[discuss] When broker crash and some bookie crash, whether there is an inconsistency in recover

[Dezhi Liu <de...@streamnative.io.INVALID>]

Hi all:
When the broker crashes，topic will be transferred to other active brokers,
at this time, the topic will be in the fencing state and will  recover,
because the last confirm msgid is not the latest.
steps(E=3, W=3, A=2) ：
1、find  the largest LAC from the bookies node where the ledger is located.
2、compare backwards， whether the entry satisfies ack >2.
3、if the conditions are met, the entry is considered safe and the LAC is
updated.
4、finally update the metadata information and close the ledger

My question is if bookie also crashes at this time，how to go to security
settings LAC?
E.g:
[image: image.png]
the LAC of bookie itself is brought over by the broker delay，therefore, the
LAC will be different between bookies.

This question has been bothering me，hope there is an accurate explanation.

Thanks,
Dezhi Liu