Will Warren

The blog of an engineer from Canada who specializes in SaaS, HA, Cloud and Product Development. I work in the Internet.

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

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Length: 162 words or 1 min Tags: sysadmin, database, oracle

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:

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Length: 229 words or 2 min Tags: aws, sysadmin

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 siteĀ http://ux.stackexchange.com/questions/35576/what-explains-the-current-shift-from-glossy-uis-to-matte-uis Looks like the main culprits would be Windows and Android, while Apple seems to be sticking with what they know (for iOS at least).

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Length: 73 words or 1 min Tags: opinion, design, ui

A working day's worth of mouse movement

I recently came across a neat piece of software that maps out your mouse movements and creates artwork out of them. Check out the image below - it’s a graph of my mouse movements on my left monitor over a 9 - 5 working day. Click to see full resolution.

The black circles represent times when the mouse did not move - the huge black circle was when I went for a 2 hour meeting.

The software I used is called IOGraphica http://iographica.com - try it out and see what you get!

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Length: 92 words or 1 min Tags: discoveries

Reverting a git commit after pushing to remote

Imagine a scenario where you have a git repo with 2 branches; master, the production-ready branch and dev, the branch where all the developmentĀ occurs.

Now imagine that you accidentally made a commit on master, when really it should have been on dev. If you have not yet pushed to a remote repository (like Github), you can undo that commit using git reset like so:

git reset --soft HEAD~1

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Length: 325 words or 2 min Tags: git, coding

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