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Create pid-file atomically 

For things that depend or watch for this pid file to know when the
container is started we need to create this file atomically.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
This commit is contained in:
Michael Crosby 2016-03-17 13:16:56 -07:00
parent bbde9c426f
commit d26cd4da40
1 changed files with 13 additions and 3 deletions
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16
utils.go
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@ -269,18 +269,28 @@ func setupIO(process *libcontainer.Process, rootuid int, console string, createT
return createStdioPipes(process, rootuid) return createStdioPipes(process, rootuid)
} }
// createPidFile creates a file with the processes pid inside it atomically
// it creates a temp file with the paths filename + '.' infront of it
// then renames the file
func createPidFile(path string, process *libcontainer.Process) error { func createPidFile(path string, process *libcontainer.Process) error {
pid, err := process.Pid() pid, err := process.Pid()
if err != nil { if err != nil {
return err return err
} }
f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666) var (
tmpDir = filepath.Dir(path)
tmpName = filepath.Join(tmpDir, fmt.Sprintf(".%s", filepath.Base(path)))
)
f, err := os.OpenFile(tmpName, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0666)
if err != nil { if err != nil {
return err return err
} }
defer f.Close()
_, err = fmt.Fprintf(f, "%d", pid) _, err = fmt.Fprintf(f, "%d", pid)
return err f.Close()
if err != nil {
return err
}
return os.Rename(tmpName, path)
} }
func createContainer(context *cli.Context, id string, spec *specs.Spec) (libcontainer.Container, error) { func createContainer(context *cli.Context, id string, spec *specs.Spec) (libcontainer.Container, error) {