Module: GRPC::GenericService::Dsl

Defined in:
src/ruby/lib/grpc/generic/service.rb

Overview

Provides a simple DSL to describe RPC services.

E.g, a Maths service that uses the serializable messages DivArgs, DivReply and Num might define its endpoint uses the following way:

rpc :div DivArgs, DivReply # single request, single response rpc :sum stream(Num), Num # streamed input, single response rpc :fib FibArgs, stream(Num) # single request, streamed response rpc :div_many stream(DivArgs), stream(DivReply)

# streamed req and resp

Each 'rpc' adds an RpcDesc to classes including this module, and #assert_rpc_descs_have_methods is used to ensure the including class provides methods with signatures that support all the descriptors.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#marshal_class_methodObject

the name of the instance method used to marshal events to a byte stream.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 113

def marshal_class_method
  @marshal_class_method ||= :marshal
end

#service_nameObject

This allows configuration of the service name.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 77

def service_name
  @service_name
end

#unmarshal_class_methodObject

the name of the class method used to unmarshal from a byte stream.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 118

def unmarshal_class_method
  @unmarshal_class_method ||= :unmarshal
end

Instance Method Details

#assert_can_marshal(cls) ⇒ Object


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# File 'src/ruby/lib/grpc/generic/service.rb', line 122

def assert_can_marshal(cls)
  cls = cls.type if cls.is_a? RpcDesc::Stream
  mth = unmarshal_class_method
  unless cls.methods.include? mth
    fail(ArgumentError, "#{cls} needs #{cls}.#{mth}")
  end
  mth = marshal_class_method
  return if cls.methods.include? mth
  fail(ArgumentError, "#{cls} needs #{cls}.#{mth}")
end

#inherited(subclass) ⇒ Object


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# File 'src/ruby/lib/grpc/generic/service.rb', line 104

def inherited(subclass)
  # Each subclass should have a distinct class variable with its own
  # rpc_descs
  subclass.rpc_descs.merge!(rpc_descs)
  subclass.service_name = service_name
end

#rpc(name, input, output) ⇒ Object

Adds an RPC spec.

Takes the RPC name and the classes representing the types to be serialized, and adds them to the including classes rpc_desc hash.

input and output should both have the methods #marshal and #unmarshal that are responsible for writing and reading an object instance from a byte buffer respectively.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 91

def rpc(name, input, output)
  fail(DuplicateRpcName, name) if rpc_descs.key? name
  assert_can_marshal(input)
  assert_can_marshal(output)
  rpc_descs[name] = RpcDesc.new(name, input, output,
                                marshal_class_method,
                                unmarshal_class_method)
  define_method(GenericService.underscore(name.to_s).to_sym) do |*|
    fail GRPC::BadStatus.new_status_exception(
      GRPC::Core::StatusCodes::UNIMPLEMENTED)
  end
end

#rpc_descsObject

the RpcDescs defined for this GenericService, keyed by name.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 141

def rpc_descs
  @rpc_descs ||= {}
end

#rpc_stub_classObject

Creates a rpc client class with methods for accessing the methods currently in rpc_descs.


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# File 'src/ruby/lib/grpc/generic/service.rb', line 147

def rpc_stub_class
  descs = rpc_descs
  route_prefix = service_name
  Class.new(ClientStub) do
    # @param host [String] the host the stub connects to
    # @param creds [Core::ChannelCredentials|Symbol] The channel
    #     credentials to use, or :this_channel_is_insecure otherwise
    # @param kw [KeywordArgs] the channel arguments, plus any optional
    #                         args for configuring the client's channel
    def initialize(host, creds, **kw)
      super(host, creds, **kw)
    end

    # Used define_method to add a method for each rpc_desc.  Each method
    # calls the base class method for the given descriptor.
    descs.each_pair do |name, desc|
      mth_name = GenericService.underscore(name.to_s).to_sym
      marshal = desc.marshal_proc
      unmarshal = desc.unmarshal_proc(:output)
      route = "/#{route_prefix}/#{name}"
      if desc.request_response?
        define_method(mth_name) do |req,  = {}|
          GRPC.logger.debug("calling #{@host}:#{route}")
          request_response(route, req, marshal, unmarshal, )
        end
      elsif desc.client_streamer?
        define_method(mth_name) do |reqs,  = {}|
          GRPC.logger.debug("calling #{@host}:#{route}")
          client_streamer(route, reqs, marshal, unmarshal, )
        end
      elsif desc.server_streamer?
        define_method(mth_name) do |req,  = {}, &blk|
          GRPC.logger.debug("calling #{@host}:#{route}")
          server_streamer(route, req, marshal, unmarshal, , &blk)
        end
      else  # is a bidi_stream
        define_method(mth_name) do |reqs,  = {}, &blk|
          GRPC.logger.debug("calling #{@host}:#{route}")
          bidi_streamer(route, reqs, marshal, unmarshal, , &blk)
        end
      end
    end
  end
end

#stream(cls) ⇒ Object


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# File 'src/ruby/lib/grpc/generic/service.rb', line 135

def stream(cls)
  assert_can_marshal(cls)
  RpcDesc::Stream.new(cls)
end