You can increase log level specifically for PID 30517 or for all processes of its type using -R log_level_increase.

According to the code this message is printed when quiry like

select ip.itemid from item_discovery id join item_preproc ip on id.itemid=ip.itemid where id.parent_itemid=...;

returns itemid which is not present in the result of query like

select id.itemid from item_discovery id join items i on id.itemid=i.itemid where id.parent_itemid=...;

with the same parent_itemid, obviously.

If i will find these

itemid's

in

item_preproc

table, is it save to delete them?

Please, send log file with DebugLevel=4, that to see the whole scenario of actions.

10000 lines from log file with error ocured
log file size 1GB in 14 minutes. it's only cut. i can add top lines or bottom if needed.

More data is necessary from log. Please, grep log file by PID

zabbix_server [30517]: ERROR [file:lld_item.c,line:716] Something impossible has just happened.

for example:

/tmp/zabbix_server.log | grep "30517"

Here is log file greped by pid with error

my guess, this problem occurs when LLD Rule filter changed and unnecessary items/triggers deleted (manualy or by server), becouse when i'm managed some LLD Rule filters and items were deleted by server more errors began to appear.

We can't reproduce this problem, reopen this issue if the problem is repeated with the latest changes.