add cgroup functionality

.chloggen/cgroups.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: hostmetricsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add support for cgroup information as a new resource attribute on process metrics, as `process.cgroup`
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [29282]
+
+# (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:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

receiver/hostmetricsreceiver/internal/scraper/processscraper/process.go

@@ -75,7 +75,6 @@ type processHandles interface {
 
 type processHandle interface {
 	NameWithContext(context.Context) (string, error)
-	CgroupWithContext(context.Context) (string, error)
 	ExeWithContext(context.Context) (string, error)
 	UsernameWithContext(context.Context) (string, error)
 	CmdlineWithContext(context.Context) (string, error)

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_darwin.go

@@ -38,13 +38,8 @@ func getProcessName(ctx context.Context, proc processHandle, _ string) (string,
 	return name, nil
 }
 
-func getProcessCgroup(ctx context.Context, proc processHandle) (string, error) {
-	cgroup, err := proc.CgroupWithContext(ctx)
-	if err != nil {
-		return "", err
-	}
-
-	return cgroup, nil
+func getProcessCgroup(_ context.Context, _ processHandle) (string, error) {
+	return "", nil
 }
 
 func getProcessExecutable(ctx context.Context, proc processHandle) (string, error) {

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_linux.go

@@ -8,8 +8,14 @@ package processscraper // import "github.com/open-telemetry/opentelemetry-collec
 
 import (
 	"context"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
 
+	"github.com/shirou/gopsutil/v3/common"
 	"github.com/shirou/gopsutil/v3/cpu"
+	"github.com/shirou/gopsutil/v3/process"
 	"go.opentelemetry.io/collector/pdata/pcommon"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver/internal/scraper/processscraper/internal/metadata"
@@ -47,12 +53,33 @@ func getProcessExecutable(ctx context.Context, proc processHandle) (string, erro
 }
 
 func getProcessCgroup(ctx context.Context, proc processHandle) (string, error) {
-	cgroup, err := proc.CgroupWithContext(ctx)
+	pid := proc.(*process.Process).Pid
+	statPath := getEnvWithContext(ctx, string(common.HostProcEnvKey), "/proc", strconv.Itoa(int(pid)), "cgroup")
+	contents, err := os.ReadFile(statPath)
 	if err != nil {
 		return "", err
 	}
 
-	return cgroup, nil
+	return strings.TrimSuffix(string(contents), "\n"), nil
+}
+
+// copied from gopsutil:
+// GetEnvWithContext retrieves the environment variable key. If it does not exist it returns the default.
+// The context may optionally contain a map superseding os.EnvKey.
+func getEnvWithContext(ctx context.Context, key string, dfault string, combineWith ...string) string {
+	var value string
+	if env, ok := ctx.Value(common.EnvKey).(common.EnvMap); ok {
+		value = env[common.EnvKeyType(key)]
+	}
+	if value == "" {
+		value = os.Getenv(key)
+	}
+	if value == "" {
+		value = dfault
+	}
+	segments := append([]string{value}, combineWith...)
+
+	return filepath.Join(segments...)
 }
 
 func getProcessCommand(ctx context.Context, proc processHandle) (*commandMetadata, error) {

receiver/hostmetricsreceiver/internal/scraper/processscraper/process_scraper_windows.go

@@ -38,12 +38,7 @@ func getProcessName(_ context.Context, _ processHandle, exePath string) (string,
 }
 
 func getProcessCgroup(ctx context.Context, proc processHandle) (string, error) {
-	cgroup, err := proc.CgroupWithContext(ctx)
-	if err != nil {
-		return "", err
-	}
-
-	return cgroup, nil
+	return "", nil
 }
 
 func getProcessExecutable(ctx context.Context, proc processHandle) (string, error) {