Hello,

What are the most common reasons for  Odoo producing a large amount of the following bus exceptions in the log file:

2016-03-15 20:37:42,160 27533 ERROR Production openerp.http: Exception during JSON request handling.

Traceback (most recent call last)
  File "/odoo9e/core/openerp/http.py", line 643, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/odoo9e/core/openerp/http.py", line 680, in dispatch
    result = self._call_function(**self.params)
  File "/odoo9e/core/openerp/http.py", line 316, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/odoo9e/core/openerp/service/model.py", line 118, in wrappet
    return f(dbname, *args, **kwargs)
  File "/odoo9e/core/openerp/http.py", line 309, in checked_call
    result = self.endpoint(*a, **kw)
  File "/odoo9e/core/openerp/http.py", line 959, in __call__
    return self.method(*args, **kw)
  File "/odoo9e/core/openerp/http.py", line 509, in response_wrap
    response = f(*args, **kw)
  File "/odoo9e/core/addons/bus/controllers/main.py", line 34, in poll
    raise Exception("bus.Bus unavailable")
Exception: bus.Bus unavailable