evankanderson/cloudevents-go-fn

Playground for authoring CloudEvents functions in golang

cloudevents-go-fn

This repository implements a Go function buildpack for wrapping functions matching one of the cloudevents/sdk-go signatures with scaffolding for the appropriate protocol binding.

This buildpack is not standalone, it should be composed with the Paketo Go buildpacks.

Build this buildpack

This buildpack can be built (from the root of the repo) with:

pack package-buildpack my-buildpack --config ./package.toml

Use this buildpack

# This runs the cloudevents-go-fn buildpack at HEAD within the Paketo Go order.
# You can pin to a release by replacing ":main" below with a release tag
# e.g. ":v0.0.1"
pack build -v test-container \
  --pull-policy if-not-present \
  --buildpack gcr.io/paketo-buildpacks/go-dist:0.2.5 \
  --buildpack ghcr.io/mattmoor/cloudevents-go-fn:main \
  --buildpack gcr.io/paketo-buildpacks/go-mod-vendor:0.0.169 \
  --buildpack gcr.io/paketo-buildpacks/go-build:0.1.2

Sample function

With this buildpack, users can define a Go function that implements one of the supported cloudevents/sdk-go signatures For example, the following function:

package fn

import (
       cloudevents "github.com/cloudevents/sdk-go/v2"
)

func Receiver(ce cloudevents.Event) (*cloudevents.Event, error) {
        r := cloudevents.NewEvent(cloudevents.VersionV1)
        r.SetType("io.mattmoor.cloudevents-go-fn")
        r.SetSource("https://github.com/mattmoor/cloudevents-go-fn")

        if err := r.SetData("application/json", struct {
                A string `json:"a"`
                B string `json:"b"`
        }{
                A: "hello",
                B: "world",
        }); err != nil {
                return nil, cloudevents.NewHTTPResult(500, "failed to set response data: %s", err)
        }

        return &r, nil
}

Configuration

You can configure aspects of the generated function scaffolding via the following configuration options in project.toml:

[[build.env]]
name = "CE_GO_PACKAGE"
value = "./blah"         # default is the root package: "."

[[build.env]]
name = "CE_GO_FUNCTION"
value = "MyReceiverName" # default is "Receiver"

[[build.env]]
name = "CE_PROTOCOL"
value = "http"           # default is "http"

Depending on the protocol, you can further customize the behavior of that protocol at runtime via environment variables prefixed with: CE_{protocol}.