Archive for January 2010

Write lots of data to local LoadRunner log files quickly

January 26, 2010 Performance Testing Comments Off

Mark Sibley and I are hoping to start work on a new testing project soon. We will simulate multiple HTTP requests into the test infrastructure and since the application doesn’t require session information for users, we should be able to allow a small number of vUsers simulate a larger number of “real users”.

Our DBA has asked us if we can give him information about the response times for EVERY transaction. He’s worked with LoadRunner before and he wants the extra detail so that he can account for any poor performance in an individual transaction after a performance test. To do this he’ll need information like this for each transaction.


{Time HH:MM:SS:sss},{Unique Transaction ID},{Any LoadRunner Parameterised Data},{Transaction Response Time}


We’ll write about 100 bytes of data for each transaction and at 200 transactions per second we could have problems if writing to disks is too slow.  I mentioned this problem to Mark and he quickly wrote a function which writes data to an array in memory and writes  50 lines of data to disk at once. Mark’s function seems pretty quick and we’re going to test this when we get on site and have a chance to use some “beefy” Load Generators, rather than VuGen on PCs.

We’ve also considered using VTS (Virtual Table Server) for this. We’ll do some more experimentation and post the results here when we have them.

The script can be downloaded on the discussion forum; where comments ,as always, are welcome.

Sample LoadRunner script – pad a string with leading zeroes

January 13, 2010 Performance Testing Comments Off

When working on the previous article, Steven Woodcock found a problem where a string was losing it’s leading zeroes. They needed to be put back before his function worked properly and this is his solution to ensure that the output string was the correct length.

A discussion article has been published on my discussion forum for any comments which you may have about this code.

A working (ZIPPED) LoadRunner script can be downloaded so you can see this function in action.

 

Inputs:
strCharToPad – The String that requires to be padded out i.e. “123456″
cParamName – The name of the parameter you want the end value to be saved to
iValLength – The length you want the string to be padded out to i.e. 9
cValueToAdd – The character you want to pad the string out with, must be a single character i.e. “0″

Outputs:
Creates a LoadRunner parameter of a name specified in the input ‘cParamName’

int PadToX(char* cCharToPad, char* cParamName, int iValLength, char* cValueToAdd)
{

char cTemp[1024] = “”;
int iLoop = 0;
int iMainLoop = 0;
int iSubLoop = 0;

for(iMainLoop = 0; iMainLoop < iValLength; iMainLoop++)
{
if (iMainLoop == strlen(cCharToPad))
{
iLoop = iValLength – iMainLoop;
for (iSubLoop = 0; iSubLoop < iLoop; iSubLoop++)
{
 strcat(cTemp, cValueToAdd);
}
}

}

strcat(cTemp, cCharToPad);
lr_save_string(cTemp, cParamName);
}

 

Sample script using Epoch Time to demonstrate large number handling in LoadRunner

January 13, 2010 Performance Testing Comments Off

This script was provided by Steven Hedley and Steven Woodcock of Sopra Group.

They had a requirement for a script which could add time to the UNIX system time (otherwise known as Epoch time or POSIX time). Epoch time is the number of milliseconds that have passed since 00:00:00 on 1st January 1970. Many computer systems use this system to store the time as a number.

At the time of writing this article the current Epoch time is 1263400124467 this 13-digit number is too long to be used in LoadRunner calculations so to prevent errors occurring in calculations involving this number the chaps from Sopra Group have written a function to split the number into two parts (5 and 8 characters long respectively). The calculation is performed on the second 8-digit long number before the two parts are concatenated together.

The script also ensures that the final calculated time is always 13 digits long by padding any leading zeroes in the values which are used in the calculation. The function uses the web_save_timestamp_param function which returns the current EpochTime. I wasn’t familar with this function until now. Thanks!

Syntax for the function is
AddToEpoch(1800000, “ToTime”); //This takes Epoch time now and rolls it forward 30 minutes, creating a variable ToTime

The code for the function is reproduced on my discussion forum where I welcome feedback and discussion and a working sample script using the function is available for download here.

If you have samples of scripts which you feel should be shared, please let me know.


Creating uniquely named log files with details of running processes (TASKLIST)

January 8, 2010 Performance Testing, Testing Comments Off
TASKLIST screenshot

Thanks to Scott Moore (at LoadTester.com) for the idea behind this article and to the owners of DOStips.com for their article on DOS string manipulation which I used to get the string concatenation right.

When running performance tests or any kind of performance analysis it can be useful to know the processes running on a PC or server which are consuming resources. The Windows command TASKLIST gives a list of currently running processes (basically a text based version of what the Task Manager process tab shows you).

TASKLIST screenshot

By piping the output of this file to a text file you can save details of the running processes for later analysis.

Scott’s article describes a batch file which you could run before and after certain events such as batch processing or performance tests to create uniquely named log files containing the TASKLIST information. I had some difficulty getting his time and date stamps to work, possibly due to the timezone settings in Windows which “regionalise” the date and time environment variables. I’ve modified his original batch file to this one below which seems to work on UK PCs running Windows 7, Windows Vista and Windows XP.

Sample Code

for /f “tokens=1-3 delims=/ ” %%d in (“%date%”) do set d=%%d-%%e-%%f

for /f “tokens=1-3 delims=:” %%d in (“%time%”) do set t=%%d%%e

set timestr=%d:~6,4%%d:~3,2%%d:~0,2%-%t:~0,2%%t:~2,2%

tasklist /FO CSV > TASKLIST_Logfile_%timestr%.csv

 

This creates a CSV file named TASKLIST_Logfile_YYYYMMDD-HHMM.csv formatted like the sample below.


Sample Output

“Image Name”,”PID”,”Session Name”,”Session#”,”Mem Usage”

“System Idle Process”,”0″,”Services”,”0″,”24 K”

“System”,”4″,”Services”,”0″,”95,672 K”

“smss.exe”,”272″,”Services”,”0″,”64 K”

“csrss.exe”,”408″,”Services”,”0″,”2,484 K”

“csrss.exe”,”484″,”Console”,”1″,”73,224 K”

“wininit.exe”,”496″,”Services”,”0″,”172 K”

“avgchsva.exe”,”508″,”Services”,”0″,”25,816 K”

 

Sample Batch File

The batch file which creates this log file can be downloaded from my discussion forum.

http://www.bish.co.uk/forum/index.php?action=dlattach;topic=40.0;attach=44