Put nat_gateways into UserData if instance runs without public ip in …

…DMZ (#477)

We have a use-case when we want to run instances in DMZ or public subnet
but without public ips. Elastic ip would be assigned later to one of the
instances.
Without public ip instance will not be able to initialize (download
docker, push logs, use AWS api, etc...). To solve this problem taupage
will create separate routing table for outgoing https requests and use a
custom nat gateway for that.

senza/components/taupage_auto_scaling_group.py

@@ -1,3 +1,4 @@
+import boto3
 import json
 import re
 import sys
@@ -139,11 +140,28 @@ def component_taupage_auto_scaling_group(definition, configuration, args, info,
     if not force and docker_image.registry:
         check_docker_image_exists(docker_image)
 
-    userdata = generate_user_data(taupage_config, args.region)
-
     config_name = configuration["Name"] + "Config"
-    ensure_keys(definition, "Resources", config_name, "Properties", "UserData")
-    definition["Resources"][config_name]["Properties"]["UserData"]["Fn::Base64"] = userdata
+    ensure_keys(definition, "Resources", config_name, "Properties")
+    properties = definition["Resources"][config_name]["Properties"]
+
+    mappings = definition.get('Mappings', {})
+    server_subnets = set(mappings.get('ServerSubnets', {}).get(args.region, {}).get('Subnets', []))
+
+    # in dmz or public subnet but without public ip
+    if server_subnets and not properties.get('AssociatePublicIpAddress') and server_subnets ==\
+            set(mappings.get('LoadBalancerInternalSubnets', {}).get(args.region, {}).get('Subnets', [])):
+        # we need to extend taupage_config with the mapping subnet-id => net ip
+        nat_gateways = {}
+        ec2 = boto3.client('ec2', args.region)
+        for nat_gateway in ec2.describe_nat_gateways()['NatGateways']:
+            if nat_gateway['SubnetId'] in server_subnets:
+                for address in nat_gateway['NatGatewayAddresses']:
+                    nat_gateways[nat_gateway['SubnetId']] = address['PrivateIp']
+                    break
+        if nat_gateways:
+            taupage_config['nat_gateways'] = nat_gateways
+
+    properties["UserData"] = {"Fn::Base64": generate_user_data(taupage_config, args.region)}
 
     return definition