This page shows you how to orchestrate the deployment and management of an insecure three-node CockroachDB cluster as a swarm of Docker Engines.

Deploying an insecure cluster is not recommended for data in production. We'll update this page after improving the process to deploy secure clusters.

Before You Begin

Before you begin, it’s helpful to review some terminology:

Feature Description
instance A physical or virtual machine. In this tutorial, you’ll use three, one per CockroachDB node.
Docker Engine This is the core Docker application that creates and runs containers. In this tutorial, you’ll install and start Docker Engine on each of your three instances.
swarm A swarm is a group of Docker Engines joined into a single, virtual host.
swarm node Each member of a swarm is considered a node. In this tutorial, each instance will be a swarm node, one as the master node and the two others as worker nodes. You’ll submit service definitions to the master node, which will dispatch work to the worker nodes.
service A service is the definition of the tasks to execute on swarm nodes. In this tutorial, you’ll define three services, each starting a CockrochDB node inside a container and joining it into a single cluster. Each service also ensures a stable network identity on restart via a resolvable DNS name.
overlay network An overlay network enables communication between the nodes of a swarm. In this tutorial, you’ll create an overlay network and use it in each of your services.

Step 1. Create instances

Create three instances, one for each node of your cluster.

Be sure to configure your network to allow TCP communication on these ports:

  • 26257 for inter-node communication (i.e., working as a cluster) and connecting with applications
  • 8080 for exposing your Admin UI

Step 2. Install Docker Engine

On each instance:

  1. Install and start Docker Engine.

  2. Confirm that the Docker daemon is running in the background:

    $ sudo docker version
    

Step 3. Start the swarm

  1. On the instance where you want to run your manager node, initialize the swarm.

    Take note of the output for docker swarm init as it includes the command you’ll use in the next step. It should look like this:

    $ sudo docker swarm init --advertise-addr 10.142.0.2
    
    Swarm initialized: current node (414z67gr5cgfalm4uriu4qdtm) is now a manager.
    
    To add a worker to this swarm, run the following command:
    
       $ docker swarm join \
       --token SWMTKN-1-5vwxyi6zl3cc62lqlhi1jrweyspi8wblh2i3qa7kv277fgy74n-e5eg5c7ioxypjxlt3rpqorh15 \
       10.142.0.2:2377
    
    To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.
    
  2. On the other two instances, create a worker node joined to the swarm by running the docker swarm join command in the output from step 1, for example:

    $ sudo docker swarm join \
          --token SWMTKN-1-5vwxyi6zl3cc62lqlhi1jrweyspi8wblh2i3qa7kv277fgy74n-e5eg5c7ioxypjxlt3rpqorh15 \
          10.142.0.2:2377
    
    This node joined a swarm as a worker.
    
  3. On the instance running your manager node, verify that your swarm is running:

    $ sudo docker node ls
    
    ID                           HOSTNAME    STATUS  AVAILABILITY  MANAGER STATUS
    414z67gr5cgfalm4uriu4qdtm *  instance-1  Ready   Active        Leader
    ae144s35dx1p1lcegh6bblyed    instance-2  Ready   Active
    aivjg2joxyvzvbksjsix27khy    instance-3  Ready   Active
    

Step 4. Create an overlay network

On the instance running your manager node, create an overlay network so that the containers in your swarm can talk to each other:

$ sudo docker network create --driver overlay cockroachdb

Step 5. Start the CockroachDB cluster

  1. On the instance running your manager node, create the first service that the others will join to:

    $ sudo docker service create --replicas 1 --name cockroachdb-0 --network cockroachdb \
    --mount type=volume,source=cockroachdb-0,target=/cockroach/cockroach-data,volume-driver=local \
    --stop-grace-period 60s \
    cockroachdb/cockroach:beta-20170223 start --advertise-host=cockroachdb-0 --logtostderr --insecure
    

    This command creates a service that starts a container, joins it to the overlay network, and starts the first CockroachDB node inside the container mounted to a local volume for persistent storage. Let’s look at each part:

    • sudo docker service create: The Docker command to create a new service.
    • --replicas: The number of containers controlled by the service. Since each service will control one container running one CockroachDB node, this will always be 1.
    • --name: The name for the service.
    • --network: The overlay network for the container to join. See Step 4. Create an overlay network for more details.
    • --mount: This flag mounts a local volume called cockroachdb-0. This means that data and logs for the node running in this container will be stored in /cockroach/cockroach-data on the instance and will be reused on restart as long as restart happens on the same instance, which is not guaranteed.
      If you plan on replacing or adding instances, it's recommended to use remote storage instead of local disk. To do so, create a remote volume for each CockroachDB instance using the volume driver of your choice, and then specify that volume driver instead of the volume-driver=local part of the command above, e.g., volume-driver=gce if using the GCE volume driver.
    • --stop-grace-period: This flag sets a grace period to give CockroachDB enough time to shut down gracefully, when possible.
    • cockroachdb/cockroach:beta-20170223 start ...: The CockroachDB command to start a node in the container in insecure mode and instruct other cluster members to talk to it using its persistent network address, cockroachdb-0.
  2. On the same instance, create the services to start two other CockroachDB nodes and join them to the cluster:

    $ sudo docker service create --replicas 1 --name cockroachdb-1 --network cockroachdb \
    --mount type=volume,source=cockroachdb-1,target=/cockroach/cockroach-data,volume-driver=local \
    --stop-grace-period 60s \
    cockroachdb/cockroach:beta-20170223 start --advertise-host=cockroachdb-1 \
    --join=cockroachdb-0:26257 --logtostderr --insecure
    
