Enable detached exec for remote

The biggest obstacle here was cleanup - we needed a way to remove
detached exec sessions after they exited, but there's no way to
tell if an exec session will be attached or detached when it's
created, and that's when we must add the exit command that would
do the removal. The solution was adding a delay to the exit
command (5 minutes), which gives sufficient time for attached
exec sessions to retrieve the exit code of the session after it
exits, but still guarantees that they will be removed, even for
detached sessions. This requires Conmon 2.0.17, which has the new
`--exit-delay` flag.

As part of the exit command rework, we can drop the hack we were
using to clean up exec sessions (remove them as part of inspect).
This is a lot cleaner, and I'm a lot happier about it.

Otherwise, this is just plumbing - we need a bindings call for
detached exec, and that needed to be added to the tunnel mode
backend for entities.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

2 files changed, 36 insertions, 18 deletions

diff --git a/pkg/api/handlers/compat/exec.go b/pkg/api/handlers/compat/exec.go
index 6865a3319..8f7016903 100644
--- a/pkg/api/handlers/compat/exec.go
+++ b/pkg/api/handlers/compat/exec.go
@@ -10,6 +10,7 @@ import (
 	"github.com/containers/libpod/libpod/define"
 	"github.com/containers/libpod/pkg/api/handlers"
 	"github.com/containers/libpod/pkg/api/handlers/utils"
+	"github.com/containers/libpod/pkg/specgen/generate"
 	"github.com/gorilla/mux"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -54,6 +55,24 @@ func ExecCreateHandler(w http.ResponseWriter, r *http.Request) {
 	libpodConfig.Privileged = input.Privileged
 	libpodConfig.User = input.User
 
+	// Make our exit command
+	storageConfig := runtime.StorageConfig()
+	runtimeConfig, err := runtime.GetConfig()
+	if err != nil {
+		utils.InternalServerError(w, err)
+		return
+	}
+	exitCommandArgs, err := generate.CreateExitCommandArgs(storageConfig, runtimeConfig, false, true, true)
+	if err != nil {
+		utils.InternalServerError(w, err)
+		return
+	}
+	libpodConfig.ExitCommand = exitCommandArgs
+
+	// Run the exit command after 5 minutes, to mimic Docker's exec cleanup
+	// behavior.
+	libpodConfig.ExitCommandDelay = 5 * 60
+
 	sessID, err := ctr.ExecCreate(libpodConfig)
 	if err != nil {
 		if errors.Cause(err) == define.ErrCtrStateInvalid {
@@ -104,15 +123,6 @@ func ExecInspectHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	utils.WriteResponse(w, http.StatusOK, inspectOut)
-
-	// Only for the Compat API: we want to remove sessions that were
-	// stopped. This is very hacky, but should suffice for now.
-	if !utils.IsLibpodRequest(r) && inspectOut.CanRemove {
-		logrus.Infof("Pruning stale exec session %s from container %s", sessionID, sessionCtr.ID())
-		if err := sessionCtr.ExecRemove(sessionID, false); err != nil && errors.Cause(err) != define.ErrNoSuchExecSession {
-			logrus.Errorf("Error removing stale exec session %s from container %s: %v", sessionID, sessionCtr.ID(), err)
-		}
-	}
 }
 
 // ExecStartHandler runs a given exec session.
@@ -121,7 +131,7 @@ func ExecStartHandler(w http.ResponseWriter, r *http.Request) {
 
 	sessionID := mux.Vars(r)["id"]
 
-	// TODO: We should read/support Tty and Detach from here.
+	// TODO: We should read/support Tty from here.
 	bodyParams := new(handlers.ExecStartConfig)
 
 	if err := json.NewDecoder(r.Body).Decode(&bodyParams); err != nil {
@@ -129,11 +139,6 @@ func ExecStartHandler(w http.ResponseWriter, r *http.Request) {
 			errors.Wrapf(err, "failed to decode parameters for %s", r.URL.String()))
 		return
 	}
-	if bodyParams.Detach {
-		utils.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest,
-			errors.Errorf("Detached exec is not yet supported"))
-		return
-	}
 	// TODO: Verify TTY setting against what inspect session was made with
 
 	sessionCtr, err := runtime.GetExecSessionContainer(sessionID)
@@ -154,6 +159,19 @@ func ExecStartHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if bodyParams.Detach {
+		// If we are detaching, we do NOT want to hijack.
+		// Instead, we perform a detached start, and return 200 if
+		// successful.
+		if err := sessionCtr.ExecStart(sessionID); err != nil {
+			utils.InternalServerError(w, err)
+			return
+		}
+		// This is a 200 despite having no content
+		utils.WriteResponse(w, http.StatusOK, "")
+		return
+	}
+
 	// Hijack the connection
 	hijacker, ok := w.(http.Hijacker)
 	if !ok {
diff --git a/pkg/api/server/register_exec.go b/pkg/api/server/register_exec.go
index 17181d286..af9a83496 100644
--- a/pkg/api/server/register_exec.go
+++ b/pkg/api/server/register_exec.go
@@ -13,7 +13,7 @@ func (s *APIServer) registerExecHandlers(r *mux.Router) error {
 	// tags:
 	//   - exec (compat)
 	// summary: Create an exec instance
-	// description: Run a command inside a running container.
+	// description: Create an exec session to run a command inside a running container. Exec sessions will be automatically removed 5 minutes after they exit.
 	// parameters:
 	//  - in: path
 	//    name: name
@@ -153,7 +153,7 @@ func (s *APIServer) registerExecHandlers(r *mux.Router) error {
 	// tags:
 	//   - exec (compat)
 	// summary: Inspect an exec instance
-	// description: Return low-level information about an exec instance. Stale (stopped) exec sessions will be auto-removed after inspect runs.
+	// description: Return low-level information about an exec instance.
 	// parameters:
 	//  - in: path
 	//    name: id
@@ -182,7 +182,7 @@ func (s *APIServer) registerExecHandlers(r *mux.Router) error {
 	// tags:
 	//   - exec
 	// summary: Create an exec instance
-	// description: Run a command inside a running container.
+	// description: Create an exec session to run a command inside a running container. Exec sessions will be automatically removed 5 minutes after they exit.
 	// parameters:
 	//  - in: path
 	//    name: name