feat: add ALB IP address lookup by availability zone

Add new ELB module with alb_addresses method to retrieve ALB IP addresses
grouped by availability zone. Supports querying ALBs by name with optional
region override.

Author: mnutt

Gemfile.lock

@@ -9,6 +9,7 @@ PATH
       aws-sdk-ec2 (~> 1)
       aws-sdk-eks (~> 1)
       aws-sdk-elasticache (~> 1)
+      aws-sdk-elasticloadbalancingv2 (~> 1)
       aws-sdk-iam (~> 1)
       aws-sdk-lambda (~> 1)
       aws-sdk-rds (~> 1)
@@ -53,6 +54,9 @@ GEM
     aws-sdk-elasticache (1.128.0)
       aws-sdk-core (~> 3, >= 3.225.0)
       aws-sigv4 (~> 1.5)
+    aws-sdk-elasticloadbalancingv2 (1.134.0)
+      aws-sdk-core (~> 3, >= 3.225.0)
+      aws-sigv4 (~> 1.5)
     aws-sdk-iam (1.124.0)
       aws-sdk-core (~> 3, >= 3.225.0)
       aws-sigv4 (~> 1.5)

MovableInkAWS.gemspec

@@ -18,6 +18,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'aws-sdk-ec2', '~> 1'
   s.add_runtime_dependency 'aws-sdk-eks', '~> 1'
   s.add_runtime_dependency 'aws-sdk-elasticache', '~> 1'
+  s.add_runtime_dependency 'aws-sdk-elasticloadbalancingv2', '~> 1'
   s.add_runtime_dependency 'aws-sdk-iam', '~> 1'
   s.add_runtime_dependency 'aws-sdk-lambda', '~> 1'
   s.add_runtime_dependency 'aws-sdk-rds', '~> 1'

lib/movable_ink/aws.rb

@@ -9,6 +9,7 @@
 require_relative 'aws/s3'
 require_relative 'aws/iam'
 require_relative 'aws/eks'
+require_relative 'aws/elb'
 require_relative 'aws/elasticache'
 require_relative 'aws/api_gateway'
 require_relative 'aws/lambda'
@@ -26,6 +27,7 @@ class AWS
     include Athena
     include S3
     include ElastiCache
+    include ELB
     include ApiGateway
     include EKS
     include IAM
@@ -96,7 +98,9 @@ def run_with_backoff(quiet: false, tries: 9, expected_errors: [])
                MovableInk::AWS::Errors::NoEnvironmentTagError,
                Aws::IAM::Errors::LimitExceededException,
                Aws::IAM::Errors::RequestLimitExceeded,
-               Aws::IAM::Errors::Throttling
+               Aws::IAM::Errors::Throttling,
+               Aws::ElasticLoadBalancingV2::Errors::Throttling,
+               Aws::ElasticLoadBalancingV2::Errors::ThrottlingException
           sleep_time = (num+1)**2 + rand(10)
           if quiet
             (num >= tries - 1) ? notify_and_sleep(sleep_time, $!.class) : sleep(sleep_time)

lib/movable_ink/aws/elb.rb

@@ -0,0 +1,54 @@
+require 'aws-sdk-elasticloadbalancingv2'
+require 'ostruct'
+
+module MovableInk
+  class AWS
+    module ELB
+      def elbv2(region: my_region, client: nil)
+        @elbv2_client ||= {}
+        @elbv2_client[region] ||= (client) ? client : Aws::ElasticLoadBalancingV2::Client.new(region: region)
+      end
+
+      def elbv2_with_retries(region: my_region, client: nil)
+        @elbv2_client_with_retries ||= {}
+        if (client)
+          @elbv2_client_with_retries[region] ||= client
+        else
+          instance_credentials = Aws::InstanceProfileCredentials.new(retries: 5, disable_imds_v1: true)
+          @elbv2_client_with_retries[region] ||= Aws::ElasticLoadBalancingV2::Client.new(region: region, credentials: instance_credentials)
+        end
+      end
+
+      # Get load balancer addresses with their availability zones
+      #
+      # @param name [String] the name of the Application Load Balancer
+      # @param region [String] the AWS region (defaults to my_region)
+      # @return [Array<OpenStruct>] an array of address objects with ip_address and availability_zone properties
+      def alb_addresses(name:, region: my_region)
+        result = run_with_backoff do
+          elbv2_with_retries(region: region).describe_load_balancers(names: [name])
+        end
+
+        load_balancer = result.load_balancers.first
+        raise "Load balancer '#{name}' not found" unless load_balancer
+
+        addresses = []
+
+        load_balancer.availability_zones.each do |az|
+          az.load_balancer_addresses.each do |addr|
+            ip = addr.ip_address || addr.private_ipv4_address
+            next unless ip
+
+            addresses << OpenStruct.new(
+              ip_address: ip,
+              availability_zone: az.zone_name,
+              subnet_id: az.subnet_id
+            )
+          end
+        end
+
+        addresses
+      end
+    end
+  end
+end

