ProcessStatCollector: continue if PID disappears between opening and reading file

Signed-off-by: Dustin Hooten <dustinhooten@gmail.com>

collector/processes_linux.go

@@ -19,6 +19,8 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
+	"syscall"
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
@@ -111,7 +113,7 @@ func (c *processCollector) getAllocatedThreads() (int, map[string]int32, int, er
 	for _, pid := range p {
 		stat, err := pid.Stat()
 		// PIDs can vanish between getting the list and getting stats.
-		if errors.Is(err, os.ErrNotExist) {
+		if errors.Is(err, os.ErrNotExist) || errorContains(err, syscall.ESRCH) {
 			level.Debug(c.logger).Log("msg", "file not found when retrieving stats for pid", "pid", pid, "err", err)
 			continue
 		}
@@ -125,3 +127,7 @@ func (c *processCollector) getAllocatedThreads() (int, map[string]int32, int, er
 	}
 	return pids, procStates, thread, nil
 }
+
+func errorContains(err, target error) bool {
+	return err != nil && target != nil && strings.Contains(err.Error(), target.Error())
+}

collector/processes_linux_test.go

@@ -16,9 +16,11 @@
 package collector
 
 import (
-	"github.com/go-kit/kit/log"
+	"errors"
+	"syscall"
 	"testing"
 
+	"github.com/go-kit/kit/log"
 	"github.com/prometheus/procfs"
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
 )
@@ -52,3 +54,28 @@ func TestReadProcessStatus(t *testing.T) {
 		t.Fatalf("Total running pids cannot be greater than %d or equals to 0", maxPid)
 	}
 }
+
+func Test_errorContains(t *testing.T) {
+	testCases := []struct {
+		err      error
+		target   error
+		expected bool
+	}{
+		{err: nil, target: nil, expected: false},
+		{err: errors.New("e"), target: nil, expected: false},
+		{err: nil, target: errors.New("e"), expected: false},
+		{err: errors.New("abc"), target: errors.New("def"), expected: false},
+		{err: errors.New("abc"), target: errors.New("bc"), expected: true},
+		{err: errors.New("read /proc/2054/stat: no such process"), target: syscall.ESRCH, expected: true},
+	}
+	for _, tc := range testCases {
+		actual := errorContains(tc.err, tc.target)
+		if actual != tc.expected {
+			negation := " not"
+			if tc.expected {
+				negation = ""
+			}
+			t.Fatalf("Expected \"%v\"%s to contain \"%v\", got %v", tc.err, negation, tc.target, actual)
+		}
+	}
+}