Session Oddities

One of the clients we host complained about losing their session. Blackboard recommended we switch how our load balancer is handling the session persistence. Before agreeing to do that, we decided to use Blackboard’s script to determine if there is a problem before trying to fix something which may or may not exist.

An acceptable number of sessions showing on multiple nodes of a cluster is less than 5%. When I ran the test, I found 35.8% matched this criteria. But wait just a second, this seemed like an extraordinarily high number. I ran a second test for an identically configured cluster on the same hardware to find only 4.3%. Why are these so different?

Most cases of this “duplicated session” I spot checked were 1 hit for autosignon on another node. Blackboard confirmed these happen before the user has logged in, so they could appear on the other node. So I ran the test again ignoring these autosignon requests and found we were down to 7.2%. Close to acceptable but not quite.

 Similar to autosignon, the editonpro.js appeared in the majority of the cases I spot checked as the sole hit another node. Once, I removed those from the test, I was down to 0.7%. My control cluster was down to 1.4%. 

One would hope the the script used to determine the amount of duplicate sessions would ignore or remove from the data set the known false positive log entries. 

One would also hope the script instructions (requires login to Blackboard help site) would help users account for these false positives. I did leave a comment on the instructions to hopefully help the next person who has to do this.

IMS Data Going to Wrong Place

I should know better than to trust documentation over my own intuition. Or to change based on what others tell me.

I followed:

Log in to Vista Enterprise as a Server Administrator or Institution Administrator.
NOTE: To set glcid, you must log in as a Server Administrator.

From the Administration tab, click the Utilities tab.
Click Settings.

Under System Integration, click System Integration API IMS….

Enter values to configure settings. See the table that follows, Standard and IMS Adapter
details on each value.

Click Save Values. The Settings screen appears and the settings are configured.

Standard and IMS Adapter Settings
The following table describes the parameters you can set using the administration user interface.
Setting Description

• Stands for global learning context identifier.
Set by Server Administrator only.
Required to run IMS and Standard adapter

• Identifies the institution in which the adapter
command runs
• Automatically assigned by Vista Enterprise
upon creation of an institution

Of course, it doesn’t say which Glcid, right? After all, every learning context has a Glcid. Since, at the time I only had one institution (before I created the 54 others), I set the Glcid to the one for that institution. Should it be the Glcid for the server or domain learning context? If so, then couldn’t Blackboard just pre-populate it at the time of install? Why do I need to put it there?

At the same time, I didn’t believe it necessary because I had seen IMS imports work without the Glcid set at the server learning context. They worked because the command used to run the IMS import has the glcid.

The result? My imports went into the the institution with the Glcid set at the server learning context, despite the defining in the command I ran to use a different Glcid. Removing the Glcid from the server learning context settings allowed the command to work as I thought it should.

So much for a pristine, clean database.

WordPress Error: This file cannot be used on its own.

In posting a comment to a friend’s WordPress blog, it came up with the error:

Error: This file cannot be used on its own.

I was responding to a comment, so I doubted that he broke his blog between making a comment and my response. So I went looking though my own install. Essentially, at a shell I used

find . -exec grep -l "This file cannot be used on its own." {} \;

to locate the file involved is wp-comments-popup.php. This file contains code which checks for the HTTP_REFERER variable has specific values equal to the path and file name for the comments page. If this is not the case, then it should throw this error. The file mentioned in the error is wp-comments.php.

Its seems that I had configured my web browser not to pass the HTTP referrer to web servers, so the check failed and threw this error.

Maybe the WordPress developer who designed this has no idea about the ability of web browsers not to send a referrer. Searching for the error on the WP site yielded nothing. From the tons of comments about people hitting this error, lots of people turn off sending referrers.

Solution for those leaving comments: If you attempt to leave a comment and see this error, then enable referrers. WordPress actually has a decent article on enabling HTTP referrers for a number of different pieces of software.

More friendly error for WP blog owners: Edit wp-comments-popup.php. Change

die (‘Error: This file cannot be used on its own.’);


die (‘Learn how to <a href=””>enable HTTP referrers</a> to fix this. ‘);

Best Virus of the Day

Subject: Order Confirmation number: 37679041
Dear Customer,

Thank you for ordering from our internet shop. If you paid with a credit card, the charge on your statement will be from name of our shop.

This email is to confirm the receipt of your order. Please do not reply as this email was sent from our automated confirmation system.

Date : 08 Oct 2006 – 12:40
Order ID : 37679041

Payment by Credit card

Product : Quantity : Price
WJM-PSP – Sony VAIO SZ370 C2D T7200 : 1 : 2,449.99

Subtotal : 2,449.99
Shipping : 32.88
TOTAL : 2,482.87

Your Order Summary located in the attachment file ( self-extracting archive with “37679041.pdf” file ).

PDF (Portable Document Format) files are created by Adobe Acrobat software and can be viewed with Adobe Acrobat Reader. If you do not already have this viewer configured on a local drive, you may download it for free from Adobe’s Web site.

We will ship your order from the warehouse nearest to you that has your items in stock (NY, TN, UT & CA). We strive to ship all orders the same day, but please allow 24hrs for processing.

You will receive another email with tracking information soon.

We hope you enjoy your order! Thank you for shopping with us!
(Attached is a zip file)