32ca0a9170
Update wwclient such that each file in the runtime overlay is applied atomically, and only if modified. - Closes: #1307 - Closes: #1975 - Closes: #1226 Also adds --once flag to allow wwclient to be run one time. Signed-off-by: Jonathon Anderson <janderson@ciq.com>
96 lines
2.7 KiB
Go
96 lines
2.7 KiB
Go
// Package pidfile provides utilities for managing process ID files.
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// Based on original work found here, github.com/soellman/pidfile
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package pidfile
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import (
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"errors"
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"fmt"
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"os"
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"strconv"
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"strings"
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"syscall"
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)
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var (
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// ErrProcessRunning indicates that a process with the PID from the pidfile is currently running.
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ErrProcessRunning = errors.New("process is running")
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// ErrFileStale indicates that the pidfile exists but the process is not running.
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ErrFileStale = errors.New("pidfile exists but process is not running")
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// ErrFileInvalid indicates that the pidfile contains invalid or unparseable contents.
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ErrFileInvalid = errors.New("pidfile has invalid contents")
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)
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// Remove removes a pidfile from the filesystem.
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// It returns an error if the file cannot be removed.
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func Remove(filename string) error {
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return os.RemoveAll(filename)
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}
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// Write writes a pidfile containing the current process ID.
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// It returns the PID and an error if the process is already running or pidfile is orphaned.
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func Write(filename string) (int, error) {
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return WriteControl(filename, os.Getpid(), false)
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}
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// WriteControl writes a pidfile with the specified PID and control options.
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// If overwrite is false and a stale pidfile exists, it returns ErrFileStale.
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// If overwrite is true, it will overwrite stale pidfiles.
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// It returns the PID and an error if the process is already running.
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func WriteControl(filename string, pid int, overwrite bool) (int, error) {
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// Check for existing pid
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oldpid, err := pidfileContents(filename)
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if err != nil && !os.IsNotExist(err) {
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return oldpid, err
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}
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// We have a pid
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if err == nil {
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if pidIsRunning(oldpid) {
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return oldpid, ErrProcessRunning
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}
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if !overwrite {
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return -1, ErrFileStale
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}
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}
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// We're clear to (over)write the file
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return pid, os.WriteFile(filename, []byte(fmt.Sprintf("%d\n", pid)), 0644)
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}
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// pidfileContents reads and parses the PID from a pidfile.
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// It returns the PID and an error if the file cannot be read or contains invalid data.
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func pidfileContents(filename string) (int, error) {
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contents, err := os.ReadFile(filename)
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if err != nil {
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return 0, err
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}
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pid, err := strconv.Atoi(strings.TrimSpace(string(contents)))
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if err != nil {
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return 0, ErrFileInvalid
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}
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return pid, nil
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}
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// pidIsRunning checks if a process with the given PID is currently running.
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// It returns true if the process is running, false otherwise.
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func pidIsRunning(pid int) bool {
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process, err := os.FindProcess(pid)
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if err != nil {
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return false
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}
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err = process.Signal(syscall.Signal(0))
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if err != nil && err.Error() == "no such process" {
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return false
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}
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if err != nil && err.Error() == "os: process already finished" {
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return false
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}
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return true
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}
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