Refine load_balancing_strategy metric label

lib/gitlab/database/load_balancing/sidekiq_client_middleware.rb

@@ -5,27 +5,29 @@ module Gitlab
     module LoadBalancing
       class SidekiqClientMiddleware
         def call(worker_class, job, _queue, _redis_pool)
+          # Mailers can't be constantized
           worker_class = worker_class.to_s.safe_constantize
 
-          mark_data_consistency_location(worker_class, job)
+          if load_balancing_enabled?(worker_class)
+            job['worker_data_consistency'] = worker_class.get_data_consistency
+            set_data_consistency_location!(job) unless location_already_provided?(job)
+          else
+            job['worker_data_consistency'] = ::WorkerAttributes::DEFAULT_DATA_CONSISTENCY
+          end
 
           yield
         end
 
         private
 
-        def mark_data_consistency_location(worker_class, job)
-          # Mailers can't be constantized
-          return unless worker_class
-          return unless worker_class.include?(::ApplicationWorker)
-          return unless worker_class.get_data_consistency_feature_flag_enabled?
-
-          return if location_already_provided?(job)
-
-          job['worker_data_consistency'] = worker_class.get_data_consistency
-
-          return unless worker_class.utilizes_load_balancing_capabilities?
+        def load_balancing_enabled?(worker_class)
+          worker_class &&
+            worker_class.include?(::ApplicationWorker) &&
+            worker_class.utilizes_load_balancing_capabilities? &&
+            worker_class.get_data_consistency_feature_flag_enabled?
+        end
 
+        def set_data_consistency_location!(job)
           if Session.current.use_primary?
             job['database_write_location'] = load_balancer.primary_write_location
           else

lib/gitlab/database/load_balancing/sidekiq_server_middleware.rb

@@ -10,17 +10,14 @@ module Gitlab
           worker_class = worker.class
           strategy = select_load_balancing_strategy(worker_class, job)
 
-          # This is consumed by ServerMetrics and StructuredLogger to emit metrics so we only
-          # make this available when load-balancing is actually utilized.
-          job['load_balancing_strategy'] = strategy.to_s if load_balancing_available?(worker_class)
+          job['load_balancing_strategy'] = strategy.to_s
 
-          case strategy
-          when :primary, :retry_primary
+          if use_primary?(strategy)
             Session.current.use_primary!
-          when :retry_replica
+          elsif strategy == :retry
             raise JobReplicaNotUpToDate, "Sidekiq job #{worker_class} JID-#{job['jid']} couldn't use the replica."\
               "  Replica was not up to date."
-          when :replica
+          else
             # this means we selected an up-to-date replica, but there is nothing to do in this case.
           end
 
@@ -36,17 +33,24 @@ module Gitlab
           Session.clear_session
         end
 
+        def use_primary?(strategy)
+          strategy.start_with?('primary')
+        end
+
         def select_load_balancing_strategy(worker_class, job)
           return :primary unless load_balancing_available?(worker_class)
 
           location = job['database_write_location'] || job['database_replica_location']
-          return :primary unless location
+          return :primary_no_wal unless location
 
           if replica_caught_up?(location)
-            :replica
-          elsif worker_class.get_data_consistency == :delayed
-            not_yet_retried?(job) ? :retry_replica : :retry_primary
+            # Happy case: we can read from a replica.
+            retried_before?(worker_class, job) ? :replica_retried : :replica
+          elsif can_retry?(worker_class, job)
+            # Optimistic case: The worker allows retries and we have retries left.
+            :retry
           else
+            # Sad case: we need to fall back to the primary.
             :primary
           end
         end
@@ -57,6 +61,14 @@ module Gitlab
             worker_class.get_data_consistency_feature_flag_enabled?
         end
 
+        def can_retry?(worker_class, job)
+          worker_class.get_data_consistency == :delayed && not_yet_retried?(job)
+        end
+
+        def retried_before?(worker_class, job)
+          worker_class.get_data_consistency == :delayed && !not_yet_retried?(job)
+        end
+
         def not_yet_retried?(job)
           # if `retry_count` is `nil` it indicates that this job was never retried
           # the `0` indicates that this is a first retry

spec/lib/gitlab/database/load_balancing/sidekiq_client_middleware_spec.rb

@@ -5,12 +5,27 @@ require 'spec_helper'
 RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
   let(:middleware) { described_class.new }
 
