Hi Umesh, The BookKeeper protocol is closer to register protocols than it is to consensus protocols, although we do need consensus for agreement on the closed state of a ledger. A ledger has a single writer, and either the writer closes it naturally or a reader needs to close it by running a recovery protocol that includes fencing the bookies. That's from the client perspective. From the bookie perspective, if a bookie of a ledger ensemble crashes while a ledger is being written to, then it is replaced and the history of the ledger is updated in the ledger metadata according to the last add confirmed by the crashed bookie. If the bookie crashes after the ledger is closed, then auto-recovery re-replicates the data.
You also ask for pointers. Are you looking for code pointers? -Flavio > On 28 Jan 2020, at 10:15, Unmesh Joshi <unmeshjo...@gmail.com> wrote: > > Hi, > > In case of partial failures while implementing Replicated Log, there are > few requirements which need to be fulfilled to sync logs on multiple nodes > in case of node failure. e.g. In RAFT, if a node fails, there is a sync up > that happens with communication from leader to push all the entries and > truncation in case of some conflicting entries. Same happens with with > Kafka when followers start re pulling data after startup. Consistency need > to be maintained, by maintaining something like commitIndex or highwater > mark to have the index till which the majority of the servers have > acknowledged write. > > In Apache BookKeeper I see that the consistency part is described well with > last add confirmed description in below documentation, > https://bookkeeper.apache.org/archives/docs/r4.4.0/bookkeeperProtocol.html > > But who takes care of updating a particular Bookie in case it crashses (or > temporarily partitioned) and rejoins the cluster? Is there any > initialization protocol that is run at startup? > In Kafka, we have something like Controller which managers this > initialization, (or in RAFT its the current leader which will manage it) > I am going through the code to understand, but any pointers or hints will > be very helpful > > Thanks, > Unmesh
