Merge branch 'pawel/update_prometheus_gem_to_well_tested_version' into 'master'

Update Prometheus Gem version and disable Prometheus method call instrumentation by default.

Closes gitlab-ee#4139 and #40457

See merge request gitlab-org/gitlab-ce!15558

8 files changed, 83 insertions, 46 deletions

diff --git a/Gemfile b/Gemfile
index 6034323956c..53820459a16 100644
--- a/Gemfile
+++ b/Gemfile
@@ -283,7 +283,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
 
   # Prometheus
-  gem 'prometheus-client-mmap', '~>0.7.0.beta18'
+  gem 'prometheus-client-mmap', '~> 0.7.0.beta36'
   gem 'raindrops', '~> 0.18'
 end
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 4787be92365..69d20bdbbb3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -488,7 +488,7 @@ GEM
     mini_mime (0.1.4)
     mini_portile2 (2.3.0)
     minitest (5.7.0)
-    mmap2 (2.2.7)
+    mmap2 (2.2.9)
     mousetrap-rails (1.4.6)
     multi_json (1.12.2)
     multi_xml (0.6.0)
@@ -625,8 +625,8 @@ GEM
       parser
       unparser
     procto (0.0.3)
-    prometheus-client-mmap (0.7.0.beta18)
-      mmap2 (~> 2.2, >= 2.2.7)
+    prometheus-client-mmap (0.7.0.beta36)
+      mmap2 (~> 2.2, >= 2.2.9)
     pry (0.10.4)
       coderay (~> 1.1.0)
       method_source (~> 0.8.1)
@@ -1111,7 +1111,7 @@ DEPENDENCIES
   peek-sidekiq (~> 1.0.3)
   pg (~> 0.18.2)
   premailer-rails (~> 1.9.7)
-  prometheus-client-mmap (~> 0.7.0.beta18)
+  prometheus-client-mmap (~> 0.7.0.beta36)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
   rack-attack (~> 4.4.1)
diff --git a/changelogs/unreleased/pawel-update_prometheus_gem_to_well_tested_version.yml b/changelogs/unreleased/pawel-update_prometheus_gem_to_well_tested_version.yml
new file mode 100644
index 00000000000..a4133ae5cec
--- /dev/null
+++ b/changelogs/unreleased/pawel-update_prometheus_gem_to_well_tested_version.yml
@@ -0,0 +1,5 @@
+---
+title: Reenable Prometheus metrics, add more control over Prometheus method instrumentation
+merge_request: 15558
+author:
+type: fixed
diff --git a/config/initializers/7_prometheus_metrics.rb b/config/initializers/7_prometheus_metrics.rb
index e8f33593fe0..43b1e943897 100644
--- a/config/initializers/7_prometheus_metrics.rb
+++ b/config/initializers/7_prometheus_metrics.rb
@@ -12,16 +12,20 @@ Prometheus::Client.configure do |config|
   end
 
   config.pid_provider = -> do
-    wid = Prometheus::Client::Support::Unicorn.worker_id
-    wid = Process.pid if wid.nil?
-    if wid.nil?
+    worker_id = Prometheus::Client::Support::Unicorn.worker_id
+    if worker_id.nil?
       "process_pid_#{Process.pid}"
     else
-      "worker_id_#{wid}"
+      "worker_id_#{worker_id}"
     end
   end
 end
 
+Gitlab::Application.configure do |config|
+  # 0 should be Sentry to catch errors in this middleware
+  config.middleware.insert(1, Gitlab::Metrics::RequestsRackMiddleware)
+end
+
 Sidekiq.configure_server do |config|
   config.on(:startup) do
     Gitlab::Metrics::SidekiqMetricsExporter.instance.start
diff --git a/config/initializers/8_metrics.rb b/config/initializers/8_metrics.rb
index 7ef594836d6..45b39b2a38d 100644
--- a/config/initializers/8_metrics.rb
+++ b/config/initializers/8_metrics.rb
@@ -118,11 +118,6 @@ def instrument_classes(instrumentation)
 end
 # rubocop:enable Metrics/AbcSize
 
-Gitlab::Application.configure do |config|
-  # 0 should be Sentry to catch errors in this middleware
-  config.middleware.insert(1, Gitlab::Metrics::RequestsRackMiddleware)
-end
-
 if Gitlab::Metrics.enabled?
   require 'pathname'
   require 'influxdb'
diff --git a/lib/gitlab/metrics/method_call.rb b/lib/gitlab/metrics/method_call.rb
index 90235095306..65d55576ac2 100644
--- a/lib/gitlab/metrics/method_call.rb
+++ b/lib/gitlab/metrics/method_call.rb
@@ -6,29 +6,15 @@ module Gitlab
       BASE_LABELS = { module: nil, method: nil }.freeze
       attr_reader :real_time, :cpu_time, :call_count, :labels
 
-      def self.call_real_duration_histogram
-        return @call_real_duration_histogram if @call_real_duration_histogram
-
-        MUTEX.synchronize do
-          @call_real_duration_histogram ||= Gitlab::Metrics.histogram(
-            :gitlab_method_call_real_duration_seconds,
-            'Method calls real duration',
-            Transaction::BASE_LABELS.merge(BASE_LABELS),
-            [0.1, 0.2, 0.5, 1, 2, 5, 10]
-          )
-        end
-      end
-
-      def self.call_cpu_duration_histogram
-        return @call_cpu_duration_histogram if @call_cpu_duration_histogram
+      def self.call_duration_histogram
+        return @call_duration_histogram if @call_duration_histogram
 
