tika-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Luis Filipe Nassif (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TIKA-885) Possible ConcurrentModificationException while accessing Metadata produced by ParsingReader
Date Wed, 01 Aug 2012 01:02:34 GMT

    [ https://issues.apache.org/jira/browse/TIKA-885?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13426257#comment-13426257

Luis Filipe Nassif commented on TIKA-885:

But how to track updates to the metadata copy without changing parsers? Iterating through
the metadata copy in the reader thread can cause the same ConcurrentModificationException

Although not solving the above problem, i suggest using customized versions of PipedReader
and PipedWriter classes that work concurrently. It can at best double the speed of ParsingReader
on multicore machines. I can open a new improvement for this, what do you think?
> Possible ConcurrentModificationException while accessing Metadata produced by ParsingReader
> -------------------------------------------------------------------------------------------
>                 Key: TIKA-885
>                 URL: https://issues.apache.org/jira/browse/TIKA-885
>             Project: Tika
>          Issue Type: Improvement
>          Components: metadata, parser
>    Affects Versions: 1.0
>         Environment: jre 1.6_25 x64 and Windows7 Enterprise x64
>            Reporter: Luis Filipe Nassif
>            Priority: Minor
>              Labels: patch
> Oracle PipedReader and PipedWriter classes have a bug that do not allow them to execute
concurrently, because they notify each other only when the pipe is full or empty, and do not
after a char is read or written to the pipe. So i modified ParsingReader to use modified versions
of PipedReader and PipedWriter, similar to gnu versions of them, that work concurrently. However,
sometimes and with certain files, i am getting the following error:
> java.util.ConcurrentModificationException
>                 at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
>                 at java.util.HashMap$KeyIterator.next(Unknown Source)
>                 at java.util.AbstractCollection.toArray(Unknown Source)
>                 at org.apache.tika.metadata.Metadata.names(Metadata.java:146)
> It is because the ParsingReader.ParsingTask thread is writing metadata while it is being
read by the ParsingReader thread, with files containing metadata beyond its initial bytes.
It will not occur with the current implementation, because java PipedReader and PipedWriter
block each other, what is a performance bug that affect ParsingReader, but they could be fixed
in a future java release. I think it would be a defensive approach to turn access to the private
Metadata.metadata Map synchronized, what could avoid a possible future problem using ParsingReader.

This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira


View raw message