Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

internal/process/process.go

@@ -0,0 +1,215 @@
+package process
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/influxdata/telegraf"
+)
+
+// Process is a long-running process manager that will restart processes if they stop.
+type Process struct {
+	Cmd          *exec.Cmd
+	Stdin        io.WriteCloser
+	Stdout       io.ReadCloser
+	Stderr       io.ReadCloser
+	ReadStdoutFn func(io.Reader)
+	ReadStderrFn func(io.Reader)
+	RestartDelay time.Duration
+	StopOnError  bool
+	Log          telegraf.Logger
+
+	name       string
+	args       []string
+	envs       []string
+	pid        int32
+	cancel     context.CancelFunc
+	mainLoopWg sync.WaitGroup
+
+	sync.Mutex
+}
+
+// New creates a new process wrapper
+func New(command, envs []string) (*Process, error) {
+	if len(command) == 0 {
+		return nil, errors.New("no command")
+	}
+
+	p := &Process{
+		RestartDelay: 5 * time.Second,
+		name:         command[0],
+		args:         make([]string, 0),
+		envs:         envs,
+	}
+
+	if len(command) > 1 {
+		p.args = command[1:]
+	}
+
+	return p, nil
+}
+
+// Start the process. A &Process can only be started once. It will restart itself
+// as necessary.
+func (p *Process) Start() error {
+	ctx, cancel := context.WithCancel(context.Background())
+	p.cancel = cancel
+
+	if err := p.cmdStart(); err != nil {
+		return err
+	}
+
+	p.mainLoopWg.Add(1)
+	go func() {
+		defer p.mainLoopWg.Done()
+		if err := p.cmdLoop(ctx); err != nil {
+			p.Log.Errorf("Process quit with message: %v", err)
+		}
+	}()
+
+	return nil
+}
+
+// Stop is called when the process isn't needed anymore
+func (p *Process) Stop() {
+	if p.cancel != nil {
+		// signal our intent to shut down and not restart the process
+		p.cancel()
+	}
+	// close stdin so the app can shut down gracefully.
+	if err := p.Stdin.Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+		p.Log.Errorf("Stdin closed with message: %v", err)
+	}
+	p.mainLoopWg.Wait()
+}
+
+func (p *Process) Pid() int {
+	pid := atomic.LoadInt32(&p.pid)
+	return int(pid)
+}
+
+func (p *Process) State() (state *os.ProcessState, running bool) {
+	p.Lock()
+	defer p.Unlock()
+
+	return p.Cmd.ProcessState, p.Cmd.ProcessState.ExitCode() == -1
+}
+
+func (p *Process) cmdStart() error {
+	p.Cmd = exec.Command(p.name, p.args...)
+
+	if len(p.envs) > 0 {
+		p.Cmd.Env = append(os.Environ(), p.envs...)
+	}
+
+	var err error
+	p.Stdin, err = p.Cmd.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("error opening stdin pipe: %w", err)
+	}
+
+	p.Stdout, err = p.Cmd.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("error opening stdout pipe: %w", err)
+	}
+
+	p.Stderr, err = p.Cmd.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("error opening stderr pipe: %w", err)
+	}
+
+	p.Log.Infof("Starting process: %s %s", p.name, p.args)
+
+	if err := p.Cmd.Start(); err != nil {
+		return fmt.Errorf("error starting process: %w", err)
+	}
+	atomic.StoreInt32(&p.pid, int32(p.Cmd.Process.Pid))
+	return nil
+}
+
+// cmdLoop watches an already running process, restarting it when appropriate.
+func (p *Process) cmdLoop(ctx context.Context) error {
+	for {
+		err := p.cmdWait(ctx)
+		if err != nil && p.StopOnError {
+			return err
+		}
+		if isQuitting(ctx) {
+			p.Log.Infof("Process %s shut down", p.Cmd.Path)
+			return nil
+		}
+
+		p.Log.Errorf("Process %s exited: %v", p.Cmd.Path, err)
+		p.Log.Infof("Restarting in %s...", p.RestartDelay)
+
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-time.After(p.RestartDelay):
+			// Continue the loop and restart the process
+			if err := p.cmdStart(); err != nil {
+				return err
+			}
+		}
+	}
+}
+
+// cmdWait waits for the process to finish.
+func (p *Process) cmdWait(ctx context.Context) error {
+	var wg sync.WaitGroup
+
+	if p.ReadStdoutFn == nil {
+		p.ReadStdoutFn = defaultReadPipe
+	}
+	if p.ReadStderrFn == nil {
+		p.ReadStderrFn = defaultReadPipe
+	}
+
+	processCtx, processCancel := context.WithCancel(context.Background())
+	defer processCancel()
+
+	wg.Add(1)
+	go func() {
+		p.ReadStdoutFn(p.Stdout)
+		wg.Done()
+	}()
+
+	wg.Add(1)
+	go func() {
+		p.ReadStderrFn(p.Stderr)
+		wg.Done()
+	}()
+
+	wg.Add(1)
+	go func() {
+		select {
+		case <-ctx.Done():
+			p.gracefulStop(processCtx, p.Cmd, 5*time.Second)
+		case <-processCtx.Done():
+		}
+		wg.Done()
+	}()
+
+	p.Lock()
+	err := p.Cmd.Wait()
+	p.Unlock()
+	processCancel()
+	wg.Wait()
+	return err
+}
+
+func isQuitting(ctx context.Context) bool {
+	return ctx.Err() != nil
+}
+
+func defaultReadPipe(r io.Reader) {
+	//nolint:errcheck // Discarding the data, no need to handle an error
+	io.Copy(io.Discard, r)
+}