Tag: rackspace cloud

Dynamic Inventory with Ansible and Rackspace Cloud

March 4, 2014

Typically, with Ansible you create one or more hosts file which it calls Inventory file and Ansible will pick the servers from the hosts file and runs the playbooks onto the servers. This is a simple and straightforward way to do it. However, if you are using the Cloud, its very likely that your applications are creating and deleting servers based on some other logic and its very impractical to maintain a static Inventory file. In that case, Ansible can directly talk to your cloud (AWS, Rackspace, OpenStack, etc) or a dynamic source (Cobbler etc) through what it calls Dynamic Inventory plugins, without you having to maintain a static list of servers.

Here, I will go through the process of using the Rackspace Public Cloud Dynamic Inventory Plugin with Ansible.

Install Ansible
First of all, if you have not already installed Ansible, go ahead and do so. I like to install Ansible within virtualenv using pip.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python-dev python-virtualenv
virtualenv env
source env/bin/activate
pip install ansible

Install Rax Dynamic Inventory Plugin
Ansible maintains an external RAX Inventory File on its repository (Not sure why these plugins do not get bundled with the Ansible package). The rax.py script depends on pyrax module, which is the client binding for Rackspace Cloud.

pip install pyrax
wget https://raw.github.com/ansible/ansible/devel/plugins/inventory/rax.py
chmod +x rax.py

The script needs a configuration file named ~/.rackspace_cloud_credentials, which will store your auth credentials to Rackspace Cloud.

cat ~/.rackspace_cloud_credentials
username = <username>
api_key = <apikey>

Run rax.py
As you can see, rax.py is a very simple script that provides a couple of methods to list and show servers in your cloud. By default, it grabs the servers in all Rackspace regions. If you are interested in only one region, you can specify the RAX_REGION.

./rax.py --list
RAX_REGION=DFW ./rax.py --list
RAX_REGION=DFW ./rax.py --host some-cloud-server

Create Cloud Servers
Since you have already pyrax installed as a dependency of rax.py inventory plugin, you can use command-line to create a cloud server named ‘staging-apache1′ and and tag the server as staging-apache group using the metadata key-value feature.

export OS_USERNAME=<username>
export OS_PASSWORD=<apikey>
export OS_TENANT_NAME=<username>
export OS_AUTH_SYSTEM=rackspace
export OS_AUTH_URL=https://identity.api.rackspacecloud.com/v2.0/
nova keypair-add --pub-key ~/.ssh/id_rsa.pub stagingkey
nova boot --image 80fbcb55-b206-41f9-9bc2-2dd7aac6c061 --flavor 2 --meta group=staging-apache --key-name stagingkey staging-apache1

If you want to install Apache on more staging servers, you would create server named staging-apache2 and tag it with the same group name staging-apache.

Also note, we are injecting ssh keys to the servers on creation, so ansible will be able to do ssh passwordless login. With Ansible, you also have the option of using username-password if you choose so.

Once the server is booted, lets make sure ansible can ping all the servers tagged with the group staging-apache.

ansible -i rax.py staging-apache -u root -m ping

Run a sample playbook
Now, lets create a very simple playbook to install apache on the inventory.

$ cat apache.yml
- hosts: staging-apache
      - name: Installs apache web server
        apt: pkg=apache2 state=installed update_cache=true

Lets run the apache playbook on all rax servers in the region DFW and that match the hosts in the group staging-apache.

RAX_REGION=DFW ansible-playbook -i rax.py apache.yml

With static inventory, you’d be doing this instead, and manually updating the hosts file:

ansible-playbook -i hosts apache.yml

Now you can ssh into the staging-apache1 server and make sure everything is configured as per your playbook.

ssh -i ~/.ssh/id_rsa root@staging-apache1

You may add more servers to the staging-apache group, and on the next run, ansible will detect the updated inventory dynamically and run the playbooks.

Rackspace Public Cloud is based off of OpenStack Nova. So nova.py inventory should work pretty much the same. You can look at the complete lists of dynamic inventory plugins here. Adding a new inventory plugin like for say Razor that isn’t already there would be fairly simple.

Bulk creating Rackspace cloud servers using Script

October 31, 2013

I keep having to create a large number of cloud servers on Rackspace Cloud, so I can play with things like Hadoop and Cassandra.
Using the control panel to create one server at a time, and record each login password and ip, and wait till the server goes active can get really tedious very soon.
So here’s a little script that installs the REST API python binding ‘rackspace-novaclient’ on an Ubuntu server, and prompts you for the image, flavor and number of servers to create, then goes and creates the servers.

On an Ubuntu server, first export your Rackspace Cloud auth credentials (either as root or sudo user)

export OS_USERNAME=<username>
export OS_PASSWORD=<apikey>
export OS_TENANT_NAME=<username>
export OS_AUTH_SYSTEM=rackspace
export OS_AUTH_URL=https://identity.api.rackspacecloud.com/v2.0/

Here is the actual script:


set -x

# Install the Client
if [[ $EUID -ne 0 ]]; then
	sudo apt-get update
	sudo apt-get install python-dev python-pip python-virtualenv
	apt-get update
	apt-get install python-dev python-pip python-virtualenv

virtualenv ~/.env
source ~/.env/bin/activate
pip install pbr
pip install python-novaclient
pip install rackspace-novaclient

# Read AUTH Credentials
: ${OS_USERNAME:?"Need to set OS_USERNAME non-empty"}
: ${OS_PASSWORD:?"Need to set OS_PASSWORD non-empty"}
: ${OS_TENANT_NAME:?"Need to set OS_TENANT_NAME non-empty"}
: ${OS_AUTH_SYSTEM:?"Need to set OS_AUTH_SYSTEM non-empty"}
: ${OS_AUTH_URL:?"Need to set OS_AUTH_URL non-empty"}
: ${OS_REGION_NAME:?"Need to set OS_REGION_NAME non-empty"}
: ${OS_NO_CACHE:?"Need to set OS_NO_CACHE non-empty"}

# Write credentials to a file
cat > ~/novarc <> 'server_passwords.txt'

for i in $(eval echo "{1..$CLUSTER_SIZE}")

is_not_active() {
	status=`nova show $1 | grep 'status' | awk '{print $4}'`
	if [ "$status" != "ACTIVE" ] && [ "$status" != "ERROR" ]; then
		echo "$1 in $status"
		return 0
		return 1

# Wait for all the instances to go ACTIVE or ERROR
while true
	for i in $(eval echo "{1..$CLUSTER_SIZE}")
		if is_not_active $CLUSTER_NAME$i; then

	echo "READY is $READY"
	if [ "$READY" -eq "1" ]; then
	sleep 5

for i in $(eval echo "{1..$CLUSTER_SIZE}")
	echo $CLUSTER_NAME$i >> 'hosts.txt'
cat hosts.txt

	private_ip=`nova show $1 | grep 'private network' | awk '{print $5}'`
	public_ip=`nova show $1 | grep 'accessIPv4' | awk '{print $4}'`
	echo $private_ip $1 >> 'etc_hosts.txt'
	echo $public_ip $1 >> 'etc_hosts.txt'

for i in $(eval echo "{1..$CLUSTER_SIZE}"); do record_ip $CLUSTER_NAME$i; done

cat etc_hosts.txt


Then, execute the script


Alternatively, I put the script on github, so you can also do curl, pipe, bash.

bash <(curl -s https://raw.github.com/sacharya/hadoop-101/master/rax/create-clusters.sh)

The script will wait till all the servers go to an active status and will save the the ips, hostnames and passwords for each of the servers onto these three files.

  • etc_hosts.txt
  • hosts.txt
  • server_passwords.txt