Questions[operations-orchestration](server)

I'm in the process of learning kubernetes and docker swarm. I really appreciate how you can create several servers as work nodes and cluster/swarm them together. Then use commands like kubectl get pods or docker ps -a to see all pods/containers across all services connected to the same cluster/swarm.

This got me wondering if:

1. Is it a popular to run database and node js apps across VPS instances (eg. linode, digital ocean, etc...) WITHOUT the use of containerized environments like kubernetes/docker swarm?
2. If the answer to 1. is yes, then are there VPS orchestration tools comparable kubernetes/docker swarm, but for non-containerized environments? That is, most processes will probably be start/stopped via systemd/systemctl. For example, I have a naive expectation that it would be nice if I can do something like vps-orchestration-cli list api-*-services, which basically shows the health of all my systemd jobs for my nodejs api app running on each VPS in my network.

I am looking to learn Kubernetes, specifically from this resource. I only want to run Docker containers, rather than full-fat VMs. It says that I need any of these as a base from which to work:

• Docker Desktop
• kind
• Minikube

I have plumped for Minikube, as I'm on Linux, and it's pretty easy to install. I'm using these instructions. The second doc link says:

To check if virtualization is supported on Linux, run the following command and verify that the output is non-empty:

grep -E --color 'vmx|svm' /proc/cpuinfo

This does not produce any output for me, since my standard development environment runs inside a VirtualBox container. I don't plan to change this - Docker, Docker Compose and Docker Swarm run very well here.

It later says:

Install a Hypervisor

If you do not already have a hypervisor installed, install one of these now:

• KVM, which also uses QEMU

• VirtualBox

This makes it seem that hypervisor CPU support is necessary, but I do not see why that would be.

However it does go onto say:

Minikube also supports a --driver=none option that runs the Kubernetes components on the host and not in a VM. Using this driver requires Docker and a Linux environment but not a hypervisor.

This appears to be something of an addendum, and is given much less prominence that the suggestion that virtualisation instructions are a requirement. Were the documentation authors just "covering all bases", or will I bump into a roadblock later on by continuing despite not having the required CPU?

I want to create a directory with rex if it doesn't exist. I read this but I can't find how to do it.

If I send the file without the directory I get this error:

ERROR - upload: /usr/local/path/file.ext is not writable

Any hints?

We have a project where our hosting clients are offered a database (MySql) as part of their plan and I was curious how would one orchestrate this. We want to run the databases on different machines to where the web servers run.

I was thinking on using Kubernetes with the new StatefulSet feature but I'm really intrigued by the way compose.io is doing it's job. They seem to guarantee iops and CPU with the limitations being applied on RAM and Disk, as with all the databases they offer. One way would be in Kubernetes to allocate a limited persistent volume and running the container with a limited RAM without anything applied on CPU but that will create a highly unstable cluster as containers/pods start eating CPU and with Kubernetes constantly shifting them on nodes where the required resources are found. Couple that with persistent volumes which slower things down since the pod must be killed before attaching the disk elsewhere and you might get a lot of downtime for customers.

I'm just curious, what is your guess on how they are orchestrating their databases.

I'm pretty new in ansible and by now can't figure out how to make an idempotent task. E.g. file. It simply doesn't have creates or removes. In command module it does have creates, but whenever I run the provisioner and the file (symbolic link) does exist, the ansible still marks the command as "ok", not "skipped".

Here's command module example

- name: Firefox | link
  command: ln -s /opt/firefox/firefox /usr/local/bin/firefox creates=/usr/local/bin/firefox

Always gets executed.

How do I get sure that the command won't be executed >=2 times given the node's state is already accomplished by 1st run?

Thank you!