JSON Decode error while service was unavailable

[samaloney]

Bit of an edge case and realise this is probably only temporary package but while the SOAR was down for maintenance got a json decode error -

result = Fido.search(Time('2021-01-01', '2021-01-15') & Instrument('EUI'))
---------------------------------------------------------------------------
JSONDecodeError                           Traceback (most recent call last)
<ipython-input-8-1b961ccfb6a9> in <module>
----> 1 result = Fido.search(Time('2021-01-01', '2021-01-15') & Instrument('EUI'))

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy/net/fido_factory.py in search(self, *query)
    346         """
    347         query = attr.and_(*query)
--> 348         results = query_walker.create(query, self)
    349
    350         # If we have searched the VSO but no results were returned, but another

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy/net/attr.py in create(self, *args, **kwargs)
    563         Call the create function(s) matching the arguments to this method.
    564         """
--> 565         return self.createmm(self, *args, **kwargs)
    566
    567     def apply(self, *args, **kwargs):

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy/util/functools.py in wrapper(*args, **kwargs)
     16
     17     def wrapper(*args, **kwargs):
---> 18         return dispatcher.dispatch(args[1].__class__)(*args, **kwargs)
     19
     20     wrapper.dispatch = dispatcher.dispatch

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy/net/fido_factory.py in _create_and(walker, query, factory)
    275 @query_walker.add_creator(attr.AttrAnd)
    276 def _create_and(walker, query, factory):
--> 277     return factory._make_query_to_client(*query.attrs)
    278
    279

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy/net/fido_factory.py in _make_query_to_client(self, *query)
    511             if isinstance(tmpclient, vso.VSOClient):
    512                 kwargs = dict(response_format="table")
--> 513             results.append(tmpclient.search(*query, **kwargs))
    514
    515         # This method is called by `search` and the results are fed into a

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy_soar/client.py in search(self, *query, **kwargs)
     25         results = []
     26         for query_parameters in queries:
---> 27             results.append(self._do_search(query_parameters))
     28         table = astropy.table.vstack(results)
     29         qrt = QueryResponseTable(table, client=self)

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/sunpy_soar/client.py in _do_search(query)
     63
     64         # Do some list/dict wrangling
---> 65         names = [m['name'] for m in r.json()['metadata']]
     66         info = {name: [] for name in names}
     67         for entry in r.json()['data']:

~/.virtualenvs/radiospectra/lib/python3.7/site-packages/requests/models.py in json(self, **kwargs)
    898                     # used.
    899                     pass
--> 900         return complexjson.loads(self.text, **kwargs)
    901
    902     @property

~/.pyenv/versions/3.7.0/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py in loads(s, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, **kw)
    346             parse_int is None and parse_float is None and
    347             parse_constant is None and object_pairs_hook is None and not kw):
--> 348         return _default_decoder.decode(s)
    349     if cls is None:
    350         cls = JSONDecoder

~/.pyenv/versions/3.7.0/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py in decode(self, s, _w)
    335
    336         """
--> 337         obj, end = self.raw_decode(s, idx=_w(s, 0).end())
    338         end = _w(s, end).end()
    339         if end != len(s):

~/.pyenv/versions/3.7.0/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py in raw_decode(self, s, idx)
    353             obj, end = self.scan_once(s, idx)
    354         except StopIteration as err:
--> 355             raise JSONDecodeError("Expecting value", s, err.value) from None
    356         return obj, end

JSONDecodeError: Expecting value: line 1 column 1 (char 0)

[dstansby]

Would you expect the client to raise a better error, or return zero results and not error?

[samaloney]

Hum I guess raise an error, but maybe that's not very user friendly? I assume it go a 200 response but there was just no json in it hence the json decode. It's probably going to be rare occurrence so maybe it doesn't need to be "fixed"?

[dstansby]

👍 - definitely worth fixing I think. Having thought about this a bit more, it should probably just return zero results so other clients have a chance to return results too. I've opened sunpy/sunpy#5661 though, to try and get sunpy to have a way of communicating to the user that there's zero results because a server is down.