fix(cli/ssh): Avoid connection hang when workspace is stopped

mafredri · mafredri · commit 2ffea3d631a1 · 2023-04-19T11:58:55.000Z
Two issues are addressed here: 1. We were not detecting disconnects due to waiting for Stdin to close (disconnect would only propagate after entering input and failing to write to the connection). 2. In other scenarios, where the connection drop is not detected, we now also watch workspace status and drop the connection when a workspace reaches the stopped state. Fixes: https://github.com/coder/jetbrains-coder/issues/199 Refs: #6180, #6175
diff --git a/cli/ssh.go b/cli/ssh.go
@@ -100,17 +100,62 @@ func (r *RootCmd) ssh() *clibase.Cmd {
 			stopPolling := tryPollWorkspaceAutostop(ctx, client, workspace)
 			defer stopPolling()
 
+			// Enure connection is closed if the context is canceled or
+			// the workspace reaches the stopped state.
+			//
+			// Watching the stopped state is a work-around for cases
+			// where the agent is not gracefully shut down and the
+			// connection is left open. If, for instance, the networking
+			// is stopped before the agent is shut down, the disconnect
+			// will usually not propagate.
+			//
+			// See: https://github.com/coder/coder/issues/6180
+			wsWatch, err := client.WatchWorkspace(ctx, workspace.ID)
+			if err != nil {
+				return err
+			}
+			watchAndClose := func(c io.Closer) {
+				// Ensure session is ended on both context cancellation
+				// and workspace stop.
+				defer c.Close()
+
+				for {
+					select {
+					case <-ctx.Done():
+						return
+					case w, ok := <-wsWatch:
+						if !ok {
+							return
+						}
+
+						// Note, we only react to the stopped state here because we
+						// want to give the agent a chance to gracefully shut down
+						// during "stopping".
+						if w.LatestBuild.Status == codersdk.WorkspaceStatusStopped {
+							_, _ = fmt.Fprintf(inv.Stderr, "Workspace %q has stopped. Closing connection.\r\n", workspace.Name)
+							return
+						}
+					}
+				}
+			}
+
 			if stdio {
 				rawSSH, err := conn.SSH(ctx)
 				if err != nil {
 					return err
 				}
 				defer rawSSH.Close()
+				defer watchAndClose(rawSSH)
 
 				go func() {
-					_, _ = io.Copy(inv.Stdout, rawSSH)
+					// Ensure stdout copy closes inc ase stdin is closed
+					// unexpectedly. Typically we wouldn't worry about
+					// this since OpenSSH should kill the proxy command.
+					defer rawSSH.Close()
+
+					_, _ = io.Copy(rawSSH, inv.Stdin)
 				}()
-				_, _ = io.Copy(rawSSH, inv.Stdin)
+				_, _ = io.Copy(inv.Stdout, rawSSH)
 				return nil
 			}
 
@@ -125,13 +170,7 @@ func (r *RootCmd) ssh() *clibase.Cmd {
 				return err
 			}
 			defer sshSession.Close()
-
-			// Ensure context cancellation is propagated to the
-			// SSH session, e.g. to cancel `Wait()` at the end.
-			go func() {
-				<-ctx.Done()
-				_ = sshSession.Close()
-			}()
+			defer watchAndClose(sshSession)
 
 			if identityAgent == "" {
 				identityAgent = os.Getenv("SSH_AUTH_SOCK")
