Tag Archives: Containers & Kubernetes

CoreOS overview

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This blog is part of my ongoing series on Docker containers. In this blog, I will cover basics of CoreOS and some hands-on stuff I tried with CoreOS. As mentioned in my other blog on Docker  orchestration, CoreOS falls in the category of specialized Linux distributions that can host Containers and are suitable for massive server deployments.

CoreOS is a Linux distribution with very minimal services installed and the primary goal is to have a scalable clustering system. Following 2 pictures from CoreOS shows the details from both single host perspective as well as Cluster perspective.

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Docker Networking – Weave

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This blog is part of my ongoing series on Docker containers. Weaveworks is developing a Docker Networking solution to connect Containers. I recently played around with their solution and in this blog, I will capture some of my thoughts.

Following are some internals on their implementation as I understood:

  • Weave creates a Weave bridge as well as a Weave router in the host machine.
  • Weave router establishes both tcp and udp connection across hosts to other Weave routers. TCP connection is used for discovery and protocol related exchange. UDP is used for data encapsulation. Encryption can be done if needed.
  • The Weave bridge is configured to sniff the packets that needs to be sent across hosts and redirect to the Weave router. For local switching, weave router is not used.

Following is a picture of the data path between 2 containers on 2 different hosts.

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Docker Networking – Socketplane

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This blog is part of my ongoing series on Docker containers. In my previous blogs 1 and 2, I covered basics of Docker Networking and also covered some of the limitations with the current solutions. In the next few blogs, I will cover Docker Networking solutions from Socketplane, Weaveworks, CoreOS. Socketplane is developing a Docker networking solution that links containers across multiple hosts. They released a technology preview recently of their initial implementation. In this blog, I will cover some of my thoughts related to trying out the their initial solution.

Following are some internals of the implementation as I understood:

  • Openvswitch is used as the bridge where container interfaces are connected.
  • Multicast DNS is used to discover other cluster members. As of now, multicast is a requirement in Underlay network.
  • Consul is used as a service discovery mechanism where the key, data values for the whole cluster is stored. When socketplane agent is started, it prompts to choose the primary and secondary cluster members.
  • vxlan is used as a tunneling mechanism for data encapsulation between hosts.

Following is a picture of the data path between 2 containers on 2 different hosts.

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Docker Orchestration

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This blog is part of my ongoing series on Docker containers. Orchestrating Containers is a pretty complex task and there is a lot of work ongoing to solve this particular problem. There are big companies, startups as well as Opensource projects involved with this work. There are many different technologies and projects ongoing that got me really confused when I started looking at this. In this blog, I have tried to break down the Docker orchestration problem into smaller pieces and have tried to map different existing/developing solutions into the smaller pieces. Considering that the technologies are evolving and that my knowledge in this area is limited, this blog might need updates and corrections as we move forward. Also, I might have missed few technologies as well as companies..

Problem statement:

Docker does a great job in packaging and transporting single containers. Following are specific problems we need to address:

  • Distributed Applications split between multiple containers.
  • Manage a large number of containers both in terms of allocating the containers to the cluster of hosts as well as handling container failures.

Orchestration blocks:

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Docker Overview

Containers & Kubernetes,

Even though Linux container technology has been available for quite some time, Docker has revolutionized the container technology with its simple packaging that allows portability of applications. Docker packages the applications along with the dependencies like related libraries into an simple image. This single image can be then run on different locations like bare-metal, VM, Cloud etc. In this blog, I will cover comparison of Containers with VM, technologies that Docker uses, Docker architecture and Container use cases. In the next series of blogs, I will cover more on Docker.

Comparing Containers with VM:

Virtual machines did the hardware Virtualization and this allowed multiple Operating systems to run in a single Server. Virtualization technologies have matured now with popular hypervisors being ESX, Xen, HyperV etc. Following picture from Linuxjournal article compares the blocks involved in VM and Containers.

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