Tried it, found it could trigger NFS issue.
The test is on one machine runs the script to lock the dovecot-uidlist, moving mail into cur/new, append one line to dovecot-uidlist, and unlock it. On another different machine, run one script to SELECT, another script to COPY. Found the similar issue in http://dovecot.org/pipermail/dovecot/2012-February/063539.html
Whether it means the dovecot LDA also needs to run on the same server with the backend server?
Timo Sirainen
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On 15.2.2012, at 6.13, Andy YB Hu wrote:
I can generate the UID once I create the uidlist lock, and the UID is incremental globally.
Some questions: 1, Whether I can write the mail to tmp/ after creating dovecot-uidlist.lock?
Yes, then you'll just keep the lock longer than necessary.
2, I did the 5 steps manually, found that new mail is set to OLD flag, so that when SELECT command, it told there was no NEW mail. Looks like need to change code in maildir_uidlist_sync_next_uid()?
I guess that means that the mail didn't get a \Recent flag. Wht Dovecot version is this? Are you saving the mail to new/?
3, About the dovecot-uidlist.lock file creation and deletion, I checked the code, there are functions in dovecot like maildir_uidlist_lock_timeout and maildir_uidlist_unlock. If I did that via calling these functions, there are lots of extra codes need to call(like auth, mailbox open...).
Yes, way too much work to do that way.
So the question is if I do that in my codes, how to handle the race condition correctly? (At least there would be other sessions want to lock the files also / already locked it while I want to create the dovecot-uidlist.lock)
It's a typical dotlock file. You can create it with either open(.., O_EXCL) or creating a temp file and trying to link() it to the .lock file. Or you can also directly call the file_dotlock_create() in src/lib/file-dotlock.h
