Add a health checker service implementation.

- adds the code-generated health service classes to the pb along with
  a README explaining how to regenerate the generated code

- adds an implementation of the Health Checker Service along with unit
  tests and an integration test

Also:
- adds a pb folder
  : in a follow-up PR, all ruby pbs + generated code will be moved to it

11 files changed, 440 insertions, 3 deletions

diff --git a/src/ruby/.rspec b/src/ruby/.rspec
index cd7c5fb5b2..2320752db4 100755
--- a/src/ruby/.rspec
+++ b/src/ruby/.rspec
@@ -1,4 +1,5 @@
 -I.
+-Ipb
 --require spec_helper
 --format documentation
 --color
diff --git a/src/ruby/.rubocop.yml b/src/ruby/.rubocop.yml
index 47e382afa7..1b255f3963 100644
--- a/src/ruby/.rubocop.yml
+++ b/src/ruby/.rubocop.yml
@@ -8,3 +8,4 @@ AllCops:
     - 'bin/interop/test/**/*'
     - 'bin/math.rb'
     - 'bin/math_services.rb'
+    - 'pb/grpc/health/v1alpha/*'
diff --git a/src/ruby/Rakefile b/src/ruby/Rakefile
index 02af9a84b8..cc7832b12d 100755
--- a/src/ruby/Rakefile
+++ b/src/ruby/Rakefile
@@ -20,7 +20,8 @@ SPEC_SUITES = [
   { id: :bidi, title: 'bidi tests', dir: %w(spec/generic),
     tag: 'bidi' },
   { id: :server, title: 'rpc server thread tests', dir: %w(spec/generic),
-    tag: 'server' }
+    tag: 'server' },
+  { id: :pb, title: 'protobuf service tests', dir: %w(spec/pb) }
 ]
 namespace :suite do
   SPEC_SUITES.each do |suite|
@@ -50,7 +51,8 @@ task 'suite:wrapper' => [:compile, :rubocop]
 task 'suite:idiomatic' => 'suite:wrapper'
 task 'suite:bidi' => 'suite:wrapper'
 task 'suite:server' => 'suite:wrapper'
+task 'suite:pb' => 'suite:server'
 
 desc 'Compiles the gRPC extension then runs all the tests'
-task all: ['suite:idiomatic', 'suite:bidi', 'suite:server']
+task all: ['suite:idiomatic', 'suite:bidi', 'suite:pb', 'suite:server']
 task default: :all
diff --git a/src/ruby/grpc.gemspec b/src/ruby/grpc.gemspec
index eb748458b9..22fafe1b50 100755
--- a/src/ruby/grpc.gemspec
+++ b/src/ruby/grpc.gemspec
@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   %w(math noproto).each do |b|
     s.executables += ["#{b}_client.rb", "#{b}_server.rb"]
   end
-  s.require_paths = %w( bin lib )
+  s.require_paths = %w( bin lib pb )
   s.platform      = Gem::Platform::RUBY
 
