concatMap((action: actions.KillKernelAction) => {
      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);

      const kernel = selectors.currentKernel(state);
      if (!kernel) {
        return of(
          actions.killKernelFailed({
            error: new Error("kernel not available for killing"),
            kernelRef: action.payload.kernelRef
          })
        );
      }

      if (kernel.type !== "websocket" || !kernel.id || !kernel.sessionId) {
        return of(
          actions.killKernelFailed({
            error: new Error(
              "websocket kernel epic can only kill websocket kernels with an id"
            ),
            kernelRef: action.payload.kernelRef
          })
        );
      }

      // TODO: If this was a kernel language change, we shouldn't be using this
      //       kill kernel epic because we need to make sure that creation happens
      //       after deletion
      return sessions.destroy(serverConfig, kernel.sessionId).pipe(
        map(() =>
          actions.killKernelSuccessful({
            kernelRef: action.payload.kernelRef
          })
        ),
        catchError(err =>
          of(
            actions.killKernelFailed({
              error: err,
              kernelRef: action.payload.kernelRef
            })
          )
        )
      );
    })

export function createExecuteCellStream(
  action$: ActionsObservable<
    | ExecuteCanceled
    | DeleteCell
    | LaunchKernelAction
    | LaunchKernelByNameAction
    | KillKernelAction
    | ExecuteCell
    | ExecuteFocusedCell
  >,
  state: any,
  message: ExecuteRequest,
  id: string,
  contentRef: ContentRef
): Observable<any> {
  const kernel = selectors.currentKernel(state);

  const channels = kernel ? kernel.channels : null;

  const kernelConnected =
    kernel &&
    channels &&
    !(kernel.status === "starting" || kernel.status === "not connected");

  if (!kernelConnected || !channels) {
    return of(
      actions.executeFailed({
        error: new Error("Kernel not connected!"),
        contentRef
      })
    );
  }

  const cellStream = executeCellStream(channels, id, message, contentRef).pipe(
    takeUntil(
      merge(
        action$.pipe(
          ofType(actions.EXECUTE_CANCELED, actions.DELETE_CELL),
          filter(
            (
              action:
                | actions.ExecuteCanceled
                | actions.DeleteCell
                | actions.LaunchKernelAction
                | actions.LaunchKernelByNameAction
                | actions.KillKernelAction
                | actions.ExecuteCell
                | actions.ExecuteFocusedCell
            ) => (action as actions.ExecuteCanceled).payload.id === id
          )
        ),
        action$.pipe(
          ofType(
            actions.LAUNCH_KERNEL,
            actions.LAUNCH_KERNEL_BY_NAME,
            actions.KILL_KERNEL
          )
        )
      )
    )
  );

  return merge(
    // We make sure to propagate back to "ourselves" the actual message
    // that we sent to the kernel with the sendExecuteRequest action
    of(actions.sendExecuteRequest({ id, message, contentRef })),
    // Merging it in with the actual stream
    cellStream
  );
}