Parallel file upload fails

A 403 error with an HTML body is unexpected when using the API. Can you share some sample code that reproduces this? Thanks in advance! 

My bad, the 403 response was not for these requests. However some files are still missing. It can be reproduced with this:

#!/bin/bash
for i in `seq 10 19`;
do
curl -H "Authorization: Bearer <my token>" https://api-content.dropbox.com/1/files_put/auto/ -T file$i &
done;

Now I can see that the response for the missing files is:

{"error": "Failed to grab locks for 532934897: lock held by connection 4695316.Please re-issue the request."}

Is there a queue I can use on your side for file upload? Else I guess I have to check the response and retry if necessary. Thanks!

That error can occur in some cases, in which case the response status code will be 503. If the response status code is non-200, you should consider the upload failed.

This error generally indicates that there was simultaneous activity in the account preventing your app from making the state-modifying call (e.g., adding or removing files) it is attempting. The simultaneous activity could be coming from your app itself, or elsewhere, e.g., from a user's desktop client.

You can't queue these on our side, so the best practice is to reduce the number of simultaneous requests and to just retry a request, respecting the Retry-After header if given, or after a small delay possibly with an exponential back-off, when receiving this error.