Cyrus replica 2.4 to 3.2.2 issues

[Marco]

Hello, I'm trying to replicate from Cyrus IMAP 2.4.20 to Cyrus IMAP 
3.2.2 using replication.

Because Cyrus 2.4 doesn't support IMAP replication (is this true?), I 
configured the replica with

replica2to3syncserver cmd="/usr/libexec/cyrus-imapd/sync_server" 
proto=tcp4 listen="csync"

in SERVICES of cyrus.conf.

The sync_client in master works in rolling mode, such as

/usr/lib/cyrus-imapd/sync_client -r -n replica2-3

Both master and replica hosts work with delayed deleted and delayed 
expunge fashion.

I experience some problems.
In the below logs tst-msg01 is the master, tst-msg03 is the replica.

== 1 ==
I found "errors" of this kind:

2020-07-21T15:05:16.803765+02:00 tst-msg03 
cyrus/replica2to3syncserver[1238 sync_log(): Failed to lock 
/var/lib/imap/sync/squatter/log for MAILBOX 
example.com!user.demo^gruppoarchivio.ticket.Vecchi#012 after 65 attempts
2020-07-21T15:05:16.803898+02:00 tst-msg03 
cyrus/replica2to3syncserver[1238 mailbox: longlock 
example.com!user.demo^gruppoarchivio.ticket.Vecchi for 2.5 seconds
2020-07-21T15:05:17.090124+02:00 tst-msg03 
cyrus/replica2to3syncserver[1238 sync_log(): Failed to lock 
/var/lib/imap/sync/squatter/log for MAILBOX 
example.com!user.demo^gruppoarchivio.ticket.Vecchi#012 after 65 attempts
2020-07-21T15:05:17.101288+02:00 tst-msg03 
cyrus/replica2to3syncserver[1238 mappedfile: longlock 
/var/lib/imap/domain/Q/example.com/user/E/demo.gruppoarchivio.conversations 
for 2.7 seconds
2020-07-21T15:05:17.101410+02:00 tst-msg03 cyrus/squatter[27276]: 
indexing mailbox user/demo.gruppoarchivio/ticket/Vecchi at example.com...
2020-07-21T15:05:18.132371+02:00 tst-msg03 cyrus/squatter[27276]: Xapian 
committed 740 updates in 0.374236 sec
2020-07-21T15:05:18.145507+02:00 tst-msg03 cyrus/squatter[27276]: 
mappedfile: longlock 
/var/lib/imap/domain/Q/example.com/user/E/demo.gruppoarchivio.xapianactive 
for 1.0 seconds

But the xapian index seems to be ok:

-rw------- 1 cyrus mail      864 Jul 21 15:05 cyrus.indexed.db
-rw------- 1 cyrus mail        0 Jul 21 15:05 flintlock
-rw------- 1 cyrus mail      116 Jul 21 15:05 iamglass
-rw------- 1 cyrus mail 13115392 Jul 21 15:05 position.glass
-rw------- 1 cyrus mail  5545984 Jul 21 15:05 postlist.glass
-rw------- 1 cyrus mail  3530752 Jul 21 15:05 termlist.glass

I hope I can ignore this. I've found these errors only for one mailbox.


== 2 ==
Another problem is that the "expire" annotation value is not configured 
as an "expire" metadata value on Cyrus 3.2.2. I don't know if this is 
expected or if this is a bug. But it is a problem for me, I have to 
rewrite all these mailboxes metadata.

To be more clear, the Cyrus IMAP 2.4.20 annotation like

* ANNOTATION "user/marco/Trash at example.com" 
"/vendor/cmu/cyrus-imapd/expire" ("value.shared" "14" 
"content-type.shared" "text/plain" "size.shared" "2" 
"modifiedsince.shared" "1406624279")

become in Cyrus IMAP 3.2.2 after the sync:
* METADATA user/marco/Trash at example.com 
("/shared/vendor/cmu/cyrus-imapd/expire" NIL)

I expected "14" and not NIL.

== 3 ==
The specialuse flags are not kept in the replica server:

* LIST (\HasNoChildren \Sent) "/" INBOX/Sent
become
* LIST (\HasNoChildren) "/" INBOX/Sent

Do I have to suppose that I must run the cvt_xlist_specialuse tool as 
described in 
https://www.cyrusimap.org/3.2/imap/download/upgrade.html#upgrade-specific-items 
?
It's not clear to me if this instruction is related to the in place 
upgrade only or to the replication mode too.


== 4 ==
This is a severe error. When I expunge a message in the master, the 
expunge action is not replicated on the replica, and the sync_client dies:

2020-07-23T14:50:44.695378+02:00 tst-msg01 cyrus/imap[26851]: Expunged 1 
messages from example.com!user.marco^fff.Trash
2020-07-23T14:51:10.147600+02:00 tst-msg03 
cyrus/replica2to3syncserver[1207 Fatal error: Internal error: assertion 
failed: imap/dlist.c: 156: base != NULL
2020-07-23T14:51:10.693261+02:00 tst-msg01 cyrus/sync_client[26834]: 
RESERVE received * response:
2020-07-23T14:51:10.693321+02:00 tst-msg01 cyrus/sync_client[26834]: 
reserve messages: failed: Bad protocol
2020-07-23T14:51:10.693730+02:00 tst-msg01 cyrus/sync_client[26834]: 
Error in do_sync(): bailing out! Bad protocol
2020-07-23T14:51:10.693750+02:00 tst-msg01 cyrus/sync_client[26834]: 
Processing sync log file /var/lib/imap/sync/replica2-3/log-26834 failed: 
Bad protocol
2020-07-23T14:51:10.706750+02:00 tst-msg03 cyrus/master[24009]: process 
type:SERVICE name:replica2to3syncserver 
path:/usr/libexec/cyrus-imapd/sync_server age:1142.993s pid:1207 exited, 
status 70

I can't no more suppress this error. All sync_client die, even in non 
rolling mode. I have to delete permanently the replicated mailboxes to 
resume the right working.

I see the same error when I delete a mailbox on replica and after that I 
do a sync_client on master. In this last case the error disappear only 
when I delete the delayed DELETED mailbox too.

I read the documentation, I didn't find restrictions on replica with the 
delayed expunged or the delayed deleted configuration in master and or 
in replica.
In my environment I simply configured delayed deleted and delayed 
expunge in the same way, on master and on replica hosts.


Could you help me to understand?
Thank you very much

Cheers
Marco