Fix NVMe raw_instance_storage device enumeration for all instance families

src/bosh_aws_cpi/lib/cloud/aws.rb

@@ -48,6 +48,7 @@ module AwsCloud; end
 require 'cloud/aws/instance_param_mapper'
 require 'cloud/aws/security_group_mapper'
 require 'cloud/aws/block_device_manager'
+require 'cloud/aws/instance_type_info'
 require 'cloud/aws/instance_type_mapper'
 require 'cloud/aws/classic_lb'
 require 'cloud/aws/lb_target_group'

src/bosh_aws_cpi/lib/cloud/aws/block_device_manager.rb

@@ -3,13 +3,10 @@ class BlockDeviceManager
     DEFAULT_INSTANCE_STORAGE_DISK_MAPPING = { device_name: '/dev/sdb', virtual_name: 'ephemeral0' }.freeze
     NVME_EBS_BY_ID_DEVICE_PATH_PREFIX = '/dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_'
 
-    # Newer, nitro-based instances use NVMe storage volumes.
-    # https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instance-types.html#ec2-nitro-instances
-    NVME_INSTANCE_FAMILIES = %w[a1 c5 c5a c5ad c5d c5n c6a c6g c6gd c6gn c6i c6id c6in c7i c7a d3 d3en g4dn g4ad g5 g6 g6e i3en i4i inf1 m5 m5a m5ad m5d m5dn m5n m5zn m6a m6g m6gd m6i m6id m6idn m6in m7i m7a m7i-flex p3dn p4d p5 r5 r5a r5ad r5b r5d r5dn r5n r6a r6g r6gd r6i r6in r6id r6idn r7i r7a r7iz t3 t3a t4g z1d x2iezn].freeze
-
-    def initialize(logger, stemcell, vm_cloud_props)
+    def initialize(logger, stemcell, vm_cloud_props, instance_type_info)
       @logger = logger
       @vm_cloud_props = vm_cloud_props
+      @instance_type_info = instance_type_info
       @virtualization_type = stemcell.ami.virtualization_type
       @root_device_name = stemcell.ami.root_device_name
       @ami_block_device_names = stemcell.ami.block_device_mappings.map { |blk| blk.device_name }
@@ -21,8 +18,8 @@ def mappings_and_info
       return mappings(info), agent_info(info)
     end
 
-    def self.device_path(device_name, instance_type, volume_id)
-      if BlockDeviceManager.requires_nvme_device(instance_type)
+    def self.device_path(device_name, instance_type, volume_id, instance_type_info)
+      if instance_type_info.ebs_requires_nvme_path?(instance_type)
         NVME_EBS_BY_ID_DEVICE_PATH_PREFIX + volume_id.sub('-', '')
       else
         device_name
@@ -49,18 +46,16 @@ def self.block_device_ready?(device_path)
       cloud_error('Cannot find EBS volume on current instance')
     end
 
-    def self.requires_nvme_device(instance_type)
-      instance_type = instance_type.nil? ? 'unspecified' : instance_type
-      instance_family = instance_type.split(".")[0]
-      NVME_INSTANCE_FAMILIES.include?(instance_family)
-    end
-
     private
 
     def mappings(info)
-      instance_type = @vm_cloud_props.instance_type.nil? ? 'unspecified' : @vm_cloud_props.instance_type
-      if instance_type =~ /^i3\./ || instance_type =~ /^i3en\./
-        info = info.reject { |device| device[:bosh_type] == 'raw_ephemeral' }
+      # For NVMe instances with instance storage, AWS auto-attaches the disks,
+      # so we don't include them in the block device mappings
+      if info.any? { |device| device[:bosh_type] == 'raw_ephemeral' }
+        instance_type = @vm_cloud_props.instance_type.nil? ? 'unspecified' : @vm_cloud_props.instance_type
+        if @instance_type_info.instance_storage_nvme_naming?(instance_type)
+          info = info.reject { |device| device[:bosh_type] == 'raw_ephemeral' }
+        end
       end
 
       info.map { |entry| entry.reject { |k| k == :bosh_type } }
@@ -150,34 +145,37 @@ def ephemeral_disk_mapping(instance_type, disk_info)
       result
     end
 
