component-dev.md

Implementing a Component

The component runtime provides a framework for building components for both component-initiated and client-initiated workflows. To implement a component for use with this framework:

• Implement each measurement, query, or other action performed by the component as a subclass of mplane.scheduler.Service. Each service is bound to a single capability. Your service must implement at least the mplane.scheduler.Service.run(self, specification, check_interrupt) method. This method should run the implemented measurement or query to completion. This measurement corresponds to the specification (an instance of mplane.model.Specification), which itself corresponds to the capability bound to the service (an instance of mplane.model.Capability). The method should return an mplane.model.Result. Long-running methods (with common runtimes measured in seconds or more) should periodically call the function passed as check_interrupt and return a truncated mplane.model.Result when that function returns True.

• Implement a services function in your module that takes a set of keyword arguments derived from the configuration file section, and returns a list of Services provided by your component. For example:

def service(**kwargs):
    return [MyFirstService(kwargs['local-ip-address']),
            MySecondService(kwargs['local-ip-address'])]

• Create a module section in the component configuration file; for example if your module is called mplane.components.mycomponent:

[service_mycomponent]
module: mplane.components.mycomponent
local-ip-address: 10.2.3.4

• Run mpcom to start your component. The --config argument points to the configuration file to use.