I'm trying to change a simple python to kotlin, bu...

# announcements

[Ifvwm]

I'm trying to change a simple python to kotlin, but I don't know where is wrong, https://paste.ubuntu.com/p/zp4x9yz36X/

[Ifvwm]

it's just simple post requests, but in the function step2(), it just doesn't work, I don't know why

[Ifvwm]

but python and curl worked, something is wrong with httpurlconnection?

[nanodeath]

recommend using an http library here, but I'm trying to see what's going wrong here. maybe you need to read the response and close the connection.

[Ifvwm]

which http library you suggest? the official doc is here https://docs.confluent.io/5.5.2/kafka-rest/quickstart.html

[gildor]

Probably use ktor-client is the easiest way, it has support of json parsing too

[gildor]

HttpUrlConnection also works, but it has very clunky interface and a lot of boilerplate

[gildor]

Also looks that you really don't need all those try/catch which rethrow exceptions

[gildor]

There are many Kotlin stdlib functions which can improve this code too

[gildor]

What is exactly doesn't work on step2?

[Ifvwm]

step2 is subscription

[Ifvwm]

curl -X POST -H "Content-Type: application/vnd.kafka.v2+json" --data '{"name": "my_consumer_instance", "format": "json", "auto.offset.reset": "earliest"}' http://49.5.6.84:8082/consumers/testName

[Ifvwm]

curl -X POST -H "Content-Type: application/vnd.kafka.v2+json" --data '{"topics":["jsontest"]}' http://49.5.6.84:8082/consumers/testName/instances/my_consumer_instance/subscription

[Ifvwm]

curl -X GET -H "Accept: application/vnd.kafka.json.v2+json" http://49.5.6.84:8082/consumers/testName/instances/my_consumer_instance/records

[Ifvwm]

those three curl is step1 step2 and step3

[Ifvwm]

step1 create an instace for consumer, step2 to subscript a topic, step3 to get messages from that topic, python code and curl worked well

[Ifvwm]

but with kotlin, the step2 doesn't work, there's no response in step2, see https://docs.confluent.io/5.5.2/kafka-rest/quickstart.html

[Ifvwm]

I also tried OkHttp, same as httpurlconnection

[gildor]

What do you mean no response? I don't see that you read response on step 2

[gildor]

Also in docs there is no response

[Ifvwm]

aha, after I add read in step2, it worked!

[Ifvwm]

I add this

try {
        val reader: BufferedReader = BufferedReader(InputStreamReader(httpconn2.inputStream))
        val response = reader.readLine()
        println(response)

    } catch (exception: Exception) {
        throw Exception("Exception while push the notification  $exception.message")
    }

[Ifvwm]

step2 worked! and step3 can get messgaes now

[gildor]

I think your issue not even lack of reading, but because you do not close output stream

[Ifvwm]

no, I tried to close the output stream, it still be error 500

[gildor]

So, your “not working” was 500 error? 500 means server error, looks like a bug of server

It still related to what kind api you use, using raw httpurlconnection or even Okhttp is kinda low level, and you have to handle all possible edge cases yourself, now your code is leaking connection

[gildor]

You should use use blocks to handle resources

[gildor]

Also there are many helper extensions which allow you to read input/output strwams

[Ifvwm]

ok, I would try ktor-client, any other lib suggested?

[Animesh Sahu]

You can have a look at Fuel if you just want to parse the response (as a Client)

[Animesh Sahu]

https://github.com/kittinunf/fuel

[gildor]

I would recommend Ktor/Retrofit.