         MUTEX.synchronize do
           @call_duration_histogram ||= Gitlab::Metrics.histogram(
-            :gitlab_method_call_cpu_duration_seconds,
-            'Method calls cpu duration',
+            :gitlab_method_call_duration_seconds,
+            'Method calls real duration',
             Transaction::BASE_LABELS.merge(BASE_LABELS),
-            [0.1, 0.2, 0.5, 1, 2, 5, 10]
-          )
+            [0.01, 0.05, 0.1, 0.5, 1])
         end
       end
 
@@ -59,8 +45,9 @@ module Gitlab
         @cpu_time += cpu_time
         @call_count += 1
 
-        self.class.call_real_duration_histogram.observe(@transaction.labels.merge(labels), real_time / 1000.0)
-        self.class.call_cpu_duration_histogram.observe(@transaction.labels.merge(labels), cpu_time / 1000.0)
+        if call_measurement_enabled? && above_threshold?
+          self.class.call_duration_histogram.observe(@transaction.labels.merge(labels), real_time / 1000.0)
+        end
 
         retval
       end
@@ -83,6 +70,10 @@ module Gitlab
       def above_threshold?
         real_time >= Metrics.method_call_threshold
       end
+
+      def call_measurement_enabled?
+        Feature.get(:prometheus_metrics_method_instrumentation).enabled?
+      end
     end
   end
 end
diff --git a/lib/gitlab/metrics/prometheus.rb b/lib/gitlab/metrics/prometheus.rb
index 4f165d12a94..09103b4ca2d 100644
--- a/lib/gitlab/metrics/prometheus.rb
+++ b/lib/gitlab/metrics/prometheus.rb
@@ -17,9 +17,9 @@ module Gitlab
       end
 
       def prometheus_metrics_enabled?
-        # force disable prometheus_metrics until
-        # https://gitlab.com/gitlab-org/prometheus-client-mmap/merge_requests/11 is ready
-        false
+        return @prometheus_metrics_enabled if defined?(@prometheus_metrics_enabled)
+
+        @prometheus_metrics_enabled = prometheus_metrics_enabled_unmemoized
       end
 
       def registry
diff --git a/spec/lib/gitlab/metrics/method_call_spec.rb b/spec/lib/gitlab/metrics/method_call_spec.rb
index f1e9e414e0d..5341addf911 100644
--- a/spec/lib/gitlab/metrics/method_call_spec.rb
+++ b/spec/lib/gitlab/metrics/method_call_spec.rb
@@ -13,16 +13,52 @@ describe Gitlab::Metrics::MethodCall do
       expect(method_call.call_count).to eq(1)
     end
 
-    it 'observes the performance of the supplied block' do
-      expect(described_class.call_real_duration_histogram)
-        .to receive(:observe)
-              .with({ module: :Foo, method: '#bar' }, be_a_kind_of(Numeric))
+    context 'when measurement is above threshold' do
+      before do
+        allow(method_call).to receive(:above_threshold?).and_return(true)
+      end
 
-      expect(described_class.call_cpu_duration_histogram)
-        .to receive(:observe)
-              .with({ module: :Foo, method: '#bar' }, be_a_kind_of(Numeric))
+      context 'prometheus instrumentation is enabled' do
+        before do
+          Feature.get(:prometheus_metrics_method_instrumentation).enable
+        end
 
-      method_call.measure { 'foo' }
+        it 'observes the performance of the supplied block' do
+          expect(described_class.call_duration_histogram)
+            .to receive(:observe)
+                  .with({ module: :Foo, method: '#bar' }, be_a_kind_of(Numeric))
+
+          method_call.measure { 'foo' }
+        end
+      end
+
+      context 'prometheus instrumentation is disabled' do
+        before do
+          Feature.get(:prometheus_metrics_method_instrumentation).disable
+        end
+
+        it 'does not observe the performance' do
+          expect(described_class.call_duration_histogram)
+            .not_to receive(:observe)
+
+          method_call.measure { 'foo' }
+        end
+      end
+    end
+
+    context 'when measurement is below threshold' do
+      before do
+        allow(method_call).to receive(:above_threshold?).and_return(false)
+
+        Feature.get(:prometheus_metrics_method_instrumentation).enable
+      end
+
+      it 'does not observe the performance' do
+        expect(described_class.call_duration_histogram)
+          .not_to receive(:observe)
+
+        method_call.measure { 'foo' }
+      end
     end
   end
 
@@ -43,7 +79,13 @@ describe Gitlab::Metrics::MethodCall do
   end
 
   describe '#above_threshold?' do
+    before do
+      allow(Gitlab::Metrics).to receive(:method_call_threshold).and_return(100)
+    end
+
     it 'returns false when the total call time is not above the threshold' do
+      expect(method_call).to receive(:real_time).and_return(9)
+
       expect(method_call.above_threshold?).to eq(false)
     end