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|
package shutdown
import (
"os"
"os/signal"
"sync"
"syscall"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
var (
ErrHandlerExists error = errors.New("handler with given name already exists")
)
var (
stopped bool
sigChan chan os.Signal
cancelChan chan bool
// Synchronize accesses to the map
handlerLock sync.Mutex
// Definitions of all on-shutdown handlers
handlers map[string]func(os.Signal) error
// Ordering that on-shutdown handlers will be invoked.
handlerOrder []string
shutdownInhibit sync.RWMutex
)
// Start begins handling SIGTERM and SIGINT and will run the given on-signal
// handlers when one is called. This can be cancelled by calling Stop().
func Start() error {
if sigChan != nil {
// Already running, do nothing.
return nil
}
sigChan = make(chan os.Signal, 2)
cancelChan = make(chan bool, 1)
stopped = false
signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
go func() {
select {
case <-cancelChan:
signal.Stop(sigChan)
close(sigChan)
close(cancelChan)
stopped = true
return
case sig := <-sigChan:
logrus.Infof("Received shutdown signal %v, terminating!", sig)
shutdownInhibit.Lock()
handlerLock.Lock()
for _, name := range handlerOrder {
handler, ok := handlers[name]
if !ok {
logrus.Errorf("Shutdown handler %s definition not found!", name)
continue
}
logrus.Infof("Invoking shutdown handler %s", name)
if err := handler(sig); err != nil {
logrus.Errorf("Error running shutdown handler %s: %v", name, err)
}
}
handlerLock.Unlock()
shutdownInhibit.Unlock()
return
}
}()
return nil
}
// Stop the shutdown signal handler.
func Stop() error {
if cancelChan == nil {
return errors.New("shutdown signal handler has not yet been started")
}
if stopped {
return nil
}
cancelChan <- true
return nil
}
// Temporarily inhibit signals from shutting down Libpod.
func Inhibit() {
shutdownInhibit.RLock()
}
// Stop inhibiting signals from shutting down Libpod.
func Uninhibit() {
shutdownInhibit.RUnlock()
}
// Register registers a function that will be executed when Podman is terminated
// by a signal. Handlers are invoked LIFO - the last handler registered is the
// first run.
func Register(name string, handler func(os.Signal) error) error {
handlerLock.Lock()
defer handlerLock.Unlock()
if handlers == nil {
handlers = make(map[string]func(os.Signal) error)
}
if _, ok := handlers[name]; ok {
return ErrHandlerExists
}
handlers[name] = handler
handlerOrder = append([]string{name}, handlerOrder...)
return nil
}
// Unregister un-registers a given shutdown handler.
func Unregister(name string) error {
handlerLock.Lock()
defer handlerLock.Unlock()
if handlers == nil {
return nil
}
if _, ok := handlers[name]; !ok {
return nil
}
delete(handlers, name)
newOrder := []string{}
for _, checkName := range handlerOrder {
if checkName != name {
newOrder = append(newOrder, checkName)
}
}
handlerOrder = newOrder
return nil
}
|
