Updated: July 30th, 2021

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 – Solr was running …

Updated: September 27th, 2009

Introduction

Welcome to part 2 of the Essential Firefox Extensions And Tips – A Comprehensive Guide series. In this article I’m going to describe a number of time saving pragmatic extensions that make me a better, faster, more efficient browser user (browserer?).

Pragmatic Extensions

All-in-One Gestures

All-in-One Gestures introduces customizable gestures for all kinds of actions. To perform a gesture, hold the right (by default) button and move the mouse in the specified direction, drawing the needed shape.

I use it mostly for 3 things: history back/forward and close tab (see below). Once you start using gestures, there is no …

This may not be very obvious but this is the command line to list files within a tar.gz archive on the fly:

1

tar -tzf file.tar.gz

-t: lists files
-f: instructs tar to deal with the following filename (file.tar.gz)
-z: informs tar that the it's dealing with a gzip file (-j if it's bzip2)…