Add tutorial for writing an event source - easy way #2494

aliok · 2020-05-22T07:38:30Z

Fixes #issue-number or description of the problem the PR solves

Proposed Changes

Add a tutorial for writing an event source easy way
Tutorial is done with Javascript
Some references are pointing at personal repos/images as they're not published yet or they're not part of Knative GH org yet

aliok · 2020-05-22T07:45:19Z

/retest

aliok · 2020-05-22T07:49:03Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+  template:
+    spec:
+      containers:
+        - image: docker.io/aliok/event_display-864884f202126ec3150c5fcef437d90c@sha256:93cb4dcda8fee80a1f68662ae6bf20301471b046ede628f3c3f94f39752fbe08


At the moment there's a bug in the latest published image of gcr.io/knative-releases/knative.dev/eventing-contrib/cmd/event_display that it doesn't display events properly.

The bug is fixed but image is not published yet. Thus, I reference my own image here. This is to be updated later.

@slinkydeveloper maybe you can add a link to the bug?

Not sure we have a link for that bug, but it was fixed between sdk-go RC1 and RC2

docs/eventing/samples/writing-event-source-easy-way/README.md

aliok · 2020-05-22T07:55:27Z

cc @abrennan89 if you want to have a look

aliok · 2020-05-22T07:58:13Z

/test pull-knative-docs-go-coverage

docs/eventing/samples/writing-event-source-easy-way/README.md

knative-prow-robot · 2020-05-22T13:03:16Z

@aliok: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-knative-docs-go-coverage	`87d1f91`	link	`/test pull-knative-docs-go-coverage`

Full PR test history. Your PR dashboard.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

evankanderson

Thanks for this writeup!

/approve

/assign @n3wscott

I think Scott should probably finish the review (and this might get him off the hook on #2492).

evankanderson · 2020-05-22T23:02:21Z

docs/eventing/samples/writing-event-source-easy-way/Dockerfile

+
+# Install app dependencies
+# A wildcard is used to ensure both package.json AND package-lock.json are copied
+# where available (npm@5+)


If we're using node:10, this would be later than npm@5, right?

Deleted in #2512

evankanderson · 2020-05-22T23:03:30Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+As stated in [tutorial on writing a Source with a Receive Adapter](../writing-receive-adapter-source/README.md), there are multiple ways to
+create event sources. The way in that tutorial is to create an independent event source that has its own CRD.
+
+In this tutorial though, you will build an event source in Javascript and use it with


Suggested change

In this tutorial though, you will build an event source in Javascript and use it with

This tutorial provides a simpler mechanism to build an event source in Javascript and use it with

evankanderson · 2020-05-22T23:03:54Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+[ContainerSource](../../../eventing/sources/README.md#meta-sources) and / or [SinkBinding](../../../eventing/sources/README.md#meta-sources).
+
+[ContainerSource](../../../eventing/sources/README.md#meta-sources) is an easy way to turn any dispatcher container into an Event Source.
+Similarly, another option is using [SinkBinding](../../../eventing/sources/README.md#meta-sources)


I thought we were recommending SinkBinding over ContainerSource at this point?

@n3wscott

Added a sentence about the preferred way in #2512

evankanderson · 2020-05-22T23:04:16Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+Similarly, another option is using [SinkBinding](../../../eventing/sources/README.md#meta-sources)
+which provides a framework for injecting environment variables into any Kubernetes resource which has a `spec.template` that looks like a Pod (aka PodSpecable).
+
+Code for this tutorial is available [here](./).


I don't think this link will work correctly on the website; but you can put in git clone instructions.

evankanderson · 2020-05-22T23:06:17Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+The sink URL to post the events will be made available to the application via the `K_SINK` environment variable by `ContainerSource`.
+
+```javascript
+// File - index.js


You may want to use the {{% readfile file="index.js" %}} shortcode here.

Let's do that later if necessary. The code I embedded in the tutorial is a bit shorter and more focused than the code in the files.

evankanderson · 2020-05-22T23:06:27Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+}, 1000);
+```
+
+```dockerfile


evankanderson · 2020-05-22T23:07:46Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+docker push path/to/image/registry/node-knative-heartbeat-source:v1
+```
+
+Create the event display service which simply logs any cloudevents posted to it.


Do you want to use kn to create this service, instead of needing to fill in YAML?

Actually, that may not be necessary if this is always a fixed (published) image. Is event-display part of the released container images?

event-display is part of the released container images, yep.

evankanderson · 2020-05-22T23:13:59Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+
+Check the logs of the event display service. You will see a new message is pushed every second:
+```bash
+$ kubectl logs event-display-dpplv-deployment-67c9949cf9-bvjvk -c user-container


Suggested change

$ kubectl logs event-display-dpplv-deployment-67c9949cf9-bvjvk -c user-container

$ kubectl logs -l serving.knative.dev/service=event-display -c user-container

This avoids need to look up the name of the pods before reading the logs.

evankanderson · 2020-05-22T23:14:48Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+  }
+```
+
+If you are interested in to see what is injected into the event source, check the logs of it:


Suggested change

If you are interested in to see what is injected into the event source, check the logs of it:

If you are interested in to see what is injected into the event source, you can check the logs:

Not sure if you want to have the code dump out all the environment variables just for pedagogical purposes.

evankanderson · 2020-05-22T23:15:50Z

docs/eventing/samples/writing-event-source-easy-way/README.md

+- It is faster in terms of serialization and deserialization
+- It works better with cloudevents-aware proxies (like Knative Channels) can simply check the header instead of parsing the payload
+
+## Making use of SinkBinding


I think we're recommending SinkBinding going forward, so I'd move this above ContainerSource (or maybe prefer to just document SinkBinding).

@n3wscott to verify

knative-prow-robot · 2020-05-22T23:18:19Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aliok, evankanderson

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n3wscott

/lgtm

Thanks for the sample and write-up. Showing that sink binding and container source are interchangable at the container level is exactly the message we want to be telling.

aliok · 2020-05-27T08:37:45Z

Created #2512 for the comments that I couldn't address before the PR is merged

Add tutorial for writing an event source - easy way

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googlebot added the cla: yes Indicates the PR's author has signed the CLA. label May 22, 2020

knative-prow-robot requested review from grantr and lionelvillard May 22, 2020 07:38

knative-prow-robot added the size/L Denotes a PR that changes 100-499 lines, ignoring generated files. label May 22, 2020

mattmoor reviewed May 22, 2020

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Fix image ref

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Fix whitespace issues

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aliok commented May 22, 2020

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Fix image ref

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aliok added 2 commits May 22, 2020 15:57

Add sample code within the tutorial directory

8ebfd4d

Add bundle

87d1f91

evankanderson reviewed May 22, 2020

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knative-prow-robot added the lgtm Indicates that a PR is ready to be merged. label May 23, 2020

knative-prow-robot merged commit 3484cdb into knative:master May 23, 2020

aliok mentioned this pull request May 27, 2020

Minor fixes in easy event source tutorial #2512

Merged

	In this tutorial though, you will build an event source in Javascript and use it with
	This tutorial provides a simpler mechanism to build an event source in Javascript and use it with

	$ kubectl logs event-display-dpplv-deployment-67c9949cf9-bvjvk -c user-container
	$ kubectl logs -l serving.knative.dev/service=event-display -c user-container

	If you are interested in to see what is injected into the event source, check the logs of it:
	If you are interested in to see what is injected into the event source, you can check the logs:

Add tutorial for writing an event source - easy way #2494

Add tutorial for writing an event source - easy way #2494

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aliok commented May 22, 2020

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