This is practically invisible to the client, other than timing. It just means that the server can start transmitting without having to assemble the entire json blob in memory first, with the effect that the client sees a stready stream of data, rather than a long pause before the whole payload is dumped as fast as the network can transmit.

What I did here though wasn’t brilliant (it was a while ago….) – I constructed a JSON array which isn’t technically valid JSON until the final line is sent. So the client needs to read it as a whole anyway, but the chunk size wouldn’t be a factor, and the client code would be no different to the non-chunked approach.

Most systems doing this sort of job would send each chunk as an individually-valid JSON object, which is more reasonable with large amounts of data that would be expected to be handled individually.

edit: Technical term for this is ndjson, or new-line-delimited JSON: http://ndjson.org/

I used a simple custom function to encode the date for json.

def json_serial(obj):
“””JSON serializer for objects not serializable by default json code”””
if isinstance(obj, datetime.datetime):
return obj.__str__()

json.dumps(to_dict(r), default=json_serial)

Hi Sven glad it was useful. This looks like a solid improvement, I’ll probably integrate it into my implementation next time I work on it. Shame about the formatting but I’ll manage!

I’ve adjusted the logic for the iterator a bit to try and send the first item and then subsequently send ‘,’ + json(next item) (i.e. prefix the comma for sends after the first). I find that a bit clearer and it avoids having to keep the previous item around:

“`
def stream():
yield ‘[‘

reports = query.__iter__()
try:
r = next(reports)
yield json.dumps(to_dict(r), default=date_encoder)
except StopIteration:
# no results – close array and stop iteration
yield ‘]’
raise StopIteration

# loop over remaining results
for r in reports:
yield ‘,’ + json.dumps(to_dict(r), default=date_encoder)

# close array
yield ‘]’

return Response(stream(), content_type=’application/json’)
“`

Note I’m just sending a straight array instead of an dictionary with an array so the opening and closing elements are slightly different. I.e. replace `'[‘` with `'{“releases”: [‘` and `’]’` with `]}`.