Class: RightScale::MetadataSources::HttpMetadataSource

Inherits:
RightScale::MetadataSource show all
Defined in:
lib/clouds/metadata_sources/http_metadata_source.rb

Overview

Provides metadata via a single http connection which is kept alive in the case of a tree of metadata.

Instance Attribute Summary collapse

Attributes inherited from RightScale::MetadataSource

#logger

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from RightScale::MetadataSource

#append_branch_name, #append_leaf_name

Constructor Details

#initialize(options) ⇒ HttpMetadataSource

Returns a new instance of HttpMetadataSource.

Raises:

  • (ArgumentError) 


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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 36

def initialize(options)
  super(options)
  raise ArgumentError, "options[:hosts] is required" unless @hosts = options[:hosts]
  @host, @port = self.class.select_metadata_server(@hosts)
  @connections = {}
end

Instance Attribute Details

#host ⇒ Object

Returns the value of attribute host.



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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 34

def host
  @host
end

#port ⇒ Object

Returns the value of attribute port.



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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 34

def port
  @port
end

Class Method Details

.select_metadata_server(hosts) ⇒ Object

selects a host/port by attempting to dig one or more well-known DNS names or IP addresses.

Parameters

hosts(Array)

array of hosts in the form [=> <dns name or ip address>, :port => <port or nil>+]

Return

result(Array)

pair in form of [<selected host ip address>, <selected port>]



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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 105

def self.select_metadata_server(hosts)
  # note that .each works for strings (by newline) and arrays.
  last_exception = nil
  hosts.each do |host_data|
    begin
      # resolve metadata server hostname.
      addrs = Socket.gethostbyname(host_data[:host])[3..-1]

      # select only IPv4 addresses
      addrs = addrs.select { |x| x.length == 4 }

      # choose a random IPv4 address
      raw_ip = addrs[rand(addrs.size)]

      # transform binary IP address into string representation
      ip = []
      raw_ip.each_byte { |x| ip << x.to_s }
      return [ip.join('.'), host_data[:port] || 80]
    rescue Exception => e
      last_exception = e
    end
  end
  raise last_exception
end

Instance Method Details

#finish ⇒ Object

Closes any http connections left open after fetching metadata.



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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 86

def finish
  @connections.each_value do |connection|
    begin
      connection.finish
    rescue Exception => e
      logger.error("Failed to close metadata http connection: #{e.backtrace.join("\n")}")
    end
  end
  @connections = {}
end

#query(path) ⇒ Object

Queries for metadata using the given path.

Parameters

path(String)

metadata path

Return

metadata(String)

query result or empty

Raises

QueryFailed

on any failure to query



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# File 'lib/clouds/metadata_sources/http_metadata_source.rb', line 53

def query(path)
  http_path = "http://#{@host}:#{@port}/#{path}"
  attempts = 1
  while true
    begin
      logger.debug("Querying \"#{http_path}\"...")
      # get.
      result = http_get(http_path)
      if result
        logger.debug("Successfully retrieved from: \"#{http_path}\"  Result: #{path} = #{result}")
        return result
      end

      # retry, if allowed.
      if snooze(attempts)
        logger.info("Retrying \"#{http_path}\"...")
      else
        logger.error("Could not retrieve metadata from \"#{http_path}\"; retry limit exceeded.")
        return ""
      end
    rescue Exception => e
      logger.error("#{Time.now().to_s()}: Exception occurred while attempting to retrieve metadata from \"#{http_path}\"; Exception:#{e.message}")
      finish # Reset the connections.
      unless snooze(attempts)
        logger.error("Trace:#{e.backtrace.join("\n")}")
        return ""
      end
    end
    attempts += 1
  end
end