Add a gRPC health check to ensure Gitaly is up

app/controllers/health_controller.rb

@@ -8,7 +8,8 @@ class HealthController < ActionController::Base
     Gitlab::HealthChecks::Redis::CacheCheck,
     Gitlab::HealthChecks::Redis::QueuesCheck,
     Gitlab::HealthChecks::Redis::SharedStateCheck,
-    Gitlab::HealthChecks::FsShardsCheck
+    Gitlab::HealthChecks::FsShardsCheck,
+    Gitlab::HealthChecks::GitalyCheck
   ].freeze
 
   def readiness

changelogs/unreleased/sh-add-gitaly-health-check.yml

+---
+title: Add a gRPC health check to ensure Gitaly is up
+merge_request:
+author:
+type: added

lib/gitlab/gitaly_client.rb

 require 'base64'
 
 require 'gitaly'
+require 'grpc/health/v1/health_pb'
+require 'grpc/health/v1/health_services_pb'
 
 module Gitlab
   module GitalyClient
@@ -69,14 +71,27 @@ module Gitlab
         @stubs ||= {}
         @stubs[storage] ||= {}
         @stubs[storage][name] ||= begin
-          klass = Gitaly.const_get(name.to_s.camelcase.to_sym).const_get(:Stub)
-          addr = address(storage)
-          addr = addr.sub(%r{^tcp://}, '') if URI(addr).scheme == 'tcp'
+          klass = stub_class(name)
+          addr = stub_address(storage)
           klass.new(addr, :this_channel_is_insecure)
         end
       end
     end
 
+    def self.stub_class(name)
+      if name == :health_check
+        Grpc::Health::V1::Health::Stub
+      else
+        Gitaly.const_get(name.to_s.camelcase.to_sym).const_get(:Stub)
+      end
+    end
+
+    def self.stub_address(storage)
+      addr = address(storage)
+      addr = addr.sub(%r{^tcp://}, '') if URI(addr).scheme == 'tcp'
+      addr
+    end
+
     def self.clear_stubs!
       MUTEX.synchronize do
         @stubs = nil

lib/gitlab/gitaly_client/health_check_service.rb

+module Gitlab
+  module GitalyClient
+    class HealthCheckService
+      def initialize(storage)
+        @storage = storage
+      end
+
+      # Sends a gRPC health ping to the Gitaly server for the storage shard.
+      def check
+        request = Grpc::Health::V1::HealthCheckRequest.new
+        response = GitalyClient.call(@storage, :health_check, :check, request, timeout: GitalyClient.fast_timeout)
+
+        { success: response&.status == :SERVING }
+      rescue GRPC::BadStatus => e
+        { success: false, message: e.to_s }
+      end
+    end
+  end
+end

lib/gitlab/health_checks/gitaly_check.rb

+module Gitlab
+  module HealthChecks
+    class GitalyCheck
+      extend BaseAbstractCheck
+
+      METRIC_PREFIX = 'gitaly_health_check'.freeze
+
+      class << self
+        def readiness
+          repository_storages.map do |storage_name|
+            check(storage_name)
+          end
+        end
+
+        def metrics
+          repository_storages.flat_map do |storage_name|
+            result, elapsed = with_timing { check(storage_name) }
+            labels = { shard: storage_name }
+
+            [
+              metric("#{metric_prefix}_success", successful?(result) ? 1 : 0, **labels),
+              metric("#{metric_prefix}_latency_seconds", elapsed, **labels)
+            ].flatten
+          end
+        end
+
+        def check(storage_name)
+          serv = Gitlab::GitalyClient::HealthCheckService.new(storage_name)
+          result = serv.check
+          HealthChecks::Result.new(result[:success], result[:message], shard: storage_name)
+        end
+
+        private
+
+        def metric_prefix
+          METRIC_PREFIX
+        end
+
+        def successful?(result)
+          result[:success]
+        end
+
+        def repository_storages
+          storages.keys
+        end
+
+        def storages
+          Gitlab.config.repositories.storages
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/gitaly_client/health_check_service_spec.rb

