Virtual Table Server

I think that many readers are actively using LoadRunner. So, I’ve got a question: where do you take the test data from? The first option is to parametrize everything and save the dataset in .dat-files. It’s a good solution, but what if there are many scripts with common parameters in the use case? The second option is to use a database. It’s already better because the common parameters can be shared, but the configuration for some databases can be a nightmare for a newbie. I’ve got one more option that is both simple and effective.

Our topic will be a LoadRunner component – Virtual Table Server (VTS). To begin with, let’s sort out what it is and what to do with it. Its last versions have a js-node server on the backend, and its architecture reminds us of a database. But it just seems so at first glance. I’d rather compare VTS with a simple table because we can access practically any cell, row, or column using the column name or the row number. We can read, delete, and add data and empty the table – all of it without leaving LR. The details can be found below. First let’s discuss, where to find it and how to install it.

Installation

The habitation area is the folder \Additional Components\Virtual Table Server or OpenText site (registration is required to download the files). There shouldn’t be any difficulties during the installation. First, the temp folder should be selected, and then the main installer will run. During the installation, there will be an option to change the program folder, as well as an option to choose a server management port. It’s recommended to keep the default value of 4000 (of course, if the port is not already in use). For those who are lazy or value their time, there is an opportunity to automatically start the VTS. We activate the check-box, and after the installation, the browser with the application web interface will open.

Don’t forget to switch on the script connection to the server through “Access from Script” on the top right menu.

Data input

We’ve got several options: send the data from the database, import it from a CSV file, or use a script and do everything manually in the browser. I think the optimal version is importing data from a CSV file or using a script. I’m going to explain these two approaches. If you are interested in importing the database, take a look here.

CSV import

To begin with, we’ve got a CSV, so a regular text file with comma separators is enough. The first option is to use Import ->Import from CSV file in the web interface. Then we must choose the file, whisper the incantation, and olè; your data has already been pasted into the table. The second option is to use a script to do the job for you. You’ll need the file \VTS\web\vtscmd.js.

It works like this: 

node vtscmd /import samples/Customers.csv /port 8888

The script can also carry out other useful tasks, such as emptying a table:

node vtscmd /delete_data /port 8888

Or create another one:

node vtscmd /start /port 2000 /name table_one

The full command list: 

and parameters:

The only problem is that it doesn’t work with a remote host. For this purpose, we have to write scripts of our own. We are using a java-utility on the project that empties a table and imports a CSV. The data is sent via a POST query. Here are several examples of adding data to a cell:

Emptying a table:

Finally, here’s the most precious – CSV import. The file path can be full or relative, but the @ sign is necessary. Command run example from the folder with the file:

These requests are not working with the main table that is created by default. One more table on a separate port needs to be created and worked with.

Generally, if one expects tables to contain columns of different sizes, I recommend creating several tables in such a way that the data is comparable by size. For example, we create the first table with parameters with one value, the second table with parameters for 10 values, and so on. Of course, all of this should be used without exaggeration. A bit later, I will show the LR functions. They are very useful for receiving the whole parameter set, so it’s worth thinking about data management. The queries can be turned into a full-fledged application and used from the Jenkins script.

LoadRunner Script

Another option to add data is a VUGen script. For this purpose, a simple script is enough. To begin with, let’s prepare the data: it needs to be saved in VTS as regular parameters. Then, we write in the script the following:

I recommend checking the data and/or the return value to prevent invalidated data or script failures. It’s especially important during the data reception – I sometimes receive an empty line instead of the required value.

Finally, don’t forget to close the connection after finishing working with the table:

Data communication

I will explain several functions I’m using in my work: lrvtc_query_row ( int index ), which retrieves all parameters in the table’s index row. Each column corresponds to a parameter with the same name saved as a string. If no data exists in some cell, then NULL is written to the parameter.

It’s recommended to use indexes to optimize and speed up the search for unique values in tables with many lines.

Known problems

On the one hand, the ease of configuration and communication with LR is a big plus. On the other hand, I don’t quite like a couple of things. First, spaces appear in the table in some cases. We’ve observed that while using the rotate_xxx function. It seems that the server has problems with processing concurrent queries from virtual users. Another issue is that there is no satisfactory API for initial data input and data deletion from the tables. For those looking to improve the performance of their API architectures, utilizing a specialized tool like a gRPC load testing tool can ensure scalable and high-performing services. I hope such functionalities will be enhanced in future versions, but for now, we have to invent our bicycles.

I recommend the described approach to everyone who still keeps many of the same parameters in different scripts. Just don’t forget to check the values you received.