Tech Blog

Learnosity develops cutting edge tools for language learning and is used by the leading educational publishers and assessment companies globally. We deliver millions of assessments every year, to users on 6 continents.

We are looking for multiple roles from junior to mid level range.

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The main answer on the web is: Increase the size of you permgen by adding the following:

However, to me this just delays the problem, particularly if you are using dynamic languages which load a lot of classes eg Railo.

So a bit of further digging found these options:

These 3 options allow the permgen memory to be garbage collected. I tried to find a good reference link for them but couldn't.

The final thing that I discovered was the jmap tool - which is very helpful for understanding the memory usage.

You run it as follows and it gives a great summary of the memory usage of your running jvm.

Cheers, Mark

Getting Setup

Here is some documentation for reference and to help others:

1. Get the SDK from Amazon

• I got version 1.2.4 from here: http://aws.amazon.com/sdkforjava/
• Extract the lib/aws-java-sdk-1.2.4jar file and put it in your tomcat/lib folder

2. Get the HTTPComponents Client

• You will also need get the HTTPComponents Client from apache as it depends on this. http://hc.apache.org/downloads.cgi I downloaded the 4.1.1 release and this worked a treat
• Extract the 6 jars and drop them in your tomcat/lib folder.

3. Restart Tomcat and write some code

Comparison of techniques

I played with a few different techniques of using the AWS with tomcat and found the following:

1. CFHTTP direct API calls

2. Java AWS SDK from Railo

This worked well, but each request took on average of 1500ms from AU to US East AWS. This was disappointing, so I tried caching in the the application scope as below.

3. Java AWS SDK cached in App Scope

The first request took ~ 1500ms but then subsequent requests were about 300ms, which was 1/3 of the time of the raw CF code. With the added benefit of having full access to all the API's, this is definitely the way we'll be using it going forward.

Cheers, Mark

References

• AWS Java SDK reference
• List of endpoints for each Amazon service

• Makes it practical for students to practice Oral and Aural skills
• Is efficient and effective for teachers, as they can listen to each student individually at a time to suit them
• Can be used for homework assignments or “High Stakes Assessments”

Learnosity are creating the next generation of language and assessment technology for use in schools and education worldwide. The current product portfolio includes:

• High availability web based systems
• Cross platform software (Windows, Mac and Linux)
• iPhone/Android native applications
• Telephony/VOIP and SMS applications

We need someone who can:

• Use Javascript or Actionscript to create great user interfaces
• Develop highly scalable web applications using ColdFusion, PHP or similar
• Cut code with the best in the world

You will also need to be:

• keen to continue learning new technologies
• able to have a conversation with non technical people
• enthusiastic and ready to push the boundaries

You'll need:

• 1-3 years of programming experience
• Experience in at least one Client side language (Actionscript or Javascript/jQuery)
• Experience in at least one Server side language (eg PHP, Java, ColdFusion, etc)
• Understanding of Object Oriented design
• Understanding of XHTML and CSS

It would be good if you have:

• A degree in Computer Science, Engineering or similar.
• been working with open source tools
• Experience with Adobe AIR or Flex
• been playing around with iPhone/Android applications
• experience with some of Linux/VOIP/SIP/Asterisk/Jabber/XMPP

This is a full time role and you will be working in a casual workplace with flexible hours in the Sydney CBD. Salary commensurate with experience.

If this sounds like the job for you, email a covering letter explaining why you'll be great and your resume to mark@learnosity.com - no agencies please.

The ServerStats code wraps up a few undocumented methods for CF to make it easy to get information on the number of sessions active on a server as well as some basic information on memory usage.

Thanks to Charlie Arehart for mentioning it - keep up the good work.

I must have a look at updating it to support Railo when I get a moment.

Cheers, Mark

This has been something I've been looking at, but haven't found a compelling reason for one over the other.

Proxy AJP is claimed to be faster as it is a "Wire protocol" but I couldn't find any benchmarks around this.

So I decided to do a very quick and dirty benchmark to satisfy my curiosity. This is not a scientific process, I just ran a simple railo testpage on the same machine with 50 threads of jmeter requests hitting it.

