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From Markus Thömmes <>
Subject Re: A plan to (re) implement OpenWhisk on top of Knative
Date Mon, 20 May 2019 14:49:50 GMT
Good discussion, thanks!

Can we try to define what the desired end-goal is here? I'm a bit unclear
what resembling the OpenWhisk API actually buys us.

To me, the desired end-state would be to run OpenWhisk actions as-is on a
Knative cluster (similar to OpenFaaS' and Azure's integration). There's no
good way for us to provide the full API without spinning up a control plane
and we can only handle so much via the CLI. So to me, the end-goal looks

1. *wsk action create* actually doing all the pieces necessary to run a
piece of code on Knative.
2. *wsk action invoke* doing some HTTP call under the hood to "invoke" that
action. The action should be reachable via a sensible URL. If we really
want to keep the API surface (as I said, I'm dubious here) we can also do
that via ingress level abstractions (like VirtualService).


Am Mo., 20. Mai 2019 um 15:33 Uhr schrieb Martin Henke <

> > On 20. May 2019, at 14:55, Michele Sciabarra <>
> wrote:
> >
> >> Michele,
> >
> >> I like the idea to make the ActionLoop based runtimes to be runnable on
> Knative.
> >>
> >> My thoughts on this:
> >> - I second Markus concern to implement the invocation API onto Knative
> instead of just using Knative service syntax.
> > Can you elaborate this? I do not understand.
> Knative service syntax:    https://<service(in our case =
> action)>.<namespace>.<host>/
> OW invocation https://
> <api-host>/api/v1/namespaces/<namespace>/actions/<action>
> (I personally so no worth in inventing a distinct API for OW images, but
> as said I would see that as a valid optional feature)
> >
> >> - I would have concerns to make it dependent on Gloo which is kind of a
> minority choice for Knative load balancing
> > I do not think it will be hard to setup a test also using Istio, I do
> not want to be limited to Gloo.
> I just wanted to prevent that Gloo gets a “official” prerequisite for an
> “official” OW on Knative flow.
> It is of course free to you to use what ever you want to do in your
> prototype.
> > - In my opinion the goal should be to have some uniform behaviour for
> ActionLoop based runtimes
> >> and other ones like the adapted NodeJS runtimes demonstrated by Matt
> and Priti
> > As much as I can tell the current implementation is just the building
> and exposing the "/init" and "/run" but I can be wrong.
> > The build can be of course reused, so it continues the effort. For the
> frontend, from the documentation I think Matt wants to add a proxy, while I
> would like to implemeent the "invocation" straight in the runtime. This is
> open to discussion, but of course it is better to reach an agreement.
> Also in the work of Priti and Matt the invocation goes directly to the
> runtime. The action code is either passed with the call (not yet tested by
> me) or set via environment variable in the docker build.
> >
> >> - As Knative Build seems be on a dead end I would propose to target
> Tekton as the build system (which developed as kind of >successor out of
> Knative)
> >
> > If Knative build is dead then it would be a bit unfair that they change
> it as the scope of the Knative project!
> > It looks like the goal is  to setup some standards! And I would be very
> disappointed to know that.
> Tekton evolved out of Knative Build (or more correct out of Knative
> Pipelines) but is very similar to the Knative build.
> Flows can easily be ported from one to the other,
> If we target Tekton build we would target the platform were the Knative
> build team is focusing on.
> But again feel free to use whatever platform for your prototype work.
> > At this stage the build is the more interesting thing, and it could be
> even imported in main openwhisk to speed up deployment.
> > I have already baked it in the ActionLoop runtimes (with precompilation).
> > Also if we use Tekton, where is the Knative standard then? What is the
> point? We can build our own system instead of "Knativizing" it...
> >
> >> Maybe it would be a good solution to tackle two things independently.
> >> 1) Design and implement a common protocol of building, running and
> calling OW runtimes on Knative
> >> 2) Implement the OW invocation API on top of Knative as an additional
> option for those who have the need to expose it.
> >
> > On this, for my personal approach at building things, I want something
