[service/proctelemetry] Offer to override the HOST_PROC environment variable with a programmatic value

.chloggen/metric-server-hostproc.yaml

@@ -0,0 +1,18 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: service/proctelemetry
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Allow to override the /proc folder on Linux used by process telemetry.
+
+# One or more tracking issues or pull requests related to the change
+issues: [7434]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  This is an API change only, allowing users to set a value to override the environment variable HOST_PROC.
+  This change affects the proctelemetry.RegisterProcessMetrics function, adding a vararg argument to pass options.

service/internal/proctelemetry/process_telemetry.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/shirou/gopsutil/v3/common"
 	"github.com/shirou/gopsutil/v3/process"
 	"go.opencensus.io/metric"
 	"go.opencensus.io/stats"
@@ -27,6 +28,7 @@ type processMetrics struct {
 	startTimeUnixNano int64
 	ballastSizeBytes  uint64
 	proc              *process.Process
+	context           context.Context
 
 	processUptime *metric.Float64DerivedCumulative
 	allocMem      *metric.Int64DerivedGauge
@@ -49,17 +51,47 @@ type processMetrics struct {
 	ms         *runtime.MemStats
 }
 
+type RegisterOption interface {
+	apply(*registerOption)
+}
+
+type registerOption struct {
+	hostProc string
+}
+
+type registerOptionFunc func(*registerOption)
+
+func (fn registerOptionFunc) apply(set *registerOption) {
+	fn(set)
+}
+
+// WithHostProc overrides the /proc folder on Linux used by process telemetry.
+func WithHostProc(hostProc string) RegisterOption {
+	return registerOptionFunc(func(uo *registerOption) {
+		uo.hostProc = hostProc
+	})
+}
+
 // RegisterProcessMetrics creates a new set of processMetrics (mem, cpu) that can be used to measure
 // basic information about this process.
-func RegisterProcessMetrics(ocRegistry *metric.Registry, mp otelmetric.MeterProvider, useOtel bool, ballastSizeBytes uint64) error {
+func RegisterProcessMetrics(ocRegistry *metric.Registry, mp otelmetric.MeterProvider, useOtel bool, ballastSizeBytes uint64, opts ...RegisterOption) error {
+	set := registerOption{}
+	for _, opt := range opts {
+		opt.apply(&set)
+	}
 	var err error
 	pm := &processMetrics{
 		startTimeUnixNano: time.Now().UnixNano(),
 		ballastSizeBytes:  ballastSizeBytes,
 		ms:                &runtime.MemStats{},
 	}
 
-	pm.proc, err = process.NewProcess(int32(os.Getpid()))
+	ctx := context.Background()
+	if set.hostProc != "" {
+		ctx = context.WithValue(ctx, common.EnvKey, common.EnvMap{common.HostProcEnvKey: set.hostProc})
+	}
+	pm.context = ctx
+	pm.proc, err = process.NewProcessWithContext(pm.context, int32(os.Getpid()))
 	if err != nil {
 		return err
 	}
@@ -231,7 +263,7 @@ func (pm *processMetrics) updateSysMem() int64 {
 }
 
 func (pm *processMetrics) updateCPUSeconds() float64 {
-	times, err := pm.proc.Times()
+	times, err := pm.proc.TimesWithContext(pm.context)
 	if err != nil {
 		return 0
 	}
@@ -241,7 +273,7 @@ func (pm *processMetrics) updateCPUSeconds() float64 {
 }
 
 func (pm *processMetrics) updateRSSMemory() int64 {
-	mem, err := pm.proc.MemoryInfo()
+	mem, err := pm.proc.MemoryInfoWithContext(pm.context)
 	if err != nil {
 		return 0
 	}

service/internal/proctelemetry/process_telemetry_linux_test.go

@@ -0,0 +1,53 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build linux
+// +build linux
+
+package proctelemetry
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opencensus.io/metric"
+	"go.opentelemetry.io/otel/metric/noop"
+)
+
+func TestOCProcessTelemetryWithHostProc(t *testing.T) {
+	ocRegistry := metric.NewRegistry()
+	// Make the sure the environment variable value is not used.
+	t.Setenv("HOST_PROC", "foo/bar")
+
+	require.NoError(t, RegisterProcessMetrics(ocRegistry, noop.NewMeterProvider(), false, 0, WithHostProc("/proc")))
+
+	// Check that the metrics are actually filled.
+	time.Sleep(200 * time.Millisecond)
+
+	metrics := ocRegistry.Read()
+
+	for _, metricName := range expectedMetrics {
+		m := findMetric(metrics, metricName)
+		require.NotNil(t, m)
+		require.Len(t, m.TimeSeries, 1)
+		ts := m.TimeSeries[0]
+		assert.Len(t, ts.LabelValues, 0)
+		require.Len(t, ts.Points, 1)
+
+		var value float64
+		if metricName == "process/uptime" || metricName == "process/cpu_seconds" {
+			value = ts.Points[0].Value.(float64)
+		} else {
+			value = float64(ts.Points[0].Value.(int64))
+		}
+
+		if metricName == "process/uptime" || metricName == "process/cpu_seconds" {
+			// This likely will still be zero when running the test.
+			assert.GreaterOrEqual(t, value, float64(0), metricName)
+			continue
+		}
+		assert.Greater(t, value, float64(0), metricName)
+	}
+}

service/internal/proctelemetry/process_telemetry_test.go

@@ -140,7 +140,7 @@ func TestOCProcessTelemetry(t *testing.T) {
 	require.NoError(t, RegisterProcessMetrics(ocRegistry, noop.NewMeterProvider(), false, 0))
 
 	// Check that the metrics are actually filled.
-	<-time.After(200 * time.Millisecond)
+	time.Sleep(200 * time.Millisecond)
 
 	metrics := ocRegistry.Read()
 
@@ -164,7 +164,6 @@ func TestOCProcessTelemetry(t *testing.T) {
 			assert.GreaterOrEqual(t, value, float64(0), metricName)
 			continue
 		}
-
 		assert.Greater(t, value, float64(0), metricName)
 	}
 }