Fog sends an invalid XML request to S3 API when multipart is set on 0 byte file

[brettcave]

If multipart is set on a 0-byte file to be uploaded to Fog, an invalid request is sent to the API:

Write a 2-byte file and upload with multipart:

f=File.open("testFile",'w+')
f.write(".")
  => 2
connection=Fog::Storage::AWS.new()
upFile=connection.directories.get("abucket").files.new(:key => "testFile", :body => f, :public=>false)
upFile.multipart_chunk_size=5242880
upFile.save
   => true
f.close

Now do the same with a 0 byte file:

f=File.open("testFile",'w+')
f.write("")
  => 0
upFile=connection.directories.get("abucket").files.new(:key => "testFile", :body => f, :public => false)
upFile.save
 => true
upFile.multipart_chunk_size=5242880
upFile.save

Excon::Error::BadRequest: Expected(200) <=> Actual(400 Bad Request)
excon.error.response
  :body          => "<Error><Code>MalformedXML</Code><Message>The XML you provided was not well-formed or did not validate against our published schema</Message><RequestId>XXX</RequestId><HostId>xxx</HostId></Error>"
  :cookies       => [
  ]
  :headers       => {
    "Connection"       => "close"
    "Content-Type"     => "application/xml"
    "Date"             => "Mon, 25 Jul 2016 10:20:03 GMT"
    "Server"           => "AmazonS3"
    "x-amz-id-2"       => "redacted"
    "x-amz-request-id" => "redacted"
  }
  :host          => "s3-x-y.amazonaws.com"
  :local_address => "1.2.3.4"
  :local_port    => 52755
  :path          => "/abucket/testFile"
  :port          => 443
  :reason_phrase => "Bad Request"
  :remote_ip     => "x.y.z.w"
  :status        => 400
  :status_line   => "HTTP/1.1 400 Bad Request\r\n"

        from gems/ruby-2.1.10/gems/excon-0.51.0/lib/excon/middlewares/expects.rb:6:in `response_call'
        from gems/ruby-2.1.10/gems/excon-0.51.0/lib/excon/middlewares/response_parser.rb:8:in `response_call'
        from gems/ruby-2.1.10/gems/excon-0.51.0/lib/excon/connection.rb:389:in `response'
        from ruby-2.1.10/gems/excon-0.51.0/lib/excon/connection.rb:253:in `request'
        from gems/ruby-2.1.10/gems/fog-xml-0.1.2/lib/fog/xml/sax_parser_connection.rb:35:in `request'
        from gems/ruby-2.1.10/gems/fog-xml-0.1.2/lib/fog/xml/connection.rb:7:in `request'
        from gems/ruby-2.1.10/gems/fog-aws-0.9.4/lib/fog/aws/storage.rb:611:in `_request'
        from ruby-2.1.10/gems/fog-aws-0.9.4/lib/fog/aws/storage.rb:606:in `request'
        from ruby-2.1.10/gems/fog-aws-0.9.4/lib/fog/aws/requests/storage/complete_multipart_upload.rb:36:in `complete_multipart_upload'
        from ruby-2.1.10/gems/fog-aws-0.9.4/lib/fog/aws/models/storage/file.rb:278:in `multipart_save'
        from ruby-2.1.10/gems/fog-aws-0.9.4/lib/fog/aws/models/storage/file.rb:209:in `save'

The library allows non-multipart uploads of 0 byte files and multipart uploads of >=1 byte files, but fails on 0 byte multipart.

[brettcave]

How to safely implement a generic upload (set multipart only if a large file).

upFile.multipart_chunk_size=5242880 if sourceFile.size >= 5242880

[geemus]

@brettcave so, should we maybe just add a check to the multipart uploading stuff to skip if size == 0? ie I think the change would be here: https://github.com/fog/fog-aws/blob/master/lib/fog/aws/models/storage/file.rb#L208

[brettcave]

would make sense @geemus. might make sense to skip multipart if size < multipart_chunk_size. i vaguely remember getting an error that was not very conclusive when setting the multipart size lower than 5242880 (think the error was returned from api) so maybe also include a local check before making the calll

[geemus]

closing in favor of fog/fog-aws#283