Kubernetes allows to manage large clusters which are composed of docker containers. And where is large computation power there is large amount of data throughput. However, there is still a need to spread the data throughput so it can reach and utilize particular docker container(s). This is called load balancing. Kubernetes supports two basic forms of load balancing. Internal among docker containers themselves and external for clients which call you application from outside environment - just users.
Internal Load Balancing with Kubernetes
Usual approach during the modeling of an application in kubernetes is to provide domain models for pods, replications controllers and services. Look at the great documentation if you are not aware of all these principles.
For simplification, pod is a set of docker containers which are always located on the same node. Replication controller allows and guarantees scalability. The last but not least is the service which hides all instances of pods - cre…
I try to setup nginx as a load balancer. The configuration is just a file with a lot of constrains so I need a validation. There is no online validation service, as e.g. CoreOS has, and I don't want to install nginx on my laptop as I work on a distributed app.
Docker is right approach for me. Let say I have following config:
In short, I'm going to pass nginx config to running nginx instance and look to the logs.
Put you nginx.config to the temp and start the docker image:
sudo docker run --name nginx -v /tmp/nginx.config:/etc/nginx/nginx.conf:ro -d nginx
It uses volume mapping so the command just starts a new docker container and mounts a local /tmp/nginx.config to the given in-container path. You can obviously change the volume path to your personal path. Is it working or not? Look at logs.
sudo docker logs nginx
If there is no entry, your file is fine. In the case of an error, you can see something like this:
2016/01/08 11:37:31 [emerg] 1#1: unexpected "}" in /etc/…
Go is not java, and go building system is not maven. Setting up the environment was not straightforward. I was facing couple troubles but I'm going to take it from the beginning. My laptop uses ubuntu 15.04 - well 15.10 since 9pm :-) - and I have never installed go lang yet.
Go lang installation on Ubuntu
First of all, you need to install go lang. You can use official repo, but it contains older version 1.3. However, do not install it using apt-get as kubernetes or it's dependencies require higher version of go-lang. Of course, I originally installed version 1.3 but some fatal error occurred later. It forced me do to the manual installation anyway.
I'd like to deal in this part with potential benefits resulting from using CoreOS as an operating system in your cloud deployment. You can install kubernetes on various operating systems so you can make a decision what to choose. So why CoreOS? What is my experience?
Etcd, Fleet and Flannel Preinstalled
First reason is obvious. CoreOS always provides latest version of all components in Kubernetes cluster. My experience: we have profited from pre-installed components from the beginning. E.g. in early stages when etcd was coming with new beautiful and powerful API (v.2), they put both - old and new - versions together so we just enabled one of them. The setup of all components together is not very simple so you can save couple hours by choosing preinstalled and pre-setuped CoreOS.
No Package Manager, Read Only Partitions
It sounds more like disadvantage than benefit, but ...
Look at CoreOS releases what it consist of.
Fore example, CoreOS includes basic linux utils so you can employ…