spec/elb_spec.rb

@@ -0,0 +1,99 @@
+require_relative '../lib/movable_ink/aws'
+
+describe MovableInk::AWS::ELB do
+  let(:aws) { MovableInk::AWS.new(availability_zone: 'us-east-1a') }
+
+  context 'alb_addresses' do
+    let(:elbv2) { Aws::ElasticLoadBalancingV2::Client.new(stub_responses: true) }
+
+    it "should return ALB IP addresses with availability zones" do
+      lb_data = elbv2.stub_data(:describe_load_balancers, load_balancers: [{
+        load_balancer_name: 'test-alb',
+        load_balancer_arn: 'arn:aws:elasticloadbalancing:us-east-1:123456789012:loadbalancer/app/test-alb/50dc6c495c0c9188',
+        availability_zones: [
+          {
+            zone_name: 'us-east-1a',
+            subnet_id: 'subnet-12345',
+            load_balancer_addresses: [
+              { ip_address: '10.0.1.5' }
+            ]
+          },
+          {
+            zone_name: 'us-east-1b',
+            subnet_id: 'subnet-67890',
+            load_balancer_addresses: [
+              { ip_address: '10.0.2.7' }
+            ]
+          }
+        ]
+      }])
+
+      elbv2.stub_responses(:describe_load_balancers, lb_data)
+      allow(aws).to receive(:elbv2_with_retries).and_return(elbv2)
+
+      addresses = aws.alb_addresses(name: 'test-alb')
+      expect(addresses.count).to eq(2)
+      expect(addresses[0].ip_address).to eq('10.0.1.5')
+      expect(addresses[0].availability_zone).to eq('us-east-1a')
+      expect(addresses[0].subnet_id).to eq('subnet-12345')
+      expect(addresses[1].ip_address).to eq('10.0.2.7')
+      expect(addresses[1].availability_zone).to eq('us-east-1b')
+      expect(addresses[1].subnet_id).to eq('subnet-67890')
+    end
+
+    it "should handle ALBs with no IP addresses" do
+      lb_data = elbv2.stub_data(:describe_load_balancers, load_balancers: [{
+        load_balancer_name: 'test-alb',
+        load_balancer_arn: 'arn:aws:elasticloadbalancing:us-east-1:123456789012:loadbalancer/app/test-alb/50dc6c495c0c9188',
+        availability_zones: [
+          {
+            zone_name: 'us-east-1a',
+            subnet_id: 'subnet-12345',
+            load_balancer_addresses: []
+          }
+        ]
+      }])
+
+      elbv2.stub_responses(:describe_load_balancers, lb_data)
+      allow(aws).to receive(:elbv2_with_retries).and_return(elbv2)
+
+      addresses = aws.alb_addresses(name: 'test-alb')
+      expect(addresses.count).to eq(0)
+    end
+
+    it "should raise error when load balancer not found" do
+      lb_data = elbv2.stub_data(:describe_load_balancers, load_balancers: [])
+
+      elbv2.stub_responses(:describe_load_balancers, lb_data)
+      allow(aws).to receive(:elbv2_with_retries).and_return(elbv2)
+
+      expect { aws.alb_addresses(name: 'nonexistent-alb') }.to raise_error("Load balancer 'nonexistent-alb' not found")
+    end
+
+    it "should support querying ALBs in a different region" do
+      elbv2_west = Aws::ElasticLoadBalancingV2::Client.new(stub_responses: true)
+      lb_data = elbv2_west.stub_data(:describe_load_balancers, load_balancers: [{
+        load_balancer_name: 'west-alb',
+        load_balancer_arn: 'arn:aws:elasticloadbalancing:us-west-2:123456789012:loadbalancer/app/west-alb/50dc6c495c0c9188',
+        availability_zones: [
+          {
+            zone_name: 'us-west-2a',
+            subnet_id: 'subnet-west1',
+            load_balancer_addresses: [
+              { ip_address: '10.1.1.5' }
+            ]
+          }
+        ]
+      }])
+
+      elbv2_west.stub_responses(:describe_load_balancers, lb_data)
+      allow(aws).to receive(:elbv2_with_retries).with(region: 'us-west-2').and_return(elbv2_west)
+
+      addresses = aws.alb_addresses(name: 'west-alb', region: 'us-west-2')
+      expect(addresses.count).to eq(1)
+      expect(addresses[0].ip_address).to eq('10.1.1.5')
+      expect(addresses[0].availability_zone).to eq('us-west-2a')
+      expect(addresses[0].subnet_id).to eq('subnet-west1')
+    end
+  end
+end