Kubernetes Blog

Monday, July 13, 2015

Weekly Kubernetes Community Hangout Notes - July 10 2015

Every week the Kubernetes contributing community meet virtually over Google Hangouts. We want anyone who’s interested to know what’s discussed in this forum.

Here are the notes from today’s meeting:

  • Eric Paris: replacing salt with ansible (if we want)
    • In contrib, there is a provisioning tool written in ansible
    • The goal in the rewrite was to eliminate as much of the cloud provider stuff as possible
    • The salt setup does a bunch of setup in scripts and then the environment is setup with salt
      • This means that things like generating certs is done differently on GCE/AWS/Vagrant
    • For ansible, everything must be done within ansible
    • Background on ansible
      • Does not have clients
      • Provisioner ssh into the machine and runs scripts on the machine
      • You define what you want your cluster to look like, run the script, and it sets up everything at once
      • If you make one change in a config file, ansible re-runs everything (which isn’t always desirable)
      • Uses a jinja2 template
    • Create machines with minimal software, then use ansible to get that machine into a runnable state
      • Sets up all of the add-ons
    • Eliminates the provisioner shell scripts
    • Full cluster setup currently takes about 6 minutes
      • CentOS with some packages
      • Redeploy to the cluster takes 25 seconds
    • Questions for Eric
      • Where does the provider-specific configuration go?
        • The only network setup that the ansible config does is flannel; you can turn it off
      • What about init vs. systemd?
        • Should be able to support in the code w/o any trouble (not yet implemented)
    • Discussion
      • Why not push the setup work into containers or kubernetes config?
        • To bootstrap a cluster drop a kubelet and a manifest
      • Running a kubelet and configuring the network should be the only things required. We can cut a machine image that is preconfigured minus the data package (certs, etc)
        • The ansible scripts install kubelet & docker if they aren’t already installed
      • Each OS (RedHat, Debian, Ubuntu) could have a different image. We could view this as part of the build process instead of the install process.
      • There needs to be solution for bare metal as well.
      • In favor of the overall goal – reducing the special configuration in the salt configuration
      • Everything except the kubelet should run inside a container (eventually the kubelet should as well)
        • Running in a container doesn’t cut down on the complexity that we currently have
        • But it does more clearly define the interface about what the code expects
      • These tools (Chef, Puppet, Ansible) conflate binary distribution with configuration
        • Containers more clearly separate these problems
      • The mesos deployment is not completely automated yet, but the mesos deployment is completely different: kubelets get put on top on an existing mesos cluster
        • The bash scripts allow the mesos devs to see what each cloud provider is doing and re-use the relevant bits
        • There was a large reverse engineering curve, but the bash is at least readable as opposed to the salt
      • Openstack uses a different deployment as well
      • We need a well documented list of steps (e.g. create certs) that are necessary to stand up a cluster
        • This would allow us to compare across cloud providers
        • We should reduce the number of steps as much as possible
        • Ansible has 241 steps to launch a cluster
  • 1.0 Code freeze
    • How are we getting out of code freeze?
    • This is a topic for next week, but the preview is that we will move slowly rather than totally opening the firehose
      • We want to clear the backlog as fast as possible while maintaining stability both on HEAD and on the 1.0 branch
      • The backlog of almost 300 PRs but there are also various parallel feature branches that have been developed during the freeze
    • Cutting a cherry pick release today (1.0.1) that fixes a few issues
    • Next week we will discuss the cadence for patch releases
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