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https://issues.apache.org/jira/browse/LUCENE-5987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14235705#comment-14235705
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Robert Muir commented on LUCENE-5987:
-------------------------------------
Overall looks good. I have not nitpicked, but we could stare at it for days and
maybe not see bugs. I would rather us get it in jenkins sooner and iterate on
adding more testing around this to really harden indexwriter for good, and not
feel so scared in the future when trying to do cleanups.
What is IgnoreAlreadyClosedExceptionConcurrentMergeScheduler? This is a little
awkward and I can't figure out why we need it, or if we could do something else
better instead.
> 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
> Assignee: Michael McCandless
> Attachments: LUCENE-5987.patch, LUCENE-5987.patch, LUCENE-5987.patch
>
>
> 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 mergeMiddle 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.
> edit: just to be clear I am referring to abort (low level exception during
> flush) and exceptions during merge. For simple non-aborting cases like
> analyzer errors, of course we can deal with this. We already made great
> progress on turning a lot of BS exceptions that would cause aborts into
> non-aborting ones recently.
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