Aws::S3::Errors::BadDigest while trying to store a Tempfile

Question

I have the following snippet:

tempfile = Tempfile.new(export_file.filename)
begin
  tempfile.write(contents)
  file_storage_service.store(export_file.filename, tempfile)
ensure
  tempfile.close!
end

And the store method is as follows:

def store(filename, file)
  client = Aws::S3::Client.new(options)
  object = Aws::S3::Object.new(bucket_name, filename, client: client)
  object.upload_file(file)
end

My issue is that I seem to get a Aws::S3::Errors::BadDigest error on one of my cloud machines, but locally this works as expected.

I believe the tempfile is unlinked while the store method is being called, resulting in AWS comparing two different digests, but I'm not very sure about this. I have Ruby 2.1.6 on both machines, the local one running OS X and the cloud one Linux.

What can I do to fix this? And what's the cause of the problem?

P.S.: I've tried both close! and close on the tempfile, with the same results.

Answer 1

It seems that S3's upload_file expects a file with the cursor reset. Calling tempfile.rewind just before calling store solves this issue.

Answer 2

Ok folks, my problem was even deeper. With tempfile.rewind the error disappeared but the changes made to the file directly were not reflected in memory, so instead of using rewind, I ended up using:

tempfile.close
tempfile.open

That fixed my problem completely !