Class: GraphQL::Stitching::Supergraph

Inherits:
Object
  • Object
show all
Defined in:
lib/graphql/stitching/supergraph.rb

Constant Summary collapse

LOCATION = 
"__super"
INTROSPECTION_TYPES = 
[
  "__Schema",
  "__Type",
  "__Field",
  "__Directive",
  "__EnumValue",
  "__InputValue",
  "__TypeKind",
  "__DirectiveLocation",
].freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(schema:, fields:, boundaries:, executables: {}) ⇒ Supergraph

Returns a new instance of Supergraph.



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# File 'lib/graphql/stitching/supergraph.rb', line 20

def initialize(schema:, fields:, boundaries:, executables: {})
  @schema = schema
  @boundaries = boundaries
  @locations_by_type_and_field = INTROSPECTION_TYPES.each_with_object(fields) do |type_name, memo|
    introspection_type = schema.get_type(type_name)
    next unless introspection_type.kind.fields?

    memo[type_name] = introspection_type.fields.keys.each_with_object({}) do |field_name, m|
      m[field_name] = [LOCATION]
    end
  end

  @possible_keys_by_type_and_location = {}
  @executables = { LOCATION => @schema }.merge!(executables)
end

Instance Attribute Details

#boundaries ⇒ Object (readonly)

Returns the value of attribute boundaries.



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# File 'lib/graphql/stitching/supergraph.rb', line 18

def boundaries
  @boundaries
end

#executables ⇒ Object (readonly)

Returns the value of attribute executables.



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# File 'lib/graphql/stitching/supergraph.rb', line 18

def executables
  @executables
end

#locations_by_type_and_field ⇒ Object (readonly)

Returns the value of attribute locations_by_type_and_field.



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# File 'lib/graphql/stitching/supergraph.rb', line 18

def locations_by_type_and_field
  @locations_by_type_and_field
end

#schema ⇒ Object (readonly)

Returns the value of attribute schema.



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# File 'lib/graphql/stitching/supergraph.rb', line 18

def schema
  @schema
end

Class Method Details

.from_export(schema, delegation_map, executables: {}) ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 47

def self.from_export(schema, delegation_map, executables: {})
  schema = GraphQL::Schema.from_definition(schema) if schema.is_a?(String)
  new(
    schema: schema,
    fields: delegation_map["fields"],
    boundaries: delegation_map["boundaries"],
    executables: executables,
  )
end

Instance Method Details

#assign_executable(location, executable = nil, &block) ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 57

def assign_executable(location, executable = nil, &block)
  executable ||= block
  unless executable.is_a?(Class) && executable <= GraphQL::Schema
    raise "A client or block handler must be provided." unless executable
    raise "A client must be callable" unless executable.respond_to?(:call)
  end
  @executables[location] = executable
end

#execute_at_location(location, query, variables) ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 66

def execute_at_location(location, query, variables)
  executable = executables[location]

  if executable.nil?
    raise "No executable assigned for #{location} location."
  elsif executable.is_a?(Class) && executable <= GraphQL::Schema
    executable.execute(
      query: query,
      variables: variables,
      validate: false,
    )
  elsif executable.respond_to?(:call)
    executable.call(location, query, variables)
  else
    raise "Missing valid executable for #{location} location."
  end
end

#export ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 40

def export
  return GraphQL::Schema::Printer.print_schema(@schema), {
    "fields" => fields,
    "boundaries" => @boundaries,
  }
end

#fields ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 36

def fields
  @locations_by_type_and_field.reject { |k, _v| INTROSPECTION_TYPES.include?(k) }
end

#fields_by_type_and_location ⇒ Object

inverts fields map to provide fields for a type/location



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# File 'lib/graphql/stitching/supergraph.rb', line 85

def fields_by_type_and_location
  @fields_by_type_and_location ||= @locations_by_type_and_field.each_with_object({}) do |(type_name, fields), memo|
    memo[type_name] = fields.each_with_object({}) do |(field_name, locations), memo|
      locations.each do |location|
        memo[location] ||= []
        memo[location] << field_name
      end
    end
  end
end

#locations_by_type ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 96

def locations_by_type
  @locations_by_type ||= @locations_by_type_and_field.each_with_object({}) do |(type_name, fields), memo|
    memo[type_name] = fields.values.flatten.uniq
  end
end

#possible_keys_for_type_and_location(type_name, location) ⇒ Object 



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# File 'lib/graphql/stitching/supergraph.rb', line 102

def possible_keys_for_type_and_location(type_name, location)
  possible_keys_by_type = @possible_keys_by_type_and_location[type_name] ||= {}
  possible_keys_by_type[location] ||= begin
    location_fields = fields_by_type_and_location[type_name][location] || []
    location_fields & @boundaries[type_name].map { _1["selection"] }
  end
end

#route_type_to_locations(type_name, start_location, goal_locations) ⇒ Object

For a given type, route from one origin service to one or more remote locations. Tunes a-star search to favor paths with fewest joining locations, ie: favor longer paths through target locations over shorter paths with additional locations.



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# File 'lib/graphql/stitching/supergraph.rb', line 113

def route_type_to_locations(type_name, start_location, goal_locations)
  results = {}
  costs = {}

  paths = possible_keys_for_type_and_location(type_name, start_location).map do |possible_key|
    [{ location: start_location, selection: possible_key, cost: 0 }]
  end

  while paths.any?
    path = paths.pop
    current_location = path.last[:location]
    current_selection = path.last[:selection]
    current_cost = path.last[:cost]

    @boundaries[type_name].each do |boundary|
      forward_location = boundary["location"]
      next if current_selection != boundary["selection"]
      next if path.any? { _1[:location] == forward_location }

      best_cost = costs[forward_location] || Float::INFINITY
      next if best_cost < current_cost

      path.pop
      path << {
        location: current_location,
        selection: current_selection,
        cost: current_cost,
        boundary: boundary,
      }

      if goal_locations.include?(forward_location)
        current_result = results[forward_location]
        if current_result.nil? || current_cost < best_cost || (current_cost == best_cost && path.length < current_result.length)
          results[forward_location] = path.map { _1[:boundary] }
        end
      else
        path.last[:cost] += 1
      end

      forward_cost = path.last[:cost]
      costs[forward_location] = forward_cost if forward_cost < best_cost

      possible_keys_for_type_and_location(type_name, forward_location).each do |possible_key|
        paths << [*path, { location: forward_location, selection: possible_key, cost: forward_cost }]
      end
    end

    paths.sort! do |a, b|
      cost_diff = a.last[:cost] - b.last[:cost]
      next cost_diff unless cost_diff.zero?
      a.length - b.length
    end.reverse!
  end

  results
end