Thank you very much. Enrico Olivelli <[email protected]> 于2019年7月30日周二 下午12:56写道：
> > > Il mar 30 lug 2019, 04:17 Wei Liu <[email protected]> ha scritto: > >> Thank you very much for your explanation. >> >> I think the current design is therefore a single writer, who writes the >> same message to multiple bookies in parallel(no leader) and the server >> updates lac only rely on client submit. >> It may result in delay in receiving the last message or in user usage >> complexity. >> > > If you have a continuous stream of data from the writer you get a great > throughput and all of the guarantees of BK. > > If you have very few writes you have to do what I said before . > > If you are experiencing low throughput consider using the asynchronous API > and tune you journal settings on the bookie > > Enrico > > > >> Enrico Olivelli <[email protected]> 于2019年7月29日周一 下午7:07写道： >> >>> Hello Wei Liu, >>> This is about the core feature of BookKeeper, that is the Last >>> AddConfirmed Protocol (LAC for friends). >>> >>> BookKeeper guarantees to the readers that once you read an entry you >>> will always be able to read it. >>> The reader is able to "see" the entries only after it has the guarantee >>> that the writer has received the acknowledgement of a successful write with >>> an quorum of bookies. >>> >>> In order to make it possible the writer "piggy backs" the id of the >>> LastAddConfirmed entry to the bookies and the reader then is able to use >>> this value (by reading it with readLastAddConfirmed) in order to have this >>> reference id. >>> >>> You have these ways to get your work done: >>> 1) write no-operation entries to the ledger, this will make the LAC >>> advance even in absence of "application" entries >>> 2) use the "ExplicitLAC" feature, that is a background activity that >>> sends the current LastAddConfirmed to the bookies even in absence of writes >>> after a configurable delay (this is like option 1 but is it automatic, but >>> it is still not available in the new API) >>> 3) use readUnconfirmedEntries: this bypasses the LAC protocol at all, so >>> you can read every entry, but you will need to use an out-of-band channel >>> to pass the id of the entries to read >>> >>> I hope that helps >>> >>> Enrico >>> >>> >>> >>> >>> >>> >>> >>> Il giorno lun 29 lug 2019 alle ore 12:49 Wei Liu <[email protected]> >>> ha scritto: >>> >>>> >>>> Dear All : >>>> >>>> 1) First create ledger, add msg 1, 2, 3 into the ledger >>>> 2) Do not close the current ledger; >>>> 3) Received the msg 1 and 2; >>>> 4) Received the msg 3 after closed the ledger; >>>> >>>> I want to know how to read the last message without close the >>>> current ledger? >>>> >>>> Thanks~ >>>> -- >>>> 一个人只拥有今生今世是不够的， >>>> 他还应该拥有诗意的世界。 >>>> >>>> [email protected] >>>> >>> >> >> -- >> 一个人只拥有今生今世是不够的， >> 他还应该拥有诗意的世界。 >> >> [email protected] >> > -- 一个人只拥有今生今世是不够的， 他还应该拥有诗意的世界。 [email protected]
