815
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specs/ansible-multi.rst
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specs/ansible-multi.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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Multi-node Ansible
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==================
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This blueprint specifies an approach to automate the deployment of OpenStack
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using Ansible and Docker best practices. The overriding principles used in
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this specification are simplicity, flexibility and optimized deployment speed.
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Problem description
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===================
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Kolla can be deployed multi-node currently. To do so, the environment
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variables must be hand edited to define the hosts to connect to for various
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services.
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To implement HA in our containers, we need multi-node deployment operational
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so we can validate the high availability implementation.
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To meet our community approved mission, we must implement a deployment tool
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and Ansible provides the most effecient development path while ensuring ease
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of use.
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Use cases
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---------
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1. Deploy Kolla's Docker containers multi-node and generate a one-hundred node
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working OpenStack deployment out of the box with minimal Operator
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configuration.
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2. Offer a fully customizable configuration enabling an unopinionated
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deployment of OpenStack.
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3. Upgrade an OpenStack deployment by Operator command.
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4. Offer our container content as a building block to third party downstream
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deployment tools.
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Proposed change
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===============
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The docker-compose tool is single node and does nearly the same job as Ansible
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would in this specification. As a result, we recommend deprecating
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docker-compose as the default deployment system for Kolla.
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To replace it, we recommend Ansible as a technology choice. Ansible is easy
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to learn, easy to use, and offers a base set of functionality to solve
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deployment as outlined in our four use cases.
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We recommend three models of configuration.
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The first model is based upon internally configuring the container and having
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the container take responsibility for all container configuration including
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database setup, database synchronization, and keystone registration. This
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model uses docker-compose and docker as dependencies. Existing containers will
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be maintained but new container content will use either of the two remaining
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models. James Slagle (TripleO PTL on behalf of our downstream TripleO
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community) was very clear that he would prefer to see this model stay available
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and maintained. As TripleO enters the world of Big Tent, they don't intend to
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deploy all of the services, and as such it doesn't make sense to maintain this
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legacy operational mode for new container content except on demand of our
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downstreams, hopefully with their assistance. This model is called
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CONFIG_INSIDE.
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The second model and third model configure the containers outside of the
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container. These models depend on Ansible and Docker. In the future, the
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OpenStack Puppet, OpenStack Chef and TripleO communities may decide to switch
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to one of these two models in which case these communities may maintain tooling
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to integrate with Kolla. The major difference between these two models is that
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one offers immutability and single source of truth (CONFIG_OUTSIDE_COPY_ONCE),
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while the third model trades these two properties to allow an Operator to
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directly modify configuration files on a system and have the configuration be
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live in the container (CONFIG_OUTSIDE_COPY_ALWAYS). Because
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CONFIG_OUTSIDE_COPY_ALWAYS requires direct Operator intervention on a node, and
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we prefer as a community Operators interact with the tools provided by Kolla,
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CONFIG_OUTSIDE_COPY_ONCE will be the default.
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We do not have to further enhance two sets of container configuration, but
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instead can focus our development effort on the default Ansible configuration
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methods. If a defect is found in one of the containers based upon the
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CONFIG_INSIDE model, the community will repair it.
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Finally we will implement a complete Ansible deployment system. The details
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of the implementation are covered in a later section in this specification.
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We estimate this will be approximately ~1000 LOC defining ~100 Ansible tasks.
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We further estimate the total code base when complete will be under 6 KLOC.
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The CONFIG_INSIDE model of configuration maintains the immutable,
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declarative, and idempotent nature of the Kolla containers, as defined by our
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current Kolla best practices but is opinionated in configuration.
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The CONFIG_OUTSIDE_COPY_ONCE model of configuration maintains the immutable and
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declarative nature of the Kolla containers, as defined by our current Kolla
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best practices while introducing completely customizable configuration.
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The CONFIG_OUTSIDE_COPY_ALWAYS model of configuration offers the Operator
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greater flexibility in managing their deployment, at greater risk of damaging
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their deployment. It trades one set of best practices for another,
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specifically the Kolla container best practices for flexibility.
