Common Problems & Solutions For Performance Testing Flex Applications Using LoadRunner

This article lists the common problems & solutions that performance engineers come across when testing flex applications.

Problem #1 : Overlapped transmission error occurs when a flex script is run for the first time from controller. But the same script works fine in VuGen.

Error -27740: Overlapped transmission of request to “www.url.com” for URL“http://www.url.com/ProdApp/” failed: WSA_IO_PENDING.

Solution : The transmission of data to the server failed. It could be a network, router, or server problem. The word Overlapped refers to the way LoadRunner sends data in order to get a Web Page Breakdown. To resolve this problem, add the following statement to the beginning of the script to disable the breakdown of the “First Buffer” into server and network time.

web_set_sockets_option (“OVERLAPPED_SEND”, “0″);


Problem #2 : During script replay Vugen crashes due to mmdrv error. mmdrv has encountered a problem and needs to close. Additional details Error: mmdrv.exe caused an Microsoft C++ Exception in module kernel32.dll at 001B:7C81EB33, RaiseException () +0082 byte(s)

Solution : The cause of this issue is unknown. HP released a patch that can be downloaded from their site.

Problem #3 : AMF error: Failed to find request and response

Solution : LoadRunner web protocol has a mechanism to prevent large body requests to appear in the action files, by having the body in the lrw_custom_body.h. In AMF and Flex protocol, LR cannot handle these values and fails to generate the steps. Follow these steps to fix the problem:

1. Go to the “generation log”
2. Search for the highest value for “Content-Length”
3. Go to <LoadRunner installation folder>/config
4. Open vugen.ini
5. Add the following:
[WebRecorder]
BodySize=<size found in step (2)>
6. Regenerate the script

Problem #4 : There are duplicate AMF calls in the recording log as well as in the generated code.

Solution : Capture level may be set to Socket and WinInet, make sure under Recording Options –> Network –> Port Mapping –> Capture level is set to WinInet (only)

Problem #5 : A Flex script which has Flex_AMF and Flex_RTMP calls, on replay will have mismatch in the tree view between the request and the response. After looking in the replay log we can see that correct calls are being made but they are being displayed incorrectly in the tree view (only the replay in tree view is incorrect). Sometimes it shows the previous or next Flex_AMF call in the tree view in place of the Flex_RTMP call.

Solution : This issue has been identified as a bug by R&D in LR 9.51 and LR 9.52. R&D issued a new flexreplay.dll which resolved the issue and will be included in the next Service Pack.

Problem #6 : Flex protocol script fails with “Error: Encoding of AMF message failed” or “Error: Decoding of AMF message failed”

Solution : The cause for this error is the presence of special characters (&gt, &lt, &amp etc…) in the flex request. Send the request enclosed in CDATA Example: <firmName>XXXXXXX &amp; CO. INC.</firm Name> in script to <firmName><![CDATA[XXXXXXXXXXXX &amp; CO. INC.]]></firmName>

Problem #7 : When creating a Multi Protocol Script that contains FLEX and WEB protocols sometimes VuGen closes automatically without any warning/error message displayed. This happens when the Web protocol is set to be in HTML Mode. When in URL mode the crash does not occur. There is no error code except a generic Windows message stating the VuGen needs to close.

Solution : This issue can be seen on Machines that are running on Windows XP, and using Mfc80.dll. Refer to Microsoft KB Article in the link below that provides a solution for the same. Microsoft released a hot fix for Windows specific issue that can cause VuGen to close.
http://support.microsoft.com/kb/961894

Problem #8 : When recording a FLEX script, RTMP calls are not being captured correctly so the corresponding FLEX_RTMP_Connect functions are not generated in the script.

Solution : First set the Port Mapping (Choose Recording options –> Network –> Port Mapping –> set Capture Level to ‘Socket level and WinINet level data’) set to ‘Socket level and if this doesn’t help, follow the next step. Record a FLEX + Winsock script. In Port mapping section, Set the Send-Receive buffer size threshold to 1500 under the options. Create a new entry and select Service ID as SOCKET, enter the Port (such as 2037 or whatever port the FLEX application is using for connection), Connection Type as Plain, Record Type as Proxy, and Target Server can be the default value(Any Server).