-    def first_raw_ephemeral_device
-      instance_type = @vm_cloud_props.instance_type.nil? ? 'unspecified' : @vm_cloud_props.instance_type
-      case @virtualization_type
-
-        when 'hvm'
-          if instance_type =~ /^i3\./ || instance_type =~ /^i3en\./
-            '/dev/nvme0n1'
-          else
-            '/dev/xvdba'
-          end
-        when 'paravirtual'
-          '/dev/sdc'
-        else
-          raise Bosh::Clouds::CloudError, "unknown virtualization type #{@virtualization_type}"
-      end
-    end
-
     def raw_instance_mappings(num_of_devices)
-      next_device = first_raw_ephemeral_device
-
+      # Device hints for raw ephemeral disks:
+      # - NVMe instances: Agent discovers instance storage at runtime (enumeration order varies)
+      #   by excluding EBS volumes identified via /dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_*
+      #   These device_name hints are informational only - agent ignores them and uses discovery.
+      # - Paravirtual/HVM instances: Agent trusts these device paths (enumeration is deterministic)
+      #
+      # In all cases, the count (num_of_devices) must be correct to trigger setup.
+
+      instance_type = @vm_cloud_props.instance_type || 'unspecified'
+      requires_nvme = @instance_type_info.instance_storage_nvme_naming?(instance_type)
+
       num_of_devices.times.map do |index|
-        result = {
+        {
           virtual_name: "ephemeral#{index}",
-          device_name: next_device,
-          bosh_type: 'raw_ephemeral',
+          device_name: raw_ephemeral_device_name(index, requires_nvme),
+          bosh_type: 'raw_ephemeral'
         }
-        next_device = next_raw_ephemeral_disk(next_device)
-        result
+      end
+    end
+
+    def raw_ephemeral_device_name(index, requires_nvme)
+      if requires_nvme
+        # Simple sequential hints - agent will discover actual devices via EBS symlink exclusion
+        "/dev/nvme#{index}n1"
+      elsif @virtualization_type == 'paravirtual'
+        "/dev/sd#{('c'.ord + index).chr}"
+      elsif @virtualization_type == 'hvm'
+        "/dev/xvdb#{('a'.ord + index).chr}"
+      else
+        raise Bosh::Clouds::CloudError, "unknown virtualization type #{@virtualization_type}"
       end
     end
 
@@ -225,16 +223,6 @@ def root_device_name
       end
     end
 
-    def next_raw_ephemeral_disk(current_disk)
-      if current_disk =~ /^\/dev\/nvme/
-        disk_id = /^\/dev\/nvme(\d+)n.*/.match(current_disk)[1]
-        disk_id = disk_id.next
-        "/dev/nvme#{disk_id}n1"
-      else
-        current_disk.next
-      end
-    end
-
     class DiskInfo
       INSTANCE_TYPE_DISK_MAPPING = {
         # previous generation

src/bosh_aws_cpi/lib/cloud/aws/cloud_core.rb

@@ -10,6 +10,7 @@ class CloudCore
 
     attr_reader :ec2_resource
     attr_reader :logger
+    attr_reader :instance_type_info
 
     ##
     # Initialize BOSH AWS CPI. The contents of sub-hashes are defined in the {file:README.md}
@@ -33,6 +34,7 @@ def initialize(config, logger, volume_manager, az_selector, stemcell_api_version
 
       @instance_manager = InstanceManager.new(@ec2_resource, @logger)
       @instance_type_mapper = InstanceTypeMapper.new
+      @instance_type_info = InstanceTypeInfo.new(@ec2_client, @logger)
 
       @props_factory = Bosh::AwsCloud::PropsFactory.new(@config)
     end
@@ -75,6 +77,7 @@ def create_vm(_agent_id, stemcell_id, vm_type, network_props, settings, disk_loc
           @logger,
           stemcell,
           vm_props,
+          @instance_type_info,
         ).mappings_and_info
 
         settings.agent_disk_info = agent_disk_info

src/bosh_aws_cpi/lib/cloud/aws/cloud_v1.rb

@@ -254,7 +254,7 @@ def attach_disk(instance_id, disk_id)
           update_agent_settings(instance_id) do |settings|
             settings['disks'] ||= {}
             settings['disks']['persistent'] ||= {}
-            settings['disks']['persistent'][disk_id] = BlockDeviceManager.device_path(device_name, instance.instance_type, disk_id)
+            settings['disks']['persistent'][disk_id] = BlockDeviceManager.device_path(device_name, instance.instance_type, disk_id, @cloud_core.instance_type_info)
           end
         end
       end
@@ -480,7 +480,8 @@ def create_ami_for_stemcell(image_path, stemcell_cloud_props)
         expected_path = BlockDeviceManager.device_path(
           requested_path,
           instance.instance_type,
-          volume.id
+          volume.id,
+          @cloud_core.instance_type_info,
         )
 
         logger.debug("Expected block device: #{expected_path}")

src/bosh_aws_cpi/lib/cloud/aws/cloud_v2.rb

@@ -78,7 +78,7 @@ def attach_disk(vm_id, disk_id)
       with_thread_name("attach_disk(#{vm_id}, #{disk_id}):v2") do
         device_path = nil
         @cloud_core.attach_disk(vm_id, disk_id) do |instance, device_name|
-          device_path = BlockDeviceManager.device_path(device_name, instance.instance_type, disk_id)
+          device_path = BlockDeviceManager.device_path(device_name, instance.instance_type, disk_id, @cloud_core.instance_type_info)
           if @stemcell_api_version < 2
             update_agent_settings(vm_id) do |settings|
               settings['disks'] ||= {}

