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Service architecture

Introduction

OpenStack-Ansible has a flexible deployment configuration model that can deploy all services in separate machine containers or on designated hosts without using containers, and all network traffic either on a single network interface or on many network interfaces.

This flexibility enables deployers to choose how to deploy OpenStack in the appropriate way for the specific use case.

The following sections describe the services that OpenStack-Ansible deploys.

Infrastructure services

OpenStack-Ansible deploys the following infrastructure components:

• MariaDB with Galera

  All OpenStack services require an underlying database. MariaDB with Galera implements a multimaster database configuration, which simplifies its use as a highly available database with a simple failover model.

• RabbitMQ

  OpenStack services use RabbitMQ for Advanced Message Queuing Protocol (AMQP). OSA deploys RabbitMQ in a clustered configuration with all queues mirrored between the cluster nodes. Because Telemetry (ceilometer) message queue traffic is quite heavy, for large environments we recommend separating Telemetry notifications into a separate RabbitMQ cluster.

• Memcached

  OpenStack services use Memcached for in-memory caching, which accelerates transactions. For example, the OpenStack Identity service (keystone) uses Memcached for caching authentication tokens, which ensures that token validation does not have to complete a disk or database transaction every time the service is asked to validate a token.

• Repository

  The repository holds the reference set of artifacts that are used for the installation of the environment. The artifacts include:

  • A Git repository that contains a copy of the source code that is used to prepare the packages for all OpenStack services

  • Python wheels for all services that are deployed in the environment

  • An apt/yum proxy cache that is used to cache distribution packages installed in the environment

• Load balancer

  At least one load balancer is required for a deployment. OSA provides a deployment of HAProxy, but we recommend using a physical load balancing appliance for production environments.

• Utility container

  If a tool or object does not require a dedicated container, or if it is impractical to create a new container for a single tool or object, it is installed in the utility container. The utility container is also used when tools cannot be installed directly on a host. The utility container is prepared with the appropriate credentials and clients to administer the OpenStack environment. It is set to automatically use the internal service endpoints.

• Unbound DNS container

  Containers running an Unbound DNS caching service can optionally be deployed to cache DNS lookups and to handle internal DNS name resolution. We recommend using this service for large-scale production environments because the deployment will be significantly faster. If this service is not used, OSA modifies /etc/hosts entries for all hosts in the environment.

OpenStack services

OSA is able to deploy a multitude of services. Have a look at the role maturity matrix to know the status of the service you want to deploy.