Question

I’m trying to upload image to Amazon S3 with this Ruby code:

    require 'net/http/post/multipart'

    url = URI.parse('http://public.domain.com/')
    File.open("/tmp/uup_1114.jpg") do |jpg|
      req = Net::HTTP::Post::Multipart.new url.path,
                      'key' => s3_key,
                      'acl' => s3_acl,
                      'content_type' => s3_content_type,
                      'AWSAccessKeyId' => s3_AWSAccessKeyId,
                      'policy' => s3_policy,
                      'signature' => s3_signature,
                      "file" => UploadIO.new(jpg, "image/png", "image.jpg")
      res = Net::HTTP.start(url.host, url.port) do |http|
        http.request(req)
      end
    end

And I’m getting error from Amazon:

InvalidArgument: Bucket POST must contain a field named ‘key’. If it is specified, please check the order of the fields.

Looks like ‘file’ field goes first in query and that causes an error above. I can’t figure out how to post file field at the end of query.

Answer 1

I have successfully used the AWS-SDK in ruby to create post forms. But in my case I was getting users to upload from a browser into an AWS account. Still this may help:

the aws-sdk has a call on a bucket called presigned_post(options) that creates a pre signed post that works fine.

See also
https://forums.aws.amazon.com/thread.jspa?messageID=296867&#296867