Add GC stats to the api

This PR introduce GC stats in the form of `collection_time` and `collection_count`, it takes the configured gc and categorize them
into old and young.

Example output:

```
gc: {
  collectors: {
    young: {
      collection_time_in_millis: 22101,
      collection_count: 5452
    },
    old: {
      collection_time_in_millis: 57,
      collection_count: 1
    }
  }
}
```

Fixes: #5730

Fixes #5788

logstash-core/lib/logstash/api/commands/stats.rb

@@ -14,7 +14,8 @@ module LogStash
               :count,
               :peak_count
             ),
-            :mem => memory
+            :mem => memory,
+            :gc => gc
           }
         end
 
@@ -59,6 +60,10 @@ module LogStash
           }
         end
 
+        def gc
+          service.get_shallow(:jvm, :gc)
+        end
+
         def hot_threads(options={})
           HotThreadsReport.new(self, options)
         end

logstash-core/lib/logstash/api/modules/node_stats.rb

@@ -12,7 +12,7 @@ module LogStash
           payload = {
             :jvm => jvm_payload,
             :process => process_payload,
-            :pipeline => pipeline_payload
+            :pipeline => pipeline_payload,
           }
           respond_with(payload, {:filter => params["filter"]})
         end

logstash-core/lib/logstash/instrument/periodic_poller/jvm.rb

@@ -1,18 +1,36 @@
 
 # encoding: utf-8
 require "logstash/instrument/periodic_poller/base"
-require 'jrmonitor'
+require "jrmonitor"
+require "set"
 
 java_import 'java.lang.management.ManagementFactory'
 java_import 'java.lang.management.OperatingSystemMXBean'
+java_import 'java.lang.management.GarbageCollectorMXBean'
 java_import 'com.sun.management.UnixOperatingSystemMXBean'
 java_import 'javax.management.MBeanServer'
 java_import 'javax.management.ObjectName'
 java_import 'javax.management.AttributeList'
 java_import 'javax.naming.directory.Attribute'
 
+
 module LogStash module Instrument module PeriodicPoller
   class JVM < Base
+    class GarbageCollectorName
+      YOUNG_GC_NAMES = Set.new(["Copy", "PS Scavenge", "ParNew", "G1 Young Generation"])
+      OLD_GC_NAMES = Set.new(["MarkSweepCompact", "PS MarkSweep", "ConcurrentMarkSweep", "G1 Old Generation"])
+
+      YOUNG = :young
+      OLD = :old
+
+      def self.get(gc_name)
+        if YOUNG_GC_NAMES.include?(gc_name)
+          YOUNG
+        elsif(OLD_GC_NAMES.include?(gc_name))
+          OLD
+        end
+      end
+    end
 
     attr_reader :metric
 
@@ -22,31 +40,46 @@ module LogStash module Instrument module PeriodicPoller
     end
 
     def collect
-      raw = JRMonitor.memory.generate      
+      raw = JRMonitor.memory.generate
       collect_heap_metrics(raw)
       collect_non_heap_metrics(raw)
       collect_pools_metrics(raw)
       collect_threads_metrics
       collect_process_metrics
+      collect_gc_stats
     end
 
     private
 
-    def collect_threads_metrics      
+    def collect_gc_stats
+      garbage_collectors = ManagementFactory.getGarbageCollectorMXBeans()
+
+      garbage_collectors.each do |collector|
+        name = GarbageCollectorName.get(collector.getName())
+        if name.nil?
+          logger.error("Unknown garbage collector name", :name => name)
+        else
+          metric.gauge([:jvm, :gc, :collectors, name], :collection_count, collector.getCollectionCount())
+          metric.gauge([:jvm, :gc, :collectors, name], :collection_time_in_millis, collector.getCollectionTime())
+        end
+      end
+    end
+
+    def collect_threads_metrics
       threads = JRMonitor.threads.generate
-      
+
       current = threads.count
       if @peak_threads.nil? || @peak_threads < current
         @peak_threads = current
-      end      
-      
-      metric.gauge([:jvm, :threads], :count, threads.count)     
+      end
+
+      metric.gauge([:jvm, :threads], :count, threads.count)
       metric.gauge([:jvm, :threads], :peak_count, @peak_threads)
     end
 
     def collect_process_metrics
       process_metrics = JRMonitor.process.generate
-      
+
       path = [:jvm, :process]
 
