An orchestrator refers to a software system programmed with workflow rules and business logic that facilitates automated actions and integrated connectors to external software systems. Many IT organizations create scripts to automate manual tasks; however, these are now considered a legacy technique. Scripts are also difficult to maintain and reuse, and their sequential processing limits their flexibility.
An orchestration system goes well beyond scripting with parallel tasking, branching workflows, situational-awareness logic, and the ability to back out from or resume workflows that fail or sense an error.
You can integrate Scripts and other automated software installation packaging tools into an orchestration workflow; however, the orchestration should always be the primary logic engine at the core of all cloud provisioning and automation workflows.
Orchestration: Use-Case Scenario and Walk-Through
In the preceding example, VMware was the hypervisor technology. There are numerous hypervisor technologies in the industry that would perform similarly; however, a key point to highlight is that the hypervisor software itself is not the same as the cloud management platform. In this example, hypervisors perform only the creation and management of VMs.
Note that some hypervisor software platforms can perform some higher-level cloud management functions but are usually not as complete and all-encompassing as a full cloud management plat- form. It is the cloud management system that performs everything from taking the customer’s order from a service catalog to the approval process; to triggering the hypervisor to provision services; updating the network management systems with the new VM configuration and status; starting utilization and invoice tracking, and finally, sending email to the end user and cloud support staff of success.
The earliest cloud systems often relied solely on the hypervisor software’s portal or configuration tools. These hypervisor configuration portals are good for technical personnel to manage basic VM services for a single tenant organization. Multitenant clouds with more advanced PaaS and Software as a Service SaaS applications utilize full cloud management platforms that automate and orchestrate the entire infrastructure and customer portals—the hypervisor software is now just an underlying component of the cloud management system.
The below figure shows a diagram published by NIST that maps service orchestration to the NIST Cloud Reference Model.
NIST model for cloud service orchestration (Source: NIST, Special Publication 5-500-291 version 2, July 2013)