Problem #9 : Replaying a Flex script containing a flex_rtmp_send() that has an XML argument string may result in the mmdrv process crashing with a failure in a Microsoft Dynamics.

Solution : The VuGen script generation functionality does not handle the XML parameter string within the function correctly. This results in the mmdrv process crashing during replay. If you have the 9.51 version, installing a specific patch (flex9.51rup.zip) or service pack 2 will resolve the problem

Problem #10 : During the test executions in controller, sometimes the scripts throw an error ‘Decoding of AMF message failed. Error is: Externalizable parsing failed’.

Solution : This is mostly due to the file transfer problem. It is always advised to place the jar files in a share path common to all load agents.

Other Flex Supported Load Testing Tools


There are other Commercial & Open Source tools available, that support the flex application testing. Some tools (For example, Neoload) have much considerable support for RTMP even when compared to LoadRunner. The way all these tools test the flex application is quite similar, each tool has its own AMF/XML conversion engine, which serializes the binary data to readable XML format
Open Source

• Data Services Stress Testing Framework
• JMeter

Commercial Tools

• Silk Performer by Borland
• NeoLoad by Neotys
• WebLOAD by RadView

Performance Improvement Recommendations


When it comes to performance improvement of an application, our first concern would be to enhance the scalability for a specified hardware & software configuration.

• In case of flex, the scalability issues derive from the fact that BlazeDS is deployed in a conventional Java Servlet container, and performance/scalability of BlazeDS also depends on the number of concurrent connections supported by the server such as Tomcat, WebSphere, Web Logic … BlazeDS runs in a servlet container, which maintains a thread pool.
• Each thread is assigned to client request and returns to a reusable pool after the request is processed. When a particular client request uses a thread for a longer duration, the thread is being locked by that corresponding client till the request is processed. So the number of the concurrent users in BlazeDS depends on the number of threads a particular servlet container can hold.
• While BlazeDS is preconfigured with just 10 simultaneous connections, it can be increased to several hundred, and the actual number depends on the server’s threading configuration, CPU and the size of its JVM heap memory. This number can also be affected by the number of messages processed by server in the unit of time and size of the messages.
• Tomcat or WebSphere can support upto several hundred of users, and any servlet container that supports Servlets 3.0, BlazeDS can be used in the more demanding applications that require support of thousands concurrent users.

Based on our project experience in performance testing Flex applications using LoadRunner we have pointed out some of the common problems that might arise during performance testing Flex applications. This will save you a lot of time as we have also provided the solutions to troubleshoot the errors if they occur.

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Loadrunner Simulation With Safari

How to Simulate the Load from Safari Browser
There was an interesting requirement where we had to simulate Safari browser at the time of  load execution.This article provides information on how to achieve this.

Client Requirement:-

• Recently we were involved in a PoC to check the feasibility of SalesForce.com with LoadRunner.

• There was one interesting requirement that the customer wanted to simulate the load from Safari browser.

• The reason behind this is that the SalesForce.com will be primarily accessed by Sales team who will be mostly traveling using iPad with Safari browser.

Challenge:-

• By default, LoadRunner supports only I.E, Mozilla & Netscape browsers.

• And it does not support safari to emulate the load.

Analysis and Solution:-

• This can be achieved through Custom settings in loadrunner.

• For this all we need is safari – User Agent String that suits our requirement.

The following is an example of Safari – user agent string:

Mozilla/5.0 (iPad; U; CPU OS 4_3 like Mac OS X; nl-nl) AppleWebKit/533.17.9 (KHTML, like Gecko) Version/5.0.2 Mobile/8F190 Safari/6533.18.5

*Please note for recording you can use any browser and simulate the user load with any required browser using User Agent String as above.

Please Visit LoadRunner Simulation To Know More . 

Database Tuning

Why Database Tuning?

It is a primary responsibility of a performance Engineer to provide tuning recommendations for a database server when it fails to respond as expected.
Performance tuning can be applied when you face the following scenarios:-

• If the real user waiting time is high
• To keep your database updated on par with your business
• If you want to use your hardware optimally

General Tuning Recommendations

• SQL Query Optimization:-

Poorly written SQL queries can push any database to respond badly. It is widely accepted that 75% of performance issues arise due to poorly written SQL. Manual Tuning of SQL query is practically difficult; but we have more SQL Profiler tools available in the market.

