Why seldon chose application/x-www-form-urlencoded as Content-Type instead of application/json when treating predict requests?

[cloga]

I just find seldon use application/x-www-form-urlencoded instead of application/json, this make me confused, in my opinion , I should use json as data for both input and out datatype.

What pros and cons when treating ml predict requests using application/x-www-form-urlencoded and application/json?

I find some discussion about this：https://stackoverflow.com/questions/11281117/x-www-form-urlencoded-vs-json-http-post

If the structure of encoded data is guaranteed to be a flat list of name-value pairs, x-www-form-urlencoded seems sufficient. If the structure could be (arbitrarily) complex (e.g. nesting lists or associative arrays), then definitely use JSON.

[ukclivecox]

We have both.

seldon-core/engine/src/main/java/io/seldon/engine/api/rest/RestClientController.java

Line 140 in 174431a

@RequestMapping(value = "/api/v0.1/predictions", method = RequestMethod.POST, consumes = "application/json; charset=utf-8", produces = "application/json; charset=utf-8")

Please reopen if I misinterpreted you.

[cloga]

Thanks @cliveseldon ，How can I post data to predict interface use application/json?
I find the example using application/x-www-form-urlencoded:

!curl -d 'json={"data":{"ndarray":[[1,2,3]]}}' http://0.0.0.0:5000/predict

And in the microservice/microservice.py file in the seldonio/seldon-core-s2i-python3 image, I find this (line 47 - 55):

def extract_message():
    jStr = request.form.get("json")
    if jStr:
        message = json.loads(jStr)
    else:
        raise SeldonMicroserviceException("Empty json parameter in data")
    if message is None:
        raise SeldonMicroserviceException("Invalid Data Format")
    return message

It means if user post data not in the form data which key is json server will raise empty json parameter error.

Is there any example about how to post data with application/json?

[ukclivecox]

You can use POST as well:
e.g.

curl  0.0.0.0:5000/predict -H "Content-Type: application/json"  -d '{"data":{"ndarray":[[1,2]]}}'

[ukclivecox]

Which version of Seldon are you using. This has changed.

seldon-core/python/seldon_core/flask_utils.py

Line 59 in 52752f0

message = request.get_json()

[axsaucedo]

@blublinsky I think this is what you had been talking about in regards to the form/json ^

[cloga]

I use seldonio/seldon-core-s2i-python3 to build model server image, and find extract_message method in microservice/microservice.py

but now I can't find extract_message method in project:

also can't find the Empty json parameter in data excpetion:

I check the seldon_core module code on my desktop, it is the new verison, which didn't have extract_message method in microservice.py

but when I dig into the image build from seldonio/seldon-core-s2i-python3 I find extract_message method in microservice/microservice.py

[eminemence]

This is what worked for me:
curl -v -s http://localhost:5000/predict -H "Content-Type: application/x-www-form-urlencoded" -d "json={\"data\":{\"ndarray\":[[123,123,123]]}}"