MKIt - Micro Kubernetes on Ruby

This is micro kubernetes(tm) on Ruby(tm), a simple tool to deploy containers to mimic a (very) minimalistic k8 cluster with a nice REST API.

It contains an internal DNS and uses HAProxy for routing/balancing/fail-over for Pods access. The database is a simple sqlite3 db and the server is a Sinatra based application.

A client is also included to access the API, e.g. mkitc ps.

The daemon is responsible for HAProxy pods routing configuration. It also provides the cluster DNS and manages the internal host interface and the docker instances.

Requirements

• Ruby
• HAProxy
• Docker
• Linux (iproute2 package)

Install

This is a simple ruby gem, so to install run

# gem install mkit

Running

The daemon requires root user (due to ip and haproxy), you can run it directly on the repository root...

# ./mkitd  --help
Usage: mkitd [options]
    -c config-dir                    set the config dir (default is /etc/mkit)
    -p port                          set the port (default is 4567)
    -b bind                          specify bind address (e.g. /tmp/app.sock)
    -s server                        specify rack server/handler
    -q                               turn on quiet mode (default is off)
    -x                               turn on the mutex lock (default is off)
    -e env                           set the environment (default is development)
    -o addr                          set the host (default is (env == 'development' ? 'localhost' : '0.0.0.0'))

or after the gem install mkit-<version>.gem. The server and client will be installed on host.

# mkitd
...
 0.65s     info: MKIt is up and running! [ec=0xbe0] [pid=45804] [2023-12-29 15:46:04 +0000]

There's also samples on the samples dir, for daemontools and systemd.

Accessing the API

• Create new service
  • mkitc create samples/apps/rabbitmq.yml
• Update service
  • mkitc update samples/apps/rabbitmq.yml
• Get service
  • mkitc ps {id|service_name}
• Delete service
  • mkitc rm {id|service_name}
• List services
  • mkitc ps [-v (verbose)]
• Control service
  • mkitc start {id|service_name}
  • mkitc stop {id|service_name}

Example:

$ mkitc ps postgres
id      name                 addr             ports                      status
4       postgres             10.210.198.10    tcp/5432                   RUNNING
  pods
    id      pod_id            pod_name          pod_ip            status
    19      4ce31a007211      5d148a16f3aa      172.17.0.2        RUNNING

The service postgres is available on IP 10.210.198.10:5432

Configuration

On startup, configuration files on config directory will be copied to /etc/mkit. HAProxy config dir and control commands are defined on mkit_config.yml

You must configure haproxy to use config directory. e.g. on Ubuntu

# /etc/default/haproxy

# Defaults file for HAProxy
#
# This is sourced by both, the initscript and the systemd unit file, so do not
# treat it as a shell script fragment.

# Change the config file location if needed
CONFIG="/etc/haproxy/haproxy.d"

# Add extra flags here, see haproxy(1) for a few options
#EXTRAOPTS="-de -m 16"

Service

service:
  name: rabbitmq # unique
  image: rabbitmq:3-management-alpine # image
  network: bridge # docker network - it will be created if it does not exists
  ports:  # haproxy port mapping
          #   <external_port>:[internal_port]:<tcp|http>:[round_robin (default)|leastconn]
          # to define a range on `external_port`, leave `internal_port` blank
          #   - 5000-5100::tcp:round_robin
          # range on `internal_port` is not supported 
    - 5672:5672:tcp:round_robin
    - 80:15672:http:round_robin
  resources:
    max_replicas: 1
    min_replicas: 1
  volumes:
    - docker://mkit_rabbitmq_data:/var/lib/rabbitmq # a docker volume - it will be created if it does not exists
    - /var/log/rabbitmq/logs:/var/log/rabbitmq # a local volume
  environment:
    RABBITMQ_DEFAULT_USER: admin
    RABBITMQ_DEFAULT_PASS: admin
    RABBITMQ_DEFAULT_VHOST: mkit

Development

• build the gem
  • rake package
• console
  • rake console

Thanks

For my kids. :)