Content-length header doesnt match request body on chunked upload

Question

Hello,

I have a problem with chunked uploading to google-cloud-storage (gcs) using dropzone.js.

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What Im Trying To Do:

I want to upload a (bigger) file to google-cloud-storage via dropzone. Since its a quite large file I'm using dropzone's internal function to chunk (and upload) it. I'm trying to upload via signed url that I'm creating, initalizing and afterwards passing to dropzone so that it knows where to send the file. Also I'm adding a Content-Range header to the request so that gcs keeps track of the current file-upload status.

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Current Status:

When the download starts, it seems to work. But after the first chunk finishes dropzone tries to reupload the first chunk, because the xhr-response status is 400.

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The Problem:

When investigated the xhr request and response it showed that the Content Length and Content-Range header are NOT the same size. And that is also what the response text told me the error is.

My code in .on("sending") by dropzone:

let procChunks = file.upload.chunks; // Get all chunks processed until now
latestChunk = procChunks[procChunks.length-1]; // Select latest chunk
const chunkFirstByte = dz.options.chunkSize * latestChunk.index; // Calc first byte
const chunkLastByte = chunkFirstByte + (latestChunk.dataBlock.data.size-1); // Calc last byte
let header = "bytes "+chunkFirstByte+"-"+chunkLastByte +"/"+ (file.size-1); // Create header value
xhr.setRequestHeader("Content-Range", header); // Set header to xhr

Request Header:

PUT /upload/storage/v1/b/(myBucket)/o?uploadType=resumable&name=test2.fna&upload_id=(myUpLoadID) HTTP/2
    Host: storage.googleapis.com
    User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:83.0) Gecko/20100101 Firefox/83.0
    Accept: application/json
    Accept-Language: de,en-US;q=0.7,en;q=0.3
    Accept-Encoding: gzip, deflate, br
    Cache-Control: no-cache
    X-Requested-With: XMLHttpRequest
    Content-Range: bytes 0-8388607/13088352
    Content-Type: multipart/form-data; boundary=---------------------------428770732237854445893641225227
    Content-Length: 8388843
    Origin: http://127.0.0.1:5000
    Connection: keep-alive
    Referer: http://127.0.0.1:5000/upload
    TE: Trailers

The request body:

-----------------------------428770732237854445893641225227
Content-Disposition: form-data; name="file"; filename="test2.fna"
Content-Type: application/octet-stream

>NC_000913.3 Escherichia coli str. K-12 substr. MG1655, complete genome
AGCTTTTCATTCTGACTGCAACGGGCAATATGTCTCTGTGTGGATTAAAAAAAGAGTGTCTGATAGCAGCTTCTGAACTG
GTTACCTGCCGTGAGTAAATTAAAATTTTATTGACTTAGGTCACTAAATACTTTAACCAATATAGGCATAGCGCACAGAC
AGATAAAAATTACAGAGTACACAACATCCATGAAACGCATTAGCACCACCATTACCACCACCATCACCATTACCACAGGT
AACGGTGCGGGCTGACGCGTACAGGAAACACAGAAAAAAGCCCGCACCTGACAGTGCGGGCTTTTTTTTTCGACCAAAGG
TAACGAGGTAACAACCATGCGAGTGTTGAAGTTCGGCGGTACATCAGTGGCAAATGCAGAACGTTTTCTGCGTGTTGCCG
ATATTCTGGAAAGCAATGCCAGGCAGGGGCAGGTGGCCACCGTCCTCTCTGCCCCCGCCAAAATCACCAACCACCTGGTG
GCGATGATTGAAAAAACCATTAGCGGCCAGGATGCTTTACCCAATATCAGCGATGCCGAACGTATTTTTGCCGAACTTTT
GACGGGACTCGCCGCCGCCCAGCCGGGGTTCCCGCTGGCGCAATTGAAAACTTTCGTCGATCAGGAATTTGCCCAAATAA
AACATGTCCTGCATGGCATTAGTTTGTTGGGGCAGTGCCCGGATAGCATCAACGCTGCGCTGATTTGCCGTGGCGAGAAA
ATGTCGATCGCCATTATGGCCGGCGTATTAGAAGCGCGCGGTCACAACGTTACTGTTATCGATCCGGTCGAAAAACTGCT
GGCAGTGGGGCATTACCTCGAATCTACCGTCGATATTGCTGAGTCCACCCGCCGTATTGCGGCAAGCCGCATTCCGGCTG
ATCACATGGTGCTGATGGCAGGTTTCACCGCCGGTAATGAAAAAGGCGAACTGGTGGTGCTTGGACGCAACGGTTCCGAC
TACTCTGCTGCGGTGCTGGCTGCCTGTTTACGCGCCGATTGTTGCGAGATTTGGACGGACGTTGACGGGGTCTATACCTG
CGACCCGCGTCAGGTGCCCGATGCGAGGTTGTTGAAGTCGATGTCCTACCAGGAAGCGATGGAGCTTTCCTACTTCGGCG
CTAAAGTTCTTCACCCCCGCACCATTACCCCCATCGCCCAGTTCCAGATCCCTTGCCTGATTAAAAATACCGGAAATCCT
CAAGCACCAGGTACGCTCATTGGTGCCAGCCGTGATGAAGACGAATTACCGGTCAAGGGCATTTCCAATCTGAATAACAT
GGCAATGTTCAGCGTTTCTGGTCCGGGGATGAAAGGGATGGTCGGCATGGCGGCGCGCGTCTTTGCAGCGATGTCACGCG
CCCGTATTTCCGTGGTGCTGATTACGCAATCATCT

Response Text:

Invalid request.  There were 8388843 byte(s) (or more) in the request body.  There should have been 8388608 byte(s) (starting at offset 0 and ending at offset 8388607) according to the Content-Range header.

As you can maybe see the first 4 lines are NOT from the file.

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Additional Information:

The file is pure text data (utf-8 encoded i guess). Im chunking in 8mb large chunks (recommended by google). Somewhere on google's api guide I read that when uploading via PUT there should/must be no other data except the file data. Content-Length header gets added automatically by dropzone.

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My Questions:

1. Where does those 4 lines come from?

2. Can I (re)set the xhr request body?

3. Is my problem maybe caused by some formating problem of file-data? (Like bytes, strings)?

4. In case that's not the problem - do u have any other idea what could be the problem?

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THANK YOU VERY MUCH! Any help appricated! If u need some more information please ask!