ansible/examples/scripts/ec2_external_inventory.py

#!/usr/bin/python -tt

'''
EC2 external inventory script
=================================

NOTE: This script assumes Ansible is being executed where the environment
variables needed for Boto have been set:
    export AWS_ACCESS_KEY_ID=''
    export AWS_SECRET_ACCESS_KEY=''
For more details, see: http://docs.pythonboto.org/en/latest/boto_config_tut.html




mdehaan
1:14 I'd break the get_instances_by_region function up so it calls a few smaller functions

1:18 each function having a comment is a good thing

1:19 parser script needs to support taking a hostname to get the variables, right?
1:22 pas256: read the source to the cobbler inventory script
1:22 it has two modes... list all my groups
1:22 and another is for this given host, what variables do I use
mdehaan
1:23 if you are not actually generating the file, and are using it as a param to -i, it will need to do both
mdehaan
1:23 API is not as friendly as YAML or JSON, but it is ok
1:23 I will not do YAML config files again if I can help it
pas256
1:26 Ooo I missed that functionality so `script --list hostname` returns just a JSON object with whatever variables that host has
1:26 very cool
1:26 I can add that
mdehaan
1:26 no
1:26 script --list is one way it is executed
1:26 script --host <hostname>, is the other, I believe
pas256
1:26 o ok
mdehaan
1:27 looks like the cobbler one needs fixing up
1:27 pilt [~pilt@h-60-43.a163.priv.bahnhof.se] entered the room.
mdehaan
1:27 sorry about that, clear no one is using it
pas256
1:27 the cobbler script doesn't care what the first arg is, only the count
1:27 lol yeah
mdehaan
1:27 I really kinda like the idea of just generating the inventory file
1:27 maybe it should just do that
1:27 faster, no need to cache
1:27 plus it's a nice record of exactly what it will use
pas256
1:27 but with EC2, it is always changing
1:28 at least for us it is
mdehaan
1:28 https://github.com/ansible/ansible/issues/560
mdehaan
1:29 pas256: yeah, true
mdehaan
1:29 either way
1:29 pilt left the room (quit: Client Quit).
mdehaan
1:29 you could still run it if you wanted to look
pas256
1:30 yep
mdehaan
1:31 so assuming there is a metadata way to get variables out of EC2 you could store them with the host
1:31 and let ansible see all of them or some of them
pas256
1:32 yeah the instance object has a lot of data in it, I am only grouping by what makes sense to group by
mdehaan
1:33 can you define your own namespaces for variables?   Maybe there could be an ansible one...
1:33 though there shouldn't be a lot of host specific variables really
1:33 group specific variables are nice to support though
1:33 I can see use in that
pas256
1:33 ec2_ everything?
mdehaan
1:33 webservers get fooserver=xyz.example.com
1:33 you need some way of doing stuff like that
1:34 I don't know EC2's API at all
1:34 or EC2, really
pas256
1:34 AWS in general is pretty sweet there is a lot to it
mdehaan
1:35 yeah, seems like you could spend a long time learning all their various services
1:35 it's kind of a specialization in itself
pas256
1:35 agreed

'''

import os
import argparse
import re
from time import time
from boto import ec2
import ConfigParser

try:
    import json
except ImportError:
    import simplejson as json


class Ec2Inventory(object):
    def __init__(self):
        ''' Main execution path '''
        
        # Inventory grouped by instance IDs, tags, security groups, regions,
        # and availability zones
        self.inventory = {}
        
        # Index of hostname (address) to instance ID
        self.index = {}
        
        # Read settings and parse CLI arguments
        self.read_settings()
        self.parse_cli_args()
        
        # Force cache refresh?
        if self.args.refresh_cache:
            json_inventory = self.do_api_calls_update_cache()
            
        # 
        if self.args.host:
            print self.args.host
            
        elif os.path.isfile(self.cache_path_cache):
            mod_time = os.path.getmtime(self.cache_path_cache)
            current_time = time()
            if (mod_time + self.cache_max_age) > current_time:
                # Use cache
                json_inventory = self.get_inventory_from_cache()
            else:
                json_inventory = self.do_api_calls_update_cache()
                
        else:
            json_inventory = self.do_api_calls_update_cache()
            
