『推荐原文』Performance Testing(版主注:已获积分20)

peimzh · 发表于 2007-8-20 17:10:27

原文作者：Tim Chase
作者联系方式：无
原文地址链接：www.loadtester.com
推荐理由：我觉得这篇文章是对自动化脚本技术的一个入门介绍。

Performance Testing
Citrix Applications
Using LoadRunner:
Citrix Virtual User Best Practices
Tim Chase
A white paper from
www.loadtester.com
Spring 2006
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
2
Table of Contents
Introduction ...........................................................................................................3
How It Works ........................................................................................................4
Citrix Scripting Best Practices...............................................................................4
Display Settings.................................................................................................4
Keyboard Entry vs. the Mouse ..........................................................................4
ICA Files............................................................................................................5
Randomizing information...................................................................................6
Debugging Vusers in the Controller...................................................................7
Generate Snapshot on Error .............................................................................8
Continue on Error ..............................................................................................9
Scripting without the Citrix Agent ..........................................................................9
ctrx_sync_on_window (window_name, event, x, y, length, width, bitmap name)
..........................................................................................................................9
ctrx_sync_on_bitmap (x, y, length, width, hash)..............................................10
ctrx_mouse_click (x, y, mouse button, key modifier, window name) ...............11
ctrx_type (string)..............................................................................................11
and ..................................................................................................................12
ctrx_key (key, key modifier).............................................................................12
ctrx_get_window_name (string buffer) ............................................................12
Scripting with the Citrix Agent .............................................................................13
ctrx_sync_on_obj_info (window name, x, y, attribute, attribute value).............13
ctrx_get_object_info (window name, x, y, attribute, buffer for value)...............13
ctrx_sync_on_text_ex (x, y, length, width, text, window_name) ......................14
Summary ............................................................................................................14
About Tim Chase ................................................................................................15
About Loadtester Incorporated ...........................................................................15
About Mercury Interactive ...................................................................................15
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
3
Introduction
In order to ease the burden of administration, save bandwidth, and improve user
experience for response times, more and more companies are leveraging the
Citrix technology platform. When moving applications to a thin environment, one
of the difficulties is determining how the application will perform when multiple
users are accessing it. Mercury addresses this by providing the Citrix recording
protocol in LoadRunner. This white paper discusses the technical aspects of
testing Citrix application with LoadRunner and offers a best practices guide to
business process creation.
Citrix allows companies to publish traditionally thick-client applications and
Windows desktops to end users in a thin-client manner. It allows users to run
applications or thin desktop sessions using the resources of the Citrix server, as
opposed to using the resources of the user’s computer. When running a Citrix
session (whether it be a published application or a thin desktop), the Citrix client
on the local machine presents essentially a bitmap image to the user. When the
user uses the mouse, it is sending x and y coordinates of the mouse activity to
the Citrix server. The server translates the coordinates into mouse movement
and sends updated bitmap images to the user’s computer.
Mercury and Citrix have formed a technology alliance which allows testing Citrix
applications using the native ICA protocol directly using LoadRunner. This allows
the performance engineer to utilize the same methodology that applies to testing
web and client/server applications in LoadRunner. Citrix is the second most
popular technology when Loadtester Incorporated services are requested. This
white paper can be used to help organizations determine the appropriate starting
point.
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
4
How It Works
LoadRunner is able to use the Citrix client to talk with the Citrix server and record
the traffic going back and forth. The script that LoadRunner generates makes
use of bitmap synchronizations. It is able to sync bitmaps based on a hash value
that LoadRunner creates. A bitmap is an uncompressed image file that is a two
dimensional array of pixel information. LoadRunner has an algorithm that takes
this pixel information and creates a hash value based on this it. When the script
is rerun, if the bitmap looks the same as before, the hash value will be the same,
and thus the sync will work. Besides bitmaps, the LoadRunner Citrix protocol
makes use of keyboard input and x and y coordinates (to know where to click or
sync).
Citrix Scripting Best Practices
Because the Citrix protocol relies heavily on bitmaps and coordinates to work
correctly, there are few things to keep in mind when recording and editing the
scripts.
Display Settings
When writing Citrix scripts in LoadRunner, check the display settings of the
generators where the scripts will be run. The color depth and resolution of the
generators need to be the same as the settings on the computer where the
scripts are written. If the settings are different, any sync_on_bitmap functions will
fail. Along the same lines, avoid using Remote Desktop Connection when writing
scripts or running scripts. When RDC connects to a computer, it changes the
display settings that are in effect on the computer.
