From d7a6c13c3ebd618390e4cdda41da9186c9f91742 Mon Sep 17 00:00:00 2001
From: Chris Leavoy <christopherleavoy@invisionapp.com>
Date: Mon, 13 Apr 2020 11:39:36 -0400
Subject: [PATCH] stub more runtime metrics

---
 plugins/metrics/runtime/runtime.go | 73 ++++++++++++++++++++++++------
 1 file changed, 58 insertions(+), 15 deletions(-)

diff --git a/plugins/metrics/runtime/runtime.go b/plugins/metrics/runtime/runtime.go
index 74fc82730ed..deea088252e 100644
--- a/plugins/metrics/runtime/runtime.go
+++ b/plugins/metrics/runtime/runtime.go
@@ -2,20 +2,34 @@ package runtime
 
 import (
 	"context"
-	"sync"
 	"time"
 
 	"go.opentelemetry.io/otel/api/metric"
+	"go.opentelemetry.io/otel/api/unit"
 	"golang.org/x/time/rate"
 
 	"github.com/open-telemetry/opentelemetry-go-contrib/plugins/metrics/runtime/internal/metrics"
 )
 
-func Runtime(ctx context.Context, meter metric.Meter) func() {
+var (
+	initialisation time.Time
+)
+
+func init() {
+	initialisation = time.Now()
+}
+
+// various runtime metrics have a certain overhead, and as such, we only measure them on a defined interval
+func Runtime(ctx context.Context, meter metric.Meter, interval time.Duration) context.CancelFunc {
 	ctx, cancel := context.WithCancel(ctx)
 
-	lock := &sync.Mutex{}
-	m, _  := metrics.Measure(ctx)
+	ctxTimeout, _ := context.WithTimeout(ctx, time.Second)
+	var m, p metrics.Metrics
+	m, _ = metrics.Measure(ctxTimeout)
+
+	if interval == 0 {
+		interval = time.Second
+	}
 
 	go func() {
 		limit := rate.NewLimiter(rate.Every(time.Second), 1)
@@ -26,21 +40,50 @@ func Runtime(ctx context.Context, meter metric.Meter) func() {
 				break
 			}
 
-			lock.Lock()
-			m, _ = metrics.Measure(ctx)
-			lock.Unlock()
+			ctxTimeout, _ := context.WithTimeout(ctx, time.Second)
+			// store the previous measurement for reporting deltas
+			p = m
+			// we assume here we are replacing m and thus do ont require a concurrency lock
+			m, _ = metrics.Measure(ctxTimeout)
+
+			metric.Must(meter).NewFloat64Counter("runtime.go.cpu.user").Bind().Add(ctx,
+				m.ProcessCPU.User-p.ProcessCPU.User,
+			)
+
+			metric.Must(meter).NewFloat64Counter("runtime.go.cpu.sys").Bind().Add(ctx,
+				m.ProcessCPU.System-p.ProcessCPU.System,
+			)
+
+			metric.Must(meter).NewInt64Counter("runtime.go.gc.count",
+				metric.WithDescription("counter of completed GC cycles")).Bind().Add(ctx,
+				int64(m.Runtime.NumGC-p.Runtime.NumGC),
+			)
 		}
 	}()
 
-	callBack := func(result metric.Int64ObserverResult) {
-		lock.Lock()
+	metric.Must(meter).RegisterInt64Observer("runtime.uptime",
+		func(result metric.Int64ObserverResult) {
+			result.Observe(time.Since(initialisation).Milliseconds())
+		},
+		metric.WithUnit(unit.Milliseconds),
+		metric.WithDescription("milliseconds since application was initialized"),
+	)
+
+	metric.Must(meter).RegisterInt64Observer("runtime.go.goroutine", func(result metric.Int64ObserverResult) {
 		result.Observe(int64(m.Runtime.NumGoroutine))
-		lock.Unlock()
-	}
+	})
 
-	metric.Must(meter).RegisterInt64Observer("runtime.go.goroutine", callBack)
+	metric.Must(meter).RegisterInt64Observer("mem.available", func(result metric.Int64ObserverResult) {
+		result.Observe(int64(m.Memory.Available))
+	})
 
-	return func() {
-		cancel()
-	}
+	metric.Must(meter).RegisterInt64Observer("mem.total", func(result metric.Int64ObserverResult) {
+		result.Observe(int64(m.Memory.Total))
+	})
+
+	metric.Must(meter).RegisterInt64Observer("runtime.go.mem.heap_alloc", func(result metric.Int64ObserverResult) {
+		result.Observe(int64(m.Memory.HeapAlloc))
+	}, metric.WithUnit(unit.Bytes), metric.WithDescription("bytes of allocated heap objects"))
+
+	return cancel
 }