On Wed, Apr 15, 2020 at 9:40 AM Xinying Song <songxinying.ftd@xxxxxxxxx> wrote: > > Hi, Greg: > Thanks for your reply! > I think master can always know if a request has been finished or not > no matter whether > there is a Commit-logevent, because it has written a EUpdate logevent > that records the > unfinished request. > > Of course, we need to do commit, in which we clean up mdcache and > trigger journal trim, > but it seems we don't need to write a logevent. We can do commit just in memory. > > For example, if we remove writing a ESlaveUpdate::OP_COMMIT logevent on slave, > when crash happens, master will know there is an unfinished request > either by replaying > its early logged EUpdate or reading from its cache, so it resends log event can be trimmed, cache get lost if master crashed > OP_FINISH to slave, > then everything will go on. > Similarly, if we remove writing a ECommitted logevent on master, when > crash happens, > master still knows there is an unfinished request and it will restart > the process from the > step of sending OP_FINISH to slave. > > What do you think? > > Sincerely > -Xinying > > Gregory Farnum <gfarnum@xxxxxxxxxx> 于2020年4月15日周三 上午2:16写道： > > > > On Sun, Apr 12, 2020 at 5:19 AM Xinying Song <songxinying.ftd@xxxxxxxxx> wrote: > > > > > > Hi, cephers: > > > What's the purpose of using LogEvent with empty metablob? > > > For example in link/unlink operation cross two active mds, > > > when slave receives OP_FINISH it will write an ESlaveUpdate::OP_COMMIT > > > to the journal, then > > > send OP_COMMITTED to master. When master receives OP_COMMITTED it will > > > write an ECommitted to the journal then allow previously logged > > > journal to be trimmed. > > > > > > Why are these two logevents necessary? > > > I guess they are originally used for a scene that crashes happen, > > > but in my opinion it seems not necessary. For example, > > > if cash happens, after failed mds are brought up again, in resolve > > > stage, master will resend OP_FINISH to slave, then things will > > > continue as expected. > > > > I don't remember the details of these transactions off the top of my > > head, but it sounds like you just answered your question: how would > > the master know it needs to tell the slave things are over or not, if > > it doesn't commit that it told the slave things are over? > > If we don't commit something indicating a finish, we'd need to > > remember the transaction forever, which would be bad. > > -Greg > > > > > > > > Could anyone give some tips on this doubt? > > > > > > Sincerely thanks! > > > _______________________________________________ > > > ceph-users mailing list -- ceph-users@xxxxxxx > > > To unsubscribe send an email to ceph-users-leave@xxxxxxx > > > > > > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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