attach: replace interface with simple type

Also add docs to detach events

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

container/container.go

@@ -48,18 +48,10 @@ var (
 	errInvalidNetwork  = fmt.Errorf("invalid network settings while building port map info")
 )
 
-// AttachError represents errors of attach
+// DetachError is special error which returned in case of container detach.
-type AttachError interface {
+type DetachError struct{}
-	IsDetached() bool
-}
 
-type detachError struct{}
+func (DetachError) Error() string {
-
-func (e detachError) IsDetached() bool {
-	return true
-}
-
-func (e detachError) Error() string {
 	return "detached from container"
 }
 
@@ -507,7 +499,7 @@ func copyEscapable(dst io.Writer, src io.ReadCloser, keys []byte) (written int64
 				}
 				if i == len(keys)-1 {
 					src.Close()
-					return 0, detachError{}
+					return 0, DetachError{}
 				}
 				nr, er = src.Read(buf)
 			}

daemon/attach.go

@@ -121,8 +121,7 @@ func (daemon *Daemon) containerAttach(c *container.Container, stdin io.ReadClose
 		}
 		err := <-c.Attach(stdinPipe, stdout, stderr, keys)
 		if err != nil {
-			e, ok := err.(container.AttachError)
+			if _, ok := err.(container.DetachError); ok {
-			if ok && e.IsDetached() {
 				daemon.LogContainerEvent(c, "detach")
 			} else {
 				logrus.Errorf("attach failed with error: %v", err)

daemon/exec.go

@@ -222,11 +222,10 @@ func (d *Daemon) ContainerExecStart(ctx context.Context, name string, stdin io.R
 		return fmt.Errorf("context cancelled")
 	case err := <-attachErr:
 		if err != nil {
-			e, ok := err.(container.AttachError)
+			if _, ok := err.(container.DetachError); !ok {
-			if !ok || !e.IsDetached() {
+				return fmt.Errorf("exec attach failed with error: %v", err)
-				return fmt.Errorf("attach failed with error: %v", err)
 			}
-			d.LogContainerEvent(c, "detach")
+			d.LogContainerEvent(c, "exec_detach")
 		}
 	}
 	return nil

docs/reference/api/docker_remote_api.md

@@ -99,6 +99,8 @@ Some container-related events are not affected by container state, so they are n
 * **export** emitted by `docker export`
 * **exec_create** emitted by `docker exec`
 * **exec_start** emitted by `docker exec` after **exec_create**
+* **detach** emitted when client is detached from container process
+* **exec_detach** emitted when client is detached from exec process
 
 Running `docker rmi` emits an **untag** event when removing an image name.  The `rmi` command may also emit **delete** events when images are deleted by ID directly or by deleting the last tag referring to the image.
 
@@ -121,6 +123,8 @@ This section lists each version from latest to oldest.  Each listing includes a
 * `GET /images/search` now takes a `filters` query parameter.
 * `GET /events` now supports a `reload` event that is emitted when the daemon configuration is reloaded.
 * `GET /events` now supports filtering by daemon name or ID.
+* `GET /events` now supports a `detach` event that is emitted on detaching from container process.
+* `GET /events` now supports an `exec_detach ` event that is emitted on detaching from exec process.
 * `GET /images/json` now supports filters `since` and `before`.
 * `POST /containers/(id or name)/start` no longer accepts a `HostConfig`.
 * `POST /images/(name)/tag` no longer has a `force` query parameter.

docs/reference/api/docker_remote_api_v1.24.md

@@ -2404,7 +2404,7 @@ Get container events from docker, either in real time via streaming, or via poll
 
 Docker containers report the following events:
 
-    attach, commit, copy, create, destroy, die, exec_create, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
+    attach, commit, copy, create, destroy, detach, die, exec_create, exec_detach, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
 
 Docker images report the following events:
 

docs/reference/commandline/events.md

@@ -21,7 +21,7 @@ parent = "smn_cli"
 
 Docker containers report the following events:
 
-    attach, commit, copy, create, destroy, die, exec_create, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
+    attach, commit, copy, create, destroy, detach, die, exec_create, exec_detach, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
 
 Docker images report the following events:
 

man/docker-events.1.md

@@ -18,7 +18,7 @@ information and real-time information.
 
 Docker containers will report the following events:
 
-    attach, commit, copy, create, destroy, die, exec_create, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
+    attach, commit, copy, create, destroy, detach, die, exec_create, exec_detach, exec_start, export, kill, oom, pause, rename, resize, restart, start, stop, top, unpause, update
 
 Docker images report the following events: