liveness.go RawHistoryFolder

1package process
2
3import (
4	"context"
5	"errors"
6	"fmt"
7	"os"
8	"syscall"
9)
10
11type processSignalFunc func(pid int, signal os.Signal) error
12
13// LivenessProbe checks whether a process is alive by sending signal 0.
14type LivenessProbe struct {
15	signal processSignalFunc
16}
17
18// NewLivenessProbe creates a LivenessProbe that uses os.FindProcess and Signal.
19func NewLivenessProbe() *LivenessProbe {
20	return &LivenessProbe{signal: signalProcess}
21}
22
23// IsProcessAlive checks whether the process with the given PID is alive.
24// It returns immediately with the context error when ctx is done, and returns
25// an error for invalid PIDs. Signal errors are mapped for cleanup safety:
26// ESRCH means the process is not alive, EPERM means the process exists but is
27// not signalable by this user, and unexpected signal errors are propagated.
28func (p *LivenessProbe) IsProcessAlive(ctx context.Context, pid int) (bool, error) {
29	if err := ctx.Err(); err != nil {
30		return false, err
31	}
32	if pid <= 0 {
33		return false, fmt.Errorf("invalid pid %d", pid)
34	}
35	signal := p.signal
36	if signal == nil {
37		signal = signalProcess
38	}
39	if err := signal(pid, syscall.Signal(0)); err != nil {
40		if errors.Is(err, syscall.ESRCH) {
41			return false, nil
42		}
43		if errors.Is(err, syscall.EPERM) {
44			return true, nil
45		}
46		return false, err
47	}
48	return true, nil
49}
50
51func signalProcess(pid int, signal os.Signal) error {
52	proc, err := os.FindProcess(pid)
53	if err != nil {
54		return err
55	}
56	return proc.Signal(signal)
57}