Introduction
The ONAP Operations Manager provides a set of capabilities that facilitate Carrier Grade deployments of ONAP. ONAP deployments need to be capable of offering service while under adverse conditions typically with overall availability measured at five-nines or 99.999% uptime or about 5 minutes of downtime per year. This requirement might be strict for an orchestration system, but keep in mind that ONAP’s closed loop control system could be providing monitoring a control for one or more critical VNFs that need to meet stringent up-time requirements as found in the TL 9000 Quality Management System Measurements Handbook.
The Road to High Availability
The progression of the ONAP project towards a fully Carrier Grade has started and will continue over the Beijing or possibly even subsequent releases. The steps along this progression are roughly as follows:
For each of these steps the following sections describe the requirements in more detail and the technologies used to achieve it.
Highly Available Kubernetes Deployments
There is a high degree of variability possible in the deployment of Kubernetes. In some cases it may be installed and managed by hand, done with 3rd party tools like Rancher or even provided by a cloud provider like Microsoft Azure Container Service - Kubernetes has a description of the options here. Kubernetes provides guidance on creating deployments that may be suitable for carrier grade deployments of ONAP on their Building High-Availability Clusters wiki page.
Reliable and Repeatable Deployment
During the Amsterdam release OOM provided a set of capabilities to deploy some or all the ONAP components rapidly and efficiently as a cloud native application with the Kubernetes container orchestration system (note that DCAE is an exception here as DCAE provides its own orchestration system). Each of the components has a deployment specification that describes not only the containers and the container requirements but the relationships or dependencies between the containers. These dependencies dictate the order in-which the containers are started for the first time such that such dependencies are always met without arbitrary sleep times between container startups. For example, the SDC back-end container requires the Elastic-Search, Cassandra and Kibana containers within SDC to be ready and is also dependent on DMaaP (or the message-router) to be ready before becoming fully operational.
Prior to having more advantage carrier grade features available, the ability to at least be able to re-deploy ONAP (or a subset of) reliably provides a level of confidence that should an outage occur the system can be brought back on-line predictably.
Backup and Restore
A critical factor in being able to recover from an ONAP outage is to ensure that critical state isn't lost after a failure. Much like ephemeral storage on VMs; any state information stored within a container will be lost once the container is restarted - containers are managed as Cattle not Pets. To ensure that critical state information is retained after a failure, the OOM deployment specifications for the ONAP components use the Kubernetes concept of a Persistent Volumes, an external storage facility that has its own lifecycle. Many different types of storage are supported by this capability such as: GCEPersistentDisk, AWSElasticBlockStore, AzureFile, AzureDisk, FC (Fibre Channel), FlexVolume, Flocker, NFS, iSCSI, RBD (Ceph Block Device), CephFS, Cinder (OpenStack block storage), Glusterfs, VsphereVolume, Quobyte Volumes, HostPath (Single node testing only), VMware Photon, Portworx Volumes, ScaleIO Volumes, and StorageOS.
As critical state is stored outside of the ONAP containers on a storage media specific to the cloud environment, specific instructions on how to backup and restore such storage is outside of the scope of ONAP.