Couchbase Cluster on Docker Swarm Using Docker Compose and Docker Machine

Want to learn how to create and scale a Couchbase Cluster using the full armor of Docker? Well, it's your lucky day!

Arun Gupta

May. 18, 16 · Cloud Zone · Tutorial

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This blog post will explain how to create and scale a Couchbase Cluster using the full armor of Docker: Docker Machine, Docker Swarm, and Docker Compose.

Here is what we’ll do:

Create a 3-node Docker Swarm Cluster using Docker Machine
Run a Couchbase instance on two nodes
Create a cluster
Rebalance the cluster
Scale and rebalance the cluster again

Docker Swarm Cluster Using Consul

Create a three-node Docker Swarm cluster using Docker Machine:

# Docker Machine for Consul
docker-machine \
   create \
   -d virtualbox \
   consul-machine

# Start Consul
docker $(docker-machine config consul-machine) run -d --restart=always \
         -p "8500:8500" \
         -h "consul" \
         progrium/consul -server -bootstrap

# Docker Swarm master
docker-machine \
  create \
  -d virtualbox \
  --swarm \
  --swarm-master \
  --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-advertise=eth1:2376" \
  swarm-master

# Docker Swarm node-01
docker-machine \
  create \
  -d virtualbox \
  --swarm \
  --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-advertise=eth1:2376" \
  swarm-node-01

# Docker Swarm node-02
docker-machine \
  create \
  -d virtualbox \
  --virtualbox-disk-size "5000" \
  --swarm \
  --swarm-discovery="consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-store=consul://$(docker-machine ip consul-machine):8500" \
  --engine-opt="cluster-advertise=eth1:2376" \
  swarm-node-02

# Configure to use Docker Swarm cluster
eval "$(docker-machine env --swarm swarm-master)"

The article "Provision a Swarm cluster with Docker Machine" provides more details about why and what’s done in this script. Here is a summary:

Create a Docker Machine and run Consul for service discovery
Create three Docker Machines: one for Master and two for Worker nodes. Each machine is configured to be part of a Swarm cluster using --swarm. It also uses the Consul service discovery specified using --swarm-discovery.

Couchbase Nodes on Docker Swarm

Create two instances of Couchbase using Docker Compose:

version: "2"
services:
  db:
    image: arungupta/couchbase
    network_mode: "host"
    ports:
      - 8091:8091
      - 8092:8092
      - 8093:8093
      - 11210:11210

arungupta/couchbase image is used here. This image is defined at Couchbase Docker Image. It uses the Official Couchbase Docker Image and configures it as explained:

Setup memory for Index and Data
Configure the Couchbase server with Index, Data, and Query service
Set up username and password credentials
Load the travel-sample bucket

The Compose file uses host network. This is equivalent to using --net=host on Docker run CLI. It allows the container to use the host networking stack. It also limits only a single Couchbase container to run on a single Docker Machine. So this means that our Couchbase cluster can scale based upon the number of Docker Machines—three in our case.

The exact command to use this Compose file is:

docker-compose scale db=2
WARNING: The "db" service specifies a port on the host. If multiple containers for this service are created on a single host, the port will clash.
Creating and starting couchbasedockerswarm_db_1 ... 
Creating and starting couchbasedockerswarm_db_2 ... 
Pulling db (arungupta/couchbase:latest)...
swarm-node-02: Pulling arungupta/couchbase:latest...
swarm-master: Pulling arungupta/couchbase:latest...
swarm-node-01: Pulling arungupta/couchbase:latest...
Pulling db (arungupta/couchbase:latest)...
swarm-node-02: Pulling arungupta/couchbase:latest... : downloaded
Creating and starting couchbasedockerswarm_db_1 ... done
Creating and starting couchbasedockerswarm_db_2 ... done

There are three nodes in the Docker Swarm cluster. The default scheduler strategy is spread and so the containers will be spread on different hosts.

This is evident by docker ps:

docker ps
CONTAINER ID        IMAGE                 COMMAND                  CREATED             STATUS              PORTS               NAMES
4c8c149f4e34        arungupta/couchbase   "/entrypoint.sh /opt/"   44 seconds ago      Up 44 seconds                           swarm-node-02/couchbasedockerswarm_db_1
d3b6a1dbddb5        arungupta/couchbase   "/entrypoint.sh /opt/"   44 seconds ago      Up 44 seconds                           swarm-node-01/couchbasedockerswarm_db_2

Note, one Couchbase server is running on swarm-node-01 and another on swarm-node-02. Each server is configured with an administrator username Administrator and password password.

