concatMap((action: actions.RestartKernel | actions.NewKernelAction) => {
      const state = state$.value;
      const oldKernelRef = action.payload.kernelRef;
      const notificationSystem = selectors.notificationSystem(state);

      if (!oldKernelRef) {
        notificationSystem.addNotification({
          title: "Failure to Restart",
          message: "Unable to restart kernel, please select a new kernel.",
          dismissible: true,
          position: "tr",
          level: "error"
        });
        return empty();
      }

      const oldKernel = selectors.kernel(state, { kernelRef: oldKernelRef });

      if (!oldKernelRef || !oldKernel) {
        notificationSystem.addNotification({
          title: "Failure to Restart",
          message: "Unable to restart kernel, please select a new kernel.",
          dismissible: true,
          position: "tr",
          level: "error"
        });

        // TODO: Wow do we need to send notifications through our store for
        // consistency
        return empty();
      }

      const newKernelRef = kernelRefGenerator();
      const initiatingContentRef = action.payload.contentRef;

      // TODO: Incorporate this into each of the launchKernelByName
      //       actions...
      //       This only mirrors the old behavior of restart kernel (for now)
      notificationSystem.addNotification({
        title: "Kernel Restarting...",
        message: `Kernel ${oldKernel.kernelSpecName ||
          "unknown"} is restarting.`,
        dismissible: true,
        position: "tr",
        level: "success"
      });

      const kill = actions.killKernel({
        restarting: true,
        kernelRef: oldKernelRef
      });

      const relaunch = actions.launchKernelByName({
        kernelSpecName: oldKernel.kernelSpecName,
        cwd: oldKernel.cwd,
        kernelRef: newKernelRef,
        selectNextKernel: true,
        contentRef: initiatingContentRef
      });

      const awaitKernelReady = action$.pipe(
        ofType(actions.LAUNCH_KERNEL_SUCCESSFUL),
        filter(
          (action: actions.NewKernelAction | actions.RestartKernel) =>
            action.payload.kernelRef === newKernelRef
        ),
        take(1),
        timeout(60000), // If kernel doesn't come up within this interval we will abort follow-on actions.
        concatMap(() => {
          const restartSuccess = actions.restartKernelSuccessful({
            kernelRef: newKernelRef,
            contentRef: initiatingContentRef
          });

          if (
            (action as actions.RestartKernel).payload.outputHandling ===
            "Run All"
          ) {
            return of(
              restartSuccess,
              actions.executeAllCells({ contentRef: initiatingContentRef })
            );
          } else {
            return of(restartSuccess);
          }
        }),
        catchError(error => {
          return of(
            actions.restartKernelFailed({
              error,
              kernelRef: newKernelRef,
              contentRef: initiatingContentRef
            })
          );
        })
      );

      return merge(of(kill, relaunch), awaitKernelReady);
    })

    switchMap((action: actions.ChangeKernelByName) => {
      const {
        payload: { contentRef, oldKernelRef, kernelSpecName }
      } = action;
      const state = state$.value;
      const host = selectors.currentHost(state);
      if (host.type !== "jupyter") {
        // Dismiss any usage that isn't targeting a jupyter server
        return empty();
      }
      const serverConfig: ServerConfig = selectors.serverConfig(host);

      // TODO: This is the case where we didn't have a kernel before
      //       and they chose to switch kernels. Instead we need to allow
      //       "switching" by disregarding the previous kernel and creating a
      //       new session
      if (!oldKernelRef) {
        return empty();
      }

      const oldKernel = selectors.kernel(state, { kernelRef: oldKernelRef });
      if (!oldKernel || oldKernel.type !== "websocket") {
        return empty();
      }
      const { sessionId } = oldKernel;
      if (!sessionId) {
        return empty();
      }

      const content = selectors.content(state, { contentRef });
      if (!content || content.type !== "notebook") {
        return empty();
      }
      const {
        filepath,
        model: { notebook }
      } = content;
      const { cwd } = extractNewKernel(filepath, notebook);

      const kernelRef = createKernelRef();
      return kernels.start(serverConfig, kernelSpecName, cwd).pipe(
        mergeMap(({ response }) => {
          const { id: kernelId } = response;
          const sessionPayload = {
            kernel: { id: kernelId, name: kernelSpecName }
          };
          // The sessions API will close down the old kernel for us if it is
          // on this session
          return sessions.update(serverConfig, sessionId, sessionPayload).pipe(
            mergeMap(({ response: session }) => {
              const kernel: RemoteKernelProps = Object.assign(
                {},
                session.kernel,
                {
                  type: "websocket",
                  sessionId,
                  cwd,
                  channels: kernels.connect(
                    serverConfig,
                    session.kernel.id,
                    sessionId
                  ),
                  kernelSpecName
                }
              );
              return of(
                actions.launchKernelSuccessful({
                  kernel,
                  kernelRef,
                  contentRef: action.payload.contentRef,
                  selectNextKernel: true
                })
              );
            }),
            catchError(error =>
              of(actions.launchKernelFailed({ error, kernelRef, contentRef }))
            )
          );
        }),
        catchError(error =>
          of(actions.launchKernelFailed({ error, kernelRef, contentRef }))
        )
      );
    })