GNgnufied·Sep 16, 2016
I will try and answer networking question.
At scale a single host can be running may be 20 containers and port collision becomes a real problem. So imagine if a container opened a port directly on host -we have to be careful that they don't step
on each other toes.
Even if all containers used some sort of contract about which port they are going to use - there are all sort of corner cases waiting to happen such as ephemeral ports(the port you bind to when you connect externally) taking over a port taken by real server app.
I have seen two approaches being used to solve this problem:
1. Using Smartstack (http://nerds.airbnb.com/smartstack-service-discovery-cloud/) the applications running inside container can run
on any port but the port on which they are externally available is decided by orchestration service. Typically, no one talks to
Read the rest
application
inside container directly but they go through the haproxy configured
on localhost. The advantage is - smartstack can remove a service if it
is failing healthcheck etc.
2. The kubernetes/openshift approach of Software defined networking(https://github.com/coreos/flannel). Although they also integrate with load balancers, so that is not the only way.
I know if someone is just getting started with containers, it seems bit overwhelming to digest all this. But having worked in some large
companies which are using containers at scale, it kinda makes sense.