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
# File lib/ohai/mixin/ec2_metadata.rb, line 50 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("/") 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 136 def fetch_dir_metadata(id, api_version) metadata = Hash.new 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 ? retr_meta : "" elsif not 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 179 def fetch_dynamic_data @fetch_dynamic_data ||= begin response = http_client.get("/#{best_api_version}/dynamic/instance-identity/document/") 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 153 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 ? retr_meta : "" json = StringIO.new(data) parser = FFI_Yajl::Parser.new metadata[metadata_key(key)] = parser.parse(json) elsif not 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 106 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 (not key.eql?(id)) && (not 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 173 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/") 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 78 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 91 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) 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
Private Instance Methods
# File lib/ohai/mixin/ec2_metadata.rb, line 193 def expand_path(file_name) path = file_name.gsub(/\=.*$/, "/") # ignore "./" and "../" path.gsub(%r{/\.\.?(?:/|$)}, "/") .sub(%r{^\.\.?(?:/|$)}, "") .sub(%r{^$}, "/") end
# File lib/ohai/mixin/ec2_metadata.rb, line 201 def metadata_key(key) key.gsub(/\-|\//, "_") end