+require 'spec_helper'
+
+describe Gitlab::GitalyClient::HealthCheckService do
+  let(:project) { create(:project) }
+  let(:storage_name) { project.repository_storage }
+
+  subject { described_class.new(storage_name) }
+
+  describe '#check' do
+    it 'successfully sends a health check request' do
+      expect(Gitlab::GitalyClient).to receive(:call).with(
+        storage_name,
+        :health_check,
+        :check,
+        instance_of(Grpc::Health::V1::HealthCheckRequest),
+        timeout: Gitlab::GitalyClient.fast_timeout).and_call_original
+
+      expect(subject.check).to eq({ success: true })
+    end
+
+    it 'receives an unsuccessful health check request' do
+      expect_any_instance_of(Grpc::Health::V1::Health::Stub)
+        .to receive(:check)
+        .and_return(double(status: false))
+
+      expect(subject.check).to eq({ success: false })
+    end
+
+    it 'gracefully handles gRPC error' do
+      expect(Gitlab::GitalyClient).to receive(:call).with(
+        storage_name,
+        :health_check,
+        :check,
+        instance_of(Grpc::Health::V1::HealthCheckRequest),
+        timeout: Gitlab::GitalyClient.fast_timeout)
+          .and_raise(GRPC::Unavailable.new('Connection refused'))
+
+      expect(subject.check).to eq({ success: false, message: '14:Connection refused' })
+    end
+  end
+end

spec/lib/gitlab/gitaly_client_spec.rb

@@ -3,6 +3,31 @@ require 'spec_helper'
 # We stub Gitaly in `spec/support/gitaly.rb` for other tests. We don't want
 # those stubs while testing the GitalyClient itself.
 describe Gitlab::GitalyClient, skip_gitaly_mock: true do
+  describe '.stub_class' do
+    it 'returns the gRPC health check stub' do
+      expect(described_class.stub_class(:health_check)).to eq(::Grpc::Health::V1::Health::Stub)
+    end
+
+    it 'returns a Gitaly stub' do
+      expect(described_class.stub_class(:ref_service)).to eq(::Gitaly::RefService::Stub)
+    end
+  end
+
+  describe '.stub_address' do
+    it 'returns the same result after being called multiple times' do
+      address = 'localhost:9876'
+      prefixed_address = "tcp://#{address}"
+
+      allow(Gitlab.config.repositories).to receive(:storages).and_return({
+        'default' => { 'gitaly_address' => prefixed_address }
+      })
+
+      2.times do
+        expect(described_class.stub_address('default')).to eq('localhost:9876')
+      end
+    end
+  end
+
   describe '.stub' do
     # Notice that this is referring to gRPC "stubs", not rspec stubs
     before do

spec/lib/gitlab/health_checks/gitaly_check_spec.rb

+require 'spec_helper'
+
+describe Gitlab::HealthChecks::GitalyCheck do
+  let(:result_class) { Gitlab::HealthChecks::Result }
+  let(:repository_storages) { ['default'] }
+
+  before do
+    allow(described_class).to receive(:repository_storages) { repository_storages }
+  end
+
+  describe '#readiness' do
+    subject { described_class.readiness }
+
+    before do
+      expect(Gitlab::GitalyClient::HealthCheckService).to receive(:new).and_return(gitaly_check)
+    end
+
+    context 'Gitaly server is up' do
+      let(:gitaly_check) { double(check: { success: true }) }
+
+      it { is_expected.to eq([result_class.new(true, nil, shard: 'default')]) }
+    end
+
+    context 'Gitaly server is down' do
+      let(:gitaly_check) { double(check: { success: false, message: 'Connection refused' }) }
+
+      it { is_expected.to eq([result_class.new(false, 'Connection refused', shard: 'default')]) }
+    end
+  end
+
+  describe '#metrics' do
+    subject { described_class.metrics }
+
+    before do
+      expect(Gitlab::GitalyClient::HealthCheckService).to receive(:new).and_return(gitaly_check)
+    end
+
+    context 'Gitaly server is up' do
+      let(:gitaly_check) { double(check: { success: true }) }
+
+      it 'provides metrics' do
+        expect(subject).to all(have_attributes(labels: { shard: 'default' }))
+        expect(subject).to include(an_object_having_attributes(name: 'gitaly_health_check_success', value: 1))
+        expect(subject).to include(an_object_having_attributes(name: 'gitaly_health_check_latency_seconds', value: be >= 0))
+      end
+    end
+
+    context 'Gitaly server is down' do
+      let(:gitaly_check) { double(check: { success: false, message: 'Connection refused' }) }
+
+      it 'provides metrics' do
+        expect(subject).to include(an_object_having_attributes(name: 'gitaly_health_check_success', value: 0))
+        expect(subject).to include(an_object_having_attributes(name: 'gitaly_health_check_latency_seconds', value: be >= 0))
+      end
+    end
+  end
+end