CloudFormation template for an Exhibitor-managed ZooKeeper cluster.

Overview

This template bootstraps a ZooKeeper cluster. The ZK nodes are managed by Exhibitor with S3 for backups and automatic node discovery.

ZooKeeper and Exhibitor are run via a Docker container. You may use the default (mbabineau/zookeeper-exhibitor) or provide your own image.

The servers are part of an auto-scaling group. Incrementing, decrementing, or otherwise modifying the server list should be handled gracefully by ZooKeeper (thanks to Exhibitor).

The template creates a security group for ZK clients, the id for which is exposed as an output (ClientSecurityGroup).

The template also creates an internal-facing ELB for clients to interact with Exhibitor via a static endpoint. This is especially useful for node discovery, so Exhibitor's /cluster/list API is exposed as an output as well (ExhibitorDiscoveryUrl).

Note that this template must be used with Amazon VPC. New AWS accounts automatically use VPC, but if you have an old account and are still using EC2-Classic, you'll need to modify this template or make the switch.

Usage

1. Clone the repository

git clone https://github.com/mbabineau/cloudformation-zookeeper.git

2. Create an Admin security group

This is a VPC security group containing access rules for cluster administration, and should be locked down to your IP range, a bastion host, or similar. This security group will be associated with the ZooKeeper servers.

Inbound rules are at your discretion, but you may want to include access to:

• 22 [tcp] - SSH port
• 2181 [tcp] - ZooKeeper client port
• 8181 [tcp] - Exhibitor HTTP port (for both web UI and REST API)

3. Launch the stack

Launch the stack via the AWS console, a script, or aws-cli.

See zookeeper.json for the full list of parameters, descriptions, and default values.

Example using aws-cli:

aws cloudformation create-stack \
    --template-body file://zookeeper.json \
    --stack-name <stack> \
    --capabilities CAPABILITY_IAM \
    --parameters \
        ParameterKey=KeyName,ParameterValue=<key> \
        ParameterKey=ExhibitorS3Bucket,ParameterValue=<bucket> \
        ParameterKey=ExhibitorS3Region,ParameterValue=<region> \
        ParameterKey=ExhibitorS3Prefix,ParameterValue=<cluster_name> \
        ParameterKey=VpcId,ParameterValue=<vpc_id> \
        ParameterKey=Subnets,ParameterValue='<subnet_id_1>\,<subnet_id_2>' \
        ParameterKey=AdminSecurityGroup,ParameterValue=<sg_id>

4. Watch the cluster converge

Once the stack has been provisioned, visit http://<host>:8181/exhibitor/v1/ui/index.html on one of the nodes. You will need to do this from a location granted access by the specified AdminSecurityGroup.

Note the Docker image may take several minutes to retrieve. This can be improved with the use of a private Docker registry.

You should see Exhibitor's management UI with a list of ZK nodes in this cluster. Exhibitor adds each node to the cluster via a rolling restart, so you may see nodes getting added and restarting during the first few minutes they're up.