   s.add_dependency 'google-protobuf', '~> 3.0.0alpha.1.1'
diff --git a/src/ruby/pb/README.md b/src/ruby/pb/README.md
new file mode 100644
index 0000000000..0b067edd0e
--- /dev/null
+++ b/src/ruby/pb/README.md
@@ -0,0 +1,27 @@
+Protocol Buffers
+================
+
+This folder contains protocol buffers provided with gRPC ruby, and the generated
+code to them.
+
+PREREQUISITES
+-------------
+
+The code is is generated using the protoc (> 3.0.0.alpha.1) and the
+grpc_ruby_plugin.  These must be installed to regenerate the IDL defined
+classes, but that's not necessary just to use them.
+
+health_check/v1alpha
+--------------------
+
+This package defines the surface of a simple health check service that gRPC
+servers may choose to implement, and provides an implementation for it. To
+re-generate the surface.
+
+```bash
+$ # (from this directory)
+$ protoc -I . grpc/health/v1alpha/health.proto \
+    --grpc_out=. \
+    --ruby_out=. \
+    --plugin=protoc-gen-grpc=`which grpc_ruby_plugin`
+```
diff --git a/src/ruby/pb/grpc/health/checker.rb b/src/ruby/pb/grpc/health/checker.rb
new file mode 100644
index 0000000000..8c692e74f9
--- /dev/null
+++ b/src/ruby/pb/grpc/health/checker.rb
@@ -0,0 +1,75 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+require 'grpc'
+require 'grpc/health/v1alpha/health_services'
+require 'thread'
+
+module Grpc
+  # Health contains classes and modules that support providing a health check
+  # service.
+  module Health
+    # Checker is implementation of the schema-specified health checking service.
+    class Checker < V1alpha::Health::Service
+      StatusCodes = GRPC::Core::StatusCodes
+      HealthCheckResponse = V1alpha::HealthCheckResponse
+
+      # Initializes the statuses of participating services
+      def initialize
+        @statuses = {}
+        @status_mutex = Mutex.new  # guards access to @statuses
+      end
+
+      # Implements the rpc IDL API method
+      def check(req, _call)
+        status = nil
+        @status_mutex.synchronize do
+          status = @statuses["#{req.host}/#{req.service}"]
+        end
+        fail GRPC::BadStatus, StatusCodes::NOT_FOUND if status.nil?
+        HealthCheckResponse.new(status: status)
+      end
+
+      # Adds the health status for a given host and service.
+      def add_status(host, service, status)
+        @status_mutex.synchronize { @statuses["#{host}/#{service}"] = status }
+      end
+
+      # Clears the status for the given host or service.
+      def clear_status(host, service)
+        @status_mutex.synchronize { @statuses.delete("#{host}/#{service}") }
+      end
+
+      # Clears alls the statuses.
+      def clear_all
+        @status_mutex.synchronize { @statuses = {} }
+      end
+    end
+  end
+end
diff --git a/src/ruby/pb/grpc/health/v1alpha/health.proto b/src/ruby/pb/grpc/health/v1alpha/health.proto
new file mode 100644
index 0000000000..d31df1e0a7
--- /dev/null
+++ b/src/ruby/pb/grpc/health/v1alpha/health.proto
@@ -0,0 +1,50 @@
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package grpc.health.v1alpha;
+
+message HealthCheckRequest {
+  string host = 1;
+  string service = 2;
+}
+
+message HealthCheckResponse {
+  enum ServingStatus {
+    UNKNOWN = 0;
+    SERVING = 1;
+    NOT_SERVING = 2;
+  }
+  ServingStatus status = 1;
+}
+
+service Health {
+  rpc Check(HealthCheckRequest) returns (HealthCheckResponse);
+}
\ No newline at end of file
diff --git a/src/ruby/pb/grpc/health/v1alpha/health.rb b/src/ruby/pb/grpc/health/v1alpha/health.rb
new file mode 100644
index 0000000000..9c04298ea5
--- /dev/null
+++ b/src/ruby/pb/grpc/health/v1alpha/health.rb
@@ -0,0 +1,29 @@
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# source: grpc/health/v1alpha/health.proto
+
+require 'google/protobuf'
+
+Google::Protobuf::DescriptorPool.generated_pool.build do
