Merge changes I12d74ea2,Iae424c75,I1a47821b into stable-2.16

* changes:
  Proc metrics: add average system load for the last minute
  Proc metrics: add available number of cores
  Add more metrics about Java threads

Documentation/metrics.txt

diff --git a/Documentation/metrics.txt b/Documentation/metrics.txt
index e6654c3..f729f54 100644
--- a/Documentation/metrics.txt
+++ b/Documentation/metrics.txt
@@ -33,7 +33,9 @@
 
 * `proc/birth_timestamp`: Time at which the Gerrit process started.
 * `proc/uptime`: Uptime of the Gerrit process.
+* `proc/cpu/num_cores`: Number of processors available to the Java virtual machine.
 * `proc/cpu/usage`: CPU time used by the Gerrit process.
+* `proc/cpu/system_load`: System load average for the last minute.
 * `proc/num_open_fds`: Number of open file descriptors.
 * `proc/jvm/memory/heap_committed`: Amount of memory guaranteed for user objects.
 * `proc/jvm/memory/heap_used`: Amount of memory holding user objects.
@@ -45,6 +47,9 @@
 * `proc/jvm/gc/count`: Number of GCs.
 * `proc/jvm/gc/time`: Approximate accumulated GC elapsed time.
 * `proc/jvm/thread/num_live`: Current live thread count.
+* `proc/jvm/thread/num_daemon_live`: Current live daemon threads count.
+* `proc/jvm/thread/num_peak_live`: Peak live thread count since the Java virtual machine started or peak was reset.
+* `proc/jvm/thread/num_total_started`: Total number of threads created and also started since the Java virtual machine started.
 
 === Caches
 

java/com/google/gerrit/metrics/proc/ProcMetricModule.java

diff --git a/java/com/google/gerrit/metrics/proc/ProcMetricModule.java b/java/com/google/gerrit/metrics/proc/ProcMetricModule.java
index 5af2672..be70b8c 100644
--- a/java/com/google/gerrit/metrics/proc/ProcMetricModule.java
+++ b/java/com/google/gerrit/metrics/proc/ProcMetricModule.java
@@ -29,6 +29,7 @@
 import java.lang.management.ManagementFactory;
 import java.lang.management.MemoryMXBean;
 import java.lang.management.MemoryUsage;
+import java.lang.management.OperatingSystemMXBean;
 import java.lang.management.ThreadMXBean;
 import java.util.concurrent.TimeUnit;
 
@@ -38,6 +39,7 @@
     buildLabel(metrics);
     procUptime(metrics);
     procCpuUsage(metrics);
+    procCpuLoad(metrics);
     procJvmGc(metrics);
     procJvmMemory(metrics);
     procJvmThread(metrics);
@@ -90,6 +92,23 @@
           new Description("Number of open file descriptors").setGauge().setUnit("fds"),
           provider::getOpenFileDescriptorCount);
     }
+    metrics.newCallbackMetric(
+        "proc/cpu/num_cores",
+        Integer.class,
+        new Description("Number of processors available to the Java virtual machine").setGauge(),
+        Runtime.getRuntime()::availableProcessors);
+  }
+
+  private void procCpuLoad(MetricMaker metrics) {
+    OperatingSystemMXBean provider =
+        ManagementFactory.getPlatformMXBean(OperatingSystemMXBean.class);
+    if (provider.getSystemLoadAverage() != -1) {
+      metrics.newCallbackMetric(
+          "proc/cpu/system_load",
+          Double.class,
+          new Description("System load average for the last minute").setGauge(),
+          provider::getSystemLoadAverage);
+    }
   }
 
   private void procJvmMemory(MetricMaker metrics) {
@@ -195,5 +214,26 @@
         Integer.class,
         new Description("Current live thread count").setGauge().setUnit("threads"),
         thread::getThreadCount);
+    metrics.newCallbackMetric(
+        "proc/jvm/thread/num_daemon_live",
+        Integer.class,
+        new Description("Current live daemon threads count").setGauge().setUnit("threads"),
+        thread::getDaemonThreadCount);
+    metrics.newCallbackMetric(
+        "proc/jvm/thread/num_peak_live",
+        Integer.class,
+        new Description(
+                "Peak live thread count since the Java virtual machine started or peak was reset")
+            .setGauge()
+            .setUnit("threads"),
+        thread::getPeakThreadCount);
+    metrics.newCallbackMetric(
+        "proc/jvm/thread/num_total_started",
+        Long.class,
+        new Description(
+                "Total number of threads created and also started since the Java virtual machine started")
+            .setGauge()
+            .setUnit("threads"),
+        thread::getTotalStartedThreadCount);
   }
 }