Ktor HEAD Request Fails with expected 0 bytes but received 2 kotlinlang #ktor

Ktor HEAD Request Fails with "expected 0 bytes but...

youssef hachicha

11/27/2024, 3:51 PM

Ktor HEAD Request Fails with "expected 0 bytes but received 20" Error I'm trying to perform a simple HEAD request in Ktor (with OkHttp engine) to retrieve headers, but encountering an unexpected error. My Retrofit implementation works perfectly, but Ktor consistently throws an IOException. Specific details: - Using Ktor 3.0.0-rc-1 with OkHttp engine on the Android Side - Attempting to make a HEAD request to retrieve specific header values - Error:

java.io.IOException: expected 0 bytes but received 20

- Retrofit code works without issues - I've tried multiple configuration approaches, including: - Disabling plugins - Creating fresh HttpClient - Configuring engine settings - I even used OkHttp directly and it worked: val

client = OkHttpClient.Builder().followRedirects(true).build()

- I am not trying to use neither OkHttp or Retrofit because the project is Multiplatform Code snippet demonstrating the issue:

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suspend fun getHeaderValue(header: String): String? {
    return client.head(url) {
        // Add headers
    }.headers[header]
}

Has anyone encountered similar issues with Ktor HEAD requests? Any insights into why this might be happening or how to resolve it?

Chrimaeon

11/27/2024, 4:47 PM

What are the 20 bytes returned?

youssef hachicha

11/27/2024, 7:15 PM

The "20 bytes" typically indicates some minimal response content that's being inadvertently read during the HEAD request, which should normally have no body. I wasn't really able to log them when I do this

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val result = client.head(url)
println(".....")

the println won't be reached as of the Retrofit Impl this is what returns as headers

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headers: content-type: application/json
accept-ranges: bytes
cache-control: max-age=60
content-disposition: attachment; filename="019.mp3"; filename*=UTF-8''019.mp3
content-security-policy: sandbox
pragma: public
referrer-policy: no-referrer
vary: Origin, Accept-Encoding
x-content-security-policy: sandbox
x-content-type-options: nosniff
x-robots-tag: noindex, nofollow, noimageindex
x-server-response-time: 344
x-webkit-csp: sandbox
date: Wed, 27 Nov 2024 13:12:49 GMT
server: envoy
strict-transport-security: max-age=31536000; includeSubDomains; preload
content-encoding: gzip
x-dropbox-response-origin: far_remote
x-dropbox-request-id: ca79bc683b3049588f8d4be94d37e7e4

Chrimaeon

11/27/2024, 7:21 PM

try a

curl --head -v <url>

to maybe get some more output.

youssef hachicha

11/27/2024, 7:22 PM

what is that?

Chrimaeon

11/27/2024, 7:23 PM

a command line tool for network requests https://de.wikipedia.org/wiki/CURL

👍 1

youssef hachicha

11/28/2024, 7:05 AM

* Trying 162.125.69.18:443... * Connected to www.dropbox.com (162.125.69.18) port 443 * ALPN: curl offers h2,http/1.1 * (304) (OUT), TLS handshake, Client hello (1): * CAfile: /etc/ssl/cert.pem * CApath: none * (304) (IN), TLS handshake, Server hello (2): * (304) (IN), TLS handshake, Unknown (8): * (304) (IN), TLS handshake, Certificate (11): * (304) (IN), TLS handshake, CERT verify (15): * (304) (IN), TLS handshake, Finished (20): * (304) (OUT), TLS handshake, Finished (20): * SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256 * ALPN: server accepted h2 * Server certificate: * subject: C=US; ST=California; L=San Francisco; O=Dropbox, Inc; CN=*.dropbox.com * start date: Nov 12 000000 2024 GMT * expire date: Dec 8 235959 2025 GMT * subjectAltName: host "www.dropbox.com" matched cert's "*.dropbox.com" * issuer: C=US; O=DigiCert Inc; CN=DigiCert TLS RSA SHA256 2020 CA1 * SSL certificate verify ok. * using HTTP/2 * [HTTP/2] [1] OPENED stream for https://www.dropbox.com/scl/fi/ydgdlw9sa01beir9x4jz/113.mp3?rlkey=s92qiy4ew7y7260xqkg8y2wsb&dl=1 * [HTTP/2] [1] [method HEAD] * [HTTP/2] [1] [scheme https] * [HTTP/2] [1] [authority www.dropbox.com] * [HTTP/2] [1] [path /scl/fi/ydgdlw9sa01beir9x4jz/113.mp3?rlkey=s92qiy4ew7y7260xqkg8y2wsb&dl=1] * [HTTP/2] [1] [user-agent: curl/8.4.0] * [HTTP/2] [1] [accept: /]

HEAD /scl/fi/ydgdlw9sa01beir9x4jz/113.mp3?rlkey=s92qiy4ew7y7260xqkg8y2wsb&dl=1 HTTP/2

Host: www.dropbox.com

User-Agent: curl/8.4.0

Accept: /

Aleksei Tirman [JB]

11/28/2024, 11:40 AM

Can you please share an endpoint to where you made the HEAD request? Can you please try to use the latest released version 3.0.1?

youssef hachicha

11/28/2024, 1:12 PM

I am currently using the latest version 3.0.1 this is one of the endpoints: https://www.dropbox.com/scl/fi/ygify4ps6mcdm147uyy9u/005.mp3?rlkey=ibpl8qbgvcby7cjv6ra2zxs2q&dl=1 it's just a mp3 file I tried an online mp3 file: https://file-examples.com/storage/feb06822a967475629bfe71/2017/11/file_example_MP3_700KB.mp3 and the error didn't happen, maybe it has to do with dropbox ?

Aleksei Tirman [JB]

11/28/2024, 1:59 PM

The beginning of the 20 bytes read from the response body contains the GZIP signature bytes. Unfortunately, I haven't found a way to avoid the exception apart from switching to another Ktor engine.

youssef hachicha

11/28/2024, 2:13 PM

like what? what other engines can i use in android?

Aleksei Tirman [JB]

11/28/2024, 2:14 PM

The Android engine.

thank you color 1

Aleksei Tirman [JB]

11/28/2024, 2:17 PM

I've created an issue to address the problem with ProtocolException.

youssef hachicha

11/28/2024, 2:26 PM

thank you

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