?????? something want to konw about Journal

[735367737]

thanks. i got it 


------------------ ???????? ------------------
??????:                                                                         
                                               "user"                           
                                                         
<jack.vanligh...@gmail.com&gt;;
????????:&nbsp;2021??11??21??(??????) ????11:44
??????:&nbsp;"user"<user@bookkeeper.apache.org&gt;;

????:&nbsp;Re: something want to konw about Journal



Also what is interesting is that ledger recovery reads past the LAC and can 
read an entry that got added to ledger storage cache but not to the journal due 
to a failure. These are dirty reads as the entries could still be lost if the 
bookie fails before flushing ledger storage. But these dirty reads during 
ledger recovery are also not a problem because ledger recovery writes these 
entries back to the ensemble and recovery only completes when those writes 
reach AQ.

On Sun, 21 Nov 2021, 16:30 Enrico Olivelli, <eolive...@gmail.com&gt; wrote:



Il Dom 21 Nov 2021, 16:15 735367737 <735367...@qq.com&gt; ha scritto:

hi??
&nbsp; &nbsp;I'm a newer to bookkeeper. i read the&nbsp;
Durability with BookKeeper
&nbsp; before i read bookkeeper's code. i got a question about journal.I paper 
it says journal is&nbsp; write-ahead log and stores synchronously and 
sequentially all updates the bookie executes . but when i read code .i found 
the entry write into ledgerStorage before write into 
journal(Bookie.addEntryInternal).is there something i miss ?&nbsp; &nbsp;





It is actually not a problem because:
- entries are immutabile
- the reader is prevented from reading data not acknowledged by the writer by 
the Last Add Confirmed protocol&nbsp;




Enrico


&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;thanks.