Currently, if there is a file that is being bulk loaded while a backup occurs. Backup will receive a EBUSY return when it attempts to open a cursor on the bulk file and the backup will fail.

This is an issue that replaces pull request WT-570.

It's not clear what the correct solution is. Checkpoint creates a special empty file in this situation. The options I see:

• Have backup skip any files being bulk loaded (not sure if this has metadata consequences?)
• Continue to have backup cursor_open return EBUSY when a table is being bulk loaded.
• Your good idea goes here.

It's also worth noting that this issue isn't specific to bulk loaded files. It will happen any time a handle is open with the WT_DHANDLE_EXCLUSIVE flag. Other cases where we do that are with rename, compact, etc

Once this is resolved I suspect we'll want to remove the change to test/format that retries backup on EBUSY.