Class: RightScale::MetadataSources::SelectiveMetadataSource

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

Overview

Provides metadata by attempting to get metadata from one or more listed sources; first responding successfully wins.

Instance Attribute Summary collapse

Attributes inherited from RightScale::MetadataSource

#logger

Instance Method Summary collapse

Methods inherited from RightScale::MetadataSource

#append_branch_name, #append_leaf_name

Constructor Details

#initialize(options) ⇒ SelectiveMetadataSource

Returns a new instance of SelectiveMetadataSource.

Raises:

  • (ArgumentError) 


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# File 'lib/clouds/metadata_sources/selective_metadata_source.rb', line 33

def initialize(options)
  raise ArgumentError, "options[:metadata_sources] is required" unless metadata_source_types = options[:metadata_source_types]
  raise ArgumentError, "options[:cloud] is required" unless @cloud = options[:cloud]
  @select_metadata_override = options[:select_metadata_override]

  # keep types but create selective sources on demand in case not all are used.
  @metadata_sources = []
  metadata_source_types.each do |metadata_source_type|
    @metadata_sources << { :type => metadata_source_type, :source => nil }
  end
end

Instance Attribute Details

#metadata_sources ⇒ Object

Returns the value of attribute metadata_sources.



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# File 'lib/clouds/metadata_sources/selective_metadata_source.rb', line 31

def metadata_sources
  @metadata_sources
end

Instance Method Details

#finish ⇒ Object

Attempts to finish all child metadata sources.



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# File 'lib/clouds/metadata_sources/selective_metadata_source.rb', line 103

def finish
  last_exception = nil
  @metadata_sources.each do |metadata_source|
    begin
      source = metadata_source[:source]
      source.finish if source
    rescue Exception => e
      last_exception = e
    ensure
      metadata_source[:source] = nil
    end
  end
  raise last_exception if last_exception
end

#query(path) ⇒ Object

Queries for metadata using the given path.

Parameters

path(String)

metadata path

Return

metadata(String)

query result

Raises

QueryFailed

on any failure to query



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# File 'lib/clouds/metadata_sources/selective_metadata_source.rb', line 55

def query(path)
  merged_metadata = ""
  last_query_failed = nil
  @metadata_sources.each do |metadata_source|
    type = metadata_source[:type]
    unless source = metadata_source[:source]
      # note that sources are special in that they ignore cloud vs. user
      # specialization unlike other dependency types.
      kind = :cloud_metadata
      source = @cloud.create_dependency_type(kind, :metadata_source, type)
      metadata_source[:source] = source
    end
    begin
      query_result = source.query(path)
      selected = select_metadata(path, type, query_result, merged_metadata)
      merged_metadata = selected[:merged_metadata]
      last_query_failed = nil  # reset last failed query
      break unless selected[:query_next_metadata]
    rescue QueryFailed => e
      # temporarily ignore failed query in case next source query succeeds
      last_query_failed = e
    end
  end
  raise last_query_failed if last_query_failed
  return merged_metadata
rescue Exception => e
  raise QueryFailed.new(e.message)
end

#select_metadata(path, metadata_source_type, query_result, previous_metadata) ⇒ Object

Selects metadata by determining if the metadata condition has been satisfied. Supports merging of metadata (potentially in different formats) from different sources.

Parameters

path(String)

metadata path

metadata_source_type(String)

metadata source type

query_result(String)

raw metadata from query

previous_metadata(String)

previously merged metadata or empty

Returns

result(Boolean)

when true indicates that the next metadata source should also be queried.

result(String)

result of merging any previous metadata with current query result.



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# File 'lib/clouds/metadata_sources/selective_metadata_source.rb', line 97

def select_metadata(path, metadata_source_type, query_result, previous_metadata)
  return @select_metadata_override.call(self, path, metadata_source_type, query_result, previous_metadata) if @select_metadata_override
  return {:query_next_metadata => query_result.strip.empty?, :merged_metadata => query_result}
end