Allow a list of subnet IDs for AWS label

Allow configuring a list of subnet IDs for an AWS provider label instead
of just a single one. With this change we can avoid the need to create
multiple providers that only differ on the subnet. In addition we allow
the AWS fleet service to make better decisions when all possible subnets
are included.

For AWS fleet requests we will provide launcht template overrides for
each subnet. For normal run-instance requests - which only support
requests with a single subnet - we will select a random subnet id from
the list.

Change-Id: Ib6700c54920981271daad944a642741ed6187811

tests/fixtures/layouts/aws/spot.yaml

@@ -68,7 +68,7 @@
     region: us-east-1
     az: us-east-1b
     security-group-id: testgroup
-    subnet-id: {subnet_id}
+    subnet-ids: {subnet_ids}
     public-ipv6: True
     userdata: testuserdata
     iam-instance-profile:

tests/unit/test_aws_driver.py

@@ -15,6 +15,7 @@
 import base64
 import concurrent.futures
 import contextlib
+import ipaddress
 import time
 from unittest import mock
 import urllib.parse
@@ -39,6 +40,12 @@ from tests.unit.test_launcher import ImageMocksFixture
 from tests.unit.test_cloud_driver import BaseCloudDriverTest
 
 
+def _make_ipv6_subnets(cidr_block):
+    network = ipaddress.IPv6Network(cidr_block)
+    # AWS only supports /64 prefix length
+    return [str(sn) for sn in network.subnets(new_prefix=64)]
+
+
 class TestAwsDriver(BaseCloudDriverTest):
     config_file = 'zuul-connections-nodepool.conf'
     cloud_test_image_format = 'raw'
@@ -95,6 +102,7 @@ class TestAwsDriver(BaseCloudDriverTest):
         self.register_image_calls = []
 
         # TEST-NET-3
+        self.subnet_ids = []
         ipv6 = False
         if ipv6:
             # This is currently unused, but if moto gains IPv6 support
@@ -104,17 +112,32 @@ class TestAwsDriver(BaseCloudDriverTest):
                 AmazonProvidedIpv6CidrBlock=True)
             ipv6_cidr = self.vpc['Vpc'][
                 'Ipv6CidrBlockAssociationSet'][0]['Ipv6CidrBlock']
-            ipv6_cidr = ipv6_cidr.split('/')[0] + '/64'
-            self.subnet = self.ec2_client.create_subnet(
-                CidrBlock='203.0.113.128/25',
-                Ipv6CidrBlock=ipv6_cidr,
+            ipv6_subnets = _make_ipv6_subnets(ipv6_cidr)
+
+            subnet1 = self.ec2_client.create_subnet(
+                AvailabilityZone='us-east-1a',
+                CidrBlock='203.0.113.64/26',
+                Ipv6CidrBlock=ipv6_subnets[0],
                 VpcId=self.vpc['Vpc']['VpcId'])
-            self.subnet_id = self.subnet['Subnet']['SubnetId']
+            self.subnet_ids.append(subnet1['Subnet']['SubnetId'])
+            subnet2 = self.ec2_client.create_subnet(
+                AvailabilityZone='us-east-1b',
+                CidrBlock='203.0.113.128/26',
+                Ipv6CidrBlock=ipv6_subnets[1],
+                VpcId=self.vpc['Vpc']['VpcId'])
+            self.subnet_ids.append(subnet2['Subnet']['SubnetId'])
         else:
             self.vpc = self.ec2_client.create_vpc(CidrBlock='203.0.113.0/24')
-            self.subnet = self.ec2_client.create_subnet(
-                CidrBlock='203.0.113.128/25', VpcId=self.vpc['Vpc']['VpcId'])
-            self.subnet_id = self.subnet['Subnet']['SubnetId']
+            subnet1 = self.ec2_client.create_subnet(
+                AvailabilityZone='us-east-1a',
+                CidrBlock='203.0.113.64/26',
+                VpcId=self.vpc['Vpc']['VpcId'])
+            self.subnet_ids.append(subnet1['Subnet']['SubnetId'])
+            subnet2 = self.ec2_client.create_subnet(
+                AvailabilityZone='us-east-1b',
+                CidrBlock='203.0.113.128/26',
+                VpcId=self.vpc['Vpc']['VpcId'])
+            self.subnet_ids.append(subnet2['Subnet']['SubnetId'])
 
         self.security_group = self.ec2_client.create_security_group(
             GroupName='zuul-nodes', VpcId=self.vpc['Vpc']['VpcId'],
@@ -201,7 +224,7 @@ class TestAwsDriver(BaseCloudDriverTest):
 
     @simple_layout('layouts/aws/spot.yaml', enable_nodepool=True,
                    replace=lambda test: {
-                       'subnet_id': test.subnet_id,
+                       'subnet_ids': test.subnet_ids,
                        'iam_profile_name': test.profile.name,
                    })
     @driver_config('aws', node_checks=check_spot_node_attrs)
@@ -238,7 +261,7 @@ class TestAwsDriver(BaseCloudDriverTest):
         self.commitConfigUpdate(
             'org/common-config', 'layouts/aws/spot.yaml',
             replace=lambda test: {
-                'subnet_id': test.subnet_id,
+                'subnet_ids': test.subnet_ids,
                 'iam_profile_name': test.profile.name,
             })
 

zuul/driver/aws/awsendpoint.py

@@ -23,6 +23,7 @@ import json
 import logging
 import math
 import queue
+import random
 import re
 import threading
 import time
@@ -1569,13 +1570,20 @@ class AwsProviderEndpoint(BaseProviderEndpoint):
                     },
                 ],
             }
-            if label.subnet_id:
-                override_dict['SubnetId'] = label.subnet_id
             if flavor.fleet['allocation-strategy'] in [
                 'prioritized', 'capacity-optimized-prioritized']:
                 override_dict['Priority'] = priority
                 priority += 1
-            overrides.append(override_dict)
+
+            # Duplicate overrides for each subnet
+            if label.subnet_ids:
+                for subnet_id in label.subnet_ids:
+                    overrides.append(dict(
+                        **override_dict,
+                        SubnetId=subnet_id,
+                    ))
+            else:
+                overrides.append(override_dict)
 
         if flavor.market_type == 'spot':
             capacity_type_option = {
@@ -1678,8 +1686,9 @@ class AwsProviderEndpoint(BaseProviderEndpoint):
                 label.security_group_id
             ]
 
-        if label.subnet_id:
-            args['NetworkInterfaces'][0]['SubnetId'] = label.subnet_id
+        if label.subnet_ids:
+            args['NetworkInterfaces'][0]['SubnetId'] = random.choice(
+                label.subnet_ids)
 
         if flavor.public_ipv6:
             args['NetworkInterfaces'][0]['Ipv6AddressCount'] = 1

zuul/driver/aws/awsprovider.py

@@ -172,7 +172,7 @@ class AwsProviderLabel(BaseProviderLabel):
         # TODO: aws accepts a list everywhere we use this; should this
         # be as_list?
         Optional('security-group-id'): Nullable(str),
-        Optional('subnet-id'): Nullable(str),
+        Optional('subnet-ids', default=[]): [str],  # TODO: as_list?
         Optional('iam-instance-profile'): Nullable(aws_iam_schema),
     })