Function Definition

Function

Function is the control plane of Build and Serving and it’s also the interface for users to use OpenFunction. Users needn’t to create the Build or Serving separately because Function is the only place to define a function’s Build and Serving.

Once a function is created, it will controll the lifecycle of Build and Serving without user intervention:

  • If Build is defined in a function, a builder custom resource will be created to build function’s container image once a function is deployed.

  • If Serving is defined in a function, a serving custom resource will be created to control a function’s serving and autoscalling.

  • Build and Serving can be defined together which means the function image will be built first and then it will be used in serving.

  • Build can be defined without Serving, the function is used to build image only in this case.

  • Serving can be defined without Build, the function will use a previously built function image for serving.

Function Definition - 图1

Build

OpenFunction uses Shipwright and Cloud Native Buildpacks to build the function source code into container images.

Once a function is created with Build spec in it, a builder custom resource will be created which will use Shipwright to manage the build tools and strategy. The Shipwright will then use Tekton to control the process of building container images including fetching source code, generating image artifacts, and publishing images.

Function Definition - 图2

Serving

Once a function is created with Serving spec, a Serving custom resource will be created to control a function’s serving phase. Currently OpenFunction Serving supports two runtimes: the Knative sync runtime and the OpenFunction async runtime.

The sync runtime

For sync functions, OpenFunction currently supports using Knative Serving as runtime. And we’re planning to add another sync function runtime powered by the KEDA http-addon.

The async runtime

OpenFunction’s asyn runtime is an event-driven runtime which is implemented based on KEDA and Dapr. Async functions can be triggered by various event types like message queue, cronjob, and MQTT etc.

Function Definition - 图3

Reference

For more information, see Function Specifications.