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Security impact
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---------------
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None.
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Performance Impact
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------------------
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Multi-node deployment speed will be rapidly improved.
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Implementation
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==============
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The following section uses the Keystone container as an example.
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On container start, a simple shell script will be run.
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Passed into the container will be the CONFIG_STRATEGY environment variable with
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the following options:
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CONFIG_STRATEGY="CONFIG_INSIDE"
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CONFIG_STRATEGY="CONFIG_OUTSIDE_COPY_ALWAYS"
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CONFIG_STRATEGY="CONFIG_OUTSIDE_COPY_ONCE"
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CONFIG_INSIDE will match the current crudini.sh implementation.
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The shell script will be similar in nature to the following:
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case $CONFIG_STRATEGY in
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CONFIG_INSIDE)
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# We exec on crudini.sh to keep the same behaviour as current
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exec /crudini.sh
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;;
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CONFIG_OUTSIDE_COPY_ONCE|CONFIG_OUTSIDE_COPY_ALWAYS)
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# We source this file to allow variables to be set if needed
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source /config_outside.sh
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;;
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*)
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echo '$CONFIG_STRATEGY is not set properly'
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exit 1
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;;
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esac
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exec $CONFIG_STRATEGY_BINARY_NAME
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The crudini.sh script would be almost identical to the existing start.sh script
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while the config_outside.sh would copy the files to the appropriate location
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and set the proper permissions on those files. The $CONFIG_STRATEGY variable
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would be checked to see if the files should be copied or it should exit early.
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The following bindmounts would be applied to the container in the above example
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for different CONFIG_STRATEGY values:
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CONFIG_INSIDE - no bind mount
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CONFIG_OUTSIDE_COPY_ONCE - {{ HOST_CONFIG_DIR }}/keystone:/opt/kolla/configs/keystone:ro
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CONFIG_OUTSIDE_COPY_ALWAYS - {{ HOST_CONFIG_DIR }}/keystone:/opt/kolla/configs/keystone:ro
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{{ HOST_CONFIG_DIR }} would be an Ansible variable with the default of
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/opt/kolla/configs. This same pattern will be used for most containers, unless
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there is a compelling technical reason not to do so.
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An Ansible role represents a service in OpenStack. The Ansible role contains
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3 major sections. This same pattern will be used for all supported
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OpenStack containers.
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Each Ansible role has a set of default key/value pairs. An example key/value
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file for Keystone is:
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---
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container: "keystone"
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database_password: "{{ database_keystone_password }}"
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The second major section of a Ansible role are the role tasks. The seven
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tasks we will implement per role (i.e. OpenStack Service):
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* bootstrap - database initialization and add roles to keystone
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* pull - pulls the latest container from the registry
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* main - Does the main job of orchestrating the role
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* config - Joins the default configuration and the user augmented
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configuration and saves the resulting file to be bind-mounted
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* start - Similar in nature to a docker compose YAML file - defines the
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defaults for the container start operation.
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* stop - Stops the container
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* upgrade - Upgrades to the latest container content
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The details of how these role tasks operate is an implementation detail.
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Finally each Ansible role has a default template. An example of a default
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template for Keystone is:
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[DEFAULT]
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verbose = {{ keystone_verbose }}
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debug = {{ keystone_debug }}
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bind_host = {{ ansible_br_mgmt['ipv4']['address'] }}
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admin_token = {{ keystone_admin_token }}
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public_endpoint = http://{{ keystone_service_ip }}:{{ keystone_service_public_port }}
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admin_endpoint = http://{{ keystone_service_ip }}:{{ keystone_service_admin_port }}
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log_file = {{ keystone_log_file }}
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log_dir = {{ keystone_log_dir }}
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[database]
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connection = mysql://{{ keystone_db_user }}:{{ database_keystone_password }}@{{ keystone_service_ip }}/keystone
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[revoke]
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driver = keystone.contrib.revoke.backends.sql.Revoke
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This role default will contain sufficient mandatory configuration options to
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create a working deployment. If the Operator wishes to augment the Keystone
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configuration, an augmentation file can be added to the deployment. An example
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augmentation file in /etc/kolla/keystone.aug is:
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[DEFAULT]
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public_endpoint = https://{{ keystone_service_ip }}:{{ keystone_service_public_port }}
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[ipman]
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life = "Two Words. Horizontal. Vertical. Make a mistake - Horizontal. Stay standing and you win."
