Updated: September 28th, 2009
The Problem
I am throwing up a quick post about a relatively cryptic error that Solr started throwing the other day here at Plaxo. After happily running for a few days, I suddenly started getting pages about failed Solr indexing.
Upon closer examination, I saw the following repeatedly in the log file:
catalina.2009-09-18.log:SEVERE: java.io.IOException: directory 'DATADIR/index' exists and is a directory, but cannot be listed: list() returned null
I tried to see if sending an OPTIMIZE command would help but the server returned the same response.
Digging Deeper
The reason was these errors was quite simple –…


beer planet is a blog about technology, programming, computers, and geek life. It is run by Artem Russakovskii - a local San Francisco geek who currently works at