First post! Welcome to “Hadoop Hamburgers”, where I plan to write some posts about Hadoop and other topics that seem interesting. My first one is not related to Hadoop, but instead related to DNS, a subject near and dear to the heart of my employer, Verisign. Everything in getting this site setup went fairly smoothly, including updating my registrar’s DNS records to point my domain name at my hosting provider. Being an impatient sort, I didn’t want to have to wait for the TTL on my domain name to expire, so I ran a
dig request to see if my registrar had pushed through the change:
shell$ dig grepalex.com ;; ANSWER SECTION: grepalex.com. 3600 IN A 188.8.131.52
Indeed they had! Next up was trying to hit my website from my browser. When I did that however, Chrome was showing the my registrar’s advertising content. A few pokes around led me to Chrome’s web page which lets you invalidate its DNS cache:
However even after invalidating Chrome’s cache it still showed the content from the registrar. The cool thing about Chrome’s internal page is that it actually shows you the cached IP address, which indeed was still the old value. Clearly the OSX DNS client was performing some additional caching. After some more digging around I found the (Mountain) Lion-specific command which did indeed successfully clean OSX’s cache:
shell$ sudo killall -HUP mDNSResponder
About the author
Alex Holmes is a senior software engineer with over 15 years of experience developing large scale distributed Java systems. Since 2008 he has gained expertise in using Hadoop to solve Big Data problems across a number of projects. He is the author of "Hadoop in Practice", a book published by Manning Publications. He has presented at JavaOne and Jazoon.
RECENT BLOG POSTS
Simplifying secondary sorting in MapReduce with htuple
Introducing htuple, an open-source project to simplify secondary sorting in MapReduce.
Next Generation Hadoop - It's Not Just Batch!
Slides and additional reading from my JavaOne 2013 talk on next-generation Hadoop - mixing real-time and batch.
Bucketing, multiplexing and combining in Hadoop - part 2
In this part we examine the MultipleOutputs class for a more flexible way to write out multiple outputs from your mappers and reducers.
Secondary sorting with Avro
Complete control over how partitioning, sorting and grouping work with Avro map output keys.
Avro's built-in sorting
A look at how Avro supports sorting in MapReduce.
Using Avro's code generation from Maven
Avro has a Maven plugin which lets you generate code from Avro schema, IDL and protocol files. This post looks at how to use the plugin and its various options.
Bucketing, multiplexing and combining in Hadoop - part 1
The first in a series of MapReduce data organization patterns, which will cover various common actions such as data bucketing, multiplexing and combining.
Using the libjars option with Hadoop
The Hadoop CLI has an option for indicating any JAR's that should be be loaded by the MapReduce task classloader. In this post you'll see how to use this option, as well as how to ensure that your MapReduce driver properly supports these JAR's.
Installing AsciiDoc on OSX
AsciiDoc is a cool markup language, similar to markdown, and comes with tools to generate AsciiDoc to DocBook and PDF formats. Here you'll see how to get it up and running on OSX.
Java 6 and 7 with the dotted/dotless I
The interesting case of the dotted and dotless "I" in Java.