Converting to a class, commenting methods, reading settings from a

config file, and starting to work on the host variables

examples/scripts/ec2.ini

@@ -0,0 +1,37 @@
+# Ansible EC2 external inventory script settings
+#
+
+[ec2]
+
+# When generating inventory, Ansible needs to know how to address a server.
+# Each EC2 instance has a lot of variables associated with it. Here is the list:
+#   http://docs.pythonboto.org/en/latest/ref/ec2.html#module-boto.ec2.instance
+# Below are 2 variables that are used as the address of a server:
+#   - destination_variable
+#   - vpc_destination_variable
+
+# This is the normal destination variable to use. If you are running Ansible
+# from outside EC2, then 'public_dns_name' makes the most sense. If you are
+# running Ansible from within EC2, then perhaps you want to use the internal
+# address, and should set this to 'private_dns_name'.
+destination_variable = public_dns_name
+
+# For server inside a VPC, using DNS names may not make sense. When an instance
+# has 'subnet_id' set, this variable is used. If the subnet is public, setting
+# this to 'ip_address' will return the public IP address. For instances in a
+# private subnet, this should be set to 'private_ip_address', and Ansible must
+# be run from with EC2.
+vpc_destination_variable = ip_address
+
+# API calls to EC2 are slow. For this reason, we cache the results of an API
+# call. Set this to the path you want cache files to be written to. Two files
+# will be written to this directory:
+#   - ansible-ec2.cache
+#   - ansible-ec2.index
+cache_path = /tmp
+
+# The number of seconds a cache file is considered valid. After this many
+# seconds, a new API call will be made, and the cache file will be updated.
+cache_max_age = 300
+
+

examples/scripts/ec2_external_inventory.py

@@ -1,6 +1,6 @@
 #!/usr/bin/python -tt
 
-"""
+'''
 EC2 external inventory script
 =================================
 
@@ -9,13 +9,94 @@ 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
@@ -23,37 +104,88 @@ except ImportError:
     import simplejson as json
 
 
-### Settings
+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)
+        
         
-# I can see other uses where this variable is something else, say if someone
+    def read_settings(self):
-# is running Ansible within EC2, these might be internal IP addresses
+        ''' Reads the settings from the ec2.ini file '''
-destinationVariable = "public_dns_name"
-vpcDestinationVariable = "ip_address"
         
-cachePath = "/tmp/ansible-ec2.cache"
+        config = ConfigParser.SafeConfigParser()
-cacheMaxAge = 300  # seconds
+        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 '''
         
-# 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)')
+                           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='refreshes the cache by making API requests to EC2 (default: False, use cache)')
+                           help='Force refresh of cache by making API requests to EC2 (default: False - use cache files)')
-args = parser.parse_args()
+        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)
         
-# Instance IDs, tags, security groups, regions, availability zones
+        self.write_to_cache(self.inventory, self.cache_path_cache)
-inventory = {}
+        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 '''
         
-def doApiCall(regionInfo):
-    # Loop over all regions
-    region = regionInfo.name
         conn = ec2.connect_to_region(region)
         
-    inventory[region] = []
+        self.inventory[region] = []
         
         reservations = conn.get_all_instances()
         for reservation in reservations:
@@ -63,86 +195,76 @@ def doApiCall(regionInfo):
                 
                 # Select the best destination address
                 if instance.subnet_id:
-                dest = getattr(instance, vpcDestinationVariable)
+                    dest = getattr(instance, self.vpc_destination_variable)
                 else:
-                dest =  getattr(instance, destinationVariable)
+                    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)
-            inventory[instance.id] = [dest]
+                self.inventory[instance.id] = [dest]
                 
                 # Group by region
-            inventory[region].append(dest);
+                self.inventory[region].append(dest);
                                 
                 # Group by availability zone
-            if instance.placement in inventory:
+                if instance.placement in self.inventory:
-                inventory[instance.placement].append(dest);
+                    self.inventory[instance.placement].append(dest);
                 else:
-                inventory[instance.placement] = [dest]
+                    self.inventory[instance.placement] = [dest]
                 
                 # Group by security group
                 for group in instance.groups:
-                key = toSafe("security-group_" + group.name)
+                    key = self.to_safe("security-group_" + group.name)
-                if key in inventory:
+                    if key in self.inventory:
-                    inventory[key].append(dest);
+                        self.inventory[key].append(dest);
                     else:
-                    inventory[key] = [dest]
+                        self.inventory[key] = [dest]
                         
                 # Group by tag keys
                 for k, v in instance.tags.iteritems():
-                key = toSafe("tag_" + k + "=" + v)
+                    key = self.to_safe("tag_" + k + "=" + v)
-                if key in inventory:
+                    if key in self.inventory:
-                    inventory[key].append(dest);
+                        self.inventory[key].append(dest);
                     else:
-                    inventory[key] = [dest]     
+                        self.inventory[key] = [dest]     
                        
-    return formatInventory(True)
+        return self.json_format_dict(self.inventory, True)
     
-def getInventoryFromCache():
+    def get_inventory_from_cache(self):
-    cache = open(cachePath, 'r')
+        cache = open(self.cache_path_cache, 'r')
-    jsonInventory = cache.read()
+        json_inventory = cache.read()
-    return jsonInventory
+        return json_inventory
 
-def getInventoryFromApiUpdateCache():
+    def get_index_from_cache(self):
-    for region in ec2.regions():
+        cache = open(self.cache_path_index, 'r')
-        doApiCall(region)
+        json_index = cache.read()
+        return json_index
     
-    jsonInventory = formatInventory(True)
+    def write_to_cache(self, data, file):
-    cache = open(cachePath, 'w')
+        json_data = self.json_format_dict(data, True)
-    cache.write(jsonInventory)
+        cache = open(file, 'w')
+        cache.write(json_data)
         cache.close()
-    return jsonInventory
         
-def toSafe(word):
+    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 formatInventory(pretty=False):
+    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(inventory, sort_keys=True, indent=2)
+            return json.dumps(data, sort_keys=True, indent=2)
         else:
-        return json.dumps(inventory)
+            return json.dumps(data)
-    
-    
-# Do work here
-if args.refresh_cache:
-    jsonInventory = getInventoryFromApiUpdateCache()
-    
-elif os.path.isfile(cachePath):
-    modTime = os.path.getmtime(cachePath)
-    currentTime = time()
-    if (modTime + cacheMaxAge) > currentTime:
-        # Use cache
-        jsonInventory = getInventoryFromCache()
-    else:
-        jsonInventory = getInventoryFromApiUpdateCache()
-        
-else:
-    jsonInventory = getInventoryFromApiUpdateCache()
-    
-
         
-print jsonInventory
     
+# Run the script
+Ec2Inventory()