Matthew B. Joneshttp://127.0.0.12009-10-10Matthew B. JonesNew Blog using totohttp://127.0.0.1/2011/12/17/new-blog-using-toto/2011-12-172011-12-17Matthew B. Jones<p>Welcome to the new home of my blog. I originally was hosting using
WordPress but after using Heroku for Acquaintable for a few months I
decided to switch over to using <a href="http://cloudhead.io/toto">toto</a> +
<a href="http://www.heroku.com">Heroku</a>…</p>
<p>Welcome to the new home of my blog. I originally was hosting using
WordPress but after using Heroku for Acquaintable for a few months I
decided to switch over to using <a href="http://cloudhead.io/toto">toto</a> +
<a href="http://www.heroku.com">Heroku</a>.</p>
<p>I’ll begin blogging various random thoughts, thoughtful thoughts, and
other tidbits of information that the public at large can peruse or
ignore once I get the structure of this website completed.</p>
Java Lies! IOExceptionhttp://127.0.0.1/2009/10/10/java-lies-ioexception/2009-10-102009-10-10Matthew B. Jones<p>Recently a coworker and I ran into a strange IOException that was only
occurring on our Linux servers, but Windows, OS X, and Solaris never had
the problem. Our software monitors networking equipment via SNMP, which
is a UDP-based protocol. We communicate via UDP at high rates of
hundreds of devices per second. When testing a new version of our
product we came across “IOException: No buffer space available”…</p>
<p>Recently a coworker and I ran into a strange IOException that was only
occurring on our Linux servers, but Windows, OS X, and Solaris never had
the problem. Our software monitors networking equipment via SNMP, which
is a UDP-based protocol. We communicate via UDP at high rates of
hundreds of devices per second. When testing a new version of our
product we came across “IOException: No buffer space available”.</p>
<p>Turns out that this is a misleading exception from Java. The root cause
is Linux has a hard limit of 1024 ARP entries in the local system. Since
our server’s IP address was in the same subnet as all the target IP
addresses (10.140.0.0/16), the local box issues ARP requests to
translate the IP address into the hardware MAC address in order to
transmit the UDP packet. After 1024 of these lookups are done the
magical IOException occurs.</p>
<p>Turns out I’m not the only person to encounter this. While I was looking
into the issue Google did not turn up much at all, except for this one
<a href="http://stackoverflow.com/questions/1043567/java-ioexception-no-buffer-space-available-while-sending-udp-packets-on-linux/1548174#1548174">StackOverflow
post</a> where I’ve posted my answer.</p>