src/bosh_aws_cpi/lib/cloud/aws/instance_type_info.rb

@@ -0,0 +1,74 @@
+module Bosh::AwsCloud
+  # Provides instance type metadata by querying the EC2 DescribeInstanceTypes API.
+  # Results are cached for the lifetime of the CPI process so each instance type
+  # is queried at most once. 
+  class InstanceTypeInfo
+    def initialize(ec2_client, logger)
+      @ec2_client = ec2_client
+      @logger = logger
+      @cache = {}
+    end
+
+    # Returns true if EBS volumes on this instance type are exposed exclusively via
+    # NVMe and must be located using the /dev/disk/by-id/nvme-Amazon_Elastic_Block_Store_*
+    # symlink. This is true only for Nitro instances (nvme_support = 'required').
+    # Xen instances with NVMe instance storage (e.g. i3, nvme_support = 'supported')
+    # still use traditional /dev/xvd* paths for EBS volumes.
+    def ebs_requires_nvme_path?(instance_type)
+      info = fetch(instance_type)
+      return false if info.nil?
+
+      info.ebs_info&.nvme_support == 'required'
+    end
+
+    # Returns true if instance storage (local NVMe SSDs) on this instance type uses
+    # /dev/nvme*n1 device naming. Covers both Nitro instances (nvme_support = 'required')
+    # and any instances where NVMe is supported for instance storage.
+    def instance_storage_nvme_naming?(instance_type)
+      info = fetch(instance_type)
+      return false if info.nil?
+
+      %w[required supported].include?(info.instance_storage_info&.nvme_support)
+    end
+
+    private
+
+    # Fetches and caches the DescribeInstanceTypes response for the given instance type.
+    # Returns the instance type info struct, or nil if the type is unknown/invalid.
+    def fetch(instance_type)
+      instance_type = instance_type.nil? ? 'unspecified' : instance_type
+
+      return @cache[instance_type] if @cache.key?(instance_type)
+
+      result = query(instance_type)
+      @cache[instance_type] = result
+      result
+    end
+
+    def query(instance_type)
+      @logger.debug("DescribeInstanceTypes for '#{instance_type}'")
+
+      response = nil
+      errors = [Aws::EC2::Errors::RequestLimitExceeded, Aws::EC2::Errors::InternalError, Aws::EC2::Errors::ServiceUnavailable]
+      Bosh::Common.retryable(tries: 5, sleep: 1, on: errors) do |_tries, error|
+        @logger.warn("DescribeInstanceTypes retrying for '#{instance_type}': #{error.message}") if error
+        response = @ec2_client.describe_instance_types(
+          instance_types: [instance_type],
+        )
+        true
+      end
+
+      if response.instance_types.empty?
+        @logger.warn("DescribeInstanceTypes returned no data for '#{instance_type}'")
+        return nil
+      end
+
+      response.instance_types.first
+    rescue Aws::EC2::Errors::InvalidInstanceType, Aws::EC2::Errors::InvalidParameterValue => e
+      @logger.warn("DescribeInstanceTypes failed for '#{instance_type}': #{e.message}")
+      nil
+    rescue Aws::Errors::ServiceError => e
+      raise Bosh::Clouds::CloudError, "DescribeInstanceTypes API error for '#{instance_type}': #{e.message}"
+    end
+  end
+end

src/bosh_aws_cpi/spec/spec_helper.rb

@@ -90,6 +90,7 @@ def mock_cloud_v3(options = nil)
 def mock_ec2
   client = instance_double(Aws::EC2::Client)
   allow(Aws::EC2::Client).to receive(:new).and_return(client)
+  allow(client).to receive(:describe_instance_types).and_return(double(instance_types: []))
   ec2 = double(Aws::EC2::Resource, client: client)
 
   yield ec2 if block_given?

src/bosh_aws_cpi/spec/unit/attach_disk_spec.rb

@@ -125,12 +125,24 @@
   context 'when attaching to c5 instance' do
     let(:instance_type) { 'c5.large' }
 
+    before do
+      allow(cloud.ec2_resource.client).to receive(:describe_instance_types)
+        .with(instance_types: ['c5.large'])
+        .and_return(double(instance_types: [double(ebs_info: double(nvme_support: 'required'))]))
+    end
+
     it_behaves_like 'NVMe required instance types'
   end
 
   context 'when attaching to m5 instance' do
     let(:instance_type) { 'm5.xlarge' }
 
+    before do
+      allow(cloud.ec2_resource.client).to receive(:describe_instance_types)
+        .with(instance_types: ['m5.xlarge'])
+        .and_return(double(instance_types: [double(ebs_info: double(nvme_support: 'required'))]))
+    end
+
     it_behaves_like 'NVMe required instance types'
   end