+  let(:load_balancer) { double.as_null_object }
+  let(:worker_class) { 'TestDataConsistencyWorker' }
+  let(:job) { { "job_id" => "a180b47c-3fd6-41b8-81e9-34da61c3400e" } }
+
+  before do
+    skip_feature_flags_yaml_validation
+    skip_default_enabled_yaml_check
+    allow(::Gitlab::Database::LoadBalancing).to receive_message_chain(:proxy, :load_balancer).and_return(load_balancer)
+  end
+
   after do
     Gitlab::Database::LoadBalancing::Session.clear_session
   end
 
+  def run_middleware
+    middleware.call(worker_class, job, nil, nil) {}
+  end
+
   describe '#call' do
     shared_context 'data consistency worker class' do |data_consistency, feature_flag|
+      let(:expected_consistency) { data_consistency }
       let(:worker_class) do
         Class.new do
           def self.name
@@ -31,13 +46,23 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
       end
     end
 
+    shared_examples_for 'job data consistency' do
+      it "sets job data consistency" do
+        run_middleware
+
+        expect(job['worker_data_consistency']).to eq(expected_consistency)
+      end
+    end
+
     shared_examples_for 'does not pass database locations' do
       it 'does not pass database locations', :aggregate_failures do
-        middleware.call(worker_class, job, double(:queue), redis_pool) { 10 }
+        run_middleware
 
         expect(job['database_replica_location']).to be_nil
         expect(job['database_write_location']).to be_nil
       end
+
+      include_examples 'job data consistency'
     end
 
     shared_examples_for 'mark data consistency location' do |data_consistency|
@@ -45,7 +70,9 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
 
       let(:location) { '0/D525E3A8' }
 
-      context 'when feature flag load_balancing_for_sidekiq is disabled' do
+      context 'when feature flag is disabled' do
+        let(:expected_consistency) { :always }
+
         before do
           stub_feature_flags(load_balancing_for_test_data_consistency_worker: false)
         end
@@ -59,12 +86,14 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
         end
 
         it 'passes database_replica_location' do
-          expect(middleware).to receive_message_chain(:load_balancer, :host, "database_replica_location").and_return(location)
+          expect(load_balancer).to receive_message_chain(:host, "database_replica_location").and_return(location)
 
-          middleware.call(worker_class, job, double(:queue), redis_pool) { 10 }
+          run_middleware
 
           expect(job['database_replica_location']).to eq(location)
         end
+
+        include_examples 'job data consistency'
       end
 
       context 'when write was performed' do
@@ -73,12 +102,14 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
         end
 
         it 'passes primary write location', :aggregate_failures do
-          expect(middleware).to receive_message_chain(:load_balancer, :primary_write_location).and_return(location)
+          expect(load_balancer).to receive(:primary_write_location).and_return(location)
 
-          middleware.call(worker_class, job, double(:queue), redis_pool) { 10 }
+          run_middleware
 
           expect(job['database_write_location']).to eq(location)
         end
+
+        include_examples 'job data consistency'
       end
     end
 
@@ -89,7 +120,7 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
         end
 
         it 'does not set database locations again' do
-          middleware.call(worker_class, job, double(:queue), redis_pool) { 10 }
+          run_middleware
 
           expect(job[provided_database_location]).to eq(old_location)
           expect(job[other_location]).to be_nil
@@ -101,8 +132,8 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
       let(:job) { { "job_id" => "a180b47c-3fd6-41b8-81e9-34da61c3400e", provided_database_location => old_location } }
 
       before do
-        allow(middleware).to receive_message_chain(:load_balancer, :primary_write_location).and_return(new_location)
-        allow(middleware).to receive_message_chain(:load_balancer, :database_replica_location).and_return(new_location)
+        allow(load_balancer).to receive(:primary_write_location).and_return(new_location)
+        allow(load_balancer).to receive(:database_replica_location).and_return(new_location)
       end
 
       context "when write was performed" do
@@ -114,24 +145,16 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqClientMiddleware do
       end
     end
 