Keyboard Entry vs. the Mouse
During the recording of a business process, navigate the application being
recorded using the keyboard instead of the mouse. When LoadRunner captures
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
5
mouse clicks, it records the coordinates that were clicked on the screen.
Replaying these coordinates is not very reliable. If your script relies heavily on
coordinates, the scripts are more susceptible to being broken by application
changes. As opposed to mouse clicks, navigate the application using the tab key
or shortcut keys. Even if the application changes later, the script can be easily
fixed by adding or deleting tab key entries in the script.
ICA Files
ICA files contain connection information for Citrix applications. Double-clicking
on an ICA file will launch the application. A Citrix administrator can create this
file for the person writing the LoadRunner script.
When setting up connection information inside of LoadRunner, it is best to use an
ICA file to connect. This makes the script more portable and more resilient to
server change. If any of the connection information changes, in order to point the
script to the new location, put the new ICA file in the script directory and replace
the old one. For good housekeeping, it is a good idea of keep a copy of the ICA
file that is currently in use in the root folder of the scripts folder. For example, if
you are putting all of your scripts in c:\LoadRunner scripts\Project Name, you
should put a copy of the ICA file in c:\LoadRunner scripts\Project Name.
The following is an example of what an ICA file might contain when opened in
Notepad.
[WFClient]
Version=2
HttpBrowserAddress=citrix.app.us
TcpBrowserAddress=10.1.1.1
TcpBrowserAddress2=10.1.1.2
TcpBrowserAddress3=10.1.1.3
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
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[ApplicationServers]
WEBS Load Testing=
[WEBS Load Testing]
BrowserProtocol=HTTPonTCP
Address=WEBS Load Testing
InitialProgram=#WEBS Load Testing
DesiredHRES=800
DesiredVRES=600
DesiredColor=2
TransportDriver=TCP/IP
WinStationDriver=ICA 3.0
Randomizing information
Since Citrix scripts contain a lot of bitmap and coordinate information, it can be
difficult to randomize the input data. One of the places to randomize data is
where drop down boxes are used in the business process. In order to do this,
use the rand() function combined with the ctrx_key() function. The following is an
example from a script where the value of the variable claim_type is randomized.
This value could be used to search for a different type of claim object in a drop
down list each time the script was executed.
random_number = rand() % 5+1;
claim_type = random_number;
for (counter = 1 ; counter <= claim_type; counter ++)
ctrx_key("DOWN_ARROW_KEY", 0);
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
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Debugging Vusers in the Controller
Sometimes Citrix scripts do not work the same on different computers. Most of
the time it is because of problems like color depth. If the Citrix scripts have
problems running in the Controller during the debug run, there is a way to see
visually what the scripts are doing. In the Controller, bring up the details for the
group that is having problems. Under the Details section, make sure that “More”
has been selected so that all of the options are shown. In the “Command line”
text box, type –lr_citrix_vuser_view.
If the scenario is ran with this option, it will bring up a Citrix window and show the
virtual user as it is executing the script. When using this option, do not run a test
scenario with many virtual users because the Controller will open one Citrix
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
8
window for every user in the group. Because this is so resource intensive, it may
crash the Controller if used with too many users. Set aside one group with a few
users with this setting while the rest of the users are in different groups with
standard settings.
Generate Snapshot on Error
The “snapshot on error” feature run-time setting is very helpful when debugging
Citrix virtual users. It is found in the Miscellaneous options of the Run Time
Settings. Anytime a virtual user fails, a screenshot is sent to the Controller which
contains an image of what the screen looked like at the point of failure. It is a
great way to diagnose syncing problems, or to troubleshoot other strange Citrix
errors.
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
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Continue on Error
Feature Pack 2 for LoadRunner 8.1 provides a “Continue on Error” option, which
is available for several Citrix functions. It allows individual functions to continue
when sync does not work properly. There are several uses for this option. The
most important use is for error trapping. If there is a potential for a function
failing, the Continue on Error option can be used on the function. In the
subsequent lines of the script, the error can be handled appropriately and lines
can be written to the log file to assist in debugging.
