adding cpu and memory metrics

go.mod

@@ -59,6 +59,8 @@ require (
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/pelletier/go-toml/v2 v2.0.8 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/tklauser/go-sysconf v0.3.14 // indirect
+	github.com/tklauser/numcpus v0.8.0 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.2.11 // indirect
 	go.opentelemetry.io/proto/otlp v1.2.0 // indirect

go.sum

@@ -627,6 +627,10 @@ github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o
 github.com/stretchr/testify v1.8.3/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
 github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/tklauser/go-sysconf v0.3.14 h1:g5vzr9iPFFz24v2KZXs/pvpvh8/V9Fw6vQK5ZZb78yU=
+github.com/tklauser/go-sysconf v0.3.14/go.mod h1:1ym4lWMLUOhuBOPGtRcJm7tEGX4SCYNEEEtghGG/8uY=
+github.com/tklauser/numcpus v0.8.0 h1:Mx4Wwe/FjZLeQsK/6kt2EOepwwSl7SmJrK5bV/dXYgY=
+github.com/tklauser/numcpus v0.8.0/go.mod h1:ZJZlAY+dmR4eut8epnzf0u/VwodKmryxR8txiloSqBE=
 github.com/twitchyliquid64/golang-asm v0.15.1 h1:SU5vSMR7hnwNxj24w34ZyCi/FmDZTkS4MhqMhdFk5YI=
 github.com/twitchyliquid64/golang-asm v0.15.1/go.mod h1:a1lVb/DtPvCB8fslRZhAngC2+aY1QWCk3Cedj/Gdt08=
 github.com/ugorji/go/codec v1.2.11 h1:BMaWp1Bb6fHwEtbplGBGJ498wD+LKlNSl25MjdZY4dU=

instrumentation/opentelemetry/init.go

@@ -16,6 +16,7 @@ import (
 	config "github.com/hypertrace/agent-config/gen/go/v1"
 	modbsp "github.com/hypertrace/goagent/instrumentation/opentelemetry/batchspanprocessor"
 	"github.com/hypertrace/goagent/instrumentation/opentelemetry/identifier"
+	"github.com/hypertrace/goagent/instrumentation/opentelemetry/internal/metrics"
 	"github.com/hypertrace/goagent/sdk"
 	sdkconfig "github.com/hypertrace/goagent/sdk/config"
 	"github.com/hypertrace/goagent/version"
@@ -434,6 +435,7 @@ func initializeMetrics(cfg *config.AgentConfig, versionInfoAttrs []attribute.Key
 	meterProvider := metric.NewMeterProvider(metric.WithReader(periodicReader), metric.WithResource(metricResources))
 	otel.SetMeterProvider(meterProvider)
 
+	metrics.InitializeSystemMetrics()
 	return func() {
 		err = meterProvider.Shutdown(context.Background())
 		if err != nil {

instrumentation/opentelemetry/internal/metrics/system_metrics.go

@@ -0,0 +1,120 @@
+package metrics
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"github.com/tklauser/go-sysconf"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/metric"
+)
+
+const meterName = "goagent.hypertrace.org/metrics"
+
+type systemMetrics struct {
+	memory          float64
+	cpuSecondsTotal float64
+}
+
+type processStats struct {
+	utime  float64
+	stime  float64
+	cutime float64
+	cstime float64
+	rss    float64
+}
+
+const procStatArrayLength = 52
+
+var (
+	clkTck   = getClockTicks()
+	pageSize = float64(os.Getpagesize())
+)
+
+func InitializeSystemMetrics() {
+	meterProvider := otel.GetMeterProvider()
+	meter := meterProvider.Meter(meterName)
+	err := setUpMetricRecorder(meter)
+	if err != nil {
+		log.Printf("error initialising metrics, failed to setup metric recorder: %v\n", err)
+	}
+}
+
+func processStatsFromPid(pid int) (*systemMetrics, error) {
+	sysInfo := &systemMetrics{}
+	procFilepath := filepath.Join("/proc", strconv.Itoa(pid), "stat")
+	var err error
+	if procStatFileBytes, err := os.ReadFile(filepath.Clean(procFilepath)); err == nil {
+		if stat, err := parseProcStatFile(procStatFileBytes, procFilepath); err == nil {
+			sysInfo.memory = stat.rss * pageSize
+			sysInfo.cpuSecondsTotal = (stat.stime + stat.utime + stat.cstime + stat.cutime) / clkTck
+			return sysInfo, nil
+		}
+		return nil, err
+	}
+	return nil, err
+}
+
+// ref: /proc/pid/stat section of https://man7.org/linux/man-pages/man5/proc.5.html
+func parseProcStatFile(bytesArr []byte, procFilepath string) (*processStats, error) {
+	infos := strings.Split(string(bytesArr), " ")
+	if len(infos) != procStatArrayLength {
+		return nil, fmt.Errorf("%s file could not be parsed", procFilepath)
+	}
+	return &processStats{
+		utime:  parseFloat(infos[13]),
+		stime:  parseFloat(infos[14]),
+		cutime: parseFloat(infos[15]),
+		cstime: parseFloat(infos[16]),
+		rss:    parseFloat(infos[23]),
+	}, nil
+}
+
+func parseFloat(val string) float64 {
+	floatVal, _ := strconv.ParseFloat(val, 64)
+	return floatVal
+}
+
+// sysconf for go. claims to work without cgo or external binaries
+// https://pkg.go.dev/github.com/tklauser/go-sysconf@v0.3.14#section-readme
+func getClockTicks() float64 {
+	clktck, err := sysconf.Sysconf(sysconf.SC_CLK_TCK)
+	if err != nil {
+		return float64(100)
+	}
+	return float64(clktck)
+}
+
+func setUpMetricRecorder(meter metric.Meter) error {
+	if meter == nil {
+		return fmt.Errorf("error while setting up metric recorder: meter is nil")
+	}
+	cpuSeconds, err := meter.Float64ObservableCounter("hypertrace.agent.cpu.seconds.total", metric.WithDescription("Metric to monitor total CPU seconds"))
+	if err != nil {
+		return fmt.Errorf("error while setting up cpu seconds metric counter: %v", err)
+	}
+	memory, err := meter.Float64ObservableGauge("hypertrace.agent.memory", metric.WithDescription("Metric to monitor memory usage"))
+	if err != nil {
+		return fmt.Errorf("error while setting up memory metric counter: %v", err)
+	}
+	// Register the callback function for both cpu_seconds and memory observable gauges
+	_, err = meter.RegisterCallback(
+		func(ctx context.Context, result metric.Observer) error {
+			systemMetrics, err := processStatsFromPid(os.Getpid())
+			result.ObserveFloat64(cpuSeconds, systemMetrics.cpuSecondsTotal)
+			result.ObserveFloat64(memory, systemMetrics.memory)
+			return err
+		},
+		cpuSeconds, memory,
+	)
+	if err != nil {
+		log.Fatalf("failed to register callback: %v", err)
+		return err
+	}
+	return nil
+}