Hi BookKeepers, I'm trying to understand some basic aspect of BookKeeper....
I have a strange case, and I would like to have some opinion from any "expert". I am using BookKeeper as a transaction log for a database, this is an example scenario: 1) the user inserts a record in a table the "fact" is logged to the Write-Ahead-log (Bookkeeper ledger), and the systems blocks until the asyncAddEntry completes (the callback is called with rc=0) now I (the 'writer') assume that the entry is written to durable storage and has been synched to disk then the DB applies the change to the local memory as every application with a WAL does 2) The writer 2 other entries for which the asyncAddEntry completes (the callback is called with rc=0). I block until the callback as been called 2) for tests I'm using an ensemble of 1 bookie, I "stop" the only bookie the bookie stops "gracefully" (no strange errors) 3) The writer issues other asyncAddEntry, which fail due to "notEnoughBookiesException" and then "closes" the LedgerHandle, inside the "callback" cade 4) I restart the bookie (no strange errors on logs) 5) I restart my "writer", opening the ledger with "openLedger" (with recovery and fencing...) in order to perform recovery from the WAL 6) now the LastAddConfirmed is 0 ! so my first entry is lost ! Am I missing something ? The LAC has not been advanced even with 3 successful writes to the ledger >From the "writer" point-of-view the fact that the callback as been called is not a guarantee that the entry as been written to durable storage ? I understand that of a "tailing" reader (a ledger opened with openLedgerNoRecovery) it is very important not to be able to "read" data before the LAC, but for the "writer" it is important that it can count on the fact the entry will be recovered with success Thanks -- Enrico