> that works and it is complete and useful. A "MVP”.
> Cool. Just go on.
> > So I do not plan to split the effort. Version 0.1 must be a minimal
> working subset of OpenWhisk on Knative.
> > Because otherwise there will be incomplete useless inusable pieces
> around (see for example kwsk).
> >
> > It does not mean that things cannot be modular, nor that everyone must
> but to me "openwhisk-knative" must be a single repo with all the pieces to
> make something where you can download is and deploy in a kubernetes cluster
> and be able to deploy simple actions. When this works, we can improve
> incrementally and split it but keeping it working.
> >
> >> I would looking forward to work with you on the first work item.
> > Great  but I see now more details to discuss before we can start. Most
> notably I need to understand how I can build on top of Mark and Priti work
> and continue their work. ANd I can even probably recover some of the code
> of kwsk as they implemented some openwhisk api, that I want now in the
> runtime.
> >
> I do not want to stop you in any way. My hope is that the action loop
> runtimes and the “other ones” do expose the same behaviour when being
> called. So that the users is not surprised when calling different actions
> in different languages.
> And behaving the same way might also mean to adapt the “other languages”
> to the same behaviour as the action loop based ones.
> They just should be uniform to be used.
> When your prototype is accessible it would be a good point of time to
> discuss this.
> As said I very much like your effort.
> >
> >> On 20. May 2019, at 08:55, Michele Sciabarra <>
> wrote:
> >>
> >>
> >>>> I have an idea for implementing a prototype of OpenWhisk on top of
> Knative.
> >>>> My basic ideas are: do not use any proxy, forwarding or adapter:
> extend
> >>>> the runtime to support the REST call and expose them as ingress. And
> use a
> >>>> wrapper on top of `kubectl` to generate all the needed components.
> >>
> >>> Does this tie into the work that Matt was doing to the runtimes to make
> >>> them runnable on Knative? Is this lined up with that at all?
> >> Actually yes. He suggested I can investigate how to migrate ActionLoop
> to port many other languages to Knative.
> >> Also he recommended I add my idea and this is what I am doing. Current
> code is, if I am not wrong, a Knative build of the nodejs runtime.
> >>
> >> There has been a number of attempts and proposal to move forward
> OpenWhisk. My idea that to succeed we need something small but that just
> works. This is my idea to be able to implement in the shorter time frame
> possible an actual subset of OpenWhisk that works and it is truly built on
> top of Knative. So I am putting the thing a bit further than Matt work.
> >>
> >>
> >>>> My goal is to have a functional work-alike of OpenWhisk built on top
> of
> >>>> Knative, using ActionLoop as a foundation. I will extend ActionLoop
> >>>> support the required REST calls of OpenWhisk.
> >>>
> >>>> I also want to create tool, I will call `wskn`. This tool will
> initially
> >>>> just a python script, a wrapper on top of `kubectl` as it will
> generate
> >>>> kubernetes descriptors.
> >>> Why not build this into "wsk" itself? The Azure Functions CLI as an
> example
> >>> supports multiple deployment types like this in one CLI.
> >>
> >> When it will works, yes, of course. But to start, what I really need is
> a prototype that can generate kubernetes descripttors to feed to kubectl,
> so a  simplee, quick and ditry, separate tool (that I will keep together
> the runtime) is all I need for now.
> >>
> >>>>
> >>>> It will support initially just the the action creation and
> invocation, and
> >>>> only synchronous (blocking) behaviour, as all the request will go
> straight
> >>>> to the runtimes. Hopefully also a subset of `package` and
> `activation`.
> >>>> Again triggers, rules, asynchronous for later.
> >>>>
> >>>> The idea is that you will be able to create actions and web actions
> that
> >>>> can run existing OpenWhisk actions, at least those with blocking
> behaviour
> >>>> that run with ActionLoop (Go, Java, Python, PHP, Swift, Rust, Ruby,
> >>>> Crystal...)
> >>>>
> >>>> Implementation.
> >>>> ==============
> >>>>
> >>>> This is how I plan to implement it.
> >>>>
> >>>> At this stage I want to use just Knative Serving and Knative Build,
> using
> >>>> Gloo for the ingress part. I also plan to install a local Docker
> registry
> >>>> Kubernetes registry, so we do not have to use DockerHub for
