Add RDS cluster info to EC2 dynamic inventory

Add db_clusters to the ec2 inventory. Show tags. Only show clusters
matching tags in the `.ini`. Set `include_rds_clusters = True` option to
enable RDS cluster inventory collection.

Example inventory output:

```
{
  "db_clusters": {
    "ryansb-cluster-test": {
      "AllocatedStorage": 1,
      "AvailabilityZones": [
        "us-west-2a",
        "us-west-2b",
        "us-west-2c"
      ],
      "BackupRetentionPeriod": 1,
      "DBClusterIdentifier": "ryansb-cluster-test",
      "DBClusterMembers": [
        {
          "DBClusterParameterGroupStatus": "in-sync",
          "DBInstanceIdentifier": "ryansb-test",
          "IsClusterWriter": true,
          "PromotionTier": 1
        },
        {
          "DBClusterParameterGroupStatus": "in-sync",
          "DBInstanceIdentifier": "ryansb-test-us-west-2b",
          "IsClusterWriter": false,
          "PromotionTier": 1
        }
      ],
      "DBClusterParameterGroup": "default.aurora5.6",
      "DBSubnetGroup": "default",
      "DatabaseName": "mydb",
      "DbClusterResourceId": "cluster-OB6H7JQURFKFD4BYNHG5HSRLBA",
      "Endpoint": "ryansb-cluster-test.cluster-c9ntgaejgqln.us-west-2.rds.amazonaws.com",
      "Engine": "aurora",
      "EngineVersion": "5.6.10a",
      "MasterUsername": "admin",
      "Port": 3306,
      "PreferredBackupWindow": "06:09-06:39",
      "PreferredMaintenanceWindow": "mon:11:22-mon:11:52",
      "ReadReplicaIdentifiers": [],
      "Status": "available",
      "StorageEncrypted": false,
      "VpcSecurityGroups": [
        {
          "Status": "active",
          "VpcSecurityGroupId": "sg-47eaea20"
        }
      ]
    }
  },
  "rds": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "rds_aurora": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "rds_parameter_group_default_aurora5_6": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "ryansb-test": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "ryansb-test-us-west-2b": [
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "type_db_r3_large": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "us-west-2": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "us-west-2a": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "us-west-2b": [
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ],
  "vpc_id_vpc_3ca34459": [
    "ryansb_test_c9ntgaejgqln_us_west_2_rds_amazonaws_com",
    "ryansb_test_us_west_2b_c9ntgaejgqln_us_west_2_rds_amazonaws_com"
  ]
}
```

2 files changed, 61 insertions, 0 deletions

diff --git a/contrib/inventory/ec2.ini b/contrib/inventory/ec2.ini
index de6d2d912b..984251cb2d 100644
--- a/contrib/inventory/ec2.ini
+++ b/contrib/inventory/ec2.ini
@@ -82,6 +82,9 @@ all_instances = False
 # 'all_rds_instances' to True return all RDS instances regardless of state.
 all_rds_instances = False
 
+# Include RDS cluster information (Aurora etc.)
+include_rds_clusters = True
+
 # By default, only ElastiCache clusters and nodes in the 'available' state
 # are returned. Set 'all_elasticache_clusters' and/or 'all_elastic_nodes'
 # to True return all ElastiCache clusters and nodes, regardless of state.
diff --git a/contrib/inventory/ec2.py b/contrib/inventory/ec2.py
index 9c565fdf79..c0cddca088 100755
--- a/contrib/inventory/ec2.py
+++ b/contrib/inventory/ec2.py
@@ -130,6 +130,7 @@ from boto import rds
 from boto import elasticache
 from boto import route53
 import six
+import boto3
 
 from six.moves import configparser
 from collections import defaultdict
@@ -265,6 +266,12 @@ class Ec2Inventory(object):
         if config.has_option('ec2', 'rds'):
             self.rds_enabled = config.getboolean('ec2', 'rds')
 
+        # Include RDS cluster instances?
+        if config.has_option('ec2', 'include_rds_clusters'):
+            self.include_rds_clusters = config.getboolean('ec2', 'include_rds_clusters')
+        else:
+            self.include_rds_clusters = False
+
         # Include ElastiCache instances?
         self.elasticache_enabled = True
         if config.has_option('ec2', 'elasticache'):
@@ -474,6 +481,8 @@ class Ec2Inventory(object):
             if self.elasticache_enabled:
                 self.get_elasticache_clusters_by_region(region)
                 self.get_elasticache_replication_groups_by_region(region)
+            if self.include_rds_clusters:
+                self.include_rds_clusters_by_region(region)
 
         self.write_to_cache(self.inventory, self.cache_path_cache)
         self.write_to_cache(self.index, self.cache_path_index)
@@ -574,6 +583,55 @@ class Ec2Inventory(object):
                 error = "Looks like AWS RDS is down:\n%s" % e.message
             self.fail_with_error(error, 'getting RDS instances')
 
+    def include_rds_clusters_by_region(self, region):
+        client = boto3.client('rds', region_name=region)
+        clusters = client.describe_db_clusters()["DBClusters"]
+        account_id = boto.connect_iam().get_user().arn.split(':')[4]
+        c_dict = {}
+        for c in clusters:
+            # remove these datetime objects as there is no serialisation to json
+            # currently in place and we don't need the data yet
+            if 'EarliestRestorableTime' in c:
+                del c['EarliestRestorableTime']
+            if 'LatestRestorableTime' in c:
+                del c['LatestRestorableTime']
+
+            if self.ec2_instance_filters == {}:
+                matches_filter = True
+            else:
+                matches_filter = False
+
+            try:
+                # arn:aws:rds:<region>:<account number>:<resourcetype>:<name>
+                tags = client.list_tags_for_resource(
+                    ResourceName='arn:aws:rds:' + region + ':' + account_id + ':cluster:' + c['DBClusterIdentifier'])
+                c['Tags'] = tags['TagList']
+
+                if self.ec2_instance_filters:
+                    for filter_key, filter_values in self.ec2_instance_filters.items():
+                        # get AWS tag key e.g. tag:env will be 'env'
+                        tag_name = filter_key.split(":", 1)[1]
+                        # Filter values is a list (if you put multiple values for the same tag name)
+                        matches_filter = any(d['Key'] == tag_name and d['Value'] in filter_values for d in c['Tags'])
+
+                        if matches_filter:
+                            # it matches a filter, so stop looking for further matches
+                            break
+
+            except Exception as e:
+                if e.message.find('DBInstanceNotFound') >= 0:
+                    # AWS RDS bug (2016-01-06) means deletion does not fully complete and leave an 'empty' cluster.
+                    # Ignore errors when trying to find tags for these
+                    pass
+
+            # ignore empty clusters caused by AWS bug
+            if len(c['DBClusterMembers']) == 0:
+                continue
+            elif matches_filter:
+                c_dict[c['DBClusterIdentifier']] = c
+
+        self.inventory['db_clusters'] = c_dict
+
     def get_elasticache_clusters_by_region(self, region):
         ''' Makes an AWS API call to the list of ElastiCache clusters (with
         nodes' info) in a particular region.'''