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Couchbase Cluster on Docker Swarm Using Docker Compose and Docker Machine

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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!

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May. 18, 16 · Cloud Zone ·
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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

couchbase-docker-swarm-0

Docker Swarm Cluster Using Consul

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

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:

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:

  1. Setup memory for Index and Data
  2. Configure the Couchbase server with Index, Data, and Query service
  3. Set up username and password credentials
  4. 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:

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:

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:

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

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:

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

couchbase-docker-swarm-1

couchbase-docker-swarm-2

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:

couchbase-docker-swarm-3

And finally you’ll see a rebalanced cluster:

couchbase-docker-swarm-4

Scale and Rebalance Couchbase Cluster

Scale the Couchbase cluster:

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

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:

The rebalanced cluster now looks like:

couchbase-docker-swarm-5

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

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Topics:
couchbase ,docker swarm ,docker compose ,docker machine

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