-    let(:queue) { 'default' }
-    let(:redis_pool) { Sidekiq.redis_pool }
-    let(:worker_class) { 'TestDataConsistencyWorker' }
-    let(:job) { { "job_id" => "a180b47c-3fd6-41b8-81e9-34da61c3400e" } }
-
-    before do
-      skip_feature_flags_yaml_validation
-      skip_default_enabled_yaml_check
-    end
-
     context 'when worker cannot be constantized' do
       let(:worker_class) { 'ActionMailer::MailDeliveryJob' }
+      let(:expected_consistency) { :always }
 
       include_examples 'does not pass database locations'
     end
 
     context 'when worker class does not include ApplicationWorker' do
       let(:worker_class) { ActiveJob::QueueAdapters::SidekiqAdapter::JobWrapper }
+      let(:expected_consistency) { :always }
 
       include_examples 'does not pass database locations'
     end

spec/lib/gitlab/database/load_balancing/sidekiq_server_middleware_spec.rb

@@ -6,11 +6,16 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
   let(:middleware) { described_class.new }
 
   let(:load_balancer) { double.as_null_object }
-  let(:has_replication_lag) { false }
+
+  let(:worker) { worker_class.new }
+  let(:job) { { "retry" => 3, "job_id" => "a180b47c-3fd6-41b8-81e9-34da61c3400e", 'database_replica_location' => '0/D525E3A8' } }
 
   before do
+    skip_feature_flags_yaml_validation
+    skip_default_enabled_yaml_check
     allow(::Gitlab::Database::LoadBalancing).to receive_message_chain(:proxy, :load_balancer).and_return(load_balancer)
-    allow(load_balancer).to receive(:select_up_to_date_host).and_return(!has_replication_lag)
+
+    replication_lag!(false)
   end
 
   after do
@@ -39,24 +44,34 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
       end
     end
 
-    shared_examples_for 'stick to the primary' do
+    shared_examples_for 'load balancing strategy' do |strategy|
+      it "sets load balancing strategy to #{strategy}" do
+        run_middleware do
+          expect(job['load_balancing_strategy']).to eq(strategy)
+        end
+      end
+    end
+
+    shared_examples_for 'stick to the primary' do |expected_strategy|
       it 'sticks to the primary' do
-        middleware.call(worker, job, double(:queue)) do
+        run_middleware do
           expect(Gitlab::Database::LoadBalancing::Session.current.use_primary?).to be_truthy
         end
       end
+
+      include_examples 'load balancing strategy', expected_strategy
     end
 
-    shared_examples_for 'replica is up to date' do |location|
+    shared_examples_for 'replica is up to date' do |location, expected_strategy|
       it 'does not stick to the primary', :aggregate_failures do
         expect(middleware).to receive(:replica_caught_up?).with(location).and_return(true)
 
-        middleware.call(worker, job, double(:queue)) do
+        run_middleware do
           expect(Gitlab::Database::LoadBalancing::Session.current.use_primary?).not_to be_truthy
         end
-
-        expect(job['load_balancing_strategy']).to eq('replica')
       end
+
+      include_examples 'load balancing strategy', expected_strategy
     end
 
     shared_examples_for 'sticks based on data consistency' do |data_consistency|
@@ -67,7 +82,7 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
           stub_feature_flags(load_balancing_for_test_data_consistency_worker: false)
         end
 
-        include_examples 'stick to the primary'
+        include_examples 'stick to the primary', 'primary'
       end
 
       context 'when database replica location is set' do
@@ -77,7 +92,7 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
           allow(middleware).to receive(:replica_caught_up?).and_return(true)
         end
 
-        it_behaves_like 'replica is up to date', '0/D525E3A8'
+        it_behaves_like 'replica is up to date', '0/D525E3A8', 'replica'
       end
 
       context 'when database primary location is set' do
@@ -87,46 +102,35 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
           allow(middleware).to receive(:replica_caught_up?).and_return(true)
         end
 
-        it_behaves_like 'replica is up to date', '0/D525E3A8'
+        it_behaves_like 'replica is up to date', '0/D525E3A8', 'replica'
       end
 
       context 'when database location is not set' do
         let(:job) { { 'job_id' => 'a180b47c-3fd6-41b8-81e9-34da61c3400e' } }
 
-        it_behaves_like 'stick to the primary'
+        it_behaves_like 'stick to the primary', 'primary_no_wal'
       end
     end
 
-    let(:queue) { 'default' }
-    let(:redis_pool) { Sidekiq.redis_pool }
-    let(:worker) { worker_class.new }
-    let(:job) { { "retry" => 3, "job_id" => "a180b47c-3fd6-41b8-81e9-34da61c3400e", 'database_replica_location' => '0/D525E3A8' } }
-    let(:block) { 10 }
-
-    before do
-      skip_feature_flags_yaml_validation
-      skip_default_enabled_yaml_check
-      allow(middleware).to receive(:clear)
-      allow(Gitlab::Database::LoadBalancing::Session.current).to receive(:performed_write?).and_return(true)
-    end
-
     context 'when worker class does not include ApplicationWorker' do
       let(:worker) { ActiveJob::QueueAdapters::SidekiqAdapter::JobWrapper.new }
 
