Fix pid providing for Prometheus

Use relative worker identifier for metrics (instead of Process.pid) and
identify when Unicorn/Puma/Sidekiq is used.
Previously, it was assumed that all metrics are gathered from Unicorn
due to hardcoded implementation which was incorrect.

1 files changed, 79 insertions, 0 deletions

diff --git a/spec/lib/prometheus/pid_provider_spec.rb b/spec/lib/prometheus/pid_provider_spec.rb
new file mode 100644
index 00000000000..e7d500612b1
--- /dev/null
+++ b/spec/lib/prometheus/pid_provider_spec.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Prometheus::PidProvider do
+  describe '.worker_id' do
+    subject { described_class.worker_id }
+
+    let(:sidekiq_module) { Module.new }
+
+    before do
+      allow(sidekiq_module).to receive(:server?).and_return(false)
+      stub_const('Sidekiq', sidekiq_module)
+    end
+
+    context 'when running in Sidekiq server mode' do
+      before do
+        expect(Sidekiq).to receive(:server?).and_return(true)
+      end
+
+      it { is_expected.to eq 'sidekiq' }
+    end
+
+    context 'when running in Unicorn mode' do
+      before do
+        stub_const('Unicorn::Worker', Class.new)
+        hide_const('Puma')
+      end
+
+      context 'when `Prometheus::Client::Support::Unicorn` provides worker_id' do
+        before do
+          expect(::Prometheus::Client::Support::Unicorn).to receive(:worker_id).and_return(1)
+        end
+
+        it { is_expected.to eq 'unicorn_1' }
+      end
+
+      context 'when no worker_id is provided from `Prometheus::Client::Support::Unicorn`' do
+        before do
+          expect(::Prometheus::Client::Support::Unicorn).to receive(:worker_id).and_return(nil)
+        end
+
+        it { is_expected.to eq 'unicorn_master' }
+      end
+    end
+
+    context 'when running in Puma mode' do
+      before do
+        stub_const('Puma', Module.new)
+        hide_const('Unicorn::Worker')
+      end
+
+      context 'when cluster worker id is specified in process name' do
+        before do
+          expect(described_class).to receive(:process_name).and_return('puma: cluster worker 1: 17483 [gitlab-puma-worker]')
+        end
+
+        it { is_expected.to eq 'puma_1' }
+      end
+
+      context 'when no worker id is specified in process name' do
+        before do
+          expect(described_class).to receive(:process_name).and_return('bin/puma')
+        end
+
+        it { is_expected.to eq 'puma_master' }
+      end
+    end
+
+    context 'when running in unknown mode' do
+      before do
+        hide_const('Puma')
+        hide_const('Unicorn::Worker')
+      end
+
+      it { is_expected.to eq "process_#{Process.pid}" }
+    end
+  end
+end