coredns/middleware/file/reload.go

package file

import (
	"log"
	"os"
	"path"

	"github.com/fsnotify/fsnotify"
)

// Reload reloads a zone when it is changed on disk. If z.NoRoload is true, no reloading will be done.
func (z *Zone) Reload() error {
	if z.NoReload {
		return nil
	}
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return err
	}
	err = watcher.Add(path.Dir(z.file))
	if err != nil {
		return err
	}

	go func() {
		// TODO(miek): needs to be killed on reload.
		for {
			select {
			case event := <-watcher.Events:
				if path.Clean(event.Name) == z.file {

					reader, err := os.Open(z.file)
					if err != nil {
						log.Printf("[ERROR] Failed to open `%s' for `%s': %v", z.file, z.origin, err)
						continue
					}

					serial := z.SOASerialIfDefined()
					zone, err := Parse(reader, z.origin, z.file, serial)
					if err != nil {
						log.Printf("[WARNING] Parsing zone `%s': %v", z.origin, err)
						continue
					}

					// copy elements we need
					z.reloadMu.Lock()
					z.Apex = zone.Apex
					z.Tree = zone.Tree
					z.reloadMu.Unlock()

					log.Printf("[INFO] Successfully reloaded zone `%s'", z.origin)
					z.Notify()
				}
			case <-z.ReloadShutdown:
				watcher.Close()
				return
			}
		}
	}()
	return nil
}

// SOASerialIfDefined returns the SOA's serial if the zone has a SOA record in the Apex, or
// -1 otherwise.
func (z *Zone) SOASerialIfDefined() int64 {
	z.reloadMu.Lock()
	defer z.reloadMu.Unlock()
	if z.Apex.SOA != nil {
		return int64(z.Apex.SOA.Serial)
	}
	return -1
}