Getting ERR_FS_FILE_TOO_LARGE while using unirest file send with put

Looks like this is an issue with form-data From GitHub Issues

It turns out that the unirest are using the NPM module form-data, and the form-data module requires that if it received a stream that not fs.ReadStream, we need to provide the file information by additional.

Example:

form.append( 
  'my_file', 
  stream,
  {
    filename: 'bar.jpg', 
    contentType: 'image/jpeg', 
    knownLength: 19806,
  },
)

See: https://github.com/form-data/form-data#void-append-string-field-mixed-value--mixed-options-

Streaming files with unirest is available via the .attach method:

 unirest.put(fullUri)
    .auth({
      user: self.userName,
      pass: self.password
    })
    .header('X-Checksum-Sha1', sha1Hash)
    .header('X-Checksum-Md5', md5Hash)
//    .send(fs.readFileSync(filePath))
    .attach('filename', fs.createReadStream(filePath))
    .end(function (response) {

I can't find an API to do that in unirest js library.

That's because there is none: https://github.com/Kong/unirest-nodejs/issues/49:

• You can use the underlying request library to do streaming if you want, I am open to a pull request either on this branch or the 1.0 version to add streaming.

Issue is still open.

But from this issue and from the source code you can find out that end() returns request (see https://github.com/request/request)

Unirest.request = require('request')

...

  end: function (callback) {
    ...
    Request = Unirest.request($this.options, handleRequestResponse)
    Request.on('response', handleGZIPResponse)
    ...
    return Request
  }

and from request's source code you can find out that no actual request is sent yet (it's defered). So you can hack into it. And use it's API instead:

const request = unirest.put(constants.server2)
  .auth({
    user: self.userName,
    pass: self.password
  })
  .header('X-Checksum-Sha1', sha1Hash)
  .header('X-Checksum-Md5', md5Hash)
  // .send(fs.readFileSync(filePath))
  .end(...)

fs.createReadStream(filePath).pipe(request) // just pipe it!

As a side note: unirest is based on request, request is deprecated now. So... maybe you need to steer away from unirest.