+  add_message "grpc.health.v1alpha.HealthCheckRequest" do
+    optional :host, :string, 1
+    optional :service, :string, 2
+  end
+  add_message "grpc.health.v1alpha.HealthCheckResponse" do
+    optional :status, :enum, 1, "grpc.health.v1alpha.HealthCheckResponse.ServingStatus"
+  end
+  add_enum "grpc.health.v1alpha.HealthCheckResponse.ServingStatus" do
+    value :UNKNOWN, 0
+    value :SERVING, 1
+    value :NOT_SERVING, 2
+  end
+end
+
+module Grpc
+  module Health
+    module V1alpha
+      HealthCheckRequest = Google::Protobuf::DescriptorPool.generated_pool.lookup("grpc.health.v1alpha.HealthCheckRequest").msgclass
+      HealthCheckResponse = Google::Protobuf::DescriptorPool.generated_pool.lookup("grpc.health.v1alpha.HealthCheckResponse").msgclass
+      HealthCheckResponse::ServingStatus = Google::Protobuf::DescriptorPool.generated_pool.lookup("grpc.health.v1alpha.HealthCheckResponse.ServingStatus").enummodule
+    end
+  end
+end
diff --git a/src/ruby/pb/grpc/health/v1alpha/health_checker.rb b/src/ruby/pb/grpc/health/v1alpha/health_checker.rb
new file mode 100644
index 0000000000..f04bf5ecca
--- /dev/null
+++ b/src/ruby/pb/grpc/health/v1alpha/health_checker.rb
@@ -0,0 +1,39 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+require 'grpc/health/v1alpha/health_services'
+
+module Grpc
+  # Health contains classes and modules that support providing a health check
+  # service.
+  module Health
+    class Checker
+    end
+  end
+end
diff --git a/src/ruby/pb/grpc/health/v1alpha/health_services.rb b/src/ruby/pb/grpc/health/v1alpha/health_services.rb
new file mode 100644
index 0000000000..d5cba2e9ec
--- /dev/null
+++ b/src/ruby/pb/grpc/health/v1alpha/health_services.rb
@@ -0,0 +1,28 @@
+# Generated by the protocol buffer compiler.  DO NOT EDIT!
+# Source: grpc/health/v1alpha/health.proto for package 'grpc.health.v1alpha'
+
+require 'grpc'
+require 'grpc/health/v1alpha/health'
+
+module Grpc
+  module Health
+    module V1alpha
+      module Health
+
+        # TODO: add proto service documentation here
+        class Service
+
+          include GRPC::GenericService
+
+          self.marshal_class_method = :encode
+          self.unmarshal_class_method = :decode
+          self.service_name = 'grpc.health.v1alpha.Health'
+
+          rpc :Check, HealthCheckRequest, HealthCheckResponse
+        end
+
+        Stub = Service.rpc_stub_class
+      end
+    end
+  end
+end
diff --git a/src/ruby/spec/pb/health/checker_spec.rb b/src/ruby/spec/pb/health/checker_spec.rb
new file mode 100644
index 0000000000..0aeae444fc
--- /dev/null
+++ b/src/ruby/spec/pb/health/checker_spec.rb
@@ -0,0 +1,185 @@
+# Copyright 2015, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+require 'grpc'
+require 'grpc/health/v1alpha/health'
+require 'grpc/health/checker'
+
+describe Grpc::Health::Checker do
+  StatusCodes = GRPC::Core::StatusCodes
+  ServingStatus = Grpc::Health::V1alpha::HealthCheckResponse::ServingStatus
+  HCResp = Grpc::Health::V1alpha::HealthCheckResponse
+  HCReq = Grpc::Health::V1alpha::HealthCheckRequest
+  success_tests =
+    [
+      {
+        desc: 'neither host or service are specified',
+        host: '',
+        service: ''
+      }, {
+        desc: 'only the host is specified',
+        host: 'test-fake-host',
+        service: ''
+      }, {
+        desc: 'the host and service are specified',
+        host: 'test-fake-host',
+        service: 'fake-service-1'
+      }, {
+        desc: 'only the service is specified',
+        host: '',
+        service: 'fake-service-2'
+      }
+    ]
+
+  context 'initialization' do
+    it 'can be constructed with no args' do
+      expect(subject).to_not be(nil)
+    end
+  end
+
+  context 'method `add_status` and `check`' do
+    success_tests.each do |t|
+      it "should succeed when #{t[:desc]}" do
+        subject.add_status(t[:host], t[:service], ServingStatus::NOT_SERVING)
