Updated: August 27th, 2012
Today's snippet is tremendously helpful if you are using an XML-RPC WordPress interface to read and publish your articles and are running into 500 Server Error issues due to running out of memory, manifesting themselves in something like this error message: "Invalid Server Response – The response to the metaWeblog.newMediaObject method received from the weblog server was invalid".
For example, my regular PHP memory allocation is 32MB or so, but if I load up Windows Live Writer, my favorite publishing tool, and ask it to load 1000 of the latest blog posts, I will undoubtedly get a server error back.
One solution would be to increase the memory allocated to PHP to something higher, like 256MB, which is how …
[Solr] How To Fix java.io.IOException: directory FOO exists and is a directory, but cannot be listed: list() returned null
Updated: June 11th, 2015
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.
The reason was these errors was quite simple – Solr was running into the system level limit on allowed number of open files (ulimit). This limit can be seen by running