1. ClusterController

This is a stateless app that its called with a cluster id. With the cluster id it gets the cluster configuration and cluster resources from the store.

cluster configuration is the spec that was given by the user, and cluster resources is all the resources that cluster controller has created.

Its main job is to maintain the size and health of a cluster.

A cluster configuration contains a group of clusters. Each cluster is a group of resources of the same resource type.

Sample cluster configuration
version: "0.0.1"
name: basic_cluster
groups:
  group1:
    size: 2
    resourcePlugin:
      name: aws
      version: latest
    resourceProperties:
      key: mwas
      instanceType: t2.small
      image: debian
  group2:
    sub-group1:
      size: 2
      resourcePlugin:
        name: gcd
        version: 0.0.1
      resourceProperties:
        key: mwas
        instanceType: t2.micro
        image: amazonlinux
    sub-group2:
      size: 3
      resourcePlugin:
        name: digitalOcean
        version: latest
      resourceProperties:
        instanceType: standard
        memory: 1
        sshKey: mwas
  customDatacenter:
    size: 2
    resourcePlugin:
      name: my-custom-plugin
      version: 0.0.1
      url: https://github.com/mwaaas/kadende-provider-file/releases/download/0.0.1/plugin.so
    resourceProperties:
      instanceSize: abcd
Fields that cluster configuration has:
  1. id (Optional field)

    This would be the pk of the cluster configuration in the store.

    If not defined a generic one would be generated.

  2. version (Mandatory field)

    This contains the version of the cluster

  3. name (Mandatory field) - should be unique

    This contains the name of the cluster.

  4. groups (Mandatory field)

    this is a list of one or more group.

    Fields in a group:
    • resourcePlugin

      This defines the plugin that’s going to create the resource.

      It requires the following fields:
      • name
      • version (optional defaults to latest)
      • url (optional if you want to define your own plugin)
    • resourceProperties

      This defines properties that are going to be used by the resourcePlugin to create resource.

      The fields are determined and validated by the plugin you selected.

1.1. Cluster controller workflow

cluster_controller_workflow
Flow:
  1. Given cluster id

    We get cluster configuration and cluster resources from the store.

  2. Loop.

    We then loop each group.

    In each loop we do the flowing.

    • Get all the resources via tags and return those whose status is active. check the instance that we have got are the ones in our cluster resource

      Will archive this by calling resourcePlugin describe method.

    • Delete those instance that are not in our cluster resources.

    • check if the number of the resources matches the number of the cluster group. create/delete to maintain the cluster size.

    • Store all events in the store to be used by the ui.