Scripting without the Citrix Agent
When scripting without the Citrix agent, the script will be composed entirely of
bitmap syncs, mouse clicks, and keyboard entry. It treats the application as
nothing more than a bitmap. The following are the most commonly used
functions.
ctrx_sync_on_window (window_name, event, x, y, length, width, bitmap name)
This function is automatically inserted into the script during recording.
LoadRunner recognizes when a main window of the application becomes active
or is created. When this happens, it inserts the sync function. The window name
argument captures the title of the window being synced. Be sure to check this
window title because it may contain hard coded information that could cause the
script to break during a later test (e.g. build number, company name). An
asterisk can be used in the window name argument as a wildcard. An example
of this function is:
ctrx_sync_on_window("e-Brokering System *", ACTIVATE, -4, -4, 805,
605, "87d563f2500432ec6a15b90b2f8003a5", CTRX_LAST);
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
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ctrx_sync_on_bitmap (x, y, length, width, hash)
This sync function is used when waiting on something other than a window to
change. A good example would be a “search” business process. Before
continuing with the script, a bitmap sync could be placed in the script to make
sure there were results. Inserting a bitmap sync can be done either during or
after recording the script. The bitmap sync button is located on the recording bar.
To insert one after recording, bring up the tree view of the script. Find a line that
has a screenshot of the place that needs a sync. From there, a sync_on_bitmap
step can be inserted. The inserted step will look similar to this:
ctrx_sync_on_bitmap(449, 90, 107,
18,"9c097ec91de046c32e9b632b16125913");
The bitmap sync is one of the most difficult parts of a Citrix script to maintain.
When they are used, any application changes made in the environment can
potentially break the script. If the bitmap syncs stop working, there are a couple
of ways to fix the script. The first is to rerecord the sync in a new script and copy
the newly captured bitmap sync it into the old script in place of what is there. The
second way is to find out what hash value LoadRunner is seeing at the
coordinates of the bitmap. Before running the script, turn on advanced logging in
the Vugen run-time settings and enable the advanced trace option. When it gets
to the point of failure in the script, the LoadRunner execution log will show the
expected hash value and the actual hash value of the bitmap. Copy the actual
hash value into the script and determine if the script will run. Alternatively, both
bitmaps could be used in the statement by separating them with a pipe (“|”). An
example of this would be:
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
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ctrx_sync_on_bitmap(158, 300, 312, 132,
"84e312c9701b3dbb225182ae41cdc228|571b7bccd5eb40172dbc7e79d4
61528d ");
Feature Pack 2 for LoadRunner 8.1 contains an additional feature to troubleshoot
bitmap syncing problems. The “Failed Bitmap Synchronization” dialog box helps
to solve the problem of changing bitmaps. If the bitmap values differ from the
recorded bitmap values on replay, the dialog box will display. On one side, it
displays the bitmap recorded in the original script. On the other side, it displays
the bitmap shown during the replay. The Failed Bitmap Synchronization dialog
box provides two options: Stop and Continue. Clicking Stop means that
something is wrong with the bitmap synchronization and it will not make any
changes to the script. If continue is clicked, the script will continue to replay and
the script will be changed to accept both the original bitmap value and the new
bitmap value as valid.
ctrx_mouse_click (x, y, mouse button, key modifier, window name)
If the application will not allow a business process to be navigated by the
keyboard alone, mouse clicks can not be avoided. During recording, make sure
to click slowly through the application and try to click on the center of objects. If
clicking on a button, try and click in the middle of that button. This will make the
replay more accurate because the mouse clicks are never in exactly the same
place. Clicking on menus can be tricky in a script. When clicking on a menu, be
sure to allow time in your script for the menu to appear before clicking on the
menu option. This can be done by inserting “think time” between the two mouse
clicks, or by putting a bitmap sync between the two mouse clicks.
ctrx_type (string)
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
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Copyright © 2006. All rights reserved.