-      include_examples 'stick to the primary'
+      include_examples 'stick to the primary', 'primary'
     end
 
     context 'when worker data consistency is :always' do
       include_context 'data consistency worker class', :always, :load_balancing_for_test_data_consistency_worker
 
-      include_examples 'stick to the primary'
+      include_examples 'stick to the primary', 'primary'
     end
 
     context 'when worker data consistency is :delayed' do
       include_examples 'sticks based on data consistency', :delayed
 
       context 'when replica is not up to date' do
-        let(:has_replication_lag) { true }
+        before do
+          replication_lag!(true)
+        end
 
         around do |example|
           with_sidekiq_server_middleware do |chain|
@@ -136,24 +140,34 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
         end
 
         context 'when job is executed first' do
-          it 'raise an error and retries', :aggregate_failures do
+          it 'raises an error and retries', :aggregate_failures do
             expect do
               process_job(job)
             end.to raise_error(Sidekiq::JobRetry::Skip)
 
             expect(job['error_class']).to eq('Gitlab::Database::LoadBalancing::SidekiqServerMiddleware::JobReplicaNotUpToDate')
-            expect(job['load_balancing_strategy']).to eq('retry_replica')
           end
+
+          include_examples 'load balancing strategy', 'retry'
         end
 
         context 'when job is retried' do
-          it 'stick to the primary', :aggregate_failures do
+          before do
             expect do
               process_job(job)
             end.to raise_error(Sidekiq::JobRetry::Skip)
+          end
 
-            process_job(job)
-            expect(job['load_balancing_strategy']).to eq('retry_primary')
+          context 'and replica still lagging behind' do
+            include_examples 'stick to the primary', 'primary'
+          end
+
+          context 'and replica is now up-to-date' do
+            before do
+              replication_lag!(false)
+            end
+
+            it_behaves_like 'replica is up to date', '0/D525E3A8', 'replica_retried'
           end
         end
       end
@@ -167,20 +181,24 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware do
           allow(middleware).to receive(:replica_caught_up?).and_return(false)
         end
 
-        include_examples 'stick to the primary'
-
-        it 'updates job hash with primary database chosen', :aggregate_failures do
-          middleware.call(worker, job, double(:queue)) do
-            expect(job['load_balancing_strategy']).to eq('primary')
-          end
-        end
+        include_examples 'stick to the primary', 'primary'
       end
     end
   end
 
   def process_job(job)
-    Sidekiq::JobRetry.new.local(worker_class, job, queue) do
+    Sidekiq::JobRetry.new.local(worker_class, job, 'default') do
       worker_class.process_job(job)
     end
   end
+
+  def run_middleware
+    middleware.call(worker, job, double(:queue)) { yield }
+  rescue described_class::JobReplicaNotUpToDate
+    # we silence errors here that cause the job to retry
+  end
+
+  def replication_lag!(exists)
+    allow(load_balancer).to receive(:select_up_to_date_host).and_return(!exists)
+  end
 end

spec/lib/gitlab/sidekiq_middleware/server_metrics_spec.rb

@@ -260,7 +260,7 @@ RSpec.describe Gitlab::SidekiqMiddleware::ServerMetrics do
         context 'when worker declares data consistency' do
           include_context 'worker declaring data consistency'
 
-          it 'increments load balancing counter' do
+          it 'increments load balancing counter with defined data consistency' do
             process_job
 
             expect(load_balancing_metric).to have_received(:increment).with(
@@ -272,10 +272,14 @@ RSpec.describe Gitlab::SidekiqMiddleware::ServerMetrics do
         end
 
         context 'when worker does not declare data consistency' do
-          it 'does not increment load balancing counter' do
+          it 'increments load balancing counter with default data consistency' do
             process_job
 
-            expect(load_balancing_metric).not_to have_received(:increment)
+            expect(load_balancing_metric).to have_received(:increment).with(
+              a_hash_including(
+                data_consistency: :always,
+                load_balancing_strategy: 'primary'
+              ), 1)
           end
         end
       end