Add marking and sweeping time as Process stat

Introduced in https://bugs.ruby-lang.org/issues/19437

README.md

@@ -371,6 +371,8 @@ end
 | Counter | `major_gc_ops_total`      | Major GC operations by process               |
 | Counter | `minor_gc_ops_total`      | Minor GC operations by process               |
 | Counter | `allocated_objects_total` | Total number of allocated objects by process |
+| Gauge   | `marking_time`            | Marking time spent                           |
+| Gauge   | `sweeping_time`           | Sweeping time spent                          |
 
 _Metrics marked with * are only collected when `MiniRacer` is defined._
 

lib/prometheus_exporter/instrumentation/process.rb

@@ -63,6 +63,8 @@ def collect_gc_stats(metric)
       metric[:major_gc_ops_total] = stat[:major_gc_count]
       metric[:minor_gc_ops_total] = stat[:minor_gc_count]
       metric[:allocated_objects_total] = stat[:total_allocated_objects]
+      metric[:marking_time] = stat[:mark_time]
+      metric[:sweeping_time] = stat[:sweep_time]
     end
 
     def collect_v8_stats(metric)

lib/prometheus_exporter/server/process_collector.rb

@@ -13,6 +13,8 @@ class ProcessCollector < TypeCollector
       v8_physical_size: "Physical size consumed by V8 heaps.",
       v8_heap_count: "Number of V8 contexts running.",
       rss: "Total RSS used by process.",
+      marking_time: "Time spent in GC marking.",
+      sweeping_time: "Time spent in GC sweeping.",
     }
 
     PROCESS_COUNTERS = {

test/server/process_collector_test.rb

@@ -26,14 +26,16 @@ def base_data
       "rss" => 3000,
       "major_gc_ops_total" => 4000,
       "minor_gc_ops_total" => 4001,
-      "allocated_objects_total" => 4002
+      "allocated_objects_total" => 4002,
+      "marking_time" => 4003,
+      "sweeping_time" => 4004,
     }
   end
 
   def test_metrics_collection
     collector.collect(base_data)
 
-    assert_equal 10, collector.metrics.size
+    assert_equal 12, collector.metrics.size
     assert_equal [
       'heap_free_slots{pid="1000",hostname="localhost"} 1000',
       'heap_live_slots{pid="1000",hostname="localhost"} 1001',
@@ -42,30 +44,32 @@ def test_metrics_collection
       'v8_physical_size{pid="1000",hostname="localhost"} 2003',
       'v8_heap_count{pid="1000",hostname="localhost"} 2004',
       'rss{pid="1000",hostname="localhost"} 3000',
+      'marking_time{pid="1000",hostname="localhost"} 4003',
+      'sweeping_time{pid="1000",hostname="localhost"} 4004',
       'major_gc_ops_total{pid="1000",hostname="localhost"} 4000',
       'minor_gc_ops_total{pid="1000",hostname="localhost"} 4001',
-      'allocated_objects_total{pid="1000",hostname="localhost"} 4002'
+      'allocated_objects_total{pid="1000",hostname="localhost"} 4002',
     ], collector_metric_lines
   end
 
   def test_metrics_deduplication
     collector.collect(base_data)
-    assert_equal 10, collector.metrics.size
-    assert_equal 10, collector_metric_lines.size
+    assert_equal 12, collector.metrics.size
+    assert_equal 12, collector_metric_lines.size
 
     collector.collect(base_data)
-    assert_equal 10, collector.metrics.size
-    assert_equal 10, collector_metric_lines.size
+    assert_equal 12, collector.metrics.size
+    assert_equal 12, collector_metric_lines.size
 
     collector.collect(base_data.merge({ "hostname" => "localhost2" }))
-    assert_equal 10, collector.metrics.size
-    assert_equal 20, collector_metric_lines.size
+    assert_equal 12, collector.metrics.size
+    assert_equal 24, collector_metric_lines.size
   end
 
   def test_metrics_expiration
     stub_monotonic_clock(0) do
       collector.collect(base_data)
-      assert_equal 10, collector.metrics.size
+      assert_equal 12, collector.metrics.size
     end
 
     stub_monotonic_clock(max_metric_age + 1) do