    $ sudo docker service create --replicas 1 --name cockroachdb-2 --network cockroachdb \
    --mount type=volume,source=cockroachdb-2,target=/cockroach/cockroach-data,volume-driver=local \
    --stop-grace-period 60s \
    cockroachdb/cockroach:beta-20170223 start --advertise-host=cockroachdb-2 \
    --join=cockroachdb-0:26257 --logtostderr --insecure
    

    There are only a few differences when creating the second two services:

    • The --name is unique for each service.
    • The CockroachDB command to start each node uses the the --join flag to connect it to the cluster.
  3. Verify that all three services were created successfully:

    $ sudo docker service ls
    
    ID            NAME           REPLICAS  IMAGE                                COMMAND
    6d534f6mw1jc  cockroachdb-0  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-0 --logtostderr --insecure
    a6vb0gljlxx0  cockroachdb-1  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-1 --join=cockroachdb-0:26257 --logtostderr --insecure
    b135nrlxv2kq  cockroachdb-2  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-2 --join=cockroachdb-0:26257 --logtostderr --insecure
    
    The service definitions tell the CockroachDB nodes to log to stderr, so if you ever need access to a node's logs for troubleshooting, use sudo docker logs <container id> from the instance on which the container is running.
  4. Remove the first service and recreate it again with the --join flag to ensure that, if the first node restarts, it will rejoin the original cluster instead of initiating a new cluster:

    $ sudo docker service rm cockroachdb-0
    
    $ sudo docker service create --replicas 1 --name cockroachdb-0 --network cockroachdb \
    --mount type=volume,source=cockroachdb-0,target=/cockroach/cockroach-data,volume-driver=local \
    --stop-grace-period 60s \
    cockroachdb/cockroach:beta-20170223 start --advertise-host=cockroachdb-0 --join=cockroachdb-1:26257 --logtostderr --insecure
    

    When you list the services, the start command for the first node, cockroachdb-0, should now include the --join flag:

    $ sudo docker service ls
    
    ID            NAME           REPLICAS  IMAGE                                COMMAND
    6d534f6mw1jc  cockroachdb-0  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-0 --join=cockroachdb-1:26257 --logtostderr --insecure
    a6vb0gljlxx0  cockroachdb-1  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-1 --join=cockroachdb-0:26257 --logtostderr --insecure
    b135nrlxv2kq  cockroachdb-2  1/1       cockroachdb/cockroach:beta-20161006  start --advertise-host=cockroachdb-2 --join=cockroachdb-0:26257 --logtostderr --insecure
    

Step 7. Use the built-in SQL client

  1. On any instance, use the sudo docker ps command to get the ID of the container running the CockroachDB node:

    $ sudo docker ps | grep cockroachdb
    
    9539871cc769        cockroachdb/cockroach:beta-20160908   "/cockroach/cockroach"   18 hours ago        Up 18 hours         8080/tcp, 26257/tcp   cockroachdb-0.1.0wigdh8lx0ylhuzm4on9bbldq
    
  2. Use the sudo docker exec command to open the built-in SQL shell in interactive mode inside the container:

    $ sudo docker exec -it 9539871cc769 ./cockroach sql
    
  3. Run some CockroachDB SQL statements:

    > CREATE DATABASE bank;
    
    > CREATE TABLE bank.accounts (id INT PRIMARY KEY, balance DECIMAL);
    
    > INSERT INTO bank.accounts VALUES (1234, 10000.50);
    
    > SELECT * FROM bank.accounts;
    
    +------+---------+
    |  id  | balance |
    +------+---------+
    | 1234 | 10000.5 |
    +------+---------+
    (1 row)
    
  4. When you’re done with the SQL shell, use CTRL + D, CTRL + C, or \q to exit.

Step 8. Simulate node failure

Since we have three service definitions, one for each node, Docker Swarm will ensure that there are three nodes running at all times. If a node fails, Docker Swarm will automatically create another node with the same network identity and storage.

To see this in action:

  1. On any instance, use the sudo docker ps command to get the ID of the container running the CockroachDB node:

    $ sudo docker ps | grep cockroachdb
    9539871cc769        cockroachdb/cockroach:beta-20160908   "/cockroach/cockroach"   18 hours ago        Up 18 hours         8080/tcp, 26257/tcp   cockroachdb-0.1.0wigdh8lx0ylhuzm4on9bbldq
    
  2. Stop the CockroachDB node running in the container:

    $ sudo docker exec -it 9539871cc769 ./cockroach quit
    
  3. Verify that the node was restarted in a new container:

    $ sudo docker ps | grep cockroachdb
    4a58f86e3ced        cockroachdb/cockroach:beta-20160908   "/cockroach/cockroach"   7 seconds ago       Up 1 seconds        8080/tcp, 26257/tcp   cockroachdb-0.1.cph86kmhhcp8xzq6a1nxtk9ng
    

Step 9. Scale the cluster

To increase the number of nodes in your CockroachDB cluster:

  1. Create an additional instance (see Step 1).
  2. Install Docker Enginer on the instance (see Step 2).
  3. Join the instance to the swarm as a worker node (see Step 3.2).
  4. Create a new service to start another node and join it to the CockroachDB cluster (see Step 5.2).

Step 10. Stop the cluster

To stop the CockroachDB cluster, on the instance running your manager node, remove the services:

$ sudo docker service rm cockroachdb-0 cockroachdb-1 cockroachdb-2
cockroachdb-0
cockroachdb-1
cockroachdb-2

You may want to remove the persistent volumes used by service as well. To do this, on each instance:

# Identify the name of the local volume:
$ sudo docker volume ls
cockroachdb-0

# Remove the local volume:
$ sudo docker volume rm cockroachdb-0

See Also



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