Merge branch '289838-add-vm-stats-endpoint' into 'master'

Add /-/metrics/system endpoint

See merge request gitlab-org/gitlab!51095

app/controllers/metrics_controller.rb

@@ -18,9 +18,19 @@ class MetricsController < ActionController::Base
     render plain: response, content_type: 'text/plain; version=0.0.4'
   end
 
+  def system
+    render json: system_metrics
+  end
+
   private
 
   def metrics_service
     @metrics_service ||= MetricsService.new
   end
+
+  def system_metrics
+    Gitlab::Metrics::System.summary.merge(
+      worker_id: Prometheus::PidProvider.worker_id
+    )
+  end
 end

config/routes.rb

@@ -92,7 +92,10 @@ Rails.application.routes.draw do
     # '/-/health' implemented by BasicHealthCheck middleware
     get 'liveness' => 'health#liveness'
     get 'readiness' => 'health#readiness'
-    resources :metrics, only: [:index]
+    controller :metrics do
+      get 'metrics', action: :index
+      get 'metrics/system', action: :system
+    end
     mount Peek::Railtie => '/peek', as: 'peek_routes'
 
     get 'runner_setup/platforms' => 'runner_setup#platforms'

doc/development/profiling.md

@@ -128,6 +128,62 @@ console.
 
 As a follow up to finding `N+1` queries with Bullet, consider writing a [QueryRecoder test](query_recorder.md) to prevent a regression.
 
+## System stats
+
+During or after profiling, you may want to get detailed information about the Ruby virtual machine process,
+such as memory consumption, time spent on CPU, or garbage collector statistics. These are easy to produce individually
+through various tools, but for convenience, a summary endpoint has been added that exports this data as a JSON payload:
+
+```shell
+curl localhost:3000/-/metrics/system | jq
+```
+
+Example output:
+
+```json
+{
+  "version": "ruby 2.7.2p137 (2020-10-01 revision a8323b79eb) [x86_64-linux-gnu]",
+  "gc_stat": {
+    "count": 118,
+    "heap_allocated_pages": 11503,
+    "heap_sorted_length": 11503,
+    "heap_allocatable_pages": 0,
+    "heap_available_slots": 4688580,
+    "heap_live_slots": 3451712,
+    "heap_free_slots": 1236868,
+    "heap_final_slots": 0,
+    "heap_marked_slots": 3451450,
+    "heap_eden_pages": 11503,
+    "heap_tomb_pages": 0,
+    "total_allocated_pages": 11503,
+    "total_freed_pages": 0,
+    "total_allocated_objects": 32679478,
+    "total_freed_objects": 29227766,
+    "malloc_increase_bytes": 84760,
+    "malloc_increase_bytes_limit": 32883343,
+    "minor_gc_count": 88,
+    "major_gc_count": 30,
+    "compact_count": 0,
+    "remembered_wb_unprotected_objects": 114228,
+    "remembered_wb_unprotected_objects_limit": 228456,
+    "old_objects": 3185330,
+    "old_objects_limit": 6370660,
+    "oldmalloc_increase_bytes": 21838024,
+    "oldmalloc_increase_bytes_limit": 119181499
+  },
+  "memory_rss": 1326501888,
+  "memory_uss": 1048563712,
+  "memory_pss": 1139554304,
+  "time_cputime": 82.885264633,
+  "time_realtime": 1610459445.5579069,
+  "time_monotonic": 24001.23145713,
+  "worker_id": "puma_0"
+}
+```
+
+NOTE:
+This endpoint is only available for Rails web workers. Sidekiq workers can not be inspected this way.
+
 ## Settings that impact performance
 
 ### Application settings

lib/gitlab/metrics/system.rb

@@ -17,6 +17,20 @@ module Gitlab
       RSS_PATTERN = /VmRSS:\s+(?<value>\d+)/.freeze
       MAX_OPEN_FILES_PATTERN = /Max open files\s*(?<value>\d+)/.freeze
 
+      def self.summary
+        proportional_mem = memory_usage_uss_pss
+        {
+          version: RUBY_DESCRIPTION,
+          gc_stat: GC.stat,
+          memory_rss: memory_usage_rss,
+          memory_uss: proportional_mem[:uss],
+          memory_pss: proportional_mem[:pss],
+          time_cputime: cpu_time,
+          time_realtime: real_time,
+          time_monotonic: monotonic_time
+        }
+      end
+
       # Returns the current process' RSS (resident set size) in bytes.
       def self.memory_usage_rss
         sum_matches(PROC_STATUS_PATH, rss: RSS_PATTERN)[:rss].kilobytes

spec/controllers/metrics_controller_spec.rb

@@ -28,8 +28,38 @@ RSpec.describe MetricsController, :request_store do
     end
   end
 
