Assignments

Here we will use same host name for multiple docker container.

We will run two container from elastic-search named elasticsearch1 and elasticsearch2. Both container should have same dns name, search.

From alpine, we will run nslookup and ensure, the search is the dns name of both container.

From centos we will verify. search:9200 work similar to load balancer between these two containers.

• Create 2 containers from elasticsearch:2
• Use --network-alias search while creating to provide additional DNS name
• Create container from alpine:3.10
• From alpine use --net to see, both containers with same DNS name
• Create container from centos
• curl to search:9200 and see both name field shows

Check network list.

docker network ls

Create a custom network named dns_rest, we will do all the work.

docker network create dns_res

Make sure network is created and in containers, no containers is connected.

docker network inspect dns_res

Create two container in the network dns_res, with

• named elastic_search1, and elastic_search2
• should go under network dns_res
• should have network alias search

docker container run --name elastic_search_1 --network dns_res --network-alias search -d elasticsearch:2

docker container run --name elastic_search_2 --network dns_res --network-alias search -d elasticsearch:2

Check the network and these two container should be under the dns_res network.

docker network inspect dns_res

Run a container of alpine and open shell inside,

docker container run --network dns_res -it alpine:3.10 sh

Check the two container is exist in the search hostname using nslookup tool

nslookup search

This should give output like,

Name:      search
Address 1: 172.25.0.2 elastic_search_1.dns_res
Address 2: 172.25.0.3 elastic_search_2.dns_res

Now create a container of centos and open terminal in it,

docker container run -it --network dns_res centos:7

Run the following couple of times, only these two containers should appear randomly.

curl -s search:9200