Geo: Add logging to help diagnose lack of syncing

Using error level since unhealthy shards constitute an error condition.

app/workers/concerns/each_shard_worker.rb

@@ -24,7 +24,13 @@ module EachShardWorker
   end
 
   def healthy_ready_shards
-    ready_shards.select(&:success)
+    success_checks, failed_checks = ready_shards.partition(&:success)
+
+    if failed_checks.any?
+      ::Gitlab::AppLogger.error(message: 'Excluding unhealthy shards', failed_checks: failed_checks.map(&:payload), class: self.class.name)
+    end
+
+    success_checks
   end
 
   def ready_shards

ee/app/workers/geo/repository_shard_sync_worker.rb

@@ -10,7 +10,10 @@ module Geo
     def perform(shard_name)
       @shard_name = shard_name
 
-      return unless Gitlab::ShardHealthCache.healthy_shard?(shard_name)
+      unless Gitlab::ShardHealthCache.healthy_shard?(shard_name)
+        log_error("Skipped scheduling syncs due to unhealthy shard", nil, { shard_name: shard_name })
+        return
+      end
 
       super()
     end

ee/spec/workers/geo/design_repository_shard_sync_worker_spec.rb

@@ -27,6 +27,8 @@ RSpec.describe Geo::DesignRepositoryShardSyncWorker, :geo, :clean_gitlab_redis_c
     it 'does not perform Geo::DesignRepositorySyncWorker when shard becomes unhealthy' do
       Gitlab::ShardHealthCache.update([])
 
+      log_data = { message: "Skipped scheduling syncs due to unhealthy shard", shard_name: shard_name }
+      expect(Gitlab::Geo::Logger).to receive(:error).with(a_hash_including(log_data))
       expect(Geo::DesignRepositorySyncWorker).not_to receive(:perform_async)
 
       subject.perform(shard_name)

ee/spec/workers/geo/repository_shard_sync_worker_spec.rb

@@ -24,6 +24,8 @@ RSpec.describe Geo::RepositoryShardSyncWorker, :geo, :clean_gitlab_redis_cache,
     it 'does not perform Geo::ProjectSyncWorker when shard becomes unhealthy' do
       Gitlab::ShardHealthCache.update([])
 
+      log_data = { message: "Skipped scheduling syncs due to unhealthy shard", shard_name: shard_name }
+      expect(Gitlab::Geo::Logger).to receive(:error).with(a_hash_including(log_data))
       expect(Geo::ProjectSyncWorker).not_to receive(:perform_async)
 
       subject.perform(shard_name)

ee/spec/workers/geo/scheduler/per_shard_scheduler_worker_spec.rb

@@ -56,6 +56,13 @@ RSpec.describe Geo::Scheduler::PerShardSchedulerWorker do
       it "returns an array of healthy shard names" do
         expect(per_shard_scheduler_worker.healthy_ready_shards).to eq(healthy_ready_shards)
       end
+
+      it "logs unhealthy shards" do
+        log_data = { message: "Excluding unhealthy shards", failed_checks: [{ labels: { shard: unhealthy_shard_name }, message: '14:Connect Failed', status: 'failed' }], class: described_class.name }
+        expect(Gitlab::AppLogger).to receive(:error).with(a_hash_including(log_data))
+
+        per_shard_scheduler_worker.healthy_ready_shards
+      end
     end
 
     describe '#healthy_shard_names' do

spec/workers/repository_check/dispatch_worker_spec.rb

@@ -42,5 +42,12 @@ RSpec.describe RepositoryCheck::DispatchWorker do
 
       subject.perform
     end
+
+    it 'logs unhealthy shards' do
+      log_data = { message: "Excluding unhealthy shards", failed_checks: [{ labels: { shard: unhealthy_shard_name }, message: '14:Connect Failed', status: 'failed' }], class: described_class.name }
+      expect(Gitlab::AppLogger).to receive(:error).with(a_hash_including(log_data))
+
+      subject.perform
+    end
   end
 end