Replace OpenFaaS with a really open source FaaS platform for Kubernetes

[ema-pe]

OpenFaaS cannot really be considered an open source platform, since the Community Edition (CE) is distributed under an EULA. Many features are also restricted in the CE version, like autoscaling and Prometheus metrics. We should therefore evaluate and adopt a truly open source FaaS platform, such as Knative or OpenWhisk. There is a list of FaaS platforms available for Kubernetes, but many appear unmaintained or immature, the most promising options are the ones mentioned.

We could also consider building an intermediary layer between the DFaaS Agent and the chosen FaaS platform to remain fully independent. However, I’m not sure whether that would be a good path to follow.

[aletundo]

Having an abstract layer, for example defining an "interface" and then different specific implementations (e.g., KNativeClient, OpenWhiskClient, etc.) is actually a good idea IMO. Were you thinking about this or a complete separate component/service that sits in between the DFaaS Agent and the FaaS platform?

[ema-pe]

Having an abstract layer, for example defining an "interface" and then different specific implementations (e.g., KNativeClient, OpenWhiskClient, etc.) is actually a good idea IMO. Were you thinking about this or a complete separate component/service that sits in between the DFaaS Agent and the FaaS platform?

Currently, the DFaaS Agent communicates directly with the OpenFaaS Gateway and retrieves specific metrics from Prometheus. Other FaaS platforms, such as OpenWhisk, follow a similar approach: they expose a dedicated API and publish selected metrics to Prometheus. A possible improvement would be to introduce a separate service that, on the frontend, provides a standard API for the agent along with a unified set of Prometheus metrics, while on the backend it abstracts and handles the differences across platforms like OpenFaaS, Knative, and others.

Anyway, to keep things simple at the beginning, we could drop OpenFaaS and switch to Knative or OpenWhisk, as it should not be too difficult.

[ema-pe]

I found another FaaS platform called Nuclio that might be worth considering.

[ema-pe]

Just to summarize the available FaaS platforms on Kubernetes based on the list linked above:

• Eigr Functions and Azure Functions Runtime: not our case,
• Fission: appears well-maintained, open source, and supported by several sponsors,
• Fn: maintained but has no Kubernetes support (runs on plain Docker); seems more like a minor or hobby project,
• OpenWhisk: an Apache Software Foundation project, actively maintained with major contributors and sponsors (IBM, Adobe, Red Hat). It uses Kamon instead of Prometheus, but appears compatible,
• Nuclio: offers both open-source and closed-source versions. I would skip this to prevent the same vendor-lock situation as OpenFaaS,
• Knative: the main alternative to OpenWhisk. It seems lower-level (works with containers as serverless applications, while OpenWhisk works with functions). It has native Prometheus support,
• Cloudstate, Gestalt, IronFunctions, Kubeless, Riff, VMWare Dispatch: not maintained any more.

I think the main alternatives are Knative and OpenWhisk. We should investigate on these two, aiming to minimize the effort required to maintain our DFaaS platform. Remember we use Prometheus for metrics collection, this should remain an important consideration.