Getting to the heart of what makes up OpenStack as a project would be to review the services that make up this cloud ecosystem. One thing to be kept in mind in reference to the OpenStack services is that each service will have an official name and a code name associated with it. The use of the code name has become very popular among the community and most documentation will refer to the services in that manner. Thus, becoming familiar with the code names is important and will ease the adoption process.
The other thing to be kept in mind is that each service is developed as an API driven REST web service. All the actions are executed via the API, enabling ultimate consumption flexibility. Behind the scenes, API calls are executed and interpreted even while using the CLI or web-based GUI.
As of the Kilo release, the OpenStack project consists of twelve services/programs. The services will be reviewed in the order of their release to show an overall service timeline. That timeline will show the natural progression of the OpenStack project overall, also showing how it is now surely Enterprise ready.
It was integrated in the release Austin and was one of the first and is still the most important service part of the OpenStack platform. Nova is the component that provides the bridge to the underlying hypervisor, which is used to manage the computing resources.
Note
One common misunderstanding is that Nova is a hypervisor in itself, which is simply not true. Nova is a hypervisor manager of sorts and is capable of supporting many different types of hypervisors.
Nova will be responsible for scheduling instance creation, sizing options for the instance, managing the instance location, and, as mentioned earlier, keeping track of the hypervisors available to the cloud environment. It also handles the functionality of segregating your cloud into isolation groups called cells, regions, and availability zones.
It was also integrated in the Austin release and this service is one of the first services that were a part of the OpenStack platform. Swift is the component that provides object storage as a service to your OpenStack cloud. It is capable of storing petabytes of data; in turn, adding highly available, distributed, and eventually consistent object/blob store. Object storage is intended to be a cheap and cost effective storage solution for static data such as images, backups, archives, and static content. The objects can then be streamed over standard web protocols (HTTP/HTTPS), to or from the object server to the end user initiating the web request. The other key feature of Swift is that all data is automatically made available as it is replicated across the cluster. The storage cluster is meant to scale horizontally, by simply adding new servers.
It was integrated in the Bextar release and this service was introduced during the second OpenStack release and is responsible for managing/registering/maintaining server images for your OpenStack cloud. It includes the capability to upload or export OpenStack compatible images and store instance snapshots, and is used as a template/backup for later use. Glance can store the images on a variety of locations either locally and/or on distributed storage, such as object storage. Most Linux kernel distributions already have OpenStack compatible images available for download. You can also create your own server images from existing servers. There exists support for multiple image formats including: RAW, VHD, QCOW2, VMDK, OVF, and VDI.
It was integrated in the Essex release and this service was introduced during the fifth OpenStack release. Keystone is the authentication and authorization component built into your OpenStack cloud. Its key role is to handle creation, registry, and management of users, tenants, and all the other OpenStack services. Keystone is the first component to be installed when starting an OpenStack cloud. It has the capability to connect to external directory services, such as LDAP. Another key feature of Keystone is that it is built based on role-based access controls (RBAC), thus allowing cloud operators to provide distinct role-based access to individual service features to the cloud consumers.
It was also integrated in the Essex release and this service is the second service to be introduced in the fifth OpenStack release. Horizon provides cloud operators and consumers with a web based GUI to control their compute, storage, and network resources. The OpenStack dashboard runs on top of Apache and the Django REST framework; thus, making it very easy to integrate into and extend to meet your personal use case. On the backend, Horizon also uses the native OpenStack APIs. The basic principle behind Horizon was to be able to provide cloud operators with a quick and overall view of the state of their cloud and cloud consumers a self-service provisioning portal to the cloud resources designated to them.
It was integrated in the Folsom release and this service is probably the second most powerful component within your OpenStack cloud next to Nova.
OpenStack Networking is intended to provide a pluggable, scalable, and API-driven system to manage networks and IP addresses.
This quote was taken directly from the OpenStack Networking documentation, as it best reflects exactly the purpose behind Neutron. Neutron is responsible to create your virtual networks with your OpenStack cloud. This will entail the creation of virtual networks, routers, subnets, firewalls, load balancers, and similar network functions. Neutron was developed with an extension framework, which allows the integration of additional network components (physical network device control) and models (flat, layer-2 and/or layer-3 networks). The various vendor specific plugins and adapters have been created to work in line with Neutron. This service adds to the self-service aspect of OpenStack; thus, removing the network aspect from being a roadblock to consume your cloud.
With Neutron being one of the most advanced and powerful components within OpenStack, a whole book was dedicated to it.
It was also integrated in the Folsom release, Cinder is the component that provides block storage as a service to your OpenStack cloud by leveraging local disks or attached storage devices. This translates into persistent block level storage volumes available to your instances. Cinder is responsible for managing and maintaining the block volumes created, attaching/detaching those volumes, and also backup creation of that volume. One of the highly notable features of Cinder is its ability to connect to multiple types of backend shared storage platforms at the same time. This capability spectrum spans all the way down to being able to leverage simple Linux server storage as well. As an added bonus, Quality of Service (QoS) roles can be applied to different types of backends; thus, extending the ability to use the block storage devices to meet various application requirements.
It was integrated in the Havana release and this was one of the two services to be introduced in the eighth OpenStack release. Heat provides the orchestration capability over your OpenStack cloud resource. It is described as a main-line project part of the OpenStack orchestration program. This infers the additional automation functionality that is in the pipeline for OpenStack.
The built-in orchestration engine is used to automate provisioning of applications and its components, known as stack. A stack might include instances, networks, subnets, routers, ports, router interfaces, security groups, security group rules, auto scaling rules, and so on. Heat utilizes templates to define a stack and is written in a standard markup format, YAML. You will notice these templates being referred to as Heat Orchestration Template (HOT) templates.
It was also integrated in the Havana release and this is the second of the two services introduced in the eighth OpenStack release. Ceilometer collects the cloud usage and performance statistics together into one centralized data store. This capability becomes a key component to a cloud operator as it gives clear metrics into the overall cloud, which can be used to make scaling decisions.
It was integrated in the Icehouse release, Trove is the component that provides database as a service to your OpenStack cloud. This capability includes providing scalable and reliable relational and non-relational database engines. The goal behind this service was to remove the burden of needing to understand database installation and administration. With Trove, the cloud consumers can provision database instances just by leveraging the services API. Trove supports multiple single-tenant databases within a Nova instance.
It was integrated in the Juno release, Sahara is the component that provides data processing as a service to your OpenStack cloud. This capability includes the ability to provision an application cluster tuned to handle large amounts of analytical data. The data store options available are Hadoop and/or Spark. This service will also aid the cloud consumer in being able to abstract the complication of installing and maintaining this type of cluster.
It was integrated in the Kilo release and this service has been one of the most anxiously awaited components of the OpenStack project. Ironic provides the capability to provision physical bare metal servers from within your OpenStack cloud. It is commonly known as a bare metal hypervisor API and leverages a set of plugins to enable interaction with the bare metal servers. It is the newest service to be introduced to the OpenStack family and is still under development.