dm.zopepatches.fix_responsewrite_conflict 1.0

Zope[2] patch to alleviate the effect of https://bugs.launchpad.net/zope2/+bug/740831.

This package patches the web application server Zope to work around https://bugs.launchpad.net/zope2/+bug/740831.

The bug causes Zope to deliver wrong responses after a request using Response.write has suffered a ConflictError. The patch prevents Zope from retrying such requests and logs an error message when it tries. The bug effect is thus limited to a single request.

Note that even with this patch Zope does not behave fully correctly: in case of a ConflictError, it may deliver a (maybe partial) response even though the transaction has been aborted. The client does not get feedback for the transaction rollback. The only indication is the log record written.

Response.write is inherently unsafe in the face of ConflictError. The only reliable fix is not to use it at all.

The (monkey) patch gets installed when this package is imported.