cewrap

README

cewrap

CE Wrapper is a wrapper to generate CloudEvents events for services that do not emit events themselves. It will initially work for RESTful APIs.

It is a completely stateless proxy that passes the request unmodified to the downstream service, and emits an event for requests that are of interest.

Default these are requests that change state, like POST, PUT, PATCH and DELETE, but other methods can be added.

The mandatory cloud event context attributes are set using the information of the incoming http request, or with values set by the user. This way ample information is available for filtering and subscribing.

Context Attributes

• id, will be set with an autogenerated UUID
• source, needs to be configured
• subject, the path of the request
• type, this value will be a configured prefix follow by the methodname and the suffix _handled
• time, the time the forwarded request finished
• datacontenttype, the content type of the response from the downstream service
• dataschema, can be configured

The data will contain a json struct with the response body the downstream service returned.

Example

Assume the downstream service is on service.example.com and it returns json formatted responses with person information.

A successful post request to http://service.example.com/persons/id12345 resource that contains persons will result in an event with the following attributes.

• subject: /persons/id12345
• type: com.example.persons.post_handled
• source: http://service.example.com/

Command line parameters and env vars

parameter	env var	description
-sink	K_SINK, CWE_SINK	The url of the event sink.
-source	CEW_SOURCE	The source of the event.
-type	CEW_TYPE_PREFIX	The prefix for the type.
-dataschema	CEW_DATASCHEMA	The URL for the dataschema of the event data.
-downstream	CEW_DOWNSTREAM	Downstream service.
-port	PORT	Listening port of the wrapper, defaults to 8080.
-extra-methods	CEW_EXTRA_METHODS	Extra methods to add to the standard state changing methods

Test setup

Run go-httpbin on port 9090.

podman run --rm -p 9090:8080 docker.io/mccutchen/go-httpbin:v2.11.1

Run cesourcewrap on port 8080.

podman run --rm \
    -p 8080:8080 \
    -e CEW_SINK=http://192.168.0.202:10000 \
    -e CEW_DOWNSTREAM=http://192.168.0.202:9090 \
    -e CEW_EXTRA_METHODS=GET \
    docker.io/peterzandbergen/cesourcewrap:v0.0.1

Run event display on port 10000

podman run --rm \
    -p 10000:80 \
    gcr.io/knative-releases/knative.dev/eventing/cmd/event_display

Documentation

Overview

Package cewrap implements event source proxies for knative agnostic services.

Index

• Variables
• type Source
  • func NewSource(options ...SourceOption) *Source
  • func (s *Source) Handler() http.HandlerFunc
• type SourceOption
  • func WithChangeMethods(m []string) SourceOption
  • func WithDataschema(v string) SourceOption
  • func WithDownstream(u string) SourceOption
  • func WithHTTPClient(c *http.Client) SourceOption
  • func WithLogger(l *slog.Logger) SourceOption
  • func WithPathPrefix(v string) SourceOption
  • func WithSink(s cloudevents.Client) SourceOption
  • func WithSource(v string) SourceOption
  • func WithTypePrefix(v string) SourceOption

Variables

var DefaultChangeMethods = []string{
	http.MethodPost,
	http.MethodDelete,
	http.MethodPatch,
	http.MethodPut,
}

Types

type Source

type Source struct {
	// contains filtered or unexported fields
}

func NewSource

func NewSource(options ...SourceOption) *Source

func (*Source) Handler

func (s *Source) Handler() http.HandlerFunc

Handler returns a HandlerFunc that handles the requests.

It passes the request to the downstream service and generates a cloud event and sends it to the sink.

type SourceOption

type SourceOption interface {
	// contains filtered or unexported methods
}

func WithChangeMethods

func WithChangeMethods(m []string) SourceOption

func WithDataschema

func WithDataschema(v string) SourceOption

func WithDownstream

func WithDownstream(u string) SourceOption

func WithHTTPClient

func WithHTTPClient(c *http.Client) SourceOption

func WithLogger

func WithLogger(l *slog.Logger) SourceOption

func WithPathPrefix

func WithPathPrefix(v string) SourceOption

func WithSink

func WithSink(s cloudevents.Client) SourceOption

func WithSource

func WithSource(v string) SourceOption

func WithTypePrefix

func WithTypePrefix(v string) SourceOption