+        got = subject.check(HCReq.new(host: t[:host], service: t[:service]),
+                            nil)
+        want = HCResp.new(status: ServingStatus::NOT_SERVING)
+        expect(got).to eq(want)
+      end
+    end
+  end
+
+  context 'method `check`' do
+    success_tests.each do |t|
+      it "should fail with NOT_FOUND when #{t[:desc]}" do
+        blk = proc do
+          subject.check(HCReq.new(host: t[:host], service: t[:service]), nil)
+        end
+        expected_msg = /#{StatusCodes::NOT_FOUND}/
+        expect(&blk).to raise_error GRPC::BadStatus, expected_msg
+      end
+    end
+  end
+
+  context 'method `clear_status`' do
+    success_tests.each do |t|
+      it "should fail after clearing status when #{t[:desc]}" do
+        subject.add_status(t[:host], t[:service], ServingStatus::NOT_SERVING)
+        got = subject.check(HCReq.new(host: t[:host], service: t[:service]),
+                            nil)
+        want = HCResp.new(status: ServingStatus::NOT_SERVING)
+        expect(got).to eq(want)
+
+        subject.clear_status(t[:host], t[:service])
+        blk = proc do
+          subject.check(HCReq.new(host: t[:host], service: t[:service]),
+                        nil)
+        end
+        expected_msg = /#{StatusCodes::NOT_FOUND}/
+        expect(&blk).to raise_error GRPC::BadStatus, expected_msg
+      end
+    end
+  end
+
+  context 'method `clear_all`' do
+    it 'should return NOT_FOUND after being invoked' do
+      success_tests.each do |t|
+        subject.add_status(t[:host], t[:service], ServingStatus::NOT_SERVING)
+        got = subject.check(HCReq.new(host: t[:host], service: t[:service]),
+                            nil)
+        want = HCResp.new(status: ServingStatus::NOT_SERVING)
+        expect(got).to eq(want)
+      end
+
+      subject.clear_all
+
+      success_tests.each do |t|
+        blk = proc do
+          subject.check(HCReq.new(host: t[:host], service: t[:service]), nil)
+        end
+        expected_msg = /#{StatusCodes::NOT_FOUND}/
+        expect(&blk).to raise_error GRPC::BadStatus, expected_msg
+      end
+    end
+  end
+
+  describe 'running on RpcServer' do
+    RpcServer = GRPC::RpcServer
+    StatusCodes = GRPC::Core::StatusCodes
+    CheckerStub = Grpc::Health::Checker.rpc_stub_class
+
+    before(:each) do
+      @server_queue = GRPC::Core::CompletionQueue.new
+      server_host = '0.0.0.0:0'
+      @server = GRPC::Core::Server.new(@server_queue, nil)
+      server_port = @server.add_http2_port(server_host)
+      @host = "localhost:#{server_port}"
+      @ch = GRPC::Core::Channel.new(@host, nil)
+      @client_opts = { channel_override: @ch }
+      server_opts = {
+        server_override: @server,
+        completion_queue_override: @server_queue,
+        poll_period: 1
+      }
+      @srv = RpcServer.new(**server_opts)
+    end
+
+    after(:each) do
+      @srv.stop
+    end
+
+    it 'should receive the correct status', server: true do
+      @srv.handle(subject)
+      subject.add_status('', '', ServingStatus::NOT_SERVING)
+      t = Thread.new { @srv.run }
+      @srv.wait_till_running
+
+      stub = CheckerStub.new(@host, **@client_opts)
+      got = stub.check(HCReq.new)
+      want = HCResp.new(status: ServingStatus::NOT_SERVING)
+      expect(got).to eq(want)
+      @srv.stop
+      t.join
+    end
+
+    it 'should fail on unknown services', server: true do
+      @srv.handle(subject)
+      t = Thread.new { @srv.run }
+      @srv.wait_till_running
+      blk = proc do
+        stub = CheckerStub.new(@host, **@client_opts)
+        stub.check(HCReq.new(host: 'unknown', service: 'unknown'))
+      end
+      expected_msg = /#{StatusCodes::NOT_FOUND}/
+      expect(&blk).to raise_error GRPC::BadStatus, expected_msg
+      @srv.stop
+      t.join
+    end
+  end
+end