The following types of SQL Queries are suggested to use

✔  Avoid table scan queries – especially long table scans.
✔  Utilize the indexes promptly.
✔  Avoid complex joins wherever possible – especially unions.

• Memory Tuning

Most of the Oracle Database can operate efficiently by utilizing its memory structures instead of disk IO’s.

The theme behind this is - A read from (or) write to memory is much faster than a read from (or) write to disk.


For efficient Memory
✔  Ensure that the buffer hit ratio, shared pool (library and dictionary hit ratio) meet the recommended levels.
✔  Properly size all other buffers including the redo log buffer, PGA, java pool, etc.

• Disk IO Tuning

It is crucial that there be no IO contention on the physical disk devices. It is therefore important to spread IO’s across many devices.

Spreading data across disks to avoid I/O contention

✔  You can avoid bottlenecks by spreading data storage across multiple disks and multiple disk controllers:
✔  Put databases with critical performance requirements on separate devices. If possible, also use separate controllers from those used by other databases. Use segments as needed for critical tables and partitions as needed for parallel queries.
✔  Put heavily used tables on separate disks.
✔  Put frequently joined tables on separate disks.
✔  Use segments to place tables and indexes on their own disks.
✔  Ensure that indexes are properly tuned.

• Sorting Tuning

Ensure that your sort area size is large enough so that most of your sorts are done in memory; not on disk.

• Operating System Concerns

Ensure that no memory paging or swapping is occurring.

• Lock Contention

Performance can be devastated if a user waiting for another user to free up a resource.

• Wait Events

Wait events help to locate where the database issues may be.

Conclusion

In an actual Load Testing, it is an essential practice to simulate the database as in production. Due to this, a lots of database issues may be encountered. The above given solutions are general tuning mechanisms for any database. These solutions may be ideal for most of the performance issues in a database.

Thanks For Reading This Blog. Please Visit At: Database Tuning Know More

Tips for Handling Recording Problems In LoadRunner

When we were using LoadRunner for our Business Process Testing engagements we have encountered certain recording problems. We have listed down some of the most common problems and the steps that should be followed to troubleshoot those issues.

Problem 1: NOT PROXIED error in the recording events log.

This error occurs when there is some sort of spyware software installed on the system.

To troubleshoot this issue follow the below steps:

1. Use process explorer to get the list of dlls getting hooked into Internet Explorer.

2. Compare the list with the dlls from a machine where you can record.

3. Run Ad-Aware software. To download this, visit http://www.lavasoftusa.com/software/adaware/. This usually eliminates the spyware programs.

4. Make sure to check carefully the processes running on the machine. If you find any suspicious DLL\exe, just google the name and see if it’s a known spyware. If so, uninstall the software related to this DLL\executable.

5. Sort the list of DLLs by ‘Path Name’ in Process Explorer. The DLLs to scrutinize carefully are the ones which are not located in LoadRunner\bin and c:\windows\system32 or c:\winnt\system32.

Problem 2: “Cannot connect to remote server” in the recording log

This error occurs when the communication from this server and on that particular port should not be filtered

To troubleshoot this issue follow the below steps:

Try port mapping if it is a HTTPS site.

Go to Recording Options > Port Mapping and add the Target Server’s IP address, Port Number as 443, Service ID as HTTP, Connection Type as SSL. Make sure “Test SSL” returns success. Change the SSL Ciphers and SSL Version to achieve success for “Test SSL”.

Problem 3: “Connection prematurely aborted by the client” error in the recording log.

This error occurs when the communication from this server and on that particular port should not be filtered

To troubleshoot this issue follow the below steps:

Try port mapping with Direct Trapping. Here’s how we can do direct trapping

a. Enable the Direct trapping option:

[HKEY_CURRENT_USER\Software\Mercury Interactive\LoadRunner\Protocols\WPlus\Analyzer]

“EnableWSPDebugging”=dword:00000001

“ShowWSPDirectTrapOption”=dword:00000001

“EnableWSPDirectTrapping”=dword:00000001

b. Before Recording Multi-Web, add port mapping entries for HTTP/TCP (and NOT SSL) connections.

