[GitHub] [bookkeeper] hangc0276 commented on pull request #3194: [WIP] PIP-50: Add reuse journal file feature to support Intel PMem disk

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hangc0276 commented on PR #3194:
URL: https://github.com/apache/bookkeeper/pull/3194#issuecomment-1189912416

   > when the bookie is restarted with replaying the journal, how to handle the corner cases below: 1)bookie crash with reused journal **enabled**, but the restart bookie with the flag **disabled**; 2)bookie crash with reused journal **disabled**, but the restart bookie with the flag **enabled**.
   
   @ArvinDevel Thanks for your review.
   
   Currently, we reuse the journal files by renaming the file name. 
   For example, the journal file pool size is 5, and current journal files are: [101, 102, 103, 104, 105], and the current mark deletion position is (103, 2000). We need a new journal file named 106, and if we enabled the reuse journal file, we will do the following check.
   1) The journal files list is: [101, 102, 103, 104, 105], and the mark deletion position point to file: 103, it is safe to reuse file: 101
   2) We pick up file: 101 and rename it to file: 106, after rename, the journal files list is: [102, 103, 104, 105, 106]
   
   For the first case.
   >  1)bookie crash with reused journal **enabled**, but the restart bookie with the flag **disabled**
   
   Bookie crash with reused journal enabled, the last written journal file is 106, and the last mark delete position is (103, 2000). When the bookie restarts with the flag disabled, it will replay from file: 103 to file 106.
   
   > 2) bookie crash with reused journal **disabled**, but the restart bookie with the flag **enabled**
   
   Bookie crash with reuse journal disabled, the last written journal file is 106, and the last mark delete position is (103, 2000). When the bookie restarts with the flag enabled, it will replay from file 103 to file 106 and for new file 107 to be written, it does the above check, renames file 101 to file 107, and open it for writing. 
   
   


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