That's a false statement as far as the technical aspects are concerned (Swarm is still usable and supported), but is a true statement when you look at the social aspects (Kubernetes won the container wars and now both Swarm and even Nomad is uncommon to run into).

Right now the company i'm in uses Swarm in a lot of places due to its simplicity (Compose file support) and low resource usage - Swarm hits the sweet spot when it comes to getting started with container orchestration and doing so without needing multiple people to wrangle the technical complexity of Kubernetes, or large VMs to deal with its resource usage, at least in on prem environments.

In combination with Portainer (https://www.portainer.io/) it's perhaps one of the best ways to get things done, when you expect everything to just work and aren't doing something too advanced (think along the lines of 10 servers, rather than 100, which is probably most of the deployments out there).

I actually wrote about some of its advantages in my blog post, "Docker Swarm over Kubernetes": https://blog.kronis.dev/articles/docker-swarm-over-kubernete...

That said, if there are any good options to replace Swarm, it has to either be Hashicorp Nomad (https://www.nomadproject.io/) which is a really nice platform, especially when coupled with Consul (https://www.consul.io/), as long as you can get past the weirdness of HCL, or it has to be K3s (https://k3s.io/), which gives you Kubernetes without the insane bloat and hardware usage.

I actually benchmarked K3s against Docker Swarm in similar app deployments: 1 leader server, 2 follower servers, running a Ruby on Rails app and an ingress, while they're under load testing by K6 (https://k6.io/). I was attempting to see whether COVID contract tracking with GPS would be viable as far as the system load goes in languages with high abstraction level, here's more info about the approach: https://blog.kronis.dev/articles/covid-19-contact-tracing-wi...

Honestly, the results were pretty close - on the follower servers, the overhead of the orchestrator agents were a few percent (K3s being heavier, but a few dozen MB here or there not being too relevant), whereas the bigger differences were in the leader components, where K3s was heavier almost by a factor of two, which isn't too much when you consider how lightweight Swarm is (there was a difference of a few hundred MB) and the CPU usage was reasonably close in both of the cases as well. Sadly, the text of the paper is in Latvian, so it's probably of no use to anyone, but i advise you to do your own benchmarks! Being a student back then, i couldn't afford many servers, so it's probably a good idea to benchmark those with more servers.

Of note, on those VPSes (4 GB of RAM, single core), the full Kubernetes wouldn't even start, whereas at work, trying to get the resources for also running Rancher on top of a "full" Kubernetes cluster (e.g. RKE) can also take needlessly long due to the backlash from ops. Also, personally i find the Compose syntax to be far easier to deal with, rather than the amalgamation that Kubernetes uses, Helm probably shouldn't even be a thing if the deployment descriptors weren't so bloated. Just look at this: https://docs.docker.com/compose/compose-file/compose-file-v3...

In short:

- Docker Swarm is pretty good when you're starting out with containers and is reasonably stable and easy to use
- with Portainer, you can take it pretty far, be it in regards to development environments or even production
- Compose format is great and works for Portainer and Docker Swarm (with minor changes), it's really nice
- sadly, none of that really matters, because Kubernetes has more hype and therefore you have to learn how to use it in the industry
- because of this, expect most of the tooling to be for Kubernetes and Swarm to fade into irrelevance before being retired (killed)
- on the bright side, K3s is a viable and mostly non-bloated alternative to the "full" Kubernetes distros
- also, Portainer supports both, so you don't even always need Rancher either