Adding firewall rules for Oracle Database using iptables

To connect to a box on your network that is running Oracle Database, you will first need to allow connections to Oracle through your firewall.

If you’re running CentOS, RHEL, Fedora or any other Linux variant that uses iptables, use the following commands to create a firewall exception (Assuming you’re running your listener on port 1521 - check with sudo lsnrctl status):

sudo iptables -I INPUT -p tcp --dport 1521 -j ACCEPT

Apache Tomcat with SSL behind Amazon ELB

If you’re running a high-availability system of some kind, chances are you are into some sort of Load Balancing. If you happen to be writing a Java app, and happen to be using Apache Tomcat as your servlet container, then this tip is for you.

I had a system which needed to be HTTPS-only but also have the SSL terminated at the load balancer. Naturally, I forwarded the HTTP and HTTPS ports on my Elastic Load Balancer and had my application configured to redirect any insecure connections to an SSL connection. I started having a couple of strange issues where occasionally it would leave the connection on HTTP when it should have been redirecting.

My setup was basically:

  HTTP (80) -----> ELB -----> Tomcat (8080)
HTTPS (443) -----> ELB -----> Tomcat (8080)

Turned out, I needed to set a couple of extra options in my Tomcat HTTP Connector section (find it in server.xml). This was the combination of options that did it for me:

Redacting accidental password entries from your BASH history

From time to time, I have been known to accidentally type my password into a “username” prompt in a bash shell. In that situation, the password you entered is now a part of your ~/.bash_history file forever, unless you truncate or redact it.

Timing PHP code using a simple stopwatch class

If you’re writing a performance-focused app, it’s nice to be able to time how long various pieces of code take to execute. Below is the class I use (called StopWatch) and a really simple example of how I use it.

Transition from glossy to matte UI elements

Something I noticed as a general trend with modern technology (especially in mobile development) is a trend away from shiny, glossy UI elements like icons and buttons to a more flat, conservative style.

Here’s a really interesting discussion I found about the subject on the UX stackexchange site http://ux.stackexchange.com/questions/35576/what-explains-the-current-shift-from-glossy-uis-to-matte-uis