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lock.go
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lock.go
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package main
import (
"errors"
"fmt"
"io"
"path"
fslock "github.com/ipfs/go-fs-lock"
"github.com/mtdepin/rep-mgr/cmdutils"
)
// lock logic heavily inspired by go-ipfs/repo/fsrepo/lock/lock.go
// The name of the file used for locking
const lockFileName = "cluster.lock"
var locker *lock
// lock helps to coordinate proceeds via a lock file
type lock struct {
lockCloser io.Closer
path string
}
func (l *lock) lock() {
if l.lockCloser != nil {
checkErr("", errors.New("cannot acquire lock twice"))
}
// we should have a config folder whenever we try to lock
cfgHelper := cmdutils.NewConfigHelper(configPath, identityPath, "", "")
cfgHelper.MakeConfigFolder()
// set the lock file within this function
logger.Debug("checking lock")
lk, err := fslock.Lock(l.path, lockFileName)
if err != nil {
logger.Debug(err)
l.lockCloser = nil
errStr := "%s. If no other "
errStr += "%s process is running, remove %s, or make sure "
errStr += "that the config folder is writable for the user "
errStr += "running %s."
errStr = fmt.Sprintf(
errStr,
err,
programName,
path.Join(l.path, lockFileName),
programName,
)
checkErr("obtaining execution lock", errors.New(errStr))
}
logger.Debugf("%s execution lock acquired", programName)
l.lockCloser = lk
}
func (l *lock) tryUnlock() error {
// Noop in the uninitialized case
if l.lockCloser == nil {
logger.Debug("locking not initialized, unlock is noop")
return nil
}
err := l.lockCloser.Close()
if err != nil {
return err
}
logger.Debug("successfully released execution lock")
l.lockCloser = nil
return nil
}