fix(inputs.procstat): Do not report dead processes as running for orphan PID files

plugins/inputs/procstat/filter.go

@@ -7,28 +7,32 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/influxdata/telegraf/filter"
 	"github.com/shirou/gopsutil/v3/process"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/filter"
 )
 
 type Filter struct {
-	Name            string   `toml:"name"`
-	PidFiles        []string `toml:"pid_files"`
-	SystemdUnits    []string `toml:"systemd_units"`
-	SupervisorUnits []string `toml:"supervisor_units"`
-	WinService      []string `toml:"win_services"`
-	CGroups         []string `toml:"cgroups"`
-	Patterns        []string `toml:"patterns"`
-	Users           []string `toml:"users"`
-	Executables     []string `toml:"executables"`
-	ProcessNames    []string `toml:"process_names"`
-	RecursionDepth  int      `toml:"recursion_depth"`
+	Name            string          `toml:"name"`
+	PidFiles        []string        `toml:"pid_files"`
+	SystemdUnits    []string        `toml:"systemd_units"`
+	SupervisorUnits []string        `toml:"supervisor_units"`
+	WinService      []string        `toml:"win_services"`
+	CGroups         []string        `toml:"cgroups"`
+	Patterns        []string        `toml:"patterns"`
+	Users           []string        `toml:"users"`
+	Executables     []string        `toml:"executables"`
+	ProcessNames    []string        `toml:"process_names"`
+	RecursionDepth  int             `toml:"recursion_depth"`
+	Log             telegraf.Logger `toml:"-"`
 
 	filterSupervisorUnit string
 	filterCmds           []*regexp.Regexp
 	filterUser           filter.Filter
 	filterExecutable     filter.Filter
 	filterProcessName    filter.Filter
+	finder               *processFinder
 }
 
 func (f *Filter) Init() error {
@@ -80,6 +84,8 @@ func (f *Filter) Init() error {
 		return fmt.Errorf("compiling process-names filter for %q failed: %w", f.Name, err)
 	}
 
+	// Setup the process finder
+	f.finder = newProcessFinder(f.Log)
 	return nil
 }
 
@@ -89,7 +95,7 @@ func (f *Filter) ApplyFilter() ([]processGroup, error) {
 	var groups []processGroup
 	switch {
 	case len(f.PidFiles) > 0:
-		g, err := findByPidFiles(f.PidFiles)
+		g, err := f.finder.findByPidFiles(f.PidFiles)
 		if err != nil {
 			return nil, err
 		}

plugins/inputs/procstat/procstat.go

@@ -149,6 +149,7 @@ func (p *Procstat) Init() error {
 
 		// New-style operations
 		for i := range p.Filter {
+			p.Filter[i].Log = p.Log
 			if err := p.Filter[i].Init(); err != nil {
 				return fmt.Errorf("initializing filter %d failed: %w", i, err)
 			}
@@ -200,17 +201,23 @@ func (p *Procstat) gatherOld(acc telegraf.Accumulator) error {
 		}
 		count += len(r.PIDs)
 		for _, pid := range r.PIDs {
+			// Check if the process is still running
+			proc, err := p.createProcess(pid)
+			if err != nil {
+				// No problem; process may have ended after we found it or it
+				// might be delivered from a non-checking source like a PID file
+				// of a dead process.
+				continue
+			}
+
 			// Use the cached processes as we need the existing instances
 			// to compute delta-metrics (e.g. cpu-usage).
-			proc, found := p.processes[pid]
-			if !found {
+			if cached, found := p.processes[pid]; found {
+				proc = cached
+			} else {
 				// We've found a process that was not recorded before so add it
 				// to the list of processes
-				proc, err = p.createProcess(pid)
-				if err != nil {
-					// No problem; process may have ended after we found it
-					continue
-				}
+
 				// Assumption: if a process has no name, it probably does not exist
 				if name, _ := proc.Name(); name == "" {
 					continue

plugins/inputs/procstat/service_finders.go

@@ -8,10 +8,23 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/influxdata/telegraf"
 	"github.com/shirou/gopsutil/v3/process"
 )
 
-func findByPidFiles(paths []string) ([]processGroup, error) {
+type processFinder struct {
+	errPidFiles map[string]bool
+	log         telegraf.Logger
+}
+
+func newProcessFinder(log telegraf.Logger) *processFinder {
+	return &processFinder{
+		errPidFiles: make(map[string]bool),
+		log:         log,
+	}
+}
+
+func (f *processFinder) findByPidFiles(paths []string) ([]processGroup, error) {
 	groups := make([]processGroup, 0, len(paths))
 	for _, path := range paths {
 		buf, err := os.ReadFile(path)
@@ -24,8 +37,9 @@ func findByPidFiles(paths []string) ([]processGroup, error) {
 		}
 
 		p, err := process.NewProcess(int32(pid))
-		if err != nil {
-			return nil, fmt.Errorf("failed to find process for PID %d of file %q: %w", pid, path, err)
+		if err != nil && !f.errPidFiles[path] {
+			f.log.Errorf("failed to find process for PID %d of file %q: %v", pid, path, err)
+			f.errPidFiles[path] = true
 		}
 		groups = append(groups, processGroup{
 			processes: []*process.Process{p},
@@ -46,7 +60,7 @@ func findByCgroups(cgroups []string) ([]processGroup, error) {
 
 		files, err := filepath.Glob(path)
 		if err != nil {
-			return nil, fmt.Errorf("failed to determin files for cgroup %q: %w", cgroup, err)
+			return nil, fmt.Errorf("failed to determine files for cgroup %q: %w", cgroup, err)
 		}
 
 		for _, fpath := range files {