First I enabled proxy_http and ran it four times, then enabled proxy_ajp and repeated. The config is below:

Results:

The results showed that the proxy_http module was faster - i.e. more requests per second could be pushed through.

I'm putting this down to the fact that proxy_ajp has to convert the http request into it's binary format, while proxy_http really just has to pass it along.

In different scenarios and network configurations the results may be different, but for now I'm going to stick with the http proxy.

Proxy AJP has one other benefit, in that is passes along some extra flags such as whether the request is https or not, but for our purposes we don't need this.

Cheers, Mark

I've been doing some more work on configuring railo to work flexibly in the numerous different environments we work in, and also making it simpler to set up.

To that end I investigated the use of mod_proxy for linking it to apache instead of mod_jk.

Advantages of this approach are:

• Simple - communications are in plain http
• Flexible - Load balancing can be easily added at the apache layer
• Simple - No compiling mod_jk

Here are the basic install instructions for Railo/Tomcat/Apache on Ubuntu.

Download & Install Tomcat

Download tomcat and extract content:

Move Tomcat to a more appropriate place:

Download Railo

Download Railo custom version jars file

Extract and move into Tomcat lib directory:

Make Tomcat load the railo jars by editing catalina.properties to change the shared loader path:

Make Tomcat and Railo work together by modifying the web config file:

add the following inside the <web-app> element:

add the following inside <welcome-file-list> element:

Start up tomcat:

Back to Tomcat

Linking with Apache via Mod Proxy

Ensure the modules proxy and proxy_http are enabled. On Ubuntu this is done as follows:

Create vhost

This tells apache to forward all requests for CFM files to the railo instance.

Finally restart apache and railo and you should be good to go.

I've just received a copy of the Tomcat 6 Developer's Guide from packt publishing to review.

It's nice timing as I've been working with Tomcat 6 a bit lately and in the new year plan to move some of our production systems over to running Railo on top of Tomcat.

After the extremely busy year Learnosity has had I'm looking forward to reading a few books over the break and coming back in the New Year with lots more ideas and technology to implement.

About Learnosity

Our service:

• Makes it practical for students to practice Oral and Aural skills
• Is efficient and effective for teachers, as they can listen to each student individually at a time to suit them
• Can be used for homework assignments or “High Stakes Assessments”

We are continuing to grow our core development team and we need another great developer to help us keep up with demand.

We need someone who can:

• Use Javascript or Actionscript to create great user interfaces
• Develop highly scalable web applications
• Cut code with the best in the world

You will also need to be:

• energetic with a butt kicking attitude
• ready to create cutting edge web 2.0 apps
• keen to continue learning new technologies
• able to have a conversation with non technical people

You'll need:

• 3 or more years of programming experience
• Expert in at least on Client side language (Actionscript or AJAX)
• Expert in at least one Server side language (eg PHP, Java, ColdFusion, etc)
• Understanding of Object Oriented design
• Understanding of XHTML and CSS

It would be good if you have:

• A degree in Computer Science, Engineering or similar.
• been working with open source tools
• been playing around with iPhone/Android applications
• experience with some of Linux/VOIP/SIP/Asterisk/Jabber/XMPP

This is a full time role and you will be working in a casual workplace with flexible hours in the Sydney CBD.

If this sounds like the job for you, email a covering letter explaining why you'll be great and your resume to mark@learnosity.com - no agencies please.

All the DB storage and application was using UTF8 throughout, but the PDF exports were showing nothing when they should have been showing Chinese characters.

To fix this up you need to do the following:

1. Need fonts installed on system:

2. Need fonts installed in CFAdmin

• Go to CFAdmin and Font Management
• Select directory /usr/share/fonts/truetype/arphic
• Select "Add" and you should see 2 new fonts added.

3: CFdocument Hotfix for CF7.0.2

Configure cffont.properties file

The cffont.properties file is located in /opt/jrun4/servers/{instance name}/cfusion.ear/cfusion.war/WEB-INF/cfusion/lib on the jrun multiserver version.

5. Restart CF

Once you restart CF you documents should be coming out with their Chinese fonts intact.

I'm sure there are additional fonts to add to get it working natively with all the other asian languages, so I'll add to this as and when I need/discover them. Please feel free to post a comment if you find any more font's that should be added to the list.