> everything. All
> >>>> of this can be done with existing command line tools in a few minutes
> in
> >>>> any running Kubernetes deployment.
> >>>>
> >>
> >>> Why specifying Gloo here? Do you need anything specific from Gloo
> itself?
> >>> If not I'd propose to just keep it on a Knative Serving API surface
> level.
> >> I want to build it on top of Knative serving, full stop. Currently,
> installing Gloo is pretty easy and is more  lightweight than Istio so I
> will use it for my  first implementation.
> >>
> >>>>
> >>>> When I create an action, it will use Knative build that will work
> roughly
> >>>> in this way:
> >>>>
> >>>> - create a configmap with the action code
> >>>> - build the actin using ActionLoop precompilation feature that will
> return
> >>>> a zip file including all the needed to run the action
> >>>> - create a new docker image extending the runtime with the new zip,
> using
> >>>> Kaanico
> >>>> - push the image in the local registry
> >>> This feels like a fairly heavyweight process, we should be able to
> come up
> >>> with a way to circumvent zipping entirely. Maybe the runtime can detect
> >>> that the unzipped content is already there and skip the unzip step?
> >>
> >> Actually this is my first idea of how to use Knative build. And is not
> complicated: when I create the action, a run a build that includes Kanico.
> I generate a Dockerfile on the fly. The docker file uses the action runtime
> that already know how to compile a script. And then I save an image. I
> already implemented un "autoinit" so just launching the image will give a
> runtime ready to run that execute an action already compiled.
> >>
> >>
> >>> I'm fairly hesitant on the usage of a ConfigMap for storing the action
> >>> code. It's all stored in the in-cluster etcd instance and it has a
> limit of
> >>> 1M. This is at most a stop-gap solution to provide a PoC I think. Any
> ideas
> >>> on how to "productize" this?
> >>
> >> ConfigMap can be mounted as files, so it is an easy way  to feed an
> action to a build. It is just an easy way to feed the action code to the
> Build.
> >>
> >> My initial constraint is that I want just to generate Kubernetes
> descriptors to feed to kubectl.
> >> Of course in the long run I can add some "file upload" storage.
> >>
> >> If I could to this file upload when invoking a build it could ideal as
> I do not have to store anything anywhere, just process the code and
> generate a single layer to execute actions to be store in the registry.
> >> I will investigate better this area, I understand your concern.
> >>
> >>>
> >>>> At this point you can run the action. ActionLoop will be extended to
> >>>> support invocations in the format
> >>>> "/v1/namespaces/namespace/actions/package/action".
> >>> Why bother reimplementing this exact path? To obtain API compatibility
> with
> >>> OpenWhisk as it is today?
> >>
> >> I want to implement a subset of the OpenWhisk API on top of Knative
> serving.
> >> Knative serving already does the scaling and routing, so what we need
> are the "endpoints" to invoke actions.
> >>
> >> Since I do not want to add additional components, not at the first
> stage. Just knative serve and build, the runtime and a controller script,
> the runtime is the natural place where to "handle" the API invocations,
> since Knative only generates the URL but not anything else.  If I
> understood well, Matt is adding a proxy. I do not want to add a proxy, just
> add to the runtime the ability to respond to "API like" calls, at least
> those regarding action invocation.
> >>
> >>>> It will do all the decoding required to invoke the action with the
> >>>> expected paramenters (straight invocation thrhoug the actinloop
> protocol,
> >>>> not proxies).
> >>> Does this mean moving all of the Controller's "smartness" about
> incoming
> >>> and outgoing HTTP requests (see the whole WebActions for example)?
> >>
> >> At least decoding web actions in the runtime, yes. Knative serving
> already has routing and proxying.
> >> So a true implementation on top of Knative requires IHMO this
> sacrifice. Unless there is a way to keep the controller in a "Knative"
> compatible way. Open to suggestions here.
> >>
> >>> Each action will then be exposed using an ingress with its specific
> >>> invocation path.
> >>>
> >>> If the community agrees with this plan, I would create a repo
> >>> `incubator-openwhisk-knative` to work on it.
> >>>
> >>> Thoughts?

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