There are several ways to run commands repetively in Linux.. (cron, while loop etc). Here is a simple trick. Say you want to check the size of a directory using “du” every 5 seconds, you can use the following command
[bash]watch -n 5 du -ch[/bash]
Check out all the options available in watch by running “man watch” :).
For my notes.. If you ever wanted to check the status of a bonded interface configure in Linux (esp RHEL), you can check the status by running the following command
[root@serverxyz bin]# cat /proc/net/bonding/bond0
i.e. assuming the name of your bond interface is bond0.
Output from the command
Ethernet Channel Bonding Driver: v3.4.0 (October 7, 2008) Bonding Mode: fault-tolerance (active-backup) Primary Slave: eth3 (primary_reselect always) Currently Active Slave: eth3 MII Status: up MII Polling Interval (ms): 100 Up Delay (ms): 0 Down Delay (ms): 0 Slave Interface: eth3 MII Status: up Link Failure Count: 0 Permanent HW addr: 00:10:18:6e:b8:1a Slave Interface: eth0 MII Status: up Link Failure Count: 0 Permanent HW addr: 00:21:5e:11:34:32
The configuration files involved are
/etc/sysconfig/network-scripts/ifcfg-bond0 (Bond Interface)
DEVICE=bond0 IPADDR=10.10.40.26 NETMASK=255.255.255.0 ONBOOT=yes BOOTPROTO=none USERCTL=no GATEWAY=10.10.40.1 NETWORK=10.10.40.0 BROADCAST=10.10.40.255 TYPE=Ethernet
/etc/sysconfig/network-scripts/ifcfg-eth3 (Primary Interface)
DEVICE=eth3 BOOTPROTO=none ONBOOT=yes HWADDR=00:10:18:6e:b8:1a MASTER=bond0 SLAVE=yes TYPE=Ethernet USERCTL=no
/etc/sysconfig/network-scripts/ifcfg-eth0 (Secondary Interface)
DEVICE=eth0 HWADDR=00:21:5e:11:34:32 USERCTL=no ONBOOT=yes MASTER=bond0 SLAVE=yes BOOTPROTO=none TYPE=Ethernet
We ran into an interesting issue at work recently. Documenting the solution for my records..
BACKGROUND : We had a table in one of our databases that served as a “hopping” point for some jobs. Data was inserted into this table and at jobs get kicked off at periodic intervals to “process” the data and delete it.
CURRENT METHOD : Launch multiple jobs to process the data and delete the rows as soon as the data is processed. This is causing locks on the table because there are multiple delete operations occurring at the same time. Which in turn means that the jobs cannot complete processing the data causing the table to grow in size.
PROPOSED METHOD : Add a new column to the table called “PROCESSED_STATE” and modify the “processing” jobs to set a flag “Y” in this column as soon as the data is processed. Create a new job that will be launched periodically, which checks the PROCESSED_STATE column and if the flag is set to “Y”, deletes the row.
Morale of the story.. 🙂 .. Multiple deletes on a table are bad. Better way is to have multiple updates and one delete.
Your site goes down 🙂
And traffic to the site drops!!
Things have been a bit crazy at work recently, so I didn’t get a chance to fix the site as soon as it went down (due to an error I still haven’t figured out). And as a result, the traffic to the site dropped.
I finally took the chance to move the site to a dedicated server running on the RackSpace Cloud services. Am putting together a post on how I handled this migration and will publish it soon.
The bad news is that I have lost traffic to the site that I have built over a period of time.. the good news is that I am the master of my own house (website) at last :).
I don’t have a Facebook or twitter account and that surprises a lot of my friends since I am such a geek :). And the reason I keep (kept) giving was that I want to be in control of my destiny. In this case, destiny being content. While Facebook and Twitter provide you with a easy way to connect with friends/relatives/stalkers etc, I believe it gives a lot of leeway on control over the content for the companies running these applications. I have all the means and ways to communicate with my friends and advertise what I need to world. How I do that? That is a blog post that I have been “drafting” for the last couple of months :)..Hope to publish it soon. And looks like the wider audience is finally waking up to it.
Check out this article on ReadWriteWeb regd how the tech leaders are calling for a boycott of Facebook and advocating for an open social networking protocol (http://www.readwriteweb.com/archives/more_web_industry_leaders_quit_facebook_call_for_o.php).
Another article on the same website, speaks about a study by the Advanced Institute of Science and Technology in Korea, which shows that Twitter is really not a social networking site, but more of a medium to broadcast your content (http://www.readwriteweb.com/archives/study_twitter_isnt_very_social.php). Doesn’t really support the argument I made earlier that Twitter is not going to make it..but it certainly supports the notion that once the hype is gone the influence of twitter as a medium will decrease.
I am sure a lot of people shop on express.com , but I probably get the credits for being the first blogger to post that express.com has not been responding to DNS queries since ~7:00 PM CST (4/26). Looks like Qwest is hosting DNS for Express. The name servers (most probably global load balancers) are not responding to DNS requests.
Here’s what I get, when I queried for www.express.com
I feel for the poor ops team scrambling around to bring up the service :). Another reason, you want diversity in your DNS hosting.
Instructions for configuring the mime type mappings in Jboss. Mime types essentially tells the application processing the content (typically a browser), what the content is. More information here (http://en.wikipedia.org/wiki/Internet_media_type).
Not the building :).. In fact, it just opened up officially today. But it looks like the IT team of the Burj did not anticipate the traffic spike to it’e website http://www.burjdubai.com/, when the building opens. The site has been down since early CST.
All the free publicity the site is getting from the media is wasted because the site is down (OK.. I am exagerrating things a bit 🙂 ).  If only the IT team at the Burj thought about this and deployed the site on a CDN, they could have averted this downtime. Using a CDN to power your site is becoming more of a norm than a luxury now a days. And with all the options in the market you have for a CDN, there is no excuse for any IT team to not implement this for a customer facing website.
We run multiple applications in Jboss at my work and one of the applications used to take an inordinate time to come up. A typical application would take < 1 minute to get deployed and this particular application for some reason was taking ~7-8 minutes. We initially thought it was a bug in the code and gave hell to our development team :).. But on closer investigation, we found out that a feature we enabled in the Jboss server settings which allows content to be hosted on network storage was causing the issue.
I blogged the feature in Jboss to follow sym links here (https://kudithipudi.org/2008/07/25/howto-configure-jboss-to-follow-symbolic-links/). So essentially when Jboss was started, it was checking all the content in these network path to check for applications to deploy. And traversing a network share with 1000s of directories isn’t fun :)..
We fixed it by making a simple edit to the start up script. Here’s the psuedo code for the script
And now the application starts in less than a minute :).
I guess there might be other elegant ways to do this. i.e. Configure Jboss to only deploy certain applications, but this did the trick for us :).
Jhanvi asked me to help with editing a text file recently. She had a file in the format
'512'
'345'
'876'
and needed to convert it into the format below
INSERT INTO BLAH VALUE ('512');
INSERT INTO BLAH VALUE ('345');
INSERT INTO BLAH VALUE ('876');
There are multiple ways, one can do this. Here is how I did this using Notepad++, an open source text editor. I used the regular expression capability of Notepad++ it’s search and replace function.
The data in it’s original format
Replacing the first quote mark
Data after the first search and replace operation
Replacing the second quote mark
Data in the final format
