anchor.diff:  
   ==== Docker
   
  -This example shows how to run a master and replica database
  +This example shows how to run a primary and replica database
   container on a Docker Swarm (v.1.12) cluster.
   
   First, set up a cluster. The Kubernetes libvirt coreos cluster
  
positive.code: ./run.sh
  ....
  
  You can then find the nodes that are running the master and replica containers
  by:
  ....
  docker service ps master
  docker service ps replica
  ....
  
  
negative.code: docker network create --driver overlay crunchynet
  ....
  
  We want to have the primary database always placed on
  a specific node. This is accomplished using node constraints
  as follows:
  ....
  docker node inspect kubernetes-node-1 | grep ID
  docker node update --label-add type=primary 18yrb7m650umx738rtevojpqy
  ....
  
  In the above example, the kubernetes-node-1 node with ID 18yrb7m650umx738rtevojpqy has a user defined label of *primary* added to it.  The primary service
  specifies *primary* as a constraint when created; this tells Swarm
  to place the service on that specific node.  The replica specifies
  a constraint of *node.labels.type != primary* to have the replica
  always placed on a node that is not hosting the primary service.
  
  
  