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.
Constants
- EC2_ARRAY_DIR
- EC2_ARRAY_VALUES
- EC2_JSON_DIR
- EC2_METADATA_ADDR
- EC2_SUPPORTED_VERSIONS
Public Instance Methods
best_api_version()
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# File lib/ohai/mixin/ec2_metadata.rb, line 50 def best_api_version @api_version ||= begin Ohai::Log.debug("Mixin EC2: Fetching http://#{EC2_METADATA_ADDR}/ to determine the latest supported metadata release") response = http_client.get("/") if response.code == "404" Ohai::Log.debug("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 Ohai::Log.debug("Mixin EC2: EC2 lists metadata version: #{pv} not yet supported by Ohai") unless pv == "latest" end Ohai::Log.debug("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
fetch_dir_metadata(id, api_version)
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# File lib/ohai/mixin/ec2_metadata.rb, line 134 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
fetch_dynamic_data()
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# File lib/ohai/mixin/ec2_metadata.rb, line 177 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
fetch_json_dir_metadata(id, api_version)
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# File lib/ohai/mixin/ec2_metadata.rb, line 151 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
fetch_metadata(id = "", api_version = nil)
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# File lib/ohai/mixin/ec2_metadata.rb, line 104 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
fetch_userdata()
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# File lib/ohai/mixin/ec2_metadata.rb, line 171 def fetch_userdata Ohai::Log.debug("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
http_client()
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# File lib/ohai/mixin/ec2_metadata.rb, line 75 def http_client @conn ||= Net::HTTP.start(EC2_METADATA_ADDR).tap do |h| h.read_timeout = 10 h.keep_alive_timeout = 10 end end
metadata_get(id, api_version)
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Get metadata for a given path and API version
@details
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 89 def metadata_get(id, api_version) path = "/#{api_version}/meta-data/#{id}" Ohai::Log.debug("Mixin EC2: Fetching http://#{EC2_METADATA_ADDR}#{path}") response = http_client.get(path) case response.code when "200" response.body when "404" Ohai::Log.debug("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
expand_path(file_name)
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# File lib/ohai/mixin/ec2_metadata.rb, line 191 def expand_path(file_name) path = file_name.gsub(/\=.*$/, "/") # ignore "./" and "../" path.gsub(%r{/\.\.?(?:/|$)}, "/"). sub(%r{^\.\.?(?:/|$)}, ""). sub(%r{^$}, "/") end
metadata_key(key)
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# File lib/ohai/mixin/ec2_metadata.rb, line 199 def metadata_key(key) key.gsub(/\-|\//, "_") end