[tech] variables you shouldn’t use in a rails controller
January 29th, 2010[tech] sample .gitignore files for various projects
January 17th, 2010[tech] Setting Up a Ubuntu Development Machine
November 29th, 2009Now that you have that shiny Ubuntu Linux machine… turn that into a development workstation!
[tech] Lessons from building a client-server iphone app
August 5th, 2009This is a talk I have gave at IphoneDevCamp2009 in Aug 1, 2009.
Update : Sept 2009
This is a similar to the above talk, but oriented towards rails programmers; Given at Silicon Valley Ruby Meetup.
[tech] MYSQL master/slave support in QCodo
May 17th, 2009[tech] Ubuntu 8.10 on Lenovo T61 laptop – Almost!
December 11th, 2008[politics] OBAMA win & newspaper front pages
November 6th, 2008On November 4th, 2008, Barack Obama was elected as the 44th president of the United States.
It was grand, historic night – not just for us in US, but all over the World.
I wanted to grab a newspaper – with a front page image – on Nov 05 (the day after) as a souveneir of this day. But they were sold out every where I went ! Finally, I managed to grab a ‘customer copy’ of San Jose Mercury News from a Cafe by 8pm. I am really thankful to the Cafe owner who just gave it to me FREE !!
Here is the front page image from Mercury News
And from San Francisco Chronicle:
If you have missed out on these editions, you can order a copy here:
http://www.mercurynews.net/obama/
It is really interesting to see the newspaper covers from US and around the world. Here are few links:
- The definitive place is Newseum which has over 700 newspaper covers : http://www.newseum.org/todaysfrontpages/default_archive.asp?fpArchive=110508
- Obama website : http://my.barackobama.com/page/community/post/amandascott/gGx3Xq
- http://www.buzzfeed.com/eliot/obama-newspaper-covers
-http://www.huffingtonpost.com/2008/11/05/obamas-victory-on-newspap_n_141311.html
[tech] GPS co-ordinate resolutions
October 31st, 2008Here is a typical GPS co-ordinate
san francisco,ca (lat : 37.775196, long : -122.419204)
Ever wonder how much distance each digit represents? Here is a breakdown.
[misc] Mars Phoenix lander on Twitter
May 26th, 2008Finally, some one thing worth following on Twitter – Mars Phoenix lander!
OH yeah, Phoenix landed on Mars on Sunday (May 26, 2008) around 5pm PDT
[tech] Hadoop Gotchas
April 21st, 2008I just started tinkering with Hadoop – ‘(Java) distributed computing platform’ from Apache. Even though it is a pretty nice platform, I wasted lot of time, chasing trivial / silly issues. Here they are, so some one else might find them useful.
hadoop version : 0.16.3
A) The dreaded ‘Port Out of Range’ exception in ‘NameNode’
2008-04-20 19:27:34,241 ERROR org.apache.hadoop.dfs.NameNode: java.lang.IllegalArgumentException: port out of range:-1
at java.net.InetSocketAddress.<init>(InetSocketAddress.java:118)
at org.apache.hadoop.dfs.DistributedFileSystem.initialize(DistributedFileSystem.java:65)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:1180)
at org.apache.hadoop.fs.FileSystem.access$300(FileSystem.java:53)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:1191)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:148)
at org.apache.hadoop.fs.FileSystem.getNamed(FileSystem.java:122)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:94)
at org.apache.hadoop.fs.Trash.<init>(Trash.java:63)
at org.apache.hadoop.dfs.NameNode.initialize(NameNode.java:134)
at org.apache.hadoop.dfs.NameNode.<init>(NameNode.java:176)
at org.apache.hadoop.dfs.NameNode.<init>(NameNode.java:162)
at org.apache.hadoop.dfs.NameNode.createNameNode(NameNode.java:846)
at org.apache.hadoop.dfs.NameNode.main(NameNode.java:855)
2008-04-20 19:27:34,243 INFO org.apache.hadoop.ipc.Server: IPC Server handler 9 on 9000: starting
2008-04-20 19:27:34,243 INFO org.apache.hadoop.dfs.NameNode: SHUTDOWN_MSG:
SHUTDOWN_MSG: Shutting down NameNode at sanfrancisco/127.0.1.1
This issue caused me so much aggravation. The issue is – my hostnames.
/etc/hosts
#hadoop
192.168.0.12 hadoop_master
192.168.0.2 hadoop_slave_1
hadoop-site.xml:
<property>
<name>fs.default.name</name>
<value>hadoop_master:9000</value>
</property>
<property>
<name>mapred.job.tracker</name>
<value>hadoop_master:9001</value>
</property>
For some reason, hostnames with underscores ( ‘hadoop_master’ or ‘hadoop_slave_1′ ) are causing this weired error.
Solution: after replacing all instances of
hadoop_master —-> master
hadoop_slave_1 —> slave
Every thing just worked !!!
Or you could use IP-addresses as well.
B)java.io.IOException: Incompatible namespaceIDs
At least this issue and a workaround is some what easier to find than the previous one.
go to the end of this tutorial : http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_(Multi-Node_Cluster)
http://issues.apache.org/jira/browse/HADOOP-1212
*Whew*
I have reverted back to hadoop v0.15.3, so the namespace issue went away
C) Map/Reduce tasks dying out
I kick off a simple wordcout across two machines, and my reduce tasks will die out, and process will hang for ever. Trawling through the logs revealed this is caused by some really weired reverse hostname lookups by Hadoop (or Java.net) framework.
For example, my IP address (192.168.0.10) was resolved as ’somehost.comcast.net’. After tweaking my ‘/etc/hosts’ things worked like a charm!