Robert Muir created LUCENE-5987:
-----------------------------------

             Summary: Make indexwriter a mere mortal when exceptions strike
                 Key: LUCENE-5987
                 URL: https://issues.apache.org/jira/browse/LUCENE-5987
             Project: Lucene - Core
          Issue Type: Task
            Reporter: Robert Muir


IndexWriter's exception handling is overly complicated. Every method in general 
reads like this:

{code}
try {
  try {
    try { 
     ...
     // lock order: COMPLICATED
     synchronized(this or that) {
     }
     ...
   } finally {
     if (!success5) {
       deleter.deleteThisFileOrThat();
     }
    ...
  }
}
{code}

Part of the problem is it acts like its an invincible superhero, e.g. can take 
a disk full on merge or flush to the face and just keep on trucking, and you 
can somehow fix the root cause and then just go about making commits on the 
same instance.

But we have a hard enough time ensuring exceptions dont do the wrong thing 
(e.g. cause corruption), and I don't think we really test this crazy behavior 
anywhere: e.g. making commits AFTER hitting disk full and so on.

It would probably be simpler if when such things happen, IW just considered 
them "tragic" just like OOM and rolled itself back, instead of doing all kinds 
of really scary stuff to try to "keep itself healthy" (like the little dance it 
plays with IFD in maybeMerge manually deleting CFS files).

Besides, without something like a WAL, Indexwriter isn't really fit to be a 
superhero anyway: it can't prevent you from losing data in such situations. It 
just doesn't have the right tools for the job.



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