Find out IP address of the Docker Machine:

docker-machine ls
NAME             ACTIVE      DRIVER       STATE     URL                         SWARM                   DOCKER    ERRORS
consul-machine   -           virtualbox   Running   tcp://192.168.99.106:2376                           v1.11.1   
default          -           virtualbox   Running   tcp://192.168.99.100:2376                           v1.11.0   
swarm-master     * (swarm)   virtualbox   Running   tcp://192.168.99.107:2376   swarm-master (master)   v1.11.1   
swarm-node-01    -           virtualbox   Running   tcp://192.168.99.108:2376   swarm-master            v1.11.1   
swarm-node-02    -           virtualbox   Running   tcp://192.168.99.109:2376   swarm-master            v1.11.1

If you have jq installed then the IP address can be conveniently found as:

docker-machine inspect swarm-node-01 | jq ".Driver.IPAddress"
"192.168.99.108"

Couchbase Cluster on Docker Swarm

All Couchbase server nodes are created equal. This allows the Couchbase cluster to truly scale horizontally to meet your growing application demands. Independently running Couchbase nodes can be added to a cluster by invoking the server-add CLI command. This is typically a two-step process. The first step is adding one or more nodes. The second step then rebalances the cluster where the data on the existing nodes is rebalanced across the updated cluster.

In our case, a single Couchbase container is running on each Docker Machine. Let's pick the IP address of any one Couchbase node, and add the IP address of the other node:

docker run -it arungupta/couchbase \
couchbase-cli \
server-add \
--cluster=`docker-machine inspect swarm-node-01 | jq -r ".Driver.IPAddress"`:8091 \
--user Administrator \
--password password \
--server-add=`docker-machine inspect swarm-node-02 | jq -r ".Driver.IPAddress"` \
--server-add-username=Administrator \
--server-add-password=password
SUCCESS: server-add 192.168.99.109:8091

Couchbase Web Console for both the nodes will show a similar output:

This shows that the two nodes now form a cluster and that the cluster needs to be rebalanced.

Rebalance Couchbase Cluster

Now, let's rebalance the cluster:

docker run -it arungupta/couchbase couchbase-cli rebalance --cluster=`docker-machine inspect swarm-node-01 | jq -r ".Driver.IPAddress"`:8091 --user Administrator --password password 
INFO: rebalancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
SUCCESS: rebalanced cluster

Couchbase Web Console will be updated to show that rebalance is happening:

And finally you’ll see a rebalanced cluster:

Scale and Rebalance Couchbase Cluster

Scale the Couchbase cluster:

docker-compose scale db=3
WARNING: The "db" service specifies a port on the host. If multiple containers for this service are created on a single host, the port will clash.
Creating and starting couchbasedockerswarm_db_3 ... done

Check that the container is running on a different Docker Machine:

docker ps
CONTAINER ID        IMAGE                 COMMAND                  CREATED             STATUS              PORTS               NAMES
02f94e2bbd3e        arungupta/couchbase   "/entrypoint.sh /opt/"   9 seconds ago       Up 8 seconds                            swarm-master/couchbasedockerswarm_db_3
4c8c149f4e34        arungupta/couchbase   "/entrypoint.sh /opt/"   About an hour ago   Up About an hour                        swarm-node-02/couchbasedockerswarm_db_1
d3b6a1dbddb5        arungupta/couchbase   "/entrypoint.sh /opt/"   About an hour ago   Up About an hour                        swarm-node-01/couchbasedockerswarm_db_2

As mentioned earlier, scaling a Couchbase cluster is a two-step process. This is because typically you’ll add multiple servers and then rebalance the cluster. However, in cases where you only need to add a single Couchbase node and then rebalance, the rebalance command can be used achieve that.

In our case, this is done as shown:

docker run -it arungupta/couchbase couchbase-cli rebalance --cluster=`docker-machine inspect swarm-node-01 | jq -r ".Driver.IPAddress"`:8091 --user Administrator --password password --server-add=`docker-machine inspect swarm-master | jq -r ".Driver.IPAddress"` --server-add-username=Administrator --server-add-password=password
SUCCESS: server-add 192.168.99.107:8091
INFO: rebalancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 
SUCCESS: rebalanced cluster

The rebalanced cluster now looks like:

This blog post showed how you can easily create and scale a Couchbase Cluster using Docker Swarm, Machine, and Compose.

Topics:

couchbase, docker swarm, docker compose, docker machine

Published at DZone with permission of Arun Gupta, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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