[COUCHDB-1901] Replicator needs to retry multipart requests atomically

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.5.0
• Component/s: Replication
• Assignee: Adam Kocoloski
• Reporter: Adam Kocoloski
• Created: 02/Oct/13 15:46
• Updated: 28/Apr/14 11:04
• Resolved: 04/Oct/13 07:33

Description

couch_replicator_httpc's retry mechanism interacts poorly with the multipart requests we use to transfer attachments during replication. In the case of PUTs, the replicator will retry a request even though it has already streamed part of the request body. For GETs, it can potentially interleave body data from the original response and the retried one.

I put together a fix at https://github.com/cloudant/couch_replicator/pull/36 that disables the default httpc client retry mechanism for multipart requests and manages the retry logic "atomically"; i.e., it retries the original GET request if the GET or PUT fails, and it ensures that the original GET request is properly terminated during the retry. I'll push a version of that patch to the Apache repo now.