 
@@ -91,6 +124,7 @@ module LogStash module Instrument module PeriodicPoller
       end
     end
 
+
     def build_pools_metrics(data)
       heap = data["heap"]
       old  = {}
@@ -129,9 +163,8 @@ module LogStash module Instrument module PeriodicPoller
         :committed_in_bytes => 0,
         :max_in_bytes => 0,
         :peak_used_in_bytes => 0,
-        :peak_max_in_bytes  => 0
+        :peak_max_in_bytes => 0
       }
     end
-
   end
 end; end; end

logstash-core/spec/api/lib/api/node_stats_spec.rb

@@ -16,6 +16,18 @@ describe LogStash::Api::Modules::NodeStats do
         "count"=>Numeric,
         "peak_count"=>Numeric
       },
+      "gc" => {
+        "collectors" => {
+          "young" => {
+            "collection_count" => Numeric,
+            "collection_time_in_millis" => Numeric
+          },
+          "old" => {
+            "collection_count" => Numeric,
+            "collection_time_in_millis" => Numeric
+          }
+        }
+      },
       "mem" => {
         "heap_used_in_bytes" => Numeric,
         "heap_used_percent" => Numeric,

logstash-core/spec/logstash/instrument/periodic_poller/jvm_spec.rb

@@ -3,18 +3,41 @@ require "spec_helper"
 require "logstash/instrument/periodic_poller/jvm"
 require "logstash/instrument/collector"
 
+describe LogStash::Instrument::PeriodicPoller::JVM::GarbageCollectorName do
+  subject { LogStash::Instrument::PeriodicPoller::JVM::GarbageCollectorName }
+
+  context "when the gc is of young type" do
+    LogStash::Instrument::PeriodicPoller::JVM::GarbageCollectorName::YOUNG_GC_NAMES.each do |name|
+      it "returns young for #{name}" do
+        expect(subject.get(name)).to eq(:young)
+      end
+    end
+  end
+
+  context "when the gc is of old type" do
+    LogStash::Instrument::PeriodicPoller::JVM::GarbageCollectorName::OLD_GC_NAMES.each do |name|
+      it "returns old for #{name}" do
+        expect(subject.get(name)).to eq(:old)
+      end
+    end
+  end
+
+  it "returns `nil` when we dont know the gc name" do
+      expect(subject.get("UNKNOWN GC")).to be_nil
+  end
+end
+
 describe LogStash::Instrument::PeriodicPoller::JVM do
   let(:metric) { LogStash::Instrument::Metric.new(LogStash::Instrument::Collector.new) }
   let(:options) { {} }
   subject(:jvm) { described_class.new(metric, options) }
-  
+
   it "should initialize cleanly" do
     expect { jvm }.not_to raise_error
   end
 
   describe "collections" do
     subject(:collection) { jvm.collect }
-    
     it "should run cleanly" do
       expect { collection }.not_to raise_error
     end
@@ -22,21 +45,25 @@ describe LogStash::Instrument::PeriodicPoller::JVM do
     describe "metrics" do
       before(:each) { jvm.collect }
       let(:snapshot_store) { metric.collector.snapshot_metric.metric_store }
-      subject(:jvm_metrics) { snapshot_store.get_shallow(:jvm, :process) }
+      subject(:jvm_metrics) { snapshot_store.get_shallow(:jvm) }
 
       # Make looking up metric paths easy when given varargs of keys
       # e.g. mval(:parent, :child)
       def mval(*metric_path)
         metric_path.reduce(jvm_metrics) {|acc,k| acc[k]}.value
-      end          
+      end
 
       [
-        :max_file_descriptors,
-        :open_file_descriptors,
-        :peak_open_file_descriptors,
-        [:mem, :total_virtual_in_bytes],
-        [:cpu, :total_in_millis],
-        [:cpu, :percent]
+        [:process, :max_file_descriptors],
+        [:process, :open_file_descriptors],
+        [:process, :peak_open_file_descriptors],
+        [:process, :mem, :total_virtual_in_bytes],
+        [:process, :cpu, :total_in_millis],
+        [:process, :cpu, :percent],
+        [:gc, :collectors, :young, :collection_count],
+        [:gc, :collectors, :young, :collection_time_in_millis],
+        [:gc, :collectors, :old, :collection_count],
+        [:gc, :collectors, :old, :collection_time_in_millis]
       ].each do |path|
         path = Array(path)
         it "should have a value for #{path} that is Numeric" do