Eucalyptus

Deploying Cassandra and Consul with Chef Provisioning

ConsulCassandra

Introduction

Chef Provisioning (née Chef Metal) is an incredibly flexible way to deploy infrastructure. Its many plugins allow users to develop a single methodology for deploying an application that can then be repeated against many types of infrastructure (AWS, Euca, Openstack, etc). Chef provisioning is especially useful when deploying clusters of machines that make up an application as it allows for machines to be:

  • Staged before deployment
  • Batched for parallelism
  • Deployed in serial when necessary

This level of flexibility means that deploying interesting distributed systems like Cassandra and Consul is a breeze. By leveraging community cookbooks for Consul and Cassandra, we can largely ignore the details of package installation and service management and focus our time on orchestrating the stack in the correct order and configuring the necessary attributes such that our cluster converges properly. For this tutorial we will be deploying:

  • DataStax Cassandra 2.0.x
  • Consul
    • Service discovery via DNS
    • Health checks on a per node basis
  • Consul UI
    • Allows for service health visualization

Once complete we will be able to use Consul’s DNS service to load balance our Cassandra client requests across the cluster as well as use Consul UI in order to keep tabs on our clusters’ health.

In the process of writing up this methodology, I went a step further and created a repository and toolchain for configuring and managing the lifecycle of clustered deployments. The chef-provisioning-recipes repository will allow you to configure your AWS/Euca cloud credentials and images and deploy any of the clustered applications available in the repository.

Steps to reproduce

Install prerequisites

  • Install ChefDK
  • Install package deps (for CentOS 6)
    yum install python-devel gcc git
  • Install python deps:
    easy_install fabric PyYaml
  • Clone the chef-provisioning-recipes repo:
    git clone https://github.com/viglesiasce/chef-provisioning-recipes

Edit config file

The configuration file (config.yml) contains information about how and where to deploy the cluster. There are two main sections in the file:

  1. Profiles
    1. Which credentials/cloud to use
    2. What image to use
    3. What instance type to use
    4. What username to use
  2. Credentials
    1. Cloud endpoints or region
    2. Cloud access and secret keys

Edit the config.yml file found in the repo such that the default profile points to a CentOS 6 image in your cloud and the default credentials point to the proper cloud.

Run the deployment

Once the deployer has been configured we simply need to run it and tell it which cluster we would like to deploy. In this case we’d like to deploy Cassandra so we will run the deployer as follows:

./deployer.py cassandra

This will now automate the following process:

  1. Create a chef repository
  2. Download all necessary cookbooks
  3. Create all necessary instances
  4. Deploy Cassandra and Consul

Once this is complete you should be able to see your instances running in your cloud tagged as follows: cassandra-default-N. In order to access your Consul UI dashboard go to http://instance-pub-ip:8500

You should now also be able to query any of your Consul servers for the IPs of your Cassandra cluster:

nslookup cassandra.service.paas.home <instance-pub-ip>

In order to tear down the cluster simply run:

./deployer.py cassandra --op destroy
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Eucalyptus

Chef Metal with Eucalyptus

Introduction

My pull request to chef-metal-fog was recently accepted and released in version 0.8.0 so a quick post on how to get up and running on your Eucalyptus Cloud seemed appropriate.

Chef Metal is a new way to provision your infrastructure using Chef recipes. It allows you to use the same convergent design as normal Chef recipes. You can now define your cloud or bare metal deployment in a Chef recipe then deploy, update and destroy it with chef-client. This flexibility is incredibly useful for both development of new Chef cookbooks and in exploring various topologies of distributed systems.

Game time

First, install the Chef Development Kit. This will install chef-client and a few other tools to get you well on your way to Chef bliss.

Once you have installed the Chef DK on your workstation, install the chef-metal gem into the Chef Ruby environment:

chef gem install chef-metal

You will need to create your Chef repo. This repository will contain all the information about how and where your application gets deployed using Chef Metal. In this case we are naming our app “euca-metal”.

chef generate app euca-metal

You should now see a directory structure as follows:

├── README.md
└── cookbooks
 └── euca-metal
   ├── Berksfile
   ├── chefignore
   ├── metadata.rb
   └── recipes
     └── default.rb

Now that the skeleton of our application has been created lets edit cookbooks/euca-metal/recipes/default.rb to look like this:

require 'chef_metal_fog'

### Arbitrary name of our deployment
deployment_name ='chef-metal-test'

### Use the AWS provider to provision the machines
### Here is where we set our endpoint URLs and keys for our Eucalyptus deployment
with_driver 'fog:AWS', :compute_options => { :aws_access_key_id => 'XXXXXXXXXXXXXXX',
                                             :aws_secret_access_key => 'YYYYYYYYYYYYYYYYYYYYYYYYYY',
                                             :ec2_endpoint => 'http://compute.cloud:8773/services/compute',
                                             :iam_endpoint => 'http://euare.cloud:8773/services/objectstorage'
}

### Create a keypair named after our deployment
fog_key_pair deployment_name do
  allow_overwrite true
end

### Use the key created above to login as root, all machines below
### will be run using these options
with_machine_options ssh_username: 'root', ssh_timeout: 60, :bootstrap_options => {
  :image_id => 'emi-A6EA57D5',
  :flavor_id => 't1.micro',
  :key_name => deployment_name
}

### Launch an instance and name it after our deployment
machine deployment_name do
  ### Install Java on the instance using the Java recipe
  recipe 'java'
end

Once we have defined our deployment we will need to create a local configuration file for chef-client:

mkdir -p .chef; echo 'local_mode true' > .chef/knife.rb

Now that we have defined the deployment and setup chef-client, lets run the damn thing!

chef-client -z cookbooks/euca-metal/recipes/default.rb

You can now see Chef create your keypair, launch your instance, and then attempt to run the “java” recipe as we specified. Unfortunately this has failed. We never told our euca-metal cookbook that it required the Java cookbook nor did we download that cookbook for it to use. Let’s fix that.

First we will tell our euca-metal cookbook that we need it to pull in the ‘java’ cookbook in order to provision the node. We need to add the ‘depends’ line to our cookbook’s metadata.rb file which can be found here: cookbooks/euca-metal/metadata.rb

name 'euca-metal'
maintainer ''
maintainer_email ''
license ''
description 'Installs/Configures euca-metal'
long_description 'Installs/Configures euca-metal'
version '0.1.0'
depends 'java'

Next we will need to actually download that Java cookbook that we now depend on. To do that we need to:

# Change to the euca-metal cookbook directory
cd cookbooks/euca-metal/
# Use berkshelf to download our cookbook dependencies
berks vendor
# Move the berks downloaded cookbooks to our main cookbook repository
# Note that it wont overwrite our euca-metal cookbook
mv berks-cookbooks/* ..
cd ../..
# Rerun our chef-client to deploy Java for realz
chef-client -z cookbooks/euca-metal/recipes/default.rb

You will notice that the machine is not reprovisioned (YAY convergence!). The Java recipe should now be running happily on your existing instance. You can find your ssh keys in the .chef/keys directory.

Happy AWS Compatible Private Cloud Cheffing!!!!

Many thanks to John Keiser for his great work on chef-metal.

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