[taeric]

Don't most virtualized hosts already solve the "less wasteful" point? I get that hypervisors and friends aren't bulletproof, either; but I have fewer ways to shoot yourself with those than I have with containers.

More, you have to worry about the container host anyway, so you haven't removed the need to maintain a host. You've just added to it the need to maintain the rest of the container infrastructure as well as your application stuff.

For places that have not solved the "virtual hosts should be virtually free" problem, containers are quite welcome. You can get going with them quite quickly. If you have already solved that problem, they can look an awful lot like just more work.

[smarterclayton]

Agree, virtual hosts are ubiquitous. But I don’t know that anyone loves their virtual machines the same way they love the smaller, faster, and simpler alternatives (unikernels included).

This is a somewhat pessimistic viewpoint, but lowest common denominator solutions tend to acquire the most network effects. A VM requires more touch points to manage for the person who has to set up a machine - despite ten years of solid progress, they still tend to be pretty annoying to configure and build and manage. The platform as a service approach (whether lambda, nodejs on cloudflare, various functions as a service approaches, heroku, cloud foundry, or dokku) on the other hand take away a lot more hassle by abstracting pain points out, but get accused of being too rigid. Both extremes benefit specific use cases, but have disadvantages in general purpose use.

Containers sit in the ugly, dirty, practical middle. They can do both (VMs are just processes). So the network effects they accrue just like Linux did of being “good for everything, not great” help mitigate some of the disadvantages.

The public cloud providers change this calculus a bit by offering these things as a service, but internally they are just managing the container runtimes for you.

I’m obviously biased, but I tend to see containers as “good enough” to build other abstractions on top, with specific areas where VMs and heavy PaaS abstractions clearly win.

[jacques_chester]

What's been interesting to watch from the Cloud Foundry POV is the circular migration of the boundary between development and operations.

CF built container technology before Docker or Kubernetes -- two generations of it -- because it was seen as the right primitive by people with experience of Borg. But containers were not touted as ends in themselves.

So the contract boundary given was: sourcecode. Buildpacks.

Docker comes along, then Kubernetes, and the container goes from being a hidden detail to a central concept around which a lot of other stuff orbits. And containers are a step forward on a lot of axes. Developers begin to want to use containers as their shipping unit.

So the contract boundary became: images.

Later ops realises that while opaque running containers are awesome for reducing their management complexity, it doesn't reduce all categories of risk. After all: what's in the damn containers? And so various tools have emerged from the container-oriented ecosystem to take sourcecode and turn it into a container image, so that developers and operators have a consistent handoff point.

So the contract boundary becomes: sourcecode.

It sounds like a nice story, and it might seem like we'll go in circles hereafter. But we're not doomed to do poetic laps: what's happened in the middle has been the rise of CI/CD tools, sitting between the container boundary and the sourecode boundary. Good fences make good neighbours and it turns out that fences made of helpful robots make even better neighbours.

As a Pivot with a long association with Cloud Foundry, I have enjoyed in the past few months getting to compare notes with Red Hatters and others in the k8s community.