+  shared_examples_for 'protected metrics endpoint' do |examples|
+    context 'accessed from whitelisted ip' do
+      before do
+        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(whitelisted_ip)
+      end
+
+      it_behaves_like examples
+    end
+
+    context 'accessed from ip in whitelisted range' do
+      before do
+        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(ip_in_whitelisted_range)
+      end
+
+      it_behaves_like examples
+    end
+
+    context 'accessed from not whitelisted ip' do
+      before do
+        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(not_whitelisted_ip)
+      end
+
+      it 'returns the expected error response' do
+        get :index
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+  end
+
   describe '#index' do
-    shared_examples_for 'endpoint providing metrics' do
+    shared_examples_for 'providing metrics' do
       it 'returns prometheus metrics' do
         get :index
 
@@ -51,32 +81,35 @@ RSpec.describe MetricsController, :request_store do
       end
     end
 
-    context 'accessed from whitelisted ip' do
-      before do
-        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(whitelisted_ip)
+    include_examples 'protected metrics endpoint', 'providing metrics'
   end
 
-      it_behaves_like 'endpoint providing metrics'
+  describe '#system' do
+    shared_examples_for 'providing system stats' do
+      let(:summary) do
+        {
+          version: 'ruby-3.0-patch1',
+          memory_rss: 1024
+        }
       end
 
-    context 'accessed from ip in whitelisted range' do
-      before do
-        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(ip_in_whitelisted_range)
-      end
+      it 'renders system stats JSON' do
+        expect(Prometheus::PidProvider).to receive(:worker_id).and_return('worker-0')
+        expect(Gitlab::Metrics::System).to receive(:summary).and_return(summary)
 
-      it_behaves_like 'endpoint providing metrics'
-    end
+        get :system
 
-    context 'accessed from not whitelisted ip' do
-      before do
-        allow(Gitlab::RequestContext.instance).to receive(:client_ip).and_return(not_whitelisted_ip)
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(response_json['version']).to eq('ruby-3.0-patch1')
+        expect(response_json['worker_id']).to eq('worker-0')
+        expect(response_json['memory_rss']).to eq(1024)
       end
-
-      it 'returns the expected error response' do
-        get :index
-
-        expect(response).to have_gitlab_http_status(:not_found)
     end
+
+    include_examples 'protected metrics endpoint', 'providing system stats'
   end
+
+  def response_json
+    Gitlab::Json.parse(response.body)
   end
 end

spec/lib/gitlab/metrics/system_spec.rb

@@ -96,6 +96,25 @@ RSpec.describe Gitlab::Metrics::System do
         expect(described_class.memory_usage_uss_pss).to eq(uss: 475136, pss: 515072)
       end
     end
+
+    describe '.summary' do
+      it 'contains a selection of the available fields' do
+        stub_const('RUBY_DESCRIPTION', 'ruby-3.0-patch1')
+        mock_existing_proc_file('/proc/self/status', proc_status)
+        mock_existing_proc_file('/proc/self/smaps_rollup', proc_smaps_rollup)
+
+        summary = described_class.summary
+
+        expect(summary[:version]).to eq('ruby-3.0-patch1')
+        expect(summary[:gc_stat].keys).to eq(GC.stat.keys)
+        expect(summary[:memory_rss]).to eq(2527232)
+        expect(summary[:memory_uss]).to eq(475136)
+        expect(summary[:memory_pss]).to eq(515072)
+        expect(summary[:time_cputime]).to be_a(Float)
+        expect(summary[:time_realtime]).to be_a(Float)
+        expect(summary[:time_monotonic]).to be_a(Float)
+      end
+    end
   end
 
   context 'when /proc files do not exist' do
@@ -128,6 +147,21 @@ RSpec.describe Gitlab::Metrics::System do
         expect(described_class.max_open_file_descriptors).to eq(0)
       end
     end
+
+    describe '.summary' do
+      it 'returns only available fields' do
+        summary = described_class.summary
+
+        expect(summary[:version]).to be_a(String)
+        expect(summary[:gc_stat].keys).to eq(GC.stat.keys)
+        expect(summary[:memory_rss]).to eq(0)
+        expect(summary[:memory_uss]).to eq(0)
+        expect(summary[:memory_pss]).to eq(0)
+        expect(summary[:time_cputime]).to be_a(Float)
+        expect(summary[:time_realtime]).to be_a(Float)
+        expect(summary[:time_monotonic]).to be_a(Float)
+      end
+    end
   end
 
   describe '.cpu_time' do