module Ohai::Mixin::Ec2Metadata
This code parses the EC2 Instance Metadata API to provide details of the running instance.
Earlier version of this code assumed a specific version of the metadata API was available. Unfortunately the API versions supported by a particular instance are determined at instance launch and are not extended over the life of the instance. As such the earlier code would fail depending on the age of the instance.
The updated code probes the instance metadata endpoint for available versions, determines the most advanced version known to work and executes the metadata retrieval using that version.
If no compatible version is found, an empty hash is returned.
Public Instance Methods
The latest metadata version in EC2_SUPPORTED_VERSIONS that this instance supports in AWS supported metadata versions are determined at instance start so we need to be cautious here in case an instance has been running for a long time
@return [String] the version
# File lib/ohai/mixin/ec2_metadata.rb, line 81 def best_api_version @api_version ||= begin logger.trace("Mixin EC2: Fetching http://#{EC2_METADATA_ADDR}/ to determine the latest supported metadata release") response = http_client.get("/", { 'X-aws-ec2-metadata-token': v2_token }) if response.code == "404" logger.trace("Mixin EC2: Received HTTP 404 from metadata server while determining API version, assuming 'latest'") return "latest" elsif response.code != "200" raise "Mixin EC2: Unable to determine EC2 metadata version (returned #{response.code} response)" end # NOTE: Sorting the list of versions may have unintended consequences in # non-EC2 environments. It appears to be safe in EC2 as of 2013-04-12. versions = response.body.split("\n").sort until versions.empty? || EC2_SUPPORTED_VERSIONS.include?(versions.last) pv = versions.pop logger.trace("Mixin EC2: EC2 lists metadata version: #{pv} not yet supported by Ohai") unless pv == "latest" end logger.trace("Mixin EC2: Latest supported EC2 metadata version: #{versions.last}") if versions.empty? raise "Mixin EC2: Unable to determine EC2 metadata version (no supported entries found)" end versions.last end end
# File lib/ohai/mixin/ec2_metadata.rb, line 185 def fetch_dir_metadata(id, api_version) metadata = {} retrieved_metadata = metadata_get(id, api_version) if retrieved_metadata retrieved_metadata.split("\n").each do |o| key = expand_path(o) if key[-1..-1] != "/" retr_meta = metadata_get("#{id}#{key}", api_version) metadata[metadata_key(key)] = retr_meta || "" elsif !key.eql?("/") metadata[key[0..-2]] = fetch_dir_metadata("#{id}#{key}", api_version) end end metadata end end
# File lib/ohai/mixin/ec2_metadata.rb, line 228 def fetch_dynamic_data @fetch_dynamic_data ||= begin response = http_client.get("/#{best_api_version}/dynamic/instance-identity/document/", { 'X-aws-ec2-metadata-token': v2_token }) if json?(response.body) && response.code == "200" FFI_Yajl::Parser.parse(response.body) else {} end end end
# File lib/ohai/mixin/ec2_metadata.rb, line 202 def fetch_json_dir_metadata(id, api_version) metadata = {} retrieved_metadata = metadata_get(id, api_version) if retrieved_metadata retrieved_metadata.split("\n").each do |o| key = expand_path(o) if key[-1..-1] != "/" retr_meta = metadata_get("#{id}#{key}", api_version) data = retr_meta || "" json = String(data) parser = FFI_Yajl::Parser.new metadata[metadata_key(key)] = parser.parse(json) elsif !key.eql?("/") metadata[key[0..-2]] = fetch_json_dir_metadata("#{id}#{key}", api_version) end end metadata end end
# File lib/ohai/mixin/ec2_metadata.rb, line 155 def fetch_metadata(id = "", api_version = nil) metadata = {} retrieved_metadata = metadata_get(id, best_api_version) if retrieved_metadata retrieved_metadata.split("\n").each do |o| key = expand_path("#{id}#{o}") if key[-1..-1] != "/" metadata[metadata_key(key)] = if EC2_ARRAY_VALUES.include? key retr_meta = metadata_get(key, best_api_version) retr_meta ? retr_meta.split("\n") : retr_meta else metadata_get(key, best_api_version) end elsif (!key.eql?(id)) && (!key.eql?("/")) name = key[0..-2] sym = metadata_key(name) if EC2_ARRAY_DIR.include?(name) metadata[sym] = fetch_dir_metadata(key, best_api_version) elsif EC2_JSON_DIR.include?(name) metadata[sym] = fetch_json_dir_metadata(key, best_api_version) else fetch_metadata(key, best_api_version).each { |k, v| metadata[k] = v } end end end metadata end end
# File lib/ohai/mixin/ec2_metadata.rb, line 222 def fetch_userdata logger.trace("Mixin EC2: Fetching http://#{EC2_METADATA_ADDR}/#{best_api_version}/user-data/") response = http_client.get("/#{best_api_version}/user-data/", { 'X-aws-ec2-metadata-token': v2_token }) response.code == "200" ? response.body : nil end
a net/http client with a timeout of 10s and a keepalive of 10s
@return [Net::HTTP]
# File lib/ohai/mixin/ec2_metadata.rb, line 110 def http_client @conn ||= Net::HTTP.start(EC2_METADATA_ADDR).tap do |h| h.read_timeout = 10 h.keep_alive_timeout = 10 end end
Get metadata for a given path and API version
Typically, a 200 response is expected for valid metadata. On certain instance types, traversing the provided metadata path produces a 404 for some unknown reason. In that event, return `nil` and continue the run instead of failing it.
# File lib/ohai/mixin/ec2_metadata.rb, line 140 def metadata_get(id, api_version) path = "/#{api_version}/meta-data/#{id}" logger.trace("Mixin EC2: Fetching http://#{EC2_METADATA_ADDR}#{path}") response = http_client.get(path, { 'X-aws-ec2-metadata-token': v2_token }) case response.code when "200" response.body when "404" logger.trace("Mixin EC2: Encountered 404 response retrieving EC2 metadata path: #{path} ; continuing.") nil else raise "Mixin EC2: Encountered error retrieving EC2 metadata (#{path} returned #{response.code} response)" end end
Fetch an API token for use querying AWS IMDSv2 or return nil if no token if found AWS like systems (think OpenStack) will not respond with a token here
@return [NilClass, String] API token or nil
# File lib/ohai/mixin/ec2_metadata.rb, line 123 def v2_token @v2_token ||= begin request = http_client.put("/latest/api/token", nil, { 'X-aws-ec2-metadata-token-ttl-seconds': "60" }) if request.code == "404" # not on AWS nil else request.body end end end
Private Instance Methods
# File lib/ohai/mixin/ec2_metadata.rb, line 242 def expand_path(file_name) path = file_name.gsub(/\=.*$/, "/") # ignore "./" and "../" path.gsub(%r{/\.\.?(?:/|$)}, "/") .sub(%r{^\.\.?(?:/|$)}, "") .sub(/^$/, "/") end
# File lib/ohai/mixin/ec2_metadata.rb, line 250 def metadata_key(key) key.gsub(%r{\-|/}, "_") end