Add support for filtering EC2 instances in dynamic inventory

This allows filtering out EC2 instances based on various different
filters including tags. As requested in 7480 it supports logical "OR"
instead of "AND" on the provided list of filters.

plugins/inventory/ec2.ini

@@ -73,3 +73,23 @@ nested_groups = False
 
 # If you want to exclude any hosts that match a certain regular expression
 # pattern_exclude = stage-*
+
+# Instance filters can be used to control which instances are retrieved for
+# inventory. For the full list of possible filters, please read the EC2 API
+# docs: http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-DescribeInstances.html#query-DescribeInstances-filters
+# Filters are key/value pairs separated by '=', to list multiple filters use
+# a list separated by commas. See examples below.
+
+# Retrieve only instances with (key=value) env=stage tag
+# instance_filters = tag:env=stage
+
+# Retrieve only instances with role=webservers OR role=dbservers tag
+# instance_filters = tag:role=webservers,tag:role=dbservers
+
+# Retrieve only t1.micro instances OR instances with tag env=stage
+# instance_filters = instance-type=t1.micro,tag:env=stage
+
+# You can use wildcards in filter values also. Below will list instances which
+# tag Name value matches webservers1*
+# (ex. webservers15, webservers1a, webservers123 etc) 
+# instance_filters = tag:Name=webservers1*

plugins/inventory/ec2.py

@@ -123,6 +123,7 @@ from boto import ec2
 from boto import rds
 from boto import route53
 import ConfigParser
+from collections import defaultdict
 
 try:
     import json
@@ -272,6 +273,13 @@ class Ec2Inventory(object):
         except ConfigParser.NoOptionError, e:
             self.pattern_exclude = None
 
+        # Instance filters (see boto and EC2 API docs)
+        self.ec2_instance_filters = defaultdict(list)
+        if config.has_option('ec2', 'instance_filters'):
+            for x in config.get('ec2', 'instance_filters', '').split(','):
+                filter_key, filter_value = x.split('=')
+                self.ec2_instance_filters[filter_key].append(filter_value)
+
     def parse_cli_args(self):
         ''' Command line argument processing '''
 
@@ -316,7 +324,13 @@ class Ec2Inventory(object):
                 print("region name: %s likely not supported, or AWS is down.  connection to region failed." % region)
                 sys.exit(1)
 
-            reservations = conn.get_all_instances()
+            reservations = []
+            if self.ec2_instance_filters:
+                for filter_key, filter_values in self.ec2_instance_filters.iteritems():
+                    reservations.extend(conn.get_all_instances(filters = { filter_key : filter_values }))
+            else:
+                reservations = conn.get_all_instances()
+
             for reservation in reservations:
                 for instance in reservation.instances:
                     self.add_instance(instance, region)