Odoo bus error

astcall_odoo | 2018-09-10 15:12:35,794 336 ERROR astcalls odoo.http: Exception during JSON request handling.
astcall_odoo | Traceback (most recent call last):
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 640, in _handle_exception
astcall_odoo |     return super(JsonRequest, self)._handle_exception(exception)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 677, in dispatch
astcall_odoo |     result = self._call_function(**self.params)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 333, in _call_function
astcall_odoo |     return checked_call(self.db, *args, **kwargs)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/service/model.py", line 101, in wrapper
astcall_odoo |     return f(dbname, *args, **kwargs)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 326, in checked_call
astcall_odoo |     result = self.endpoint(*a, **kw)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 935, in __call__
astcall_odoo |     return self.method(*args, **kw)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 506, in response_wrap
astcall_odoo |     response = f(*args, **kw)
astcall_odoo |   File "/usr/lib/python2.7/dist-packages/odoo/addons/bus/controllers/main.py", line 35, in poll
astcall_odoo |     raise Exception("bus.Bus unavailable")
astcall_odoo | Exception: bus.Bus unavailable