fsync is required to make sure data is flushed to disk on IW.Commit -- at least to have that guaranteed on the OS level. This one is important, although I don't think there's any use of this for folders
-- Itamar Syn-Hershko http://code972.com | @synhershko <https://twitter.com/synhershko> Freelance Developer & Consultant Author of RavenDB in Action <http://manning.com/synhershko/> On Mon, Jan 5, 2015 at 5:04 PM, Paul Irwin <[email protected]> wrote: > I believe the code was commented out because it doesn't seem like it is > needed on Windows, although my understanding of that could be wrong. I've > used Lucene.net code with the sync stuff commented out in apps in > production for a couple years and no issues. > > However, that doesn't mean that there can't be a possible issue, especially > if you factor in Mono on Linux/OS X with different filesystems. Does anyone > know the actual purpose of the fsync code in Java Lucene? Is recreating it > even needed with System.IO? > > > Paul Irwin > Lead Software Engineer > feature[23] > > Email: [email protected] > Cell: 863-698-9294 > > On Mon, Jan 5, 2015 at 8:56 AM, Laimonas Simutis <[email protected]> wrote: > > > Tests occassionally fail with Unauthorized access exception with stack > > trace pointing here: > > > > > > > https://github.com/apache/lucenenet/blob/master/src/Lucene.Net.Core/Util/IOUtils.cs#L444 > > > > To understand the full issue, you can see how it is being called from > here: > > > > > > > https://github.com/apache/lucenenet/blob/master/src/Lucene.Net.Core/Store/FSDirectory.cs#L387 > > > > Note how it first fsyncs the files and then if there were any that were > > fsynced, it fsyncs a directory containing the files. Directory part is > the > > one that is causing the problems. > > > > The issue is that fsync implementation in the IOUtils is using FileStream > > class to flush both files and directories. Doing so for directories > throws > > Access Denied exception, always. FileStream class cannot be used to > "open" > > directories. > > > > > > Trying to think how to fix this. The simplest one is to catch Access > Denied > > thrown and ignore it. You can see how the existing implementation does > this > > for IOException catch branch. if dir is true, the IOException is ignored > > and method passes. That would be the simplest thing to do to get the > tests > > passing. Heck, even ignore the whole fsync if it is for directory. > > > > I do think the complete approach would involve falling back to native > > functions (CreateFile for Windows to get directory's handle: > > > > > http://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx > > or equivalent in non Windows) and then call FlushFileBuffers or > equivalent > > in non-Windows. It is kind of what is present in FileSupport class ( > > > > > https://github.com/apache/lucenenet/blob/master/src/Lucene.Net.Core/Support/FileSupport.cs > > ) > > but not fully implemented. It seems like IOUtils tried to use FileSupport > > Sync implementation but it was commented out. Does anybody know anything > > about that? Why it was commented out, etc? > > > > Looking for advice here on how to proceed. There is a good number of > tests > > failing this way so it would be a nice issue to take care off. Perhaps go > > with the simple route and mark the full implementation for TODO? > > > > > > Laimonas > > >
