Admin: /* Managing a dynamic inventory file using Vagrant boxes */

2018-12-10T03:04:46Z

Managing a dynamic inventory file using Vagrant boxes

← Older revision		Revision as of 03:04, 10 December 2018
Line 10:		Line 10:
	[[Ansible/Vagrant/Dynamic Inventory]] - dynamic inventory uses something like an API or a database to obtain information about the machines that Ansible is managing. This makes scaling and generalization much easier.		[[Ansible/Vagrant/Dynamic Inventory]] - dynamic inventory uses something like an API or a database to obtain information about the machines that Ansible is managing. This makes scaling and generalization much easier.

	==Managing a dynamic inventory file ~~using~~ Vagrant boxes==		==Managing a dynamic inventory file for Vagrant boxes==

	The following script is a dynamic inventory script run by Ansible. This example script is written in Python. It takes two input arguments, <code>--host=X</code> and <code>--list</code>, and interacts with Vagrant to return the requested information about the managed hosts to Ansible.		The following script is a dynamic inventory script run by Ansible. This example script is written in Python. It takes two input arguments, <code>--host=X</code> and <code>--list</code>, and interacts with Vagrant to return the requested information about the managed hosts to Ansible.
Line 150:		Line 150:
	ansible -i dynamic_vagrant.py -u ubuntu myvagrantbox -m ping		ansible -i dynamic_vagrant.py -u ubuntu myvagrantbox -m ping
	</pre>		</pre>



	=Flag=		=Flag=

	{{AnsibleFlag}}		{{AnsibleFlag}}

Admin at 22:57, 14 November 2018

2018-11-14T22:57:16Z

← Older revision		Revision as of 22:57, 14 November 2018
Line 150:		Line 150:
	ansible -i dynamic_vagrant.py -u ubuntu myvagrantbox -m ping		ansible -i dynamic_vagrant.py -u ubuntu myvagrantbox -m ping
	</pre>		</pre>



			=Flag=

			{{AnsibleFlag}}

Admin: Created page with "{{Main|Ansible/Vagrant}} This page covers how to manage a dynamic inventory file when using Vagrant boxes. This avoids the need to edit a hosts file by hand. ==Static vs dy..."

2018-11-11T01:43:25Z

Created page with "{{Main|Ansible/Vagrant}} This page covers how to manage a dynamic inventory file when using Vagrant boxes. This avoids the need to edit a hosts file by hand. ==Static vs dy..."

New page

{{Main|Ansible/Vagrant}}

This page covers how to manage a dynamic inventory file when using Vagrant boxes. This avoids the need to edit a hosts file by hand.

==Static vs dynamic inventory==

[[Ansible/Vagrant/Static Inventory]] - static inventory requires the hosts file (containing the list of machines that Ansible is managing) be kept up to date by hand. This can be a burden if details are changing or if things are allocated automatically.

[[Ansible/Vagrant/Dynamic Inventory]] - dynamic inventory uses something like an API or a database to obtain information about the machines that Ansible is managing. This makes scaling and generalization much easier.

==Managing a dynamic inventory file using Vagrant boxes==

The following script is a dynamic inventory script run by Ansible. This example script is written in Python. It takes two input arguments, <code>--host=X</code> and <code>--list</code>, and interacts with Vagrant to return the requested information about the managed hosts to Ansible.

===Getting List of Hosts===

Start with how to get a list of hosts for the <code>--list</code> flag.

Vagrant provides a command to show info about all running vagrant machines:

<pre>
vagrant status
</pre>

This info can be used to create the list of hosts for the dynamic inventory file. A more convenient format for parsing is:

<pre>
vagrant status --machine-readable
</pre>

which prints everything in CSV format. The code:

<pre>

def list_running_hosts():
cmd = "vagrant status --machine-readable"
status = subprocess.check_output(cmd.split()).rstrip().decode('utf-8')
hosts = []
for line in status.split('\n'):
(_, host, key, value) = line.split(',')[:4]
if key == 'state' and value == 'running':
hosts.append(host)
return hosts
</pre>

===Getting Machine Configuration Details===

Now we need to get host-specific details for the <code>--host=X</code> flag.

Next we can use the <code>vagrant ssh-config</code> command to get info about the machine-specific configuration details of each machine, which is necessary for Ansible to connect to them. To parse SSH config files, we can use a Python library called pamiko.

<pre>
def get_host_details(host):
cmd = "vagrant ssh-config {}".format(host)
p = subprocess.Popen(cmd.split(), stdout=subprocess.PIPE)
config = paramiko.SSHConfig()
config.parse(p.stdout)
c = config.lookup(host)
return {'ansible_host': c['hostname'],
'ansible_port': c['port'],
'ansible_user': c['user'],
'ansible_private_key_file': c['identityfile'][0]}
</pre>

===Parsing user arguments===

A quick argparser tutorial for the flags we're interested in parsing:

<pre>
def parse_args():
parser = argparse.ArgumentParser(description="Vagrant inventory script")
group = parser.add_mutually_exclusive_group(required=True)
group.add_argument('--list', action='store_true')
group.add_argument('--host')
return parser.parse_args()
</pre>

Now we can call this function and use args.list or args.host to access the values of the flags.

===Putting it all together===

Here is the final dynamic inventory script:

(In the ansible repo under contrib/inventory: https://github.com/ansible/ansible/tree/devel/contrib/inventory)

'''dynamic_vagrant.py''':

<pre>
#!/usr/bin/env python
# Adapted from Mark Mandel's implementation
# https://github.com/ansible/ansible/blob/stable-2.1/contrib/inventory/vagrant.py
# License: GNU General Public License, Version 3 <http://www.gnu.org/licenses/>
import argparse
import json
import paramiko
import subprocess
import sys

def parse_args():
parser = argparse.ArgumentParser(description="Vagrant inventory script")
group = parser.add_mutually_exclusive_group(required=True)
group.add_argument('--list', action='store_true')
group.add_argument('--host')
return parser.parse_args()

def list_running_hosts():
cmd = "vagrant status --machine-readable"
status = subprocess.check_output(cmd.split()).rstrip().decode('utf-8')
hosts = []
for line in status.split('\n'):
(_, host, key, value) = line.split(',')[:4]
if key == 'state' and value == 'running':
hosts.append(host)
return hosts

def get_host_details(host):
cmd = "vagrant ssh-config {}".format(host)
p = subprocess.Popen(cmd.split(), stdout=subprocess.PIPE)
config = paramiko.SSHConfig()
config.parse(p.stdout)
c = config.lookup(host)
return {'ansible_host': c['hostname'],
'ansible_port': c['port'],
'ansible_user': c['user'],
'ansible_private_key_file': c['identityfile'][0]}

def main():
args = parse_args()
if args.list:
hosts = list_running_hosts()
json.dump({'vagrant': hosts}, sys.stdout)
else:
details = get_host_details(args.host)
json.dump(details, sys.stdout)

if __name__ == '__main__':
main()
</pre>

===Running the dynamic inventory script===

Once we've written the dynamic inventory script and we're ready to run Ansible using it, we can pass the inventory script using the -i flag:

<pre>
ansible -i dynamic_vagrant.py -u ubuntu myvagrantbox -m ping
</pre>

Ansible/Vagrant/Dynamic Inventory - Revision history

Admin: /* Managing a dynamic inventory file using Vagrant boxes */

Admin at 22:57, 14 November 2018

Admin: Created page with "{{Main|Ansible/Vagrant}} This page covers how to manage a dynamic inventory file when using Vagrant boxes. This avoids the need to edit a hosts file by hand. ==Static vs dy..."