Ignore Puma empty worker stats

In some cases (during worker start) it's possible that
Puma.stats returns an empty hash for worker's last status. In
that case we just skip sampling of the worker until these
stats are available.

2 files changed, 29 insertions, 1 deletions

diff --git a/lib/gitlab/metrics/samplers/puma_sampler.rb b/lib/gitlab/metrics/samplers/puma_sampler.rb
index 87669b253bc..25e40c70230 100644
--- a/lib/gitlab/metrics/samplers/puma_sampler.rb
+++ b/lib/gitlab/metrics/samplers/puma_sampler.rb
@@ -51,10 +51,11 @@ module Gitlab
           set_master_metrics(stats)
 
           stats['worker_status'].each do |worker|
+            last_status = worker['last_status']
             labels = { worker: "worker_#{worker['index']}" }
 
             metrics[:puma_phase].set(labels, worker['phase'])
-            set_worker_metrics(worker['last_status'], labels)
+            set_worker_metrics(last_status, labels) if last_status.present?
           end
         end
 
diff --git a/spec/lib/gitlab/metrics/samplers/puma_sampler_spec.rb b/spec/lib/gitlab/metrics/samplers/puma_sampler_spec.rb
index c471c30a194..f4a6e1fc7d9 100644
--- a/spec/lib/gitlab/metrics/samplers/puma_sampler_spec.rb
+++ b/spec/lib/gitlab/metrics/samplers/puma_sampler_spec.rb
@@ -61,6 +61,33 @@ describe Gitlab::Metrics::Samplers::PumaSampler do
       end
     end
 
+    context 'with empty worker stats' do
+      let(:puma_stats) do
+        <<~EOS
+        {
+          "workers": 2,
+          "phase": 2,
+          "booted_workers": 2,
+          "old_workers": 0,
+          "worker_status": [{
+            "pid": 32534,
+            "index": 0,
+            "phase": 1,
+            "booted": true,
+            "last_checkin": "2019-05-15T07:57:55Z",
+            "last_status": {}
+          }]
+        }
+        EOS
+      end
+
+      it 'does not log worker stats' do
+        expect(subject).not_to receive(:set_worker_metrics)
+
+        subject.sample
+      end
+    end
+
     context 'in single mode' do
       let(:puma_stats) do
         <<~EOS