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Add a shutdown signal handler #7999
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openshift-merge-robot
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containers:master
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mheon:signal_handler
Oct 20, 2020
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,131 @@ | ||
| package shutdown | ||
|
|
||
| import ( | ||
| "os" | ||
| "os/signal" | ||
| "sync" | ||
| "syscall" | ||
|
|
||
| "github.com/pkg/errors" | ||
| "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| var ( | ||
| stopped bool | ||
| sigChan chan os.Signal | ||
| cancelChan chan bool | ||
| // 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, 1) | ||
| cancelChan = make(chan bool, 1) | ||
| stopped = false | ||
|
|
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| 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() | ||
| 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) | ||
| } | ||
| } | ||
| 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 { | ||
| if handlers == nil { | ||
| handlers = make(map[string]func(os.Signal) error) | ||
| } | ||
|
|
||
| if _, ok := handlers[name]; ok { | ||
| return errors.Errorf("handler with name %s already exists", name) | ||
| } | ||
|
|
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| handlers[name] = handler | ||
| handlerOrder = append([]string{name}, handlerOrder...) | ||
|
|
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| return nil | ||
| } | ||
|
|
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| // Unregister un-registers a given shutdown handler. | ||
| func Unregister(name string) error { | ||
| if handlers == nil { | ||
| return nil | ||
| } | ||
|
|
||
| if _, ok := handlers[name]; !ok { | ||
| return nil | ||
| } | ||
|
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||
| delete(handlers, name) | ||
|
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| newOrder := []string{} | ||
| for _, checkName := range handlerOrder { | ||
| if checkName != name { | ||
| newOrder = append(newOrder, checkName) | ||
| } | ||
| } | ||
| handlerOrder = newOrder | ||
|
|
||
| return nil | ||
| } | ||
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Why not just reset handler to new func?
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I'd like to allow multiple handlers at the same time - theoretically the Libpod handler could run after the server handler and do any extra shutdown needed there.