        
        print json_inventory
        print self.json_format_dict(self.index, True)
        
        
    def read_settings(self):
        ''' Reads the settings from the ec2.ini file '''
        
        config = ConfigParser.SafeConfigParser()
        config.read('ec2.ini')
        self.destination_variable = config.get('ec2', 'destination_variable')
        self.vpc_destination_variable = config.get('ec2', 'vpc_destination_variable')
        cache_path = config.get('ec2', 'cache_path')
        self.cache_max_age = config.getint('ec2', 'cache_max_age')
        
        self.cache_path_cache = cache_path + "/ansible-ec2.cache"
        self.cache_path_index = cache_path + "/ansible-ec2.index"
        
    def parse_cli_args(self):
        ''' Command line argument processing '''
        
        parser = argparse.ArgumentParser(description='Produce an Ansible Inventory file based on EC2')
        parser.add_argument('--list', action='store_true', default=True, 
                           help='List instances (default: True)')
        parser.add_argument('--host', action='store', 
                           help='Get all the variables about a specific instance')
        parser.add_argument('--refresh-cache', action='store_true', default=False, 
                           help='Force refresh of cache by making API requests to EC2 (default: False - use cache files)')
        self.args = parser.parse_args()
        
    def do_api_calls_update_cache(self):
        ''' Do API calls to each region, and save data in cache files '''
        
        for regionInfo in ec2.regions():
            region = regionInfo.name
            self.get_instances_by_region(region)
        
        self.write_to_cache(self.inventory, self.cache_path_cache)
        self.write_to_cache(self.index, self.cache_path_index)

    def get_instances_by_region(self, region):
        ''' Makes an AWS EC2 API call to the list of instances in a particular
        region '''
        
        conn = ec2.connect_to_region(region)
        
        self.inventory[region] = []
        
        reservations = conn.get_all_instances()
        for reservation in reservations:
            for instance in reservation.instances:
                if instance.state == 'terminated':
                    continue
                
                # Select the best destination address
                if instance.subnet_id:
                    dest = getattr(instance, self.vpc_destination_variable)
                else:
                    dest =  getattr(instance, self.destination_variable)
        
                if dest == None:
                    # Skip instances we cannot address (e.g. VPC private subnet)
                    continue
        
                # Add to index
                self.index[dest] = [region, instance.id]
        
                # Group by instance ID (always a group of 1)
                self.inventory[instance.id] = [dest]
                
                # Group by region
                self.inventory[region].append(dest);
                                
                # Group by availability zone
                if instance.placement in self.inventory:
                    self.inventory[instance.placement].append(dest);
                else:
                    self.inventory[instance.placement] = [dest]
                
                # Group by security group
                for group in instance.groups:
                    key = self.to_safe("security-group_" + group.name)
                    if key in self.inventory:
                        self.inventory[key].append(dest);
                    else:
                        self.inventory[key] = [dest]
                        
                # Group by tag keys
                for k, v in instance.tags.iteritems():
                    key = self.to_safe("tag_" + k + "=" + v)
                    if key in self.inventory:
                        self.inventory[key].append(dest);
                    else:
                        self.inventory[key] = [dest]     
                       
        return self.json_format_dict(self.inventory, True)
    
    def get_inventory_from_cache(self):
        cache = open(self.cache_path_cache, 'r')
        json_inventory = cache.read()
        return json_inventory

    def get_index_from_cache(self):
        cache = open(self.cache_path_index, 'r')
        json_index = cache.read()
        return json_index
    
    def write_to_cache(self, data, file):
        json_data = self.json_format_dict(data, True)
        cache = open(file, 'w')
        cache.write(json_data)
        cache.close()
        
    def to_safe(self, word):
        '''Converts 'bad' characters in a string to underscores so they can be
        used as Ansible groups'''
        return re.sub("[^A-Za-z0-9\-]", "_", word)
        
    def json_format_dict(self, data, pretty=False):
        '''Converts a dict to a JSON object and dumps it as a formatted
        string'''
        if pretty:
            return json.dumps(data, sort_keys=True, indent=2)
        else:
            return json.dumps(data)
        
    
# Run the script
Ec2Inventory()