Octavia is an operator-grade reference implementation for Load Balancing as a Service (LBaaS) for OpenStack. The component of Octavia that does the load balancing is known as Amphora.
The component of Octavia that provides command and control of the Amphora is the Octavia controller.
Octavia requires a controller component that provides the following capabilities:
- Processing Amphora configuration updates and making them available to the Amphora driver
- Providing certificate information to the Amphora driver
- Deploying Amphora instances
- Managing the Amphora spares pool
- Cleaning up Amphora instances that are no longer needed
- Monitoring the health of Amphora instances
- Processing alerts and messages from the Amphora (example “member down”)
- Respecting colocation / apolocation / flavor requirements of the Amphora
- Processing statistical data from the Amphora including communicating with metering services, such as Ceilometer (https://blueprints.launchpad.net/ceilometer/+spec/ceilometer-meter-lbaas)
- Responding to API requests sent by the API processes
- Proxy Amphora data to other OpenStack services such as Swift for log file archival
The Octavia controller will consist of the following components:
- Amphora Driver
- Queue Consumer
- Certificate Library
- Compute Driver
- Controller Worker
- Health Manager
- Housekeeping Manager
- Network Driver
- Services Proxy
The manager and proxy components should be implemented as independent processes to provide a level of autonomy to these controller functions.
The highly available database will provide the persistent “brain” for the Octavia controller. Octavia controller processes will share state and information about the Amphora, load balancers, and listeners via the database. It is expected that the Octavia controller and Amphora driver will directly interact with the database but the Amphorae will never directly access the database.
By using a highly available database, Octavia controllers themselves do not directly keep any stateful information on Amphorae. Because of this, Amphorae are not assigned to any specific controller. Any controller is able to service monitoring, heartbeat, API, and other requests coming to or from Amphorae.
The Amphora driver abstracts the backend implementation of an Amphora. The controller will interact with Amphora via the Amphora driver. This interface is defined in the amphora-driver-interface specification.
The Queue Consumer is event driven and tasked with servicing requests from the API components via an Oslo messaging. It is also the primary lifecycle management component for Amphora.
To service requests the Queue Consumer will spawn a Controller Worker process. Spawning a separate process makes sure that the Queue Consumer can continue to service API requests while the longer running deployment process is progressing.
Messages received via Oslo messaging will include the load balancer ID, requested action, and configuration update data. Passing the configuration update data via Oslo messaging allows the deploy worker to rollback to a “last known good” configuration should there be a problem with the configuration update. The spawned worker will use this information to access the Octavia database to gather any additional details that may be required to complete the requested action.
The Compute Driver abstracts the implementation of instantiating the virtual machine, container, appliance, or device that the Amphora will run in.
The Controller Worker is spawned from the Queue Consumer or the Health Manager. It interfaces with the compute driver (in some deployment scenarios), network driver, and Amphora driver to activate Amphora instances, load balancers, and listeners.
When a request for a new instance or failover is received the Controller Worker will have responsibility for connecting the appropriate networking ports to the Amphora via the network driver and triggering a configuration push via the Amphora driver. This will include validating that the targeted Amphora has the required networks plumbed to the Amphora.
The Amphora configured by the Controller Worker may be an existing Amphora instance, a new Amphora from the spares pool, or a newly created Amphora. This determination will be made based on the apolocation requirements of the load balancer, the load balancer count on the existing Amphora, and the availability of ready spare Amphora in the spares pool.
The Controller Worker will be responsible for passing in the required metadata via config drive when deploying an Amphora. This metadata will include: a list of controller IP addresses, controller certificate authority certificate, and the Amphora certificate and key file.
The main flow of the Controller Worker is described in the amphora-lifecycle-management specification as the Activate Amphora sequence.
The Certificate Library provides an abstraction for workers to access security data stored in OpenStack Barbican from the Amphora Driver. It will provide a short term (1 minute) cache of the security contents to facilitate the efficient startup of a large number of listeners sharing security content.
The Health Manager is tasked with checking for missing or unhealthy Amphora stored in the highly available database. The amphora-lifecycle-management specification details the health monitoring sequence.
The health monitor will have a separate thread that checks these timestamps on a configurable interval to see if the Amphora has not provided a heartbeat in the required amount of time which is another configurable setting. Should a Amphora fail to report a heartbeat in the configured interval the Health Manager will initiate a failover of the Amphora by spawning a deploy worker and will update the status of the listener in the database.
The Health Manager will have to be aware of the load balancer associated with the failed listener to decide if it needs to fail over additional listeners to migrate the failed listener to a new Amphora.
The Housekeeping Manager will manage the spare Amphora pool and the teardown of Amphora that are no longer needed. On a configurable interval the Housekeeping Manager will check the Octavia database to identify the required cleanup and maintenance actions. The amphora-lifecycle-management specification details the Create, Spare, and Delete Amphora sequences the Housekeeping Manager will follow.
The operator can specify a number of Amphora instances to be held in a spares pool. Building Amphora instances can take a long time so the Housekeeping Manager will spawn threads to manage the number of Amphorae in the spares pool.
The Housekeeping Manager will interface with the compute driver, network driver, and the Certificate Manager to accomplish the create and delete actions.
The Network Driver abstracts the implementation of connecting an Amphora to the required networks.
The Services Proxy enables Amphora to reach other cloud services directly over the Load Balancer Network where the controller may need to provide authentication tokens on behalf of the Amphora, such as when archiving load balancer traffic logs into customer swift containers.