This is a good question. In theory, this would happend. But I doubt that it would be a rare case in practice. since the max bytes of a znode in zookeeper is 1MB. suppose we have bookkeeper configured as ensemble size is 3. then ~100 bytes would be enough to store an ensemble information, so we can store ~10000 ensembles for a LedgerMetadata, which I think it is enough for a ledger written life cycle.
BTW, a temp solution for this situation (if it did happen) is closing the ledger when necessary (which would make the ledger read-only and no metadata would be appended) and open a new one to write. Thanks, Sijie 2011/11/28 dennis zhuang <[email protected]> > It seems that when client add entry to one bookie server failed,it will > select an extra bookie server and try to add entry to the new one > server,then put this relationship to ensembles map in LedgerMetadata. > I am worry about that this map will grow up and reach the limit size of > zookeeper,because the metadata is stored in zookeeper.Could it happen? Or > there is a solution for this situation. > > 在 2011年11月28日 上午10:25，dennis zhuang <[email protected]>写道： > > Thanks for your answer. >> Another question about bookkeeper is that when a bookie server failed >> forever(such as disk damage etc.),will bookeeper try to replicate it's >> entries to other bookie server automically?Or just let it go,then some >> entries will lose their replications? >> >> 在 2011年11月28日 上午10:13，Samuel Guo <[email protected]>写道： >> >> Hello dennis, >>> >>> SyncThread only flushed Entry Logs and Index files not journal files. >>> >>> Step 4 only happened when entries in journal files are flushed to disk, >>> which means that when bookkeeper client received responses, the entries are >>> already persisted in journal files. >>> >>> The index may be still in Ledger Cache without being persisted when >>> bookie server shuts down or crashes. But it is OK. When bookie server >>> restarted, it can replay entries persisted in journal files to recover >>> index. >>> >>> So no entries will be lost when bookkeeper client received their >>> responses. >>> >>> You can read 'Data Management in Bookie Server' section in >>> doc/bookkeeperOverview.textile for reference. >>> >>> Thanks, >>> Sijie >>> >>> 2011/11/28 dennis zhuang <[email protected]> >>> >>>> Hi,to add a entry to bookie server,it has four steps as follow: >>>> >>>> 1. Append the entry in *Entry Log*, return its position { logId , >>>> offset } ; >>>> 2. Update the index of this entry in *Ledger Cache* ; >>>> 3. Append a transaction of update of this entry in *Journal* ; >>>> 4. Respond to BookKeeper client ; >>>> >>>> And the EntryLogger,Journal and Index files are not forced to device >>>> right now,but waiting for SyncThread to flush them. >>>> My question is that bookie server would lost data between data flushs? >>>> >>>> >>>> -- >>>> 庄晓丹 >>>> Email: [email protected] >>>> 伯岩(花名) [email protected] >>>> Site: http://fnil.net >>>> >>>> 淘宝（中国）软件有限公司 / 产品技术部 / Java中间件 >>>> >>>> >>> >> >> >> -- >> 庄晓丹 >> Email: [email protected] >> 伯岩(花名) [email protected] >> Site: http://fnil.net >> >> 淘宝（中国）软件有限公司 / 产品技术部 / Java中间件 >> >> > > > -- > 庄晓丹 > Email: [email protected] > 伯岩(花名) [email protected] > Site: http://fnil.net > > 淘宝（中国）软件有限公司 / 产品技术部 / Java中间件 > >
