I have a client server running using the Anvil Uplink. When I call a function from that server, a very large amount of data is supposed to get returned to anvil, however, when the data is passed back, the uplink disconnects and resets itself, and I never get the data back in my anvil app.
I get this error printed in the console: Anvil websocket closed (code 1006, reason=Going away)
What can I do about this?
Out of curiosity, how big is the data and in what format?
Do you have a sample that I could use to recreate that here?
How long does it take to return/send the data?
If it takes too long, it may be timing out and splitting the data in smaller chunks could help.
It’s likely to be related to this, I’m guessing (just one result from many) :
The data is in JSON and the size of the data is 109KB. I don’t know how to give you a sample of the data without pasting it here, which would take up a lot of space. I can’t give you access to the api call, as it is an internal company api.
The disconnect happens almost instantly when I try to return the data over the uplink. What is happening is that I make the api from a local server and try to return the data to anvil over the uplink. As soon as I try to return it, the error fires.
I ran this function to get the size of the response: size = sum(len(chunk) for chunk in response.iter_content(8196)), which returned a size of 4515177.
Hi @jsardonicus
How do you measure that file size? Are you returning it as dicts and lists from the uplink function, or as a string, or in a Media object?
Serialised data returned from uplink or server modules currently has a size limit of 4MB, excluding media (so, if you want to send more than 4MB of data, try sending as Media) - but it looks like your payload is well below that size, so something funny is going on…
Can you share the data you’re sending as an email attachment to support@anvil.works?
Further investigation revealed that the data was actually 4.9 MB rather than 109 KB, which explains why the transfer was failing. Until we have support for sending larger Python objects, the workaround is to send as a Media object:
return anvil.BlobMedia("application/json", json.dumps(data))
And then decode the JSON at the other end:
data = json.loads(returned_media.get_bytes())
I came to this topic searching for a solution, and noticed that while the solution is basically correct, later on there has been a change regarding Media objects, see
["TypeError: BlobMedia content must be a byte string" when generating BlobMedia csv file]
So now it seems you need to have on the server:
return anvil.BlobMedia("application/json", json.dumps(data).encode())
And at the other end:
data = json.loads(returned_media.get_bytes().decode('utf-8'))
Quite right! The change here was that the default Python version switched from Python 2 to Python 3, which distinguishes between bytes and strings. Your sample code is (at the time of writing) correct!