Set their ‘Record Type’ from ‘Proxy’ to ‘Direct’.

c. Start recording.

Problem 4: Application sends a “Client Side” certificate to the server and waits for server authentication.

This error occurs because LoadRunner sits in between the client and server, it takes this certificate information from the client and pass it on to the server. So, you need to have the certificate in .pem format.

To troubleshoot this issue follow the below steps:

Use openSSL to convert the client side certificate to .pem format and add it in the port mapping in recording options

In Internet Explorer:

1. Choose Tools > Internet Options. Select the Content tab and click Certificates.
2. Select a certificate from the list and click Export.
3. Click Next several times until you are prompted for a password.
4. Enter a password and click Next.
5. Enter a file name and click Next.
6. Click Finish

In Netscape:

1. Choose Communicator > Tools > Security Info.
2. Click on the Yours link in the Certificates category in the left pane.
3. Select a certificate from the list in the right pane, and click Export
4. Enter a password and click OK.
5. Enter a filename and save the information.

The resulting certificate file is in PKCS12 format. To convert the file to PEM format, use the openssl.exe utility located in the LoadRunner bin directory. To run the utility:

Open a DOS command window.

Set the current directory to the LoadRunner bin directory.

Type openssl pkcs12 -in <input_file> -out <output file.pem>

Enter the password you chose in the export process.

Enter a new password (it can be the same as before).

Enter the password again for verification.

In Recording Options > Port Mapping > check the option for “Use specified client side certificate” and point to the saved .pem file.

Problem 5: Server sends a certificate to the client for authorization and only when authorized by the client a connection can be established between the client and server. This is mostly true for Java based applications. The error we get is “No trusted certificate found”

This error occurs since the recorder is in between client and server, you should authorize the certificate from the server. So, your wplusca.crt should be in the server’s certificate repository.

To troubleshoot this issue follow the below steps:

Copy wplusca.crt file into the certificate repository of the server.

1. Locate keytool.exe executable (usually under JRE_ROOT\bin directory).

2. Add its directory to the PATH environment variable.

3. Locate cacerts file (with no extension) under JRE_ROOT\lib\security directory.

4. Copy the attached cacert.pem to this directory.

5. Make this to be the current directory in the command prompt.

6. Execute:

keytool -list -keystore cacerts

7. It will ask you for the password, reply:

“changeit”

8. It will list all the CA certificates installed (usually 25).

Notice the number of certificates.

9. Execute:

keytool -import -file cacert.pem -keystore cacerts -alias mercuryTrickyCA

10. It will ask you for the password, reply:

“changeit”

11. It will ask you if you are sure you want to add the certificate to the store, reply:

“yes”

12. Execute:

keytool -list -keystore cacerts

13. It will ask you for the password, reply:

“changeit”

14. It will list all the CA certificates installed.

The number of certificates should be bigger by 1

Problem 6: The recording log does not indicate any error but the connection between the client & Server has ended abruptly. This could happen possibly due to the ‘WPLUSCA’ certificate with a private key

This error occurs when because the recorder sends the ‘WPLUSCA’ certificate with a private key to the server for authentication while recording.

To troubleshoot this issue follow the below steps:

1. Go to LoadRunner\bin\certs and make a copy of the WPlusCA.crt file.

2. Open it in a notepad

3. Delete the portion between “Begin RSA Private Key” and “End RSA Private Key”

4. Save the file.

5. Now right click the file and choose “Install certificate” and follow the on screen instructions.

This will now send a certificate without the private key and if the server accepts the communication will continue.

Problem 7: “Failed to resolve hostname” error in the recording log

If VuGen box is not able to resolve the server name that is given in URL, it throws this error in the recording log and then crashes the IE

To troubleshoot this issue follow the below steps:

Modify hosts file on the vugen machine with server name and any IP address

The above problems are some of the common problems when we are using LoadRunner for Performance Testing. The above mentioned troubleshooting steps will help you to fix these issues if they occur during your performance testing assignment.

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