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and
ctrx_key (key, key modifier)
These two functions are the way to send keyboard data to the Citrix server. The
ctrx_type function sends normal keyboard data and the ctrx_key function sends
non-alphanumeric keys to the server. In order to send special keyboard
commands like Alt-F, ctrx_key can be used. For example, ctrx_key (“f”,
MODIF_ALT) will send Alt-F to the server.
ctrx_get_window_name (string buffer)
Sometimes in an application, different windows appear depending on the option
selected in the application. An example of this would be with a “claim search”
process in a claim processing application. The script may search for a random
claim and then open it. Every once in a while, a claim will not open because of
bad data. If this is the case, this data could be gotten by grabbing the window
title and then using if/else statements to exit the script gracefully. The following
is a code example.
ctrx_get_window_name(window_name);
result = strcmp(window_name, "Bad Claim Data");
if (result == 0) {
// put code here
}
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
13
Scripting with the Citrix Agent
The Citrix agent allows LoadRunner to see the application as more than just
bitmaps. After installing the LoadRunner Citrix agent on the Citrix server,
LoadRunner can see some of the objects of the application. This allows
LoadRunner to perform actions such as syncing on text and syncing on object
information. However, it does add about 2 MB to the footprint of a Citrix virtual
user – something to consider for the scalability of your LoadRunner Generators.
The Citrix agent is only launched when LoadRunner starts the application. If a
user starts the application, the Citrix agent will have no effect on his or her
session.
Any of the functions used when scripting without the agent can still be used with
the agent. Synching with objects provides a more stable script. When recoding
with the agent, the agent records mouse clicks differently (ctrx_obj_mouse_click).
The only difference is that this function includes a description of the object in its
function call.
ctrx_sync_on_obj_info (window name, x, y, attribute, attribute value)
This function syncs on certain attributes of an object before continuing. Some of
attributes that it will wait for are enabled, focused, visible, and checked. It can
also sync on the text of an object. A text check can be inserted into the script
during recording by finding the icon on the recording toolbar. When possible,
using a text check would be better then using a bitmap check. A text check
would be more easily maintainable.
ctrx_get_object_info (window name, x, y, attribute, buffer for value)
Performance Testing Citrix Applications Using LoadRunner:
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Copyright © 2006. All rights reserved.
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This function is very similar to the ctrx_sync_on_obj_info. It allows the script to
capture the attribute of an object. For example, it would allow a script to tell
whether a certain checkbox was checked.
ctrx_sync_on_text_ex (x, y, length, width, text, window_name)
This function allows the script to sync on text shown in the screen. It can be
added during the recording or after the recording from the tree view. When
adding this sync, a rectangle is drawn around the area with the text. During
playback, LoadRunner looks for text at the specified location and waits for the
text to be shown before continuing the script.
Summary
Because more companies are utilizing Citrix to deploy their legacy client/server
applications, performance testing these environments have become more
common. Successfully writing script to imitate a user’s action is made fairly easy
when using LoadRunner and the Citrix Agent. In order to write a good script,
planning must be done to ensure that the proper syncs and the proper
checkpoints are in place. Because Citrix requires more synchronization to run
properly, the scripts take more time to create than some of the easier protocols
like web.
Loadtester has world class consultants with intimate knowledge of Citrix from an
administrator perspective, as well as a performance engineer view. Loadtester
helps companies ensure their applications deployed via Citrix are scalable and
meet the performance objectives required for service level agreements.
Performance Testing Citrix Applications Using LoadRunner:
Citrix Virtual User Best Practices
9005 Overlook Blvd. Brentwood, TN. 37027 (615) 399-2459 www.loadtester.com
Copyright © 2006. All rights reserved.
15
About Tim Chase
Tim Chase has been in the IT industry for 5 years. He specializes in
performance testing Microsoft environments and Citrix environments. Tim has
been using the LoadRunner Citrix protocol since its early stages to test
infrastructures of different sizes.
About Loadtester Incorporated
Loadtester is a leading provider of services around application performance
testing and creating Performance Centers of Excellence. We teach companies
how to engineer performance into the software development lifecycle. As a
Mercury Gold Solutions Partner with Mercury Certified Consultants on staff, we
have the qualifications to implement Mercury products into your organization.
Visit www.loadtester.com to find out more information about our services.
About Mercury Interactive
Mercury Interactive Corporation, the global leader in business technology
optimization (BTO) software, is committed to helping customers optimize the
business value of information technology. Founded in 1989, Mercury conducts
business worldwide and is one of the fastest growing enterprise software
companies today. Mercury provides software and services for IT Governance,
Application Delivery, and Application Management. Customers worldwide rely on
Mercury offerings to govern the priorities, processes and people of IT and test
and manage the quality and performance of business-critical applications.
Mercury BTO offerings are complemented by technologies and services from
global business partners. For more information, please visit www.mercury.com.
LoadRunner® is a registered trademark of Mercury Corporation. All rights
reserved. All screen shots used with permission from Mercury.

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