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This augmentation file will keep the original default configurations but
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replace public_endpoint with an https endpoint instead of an http endpoint.
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Further the [ipman] section will be added to the file placed by Ansible in
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the target host's configuration directory.
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The end result of the merge will be a single file on the host that is in the
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appropriate format for the Openstack service to consume containing the content
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of both the Ansible default file and the augmentation file.
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The final implication of these Ansible best practices is that an Operator can
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deploy in 1 hour or less a one-hundred node OpenStack deployment out of the
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box using Kolla containers with Ansible deployment tooling with minimal
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configuration. If additional customization is required for the Operator's
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environment, this can be achieved via augmentation files developed by the
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Operator.
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NB: to override any default key/value pair (the key is located in {{ }} above
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and replaced by the value by Ansible), there is one global override file to
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configure the deployment called /etc/kolla/globals.yml
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We will implement a simple shell script called kolla-ansible which wraps
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ansible-playbook. It will implement four commands which operate on the
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OpenStack deployment globally. It will automatically load the globals.yml
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overrides and an invetory file located in /etc/kolla executing the appropriate
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roles for all of the deployed containers. The initial supported
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commands are:
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1. kolla-ansible deploy
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2. kolla-ansible start
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3. kolla-ansible stop
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4. kolla-ansible upgrade
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Ansible supports a model of deployment using an inventory file. The inventory
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file specifies which nodes get assigned which roles. For an example of an
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inventory file, see:
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https://github.com/SamYaple/yaodu/blob/master/ansible/inventories/production
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To the untrained eye, this looks like a bunch of heavy wizardy. I personally
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believe we will in some way merge our globals.yml and the inventory file into
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one master configuration file and generate the globals.yml and Ansible-specific
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inventory file on each kolla-ansible operation. The long term goal is to get
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to one configuration file with "all the things" needed to deploy OpenStack.
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This would permit a GUI to simply configure the deployment.
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How this is done or if it is done remains an implementation detail which may
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warrant expanding this specification or a completely new specification in the
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future. As we obtain more experience with what we are developing, we will
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have a more complete picture of what this master configuration file format will be.
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The implementation described in this section is just a sample of the
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implementation details required. We intend to refactor Sam Yaple's fantastic
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vision with yaodu (https://github.com/SamYaple/yaodu/) into Kolla to
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implement Ansible deployment of OpenStack while retaining Kolla, Docker, and
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Ansible best practices and conventions.
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Assignee(s)
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-----------
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Primary assignees:
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diga
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fangfenghua
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harmw
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samyaple
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sdake
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The kolla core team will support and execute this specification through normal
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workflow operations.
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Work Items
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----------
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1. Convert all fat containers to thin containers to facilitate this work.
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2. Move all start.sh scripts to crudini.sh and create the function to execute
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the configuration strategy across containers.
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3. Rename the kolla script to kolla-compose and create a new kolla-ansible
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script to manage playbook operation.
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4. Refactor the remaining portions of yaodu that are compatible with Kolla into
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the Kolla code base.
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5. Implement our existing crudini defaults in Ansible.
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Testing
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=======
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Functional tests will be implemented in the OpenStack check/gating system to
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automatically check that the Ansible deployment works for an AIO environment.
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Documentation Impact
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====================
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The developer quickstart must be augmented with instructions to use the new
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Ansible deployment methodology.
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