bisakhmondal commented on a change in pull request #2054:
URL: https://github.com/apache/apisix-dashboard/pull/2054#discussion_r698563234
##########
File path: api/internal/utils/pid.go
##########
@@ -18,19 +18,62 @@
package utils
import (
+ "bytes"
"fmt"
"io/ioutil"
"os"
+ "runtime"
"strconv"
+ "syscall"
+ "time"
+
+ "github.com/pkg/errors"
)
// WritePID write pid to the given file path.
func WritePID(filepath string, forceStart bool) error {
- if pid, err := ReadPID(filepath); err == nil {
- if !forceStart {
- return fmt.Errorf("Instance of Manager API maybe
running with a pid %d. If not, please run Manager API with '-f' or '--force'
flag\n", pid)
+ pidStatAction := func() error {
+ pid, err := ReadPID(filepath)
+ if err != nil {
+ return nil
+ }
+ // In unix system this always succeeds, doesn't ensure if the
process at all exist or not.
+ proc, err := os.FindProcess(pid)
+ if err != nil {
+ return errors.Errorf("instance of Manager API maybe
running with a pid %d. If not, please run Manager API with '-f' or '--force'
flag. Error :%v\n", pid, err)
+ }
+
+ // Traditional unix way to check the existence of the
particular PID.
+ err = proc.Signal(syscall.Signal(0))
+ // No entry of the process in process control block.
+ if err != nil {
+ return nil
Review comment:
Sorry couldn't get you. Do you mean it is okay or the same question
"why return nil here？"
If it is the latter one, the pr tries to avoid the false positive that
arises due to the stale pid file in `/tmp` (maybe that was left during shutdown
and wasn't got cleaned up)
so instead of blindly throwing an error just because of the presence of PID
file, the code block looks up if the process at all exists or not. If it
doesn't (err is not nil), that's completely fine. We will run a new instance
and overwrite the existing pid. That's it.
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