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Scripting Exercise: A basic AJAX application

A common question on the LoadRunner support forums is “I’ve got an application that uses this new thing called AJAX. Will LoadRunner work with my application?” …and the answer is “yes…but…”.

The “but” is a big one . An “AJAX” application can mean anything from a simple webpage that updates some fields with information from the server (without reloading the whole page), to a horribly complicated rich GUI interface created with JavaScript.

Of course LoadRunner is going to be able to handle anything that is sent over HTTP, but scripting might not be the usual simple Record-Correlate-Playback, and the chances of the new Click and Script vuser type working are much lower than with a standard web application.

As a quick introduction to AJAX I have prepared an exercise using the simplest AJAX application that I could find.

Google Suggest

Google Suggest is just like Google’s regular search interface, except that every time you type a letter in the search field, a request is made to the server that returns search suggestions.

The exercises are as follows:

  1. Become familiar with the application - both at an end-user level, and at the HTTP level. Record the script in HTML and URL mode, then try the Click and Script vuser type (at the time of writing, this vuser type will not correctly record the application).
  2. Create a script for this application. It should accept a parameter file that contains a valid search term on each line. Create the following transactions load_search_page, enter_character (called every time a character is entered in the search field), and final_search (where the Google Search button is pressed).
  3. Imagine that you’ve noticed an odd step-like pattern in the Percentile graph in LoadRunner analysis. You hypothesise that response times differ depending on how many characters have been entered in the search field. Modify the enter_character transaction name to include the length of the search term every time it is called.

Treat this with the same level of care that you would give a script that you were creating for a paying client.

I have added some notes and a solution script to the comments section of this post. If you are going to attempt this exercise, please do so before reading the comments.

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This entry was posted on Monday, August 28th, 2006 at 9:43 pm and is filed under LoadRunner, Web Vusers. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

9 Responses to “Scripting Exercise: A basic AJAX application”

  1. Stuart Moncrieff Says:
    August 29th, 2006 at 9:44 pm

    This should be a quick exercise to complete.

    Exercise 1:

    There are no deliverables for this one, but this should give people a better idea of how the application works, and what scripts recorded with the different vuser types look like.

    Exercise 2:

    There is no correlation required for this script, so it should be quick to complete.

    Here is the solution script [Note: google_suggest.zip has been removed to encouage people to complete the exercise. Email me if you would like the solution!].

    At a minimum, I would be looking for a script that functions correctly.
    Extra bonus points for

    * remembering to put some kind of verification check for every request.
    * adding think time between each keypress - will a real user send requests as fast as the server will respond?
    * removing any web_add_cookie() function calls - are you planning on simulating the same user ever time?
    * discovering the lr_save_var() function, which saves any messy and error prone string manipulation using C.
    * noticing that on the final search, all spaces are converted to plus signs, and doing the same with the script - you could take a gamble and hope that because the application still works even though you don’t do this, then any performance test results will still be valid. You could even run test to see if this was the case but, in the end, it is much simpler to just ensure that your virtual user is doing the same things as a real user.

    Exercise 3:

    Creating dynamic transaction names requires a trivial change to the script, but this is a useful technique to add to your repertoire.

  2. narayana Says:
    October 7th, 2006 at 12:15 am

    To BE CLEAR MORE ON AJAX VERSION SCALABILITY AND PERFORMANCE

  3. Stuart Moncrieff Says:
    October 9th, 2006 at 10:58 am

    Clearly this post is about creating a script for load testing a simple AJAX application, not a post about scalability and performance of AJAX as a whole.

    But how could I resist a one-line comment IN ALL CAPS?

    AJAX is a web programming technique, so clearly does not have versions.

    Just like any web application, the scalability and performance a web application that uses AJAX may be determined through appropriate testing under load.

    Unfortunately usage profiles and end-user behaviour can be significantly more complicated with an AJAX application, making scripting potentially more difficult. As the above example shows, there is likely to be significant additional effort required when scripting due to the way the technology works also. Don’t even get me started on the problems you are going to have trying to create a script for one of the new rich web toolkits that are out there.

    When used incorrectly (or for inappropriate tasks), AJAX can make the end-user more aware of response times instead of speeding things up by no longer requiring a reload of the whole page. In a development environment with low network latency this is not noticeable, but when you have 300ms of latency you will see how annoying it is. Include this in your manual performance testing if possible.

    Finally, AJAX (or frames, now that I think about it) opens the possibility of multiple HTTP requests from the same user at the same time. Normally web developers don’t have to think about threadsafety as each user’s data was safely isolated in their user session data. Now, if you do something silly, you can do two (incompatible) things at once with a single user’s data.

    I saw this recently where, under some very rare circumstances, a Java hashtable (the implementation of which is not threadsafe) in the user’s session would get stuck in an infinite loop. Sometimes an update and a read request would occur at the same time, which would cause this problem.

    Cheers,
    Stuart.

  4. Anon Says:
    October 9th, 2006 at 11:38 am

    The Wikipedia entry for AJAX agrees with you about the potential problems with network latency:

    Response-time concerns
    Network latency — or the interval between user request and server response — needs to be considered carefully during Ajax development. Without clear feedback to the user, smart preloading of data and proper handling of the XMLHttpRequest object, users might experience delay in the interface of the web application, something which users might not expect or understand. Additionally, when an entire page is rendered there is a brief moment of re-adjustment for the eye when the content changes. The lack of this re-adjustment with smaller portions of the screen changing makes the latency more apparent. The use of visual feedback (such as throbbers) to alert the user of background activity and/or preloading of content and data are often suggested solutions to these latency issues.
    In general the potential impact of latency has not been “solved” by any of the open source Ajax toolkits and frameworks available today, such as the effect of latency variance over time.

  5. Cheekoti Rajender Says:
    January 9th, 2007 at 4:59 pm

    Can u send me some docs which shows LR with AJAX supports for performance and load testing.

  6. Ganesh Says:
    July 20th, 2007 at 9:57 pm

    Hi,

    I’m currently working on a web application where the Left boundaries and Right boundaries are same across some 10 values.But here I want to capture only the 7th Value.Is using the ordinance the only way to do this?

    Regards,
    Ganesh

  7. Sue Macey Says:
    August 27th, 2007 at 11:23 pm

    Can you forward an example of a LR with AJAX supports for performance and load testing

  8. Anthony Says:
    January 2nd, 2008 at 7:10 pm

    Hi,

    Though this may not be the right place to post this, but I would like to put forward this scenario for anyone willing to try.

    I am reading a text file in LR and I wish that it would be read by the FIRST Vuser only with VuserID = 1. This may seem straightforward by using lr_whoami(), but it seems when threads are spawned in LR Controller its not clear which thread executes first. Like for e.g. if there are 10 threads VuserID =2 may execute the script first. Sometimes the thread numbering also doesn’t start from 1. Has anyone faced this situation before? Would appreciate it if someone throws some light on how to go about solving this problem.

    Thanks
    Anthony

  9. Sire Says:
    May 14th, 2008 at 7:19 pm

    Hi,
    I read this examples in order to solve my ajax problems.

    I try to explain to you….
    My HTML page contains a DIV tag and its content is loaded with the “onLoad” js function calling a struts action with a GIS map without reload the entire page (ajax).

    The Click & Script LR solution doesn’t understand this ajax code (onLoad) and load simply the background page without map (the URI doesen’t change!).
    In the other side the HTML base LR mode is unable to see ajax.

    Have you some suggestion to help me??

    Thanx in advance
    Sire

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