coredns/plugin/reload/reload.go
Miek Gieben a72f3a161c
plugin/reload: fix data races (#2567)
Reload didn't take proper care to protect the fields from use in
different goroutines. Add a mutex and add helpers for usage and
interval.

Signed-off-by: Miek Gieben <miek@miek.nl>
2019-02-17 14:57:36 +00:00

101 lines
2.1 KiB
Go

package reload
import (
"crypto/md5"
"sync"
"time"
"github.com/mholt/caddy"
)
// reload periodically checks if the Corefile has changed, and reloads if so
const (
unused = 0
maybeUsed = 1
used = 2
)
type reload struct {
dur time.Duration
u int
mtx sync.RWMutex
quit chan bool
}
func (r *reload) setUsage(u int) {
r.mtx.Lock()
defer r.mtx.Unlock()
r.u = u
}
func (r *reload) usage() int {
r.mtx.RLock()
defer r.mtx.RUnlock()
return r.u
}
func (r *reload) setInterval(i time.Duration) {
r.mtx.Lock()
defer r.mtx.Unlock()
r.dur = i
}
func (r *reload) interval() time.Duration {
r.mtx.RLock()
defer r.mtx.RUnlock()
return r.dur
}
func hook(event caddy.EventName, info interface{}) error {
if event != caddy.InstanceStartupEvent {
return nil
}
// if reload is removed from the Corefile, then the hook
// is still registered but setup is never called again
// so we need a flag to tell us not to reload
if r.usage() == unused {
return nil
}
// this should be an instance. ok to panic if not
instance := info.(*caddy.Instance)
md5sum := md5.Sum(instance.Caddyfile().Body())
log.Infof("Running configuration MD5 = %x\n", md5sum)
go func() {
tick := time.NewTicker(r.interval())
for {
select {
case <-tick.C:
corefile, err := caddy.LoadCaddyfile(instance.Caddyfile().ServerType())
if err != nil {
continue
}
s := md5.Sum(corefile.Body())
if s != md5sum {
// Let not try to restart with the same file, even though it is wrong.
md5sum = s
// now lets consider that plugin will not be reload, unless appear in next config file
// change status iof usage will be reset in setup if the plugin appears in config file
r.setUsage(maybeUsed)
_, err := instance.Restart(corefile)
if err != nil {
log.Errorf("Corefile changed but reload failed: %s", err)
continue
}
// we are done, if the plugin was not set used, then it is not.
if r.usage() == maybeUsed {
r.setUsage(unused)
}
return
}
case <-r.quit:
return
}
}
}()
return nil
}