Cloud Foundry.
Pretty much everything you need to do today is done. Multitenancy was designed in from the start and is available in several levels of hardness (orgs/spaces gives you user-level multitenancy, isolation segments give you component-level multitenancy, multi-foundation gives you the equivalent of multi-cluster multitenancy).
As time goes on it will adopt more and more of Kubernetes, Istio and other systems as they emerge and become able to take over from its own original components. But you'll get the same experience throughout. And Kubernetes will converge upwards as people realise that "It Just Works" is actually, you know, a pretty nice developer experience.
But I am, having worked on and around Cloud Foundry for several years, hilariously biased.
- Since essentially no container platform was designed for hard multi-tenancy, use automation to stand up separate copies of a platform at scale, using a platform with low overhead in controller to worker nodes.
Consider what would be the “simplest thing that could possibly work” e.g. offering tenants an AWS autoscale group (with appropriate IAM account, user, role, security group perms) behind an AWS PrivateLink endpoint:
https://docs.aws.amazon.com/vpc/latest/userguide/endpoint-se...
I say that, because most of these platforms weren’t intended for and are not marketed for hard multi-tenancy, until their engineers started getting asked the question by enterprises attempting it for regulatory/compliance/security reasons.
> Cloud Foundry. Multitenancy was designed in from the start...
This comment gives me pause, as CloudFoundry’s security model, approach, and engineering lacked hardness as of 3 - 4 years ago. We explored the multi-tenancy design, and found no guarantees, or even strong assurances, were brought by the platform.
The larger issue was we found CF’s security engineering assertions rather overconfident (flavor of the comment above). Warranted relative to other solutions without security features, but not relative to being hardened enough to trust in the face of bad actors, particularly malicious insiders.
My opinion is also “biased”, in the sense that unless a platform is doing work outside of “the server”, I don’t believe it can offer hard multi-tenancy.
Here’s an example of work outside the server:
> unless a platform is doing work outside of “the server”, I don’t believe it can offer hard multi-tenancy.
I admire the work AWS and others are doing to harden the hardware base, but I'm not sure how software would contribute or not contribute to that line of defence.
Ill add that there are few well established companies that have adopted this approach, AWS, Google and Azure to name a few.
Automating the provisioning of an entire new cluster is very easy, at least for some people with the required resources. But even for a small shop it is possible to automate it using stuff like Jenkins and Ansible. It is still relatively sophisticated stuff. It is not rocket science but not an elementary school project level either.
The aks-engine repo let you peep to what goes behind the scenes, but this is not the kind of beast you will grow at home - it is a public cloud provider with global scale, with the expected level of complexity and engineering. It is available on: https://github.com/Azure/aks-engine
This is doable through various provider/vendor-specific APIs. Pivotal's PKS has an API. GKE has one, EKS, AKS and so on have them too.
In the longer run there's meant to be a full Cluster API, which I presume will take over for that role: https://github.com/kubernetes-sigs/cluster-api
2) Service mocrosegmentation
3) 2 but using kubernetes network policies
To all your workloads.
Kubernetes was simply not designed as a multitenant system. Namespaces aren't the basis of multitenancy, for pete's sake, they're namespaces. Piling ever more extensions on top to try and plug all the holes just highlights it more completely.
The concept given above is where I expect Kubernetes will go, either explicitly (by creating a hard separation between scheduling and everything else) or by convention and tooling (we all adopt layers of indirection like Virtual Kubernetes). The latter seems most likely to me.
This will, as others are pointing out, only get more and more necessary as CRDs and Operators continue their long march to gather all the knowledge of your systems into their embrace. But it turns out that storing all the truths of dozens or hundreds of distinct systems, some of which conflict, many of which can't be fully walled off from others, means that your security posture may include a certain amount of humming loudly.
Something like Virtual Kubernetes splits the difference: you can retain Kubernetes-as-scheduler, reaping all the benefits accruing from workload consolidation. But you also get hard tenancy boundaries between workspaces, between Kubernetes masters being used as a skin over etcd.
Kubernetes is amazing. But this is one thing it got wrong. Just wrong and we'll all be wrestling with it for years. It would be like setting out to write a single-user OS, database or filesystem.
Disclosure: I work for Pivotal, we do some Kubernetes stuff, but these are personal views.