Merge pull request #7999 from mheon/signal_handler

Add a shutdown signal handler

5 files changed, 167 insertions, 11 deletions

diff --git a/libpod/runtime.go b/libpod/runtime.go
index 7da8b181f..ccd920ab0 100644
--- a/libpod/runtime.go
+++ b/libpod/runtime.go
@@ -17,6 +17,7 @@ import (
 	"github.com/containers/podman/v2/libpod/events"
 	"github.com/containers/podman/v2/libpod/image"
 	"github.com/containers/podman/v2/libpod/lock"
+	"github.com/containers/podman/v2/libpod/shutdown"
 	"github.com/containers/podman/v2/pkg/cgroups"
 	"github.com/containers/podman/v2/pkg/registries"
 	"github.com/containers/podman/v2/pkg/rootless"
@@ -174,9 +175,21 @@ func newRuntimeFromConfig(ctx context.Context, conf *config.Config, options ...R
 		}
 	}
 
+	if err := shutdown.Start(); err != nil {
+		return nil, errors.Wrapf(err, "error starting shutdown signal handler")
+	}
+
 	if err := makeRuntime(ctx, runtime); err != nil {
 		return nil, err
 	}
+
+	if err := shutdown.Register("libpod", func(sig os.Signal) error {
+		os.Exit(1)
+		return nil
+	}); err != nil {
+		logrus.Errorf("Error registering shutdown handler for libpod: %v", err)
+	}
+
 	return runtime, nil
 }
 
diff --git a/libpod/runtime_ctr.go b/libpod/runtime_ctr.go
index 51b4c5f03..de73a9ff3 100644
--- a/libpod/runtime_ctr.go
+++ b/libpod/runtime_ctr.go
@@ -12,6 +12,7 @@ import (
 	"github.com/containers/common/pkg/config"
 	"github.com/containers/podman/v2/libpod/define"
 	"github.com/containers/podman/v2/libpod/events"
+	"github.com/containers/podman/v2/libpod/shutdown"
 	"github.com/containers/podman/v2/pkg/cgroups"
 	"github.com/containers/podman/v2/pkg/rootless"
 	"github.com/containers/storage"
@@ -149,6 +150,10 @@ func (r *Runtime) setupContainer(ctx context.Context, ctr *Container) (_ *Contai
 		return nil, err
 	}
 
+	// Inhibit shutdown until creation succeeds
+	shutdown.Inhibit()
+	defer shutdown.Uninhibit()
+
 	// Allocate a lock for the container
 	lock, err := r.lockManager.AllocateLock()
 	if err != nil {
diff --git a/libpod/shutdown/handler.go b/libpod/shutdown/handler.go
new file mode 100644
index 000000000..87538dec9
--- /dev/null
+++ b/libpod/shutdown/handler.go
@@ -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
+
+	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)
+	}
+
+	handlers[name] = handler
+	handlerOrder = append([]string{name}, handlerOrder...)
+
+	return nil
+}
+
+// Unregister un-registers a given shutdown handler.
+func Unregister(name string) error {
+	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
+}
diff --git a/pkg/api/server/server.go b/pkg/api/server/server.go
index 355a46fb7..64008767b 100644
--- a/pkg/api/server/server.go
+++ b/pkg/api/server/server.go
@@ -7,7 +7,6 @@ import (
 	"net"
 	"net/http"
 	"os"
-	"os/signal"
 	goRuntime "runtime"
 	"strings"
 	"sync"
@@ -15,6 +14,7 @@ import (
 	"time"
 
 	"github.com/containers/podman/v2/libpod"
+	"github.com/containers/podman/v2/libpod/shutdown"
 	"github.com/containers/podman/v2/pkg/api/handlers"
 	"github.com/containers/podman/v2/pkg/api/server/idle"
 	"github.com/coreos/go-systemd/v22/activation"
@@ -180,8 +180,17 @@ func setupSystemd() {
 // Serve starts responding to HTTP requests.
 func (s *APIServer) Serve() error {
 	setupSystemd()
-	sigChan := make(chan os.Signal, 1)
-	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	// Start the shutdown signal handler.
+	if err := shutdown.Start(); err != nil {
+		return err
+	}
+	if err := shutdown.Register("server", func(sig os.Signal) error {
+		return s.Shutdown()
+	}); err != nil {
+		return err
+	}
+
 	errChan := make(chan error, 1)
 
 	go func() {
@@ -217,14 +226,7 @@ func (s *APIServer) Serve() error {
 		errChan <- nil
 	}()
 
-	select {
-	case err := <-errChan:
-		return err
-	case sig := <-sigChan:
-		logrus.Infof("APIServer terminated by signal %v", sig)
-	}
-
-	return nil
+	return <-errChan
 }
 
 // Shutdown is a clean shutdown waiting on existing clients
diff --git a/pkg/domain/infra/abi/terminal/sigproxy_linux.go b/pkg/domain/infra/abi/terminal/sigproxy_linux.go
index f484e926c..0c586cf5c 100644
--- a/pkg/domain/infra/abi/terminal/sigproxy_linux.go
+++ b/pkg/domain/infra/abi/terminal/sigproxy_linux.go
@@ -5,12 +5,17 @@ import (
 	"syscall"
 
 	"github.com/containers/podman/v2/libpod"
+	"github.com/containers/podman/v2/libpod/shutdown"
 	"github.com/containers/podman/v2/pkg/signal"
 	"github.com/sirupsen/logrus"
 )
 
 // ProxySignals ...
 func ProxySignals(ctr *libpod.Container) {
+	// Stop catching the shutdown signals (SIGINT, SIGTERM) - they're going
+	// to the container now.
+	shutdown.Stop()
+
 	sigBuffer := make(chan os.Signal, 128)
 	signal.CatchAll(sigBuffer)