src/ruby/bin/math_server.rb

# Copyright 2014, Google Inc.
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#
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# modification, are permitted provided that the following conditions are
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#
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# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
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# this software without specific prior written permission.
#
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#!/usr/bin/env ruby
#
# Sample gRPC Ruby server that implements the Math::Calc service and helps
# validate GRPC::RpcServer as GRPC implementation using proto2 serialization.
#
# Usage: $ path/to/math_server.rb

this_dir = File.expand_path(File.dirname(__FILE__))
lib_dir = File.join(File.dirname(this_dir), 'lib')
$LOAD_PATH.unshift(lib_dir) unless $LOAD_PATH.include?(lib_dir)
$LOAD_PATH.unshift(this_dir) unless $LOAD_PATH.include?(this_dir)

require 'forwardable'
require 'grpc'
require 'grpc/generic/service'
require 'grpc/generic/rpc_server'
require 'math.pb'

# Holds state for a fibonacci series
class Fibber

  def initialize(limit)
    raise "bad limit: got #{limit}, want limit > 0" if limit < 1
    @limit = limit
  end

  def generator
    return enum_for(:generator) unless block_given?
    idx, current, previous = 0, 1, 1
    until idx == @limit
      if idx == 0 || idx == 1
        yield Math::Num.new(:num => 1)
        idx += 1
        next
      end
      tmp = current
      current = previous + current
      previous = tmp
      yield Math::Num.new(:num => current)
      idx += 1
    end
  end
end

# A EnumeratorQueue wraps a Queue to yield the items added to it.
class EnumeratorQueue
  extend Forwardable
  def_delegators :@q, :push

  def initialize(sentinel)
    @q = Queue.new
    @sentinel = sentinel
  end

  def each_item
    return enum_for(:each_item) unless block_given?
    loop do
      r = @q.pop
      break if r.equal?(@sentinel)
      raise r if r.is_a?Exception
      yield r
    end
  end

end

# The Math::Math:: module occurs because the service has the same name as its
# package. That practice should be avoided by defining real services.
class Calculator < Math::Math::Service

  def div(div_args, call)
    if div_args.divisor == 0
      # To send non-OK status handlers raise a StatusError with the code and
      # and detail they want sent as a Status.
      raise GRPC::StatusError.new(GRPC::Status::INVALID_ARGUMENT,
                                  'divisor cannot be 0')
    end

    Math::DivReply.new(:quotient => div_args.dividend/div_args.divisor,
                       :remainder => div_args.dividend % div_args.divisor)
  end

  def sum(call)
    # the requests are accesible as the Enumerator call#each_request
    nums = call.each_remote_read.collect { |x| x.num }
    sum = nums.inject { |sum,x| sum + x }
    Math::Num.new(:num => sum)
  end

  def fib(fib_args, call)
    if fib_args.limit < 1
      raise StatusError.new(Status::INVALID_ARGUMENT, 'limit must be >= 0')
    end

    # return an Enumerator of Nums
    Fibber.new(fib_args.limit).generator()
    # just return the generator, GRPC::GenericServer sends each actual response
  end

  def div_many(requests)
    # requests is an lazy Enumerator of the requests sent by the client.
    q = EnumeratorQueue.new(self)
    t = Thread.new do
      begin
        requests.each do |req|
          logger.info("read #{req.inspect}")
          resp = Math::DivReply.new(:quotient => req.dividend/req.divisor,
                                    :remainder => req.dividend % req.divisor)
          q.push(resp)
          Thread::pass  # let the internal Bidi threads run
        end
        logger.info('finished reads')
        q.push(self)
      rescue StandardError => e
        q.push(e)  # share the exception with the enumerator
        raise e
      end
    end
    t.priority = -2  # hint that the div_many thread should not be favoured
    q.each_item
  end

end

def main
  host_port = 'localhost:7070'
  if ARGV.size > 0
    host_port = ARGV[0]
  end

  s = GRPC::RpcServer.new()
  s.add_http2_port(host_port)
  s.handle(Calculator)
  s.run
end

main