[Reprint] a deep understanding of browser emulation in LoadRunner

I. Basic Introduction

In LoadRunner usage, browser emulation settings under run-time settings are confusing. Next we will take a look at the use of each option in conjunction with sniffer, andTest.

　

Browser emulation Diagram

　　Ii. Cases and tools

　　1.Test Case:

Open the homepage twice and compare the LoadRunner behavior in different browser emulation settings. The script is as follows.

Action()
{
web_url("www.primeton.com",
"URL=http://www.primeton.com/",
"Resource=0",
"RecContentType=text/html",
"Referer=",
"Snapshot=t2.inf",
"Mode=HTML",
LAST);

web_url("www.primeton.com",
"URL=http://www.primeton.com/",
"Resource=0",
"RecContentType=text/html",
"Referer=",
"Snapshot=t2.inf",
"Mode=HTML",
LAST);

return0;
}

　　2.SnifferTools

Open-source tool: Wireshark (formerly Ethereal) (www.wireshark.org)

　　Iii. Test process

To facilitate the description, we agree to use:

　　ASimulate browser cache

　　BIndicates cache URLs requiring content (htmls)

　　CRepresents check for newer versions of stored pages every visit to the page

　　DDownload non-HTML Resources

　　ESimulate a new user on each iteratioin

　　FClear cache on each iteration

First, set iteration in run logic to 2. Let action run twice to check the changes in data packets and connections when the script runs cyclically twice.

　　1.Remove all options

Results: A total of 95 data packets were obtained, 1 was established (marked in red), and 1 was disconnected (marked in blue)

No.     Time        Source            Destination       Protocol Info
      1 0.000000    192.168.1.61      203.81.29.137     TCP      13835 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      2 0.036053    203.81.29.137     192.168.1.61      TCP      http > 13835 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
     92 1.415887    192.168.1.61      203.81.29.137     TCP      13835 > http [FIN, ACK] Seq=817 Ack=71762 Win=257760 Len=0
     94 1.449960    203.81.29.137     192.168.1.61      TCP      http > 13835 [FIN, ACK] Seq=71762 Ack=818 Win=16464 Len=0

In this case, there are very few data packets (no choice to download the resource file into CSS, JS, GIF, etc.), and you can see that only one TCP connection is established when you open the home page four times.

At this time, even if you select a, you will find that the number of data packets page does not change, because the cache is mainly for resource files

　　2.Select E (f)

Result: a total of 102 data packets are obtained, two connections are established (marked in red), and two are disconnected (marked in blue)

No.     Time        Source            Destination       Protocol Info
      1 0.000000    192.168.1.61      203.81.29.137     TCP      13886 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      2 0.037013    203.81.29.137     192.168.1.61      TCP      http > 13886 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
     48 0.618117    192.168.1.61      203.81.29.137     TCP      13886 > http [FIN, ACK] Seq=409 Ack=35882 Win=257760 Len=0
     49 0.644106    192.168.1.61      203.81.29.137     TCP      13887 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
     51 0.651919    203.81.29.137     192.168.1.61      TCP      http > 13886 [FIN, ACK] Seq=35882 Ack=410 Win=16872 Len=0
     53 0.676377    203.81.29.137     192.168.1.61      TCP      http > 13887 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
     99 1.310379    192.168.1.61      203.81.29.137     TCP      13887 > http [FIN, ACK] Seq=409 Ack=35882 Win=257760 Len=0
101 1.347949    203.81.29.137     192.168.1.61      TCP      http > 13887 [FIN, ACK] Seq=35882 Ack=410 Win=16872 Len=0

In this case, there are very few data packets (no choice to download the resource file into CSS, JS, GIF, etc.). Compared with the first case, you will find that it has established two connections, this is the role of E. For every iteration, it is regarded as a new user, and a new connection needs to be established.

3.Select de (f)

Result: A total of 1782 data packets are obtained, 6 connections are established (marked in red), and 6 are disconnected (marked in blue)

No.     Time        Source            Destination       Protocol Info
      1 0.000000    192.168.1.61      203.81.29.137     TCP      14016 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      2 0.037911    203.81.29.137     192.168.1.61      TCP      http > 14016 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
      6 0.107432    192.168.1.61      203.81.29.137     TCP      14017 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      9 0.141816    203.81.29.137     192.168.1.61      TCP      http > 14017 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    426 3.334889    192.168.1.61      203.81.29.137     TCP      14017 > http [FIN, ACK] Seq=1852 Ack=150284 Win=257484 Len=0
    428 3.372253    203.81.29.137     192.168.1.61      TCP      http > 14017 [FIN, ACK] Seq=150284 Ack=1853 Win=16998 Len=0
    448 4.395488    192.168.1.61      203.81.29.137     TCP      14020 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    457 4.439604    203.81.29.137     192.168.1.61      TCP      http > 14020 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    859 7.593610    192.168.1.61      203.81.29.137     TCP      14016 > http [FIN, ACK] Seq=2849 Ack=377404 Win=257484 Len=0
    870 7.659680    203.81.29.137     192.168.1.61      TCP      http > 14016 [FIN, ACK] Seq=377404 Ack=2850 Win=15935 Len=0
    888 8.511308    192.168.1.61      203.81.29.137     TCP      14020 > http [FIN, ACK] Seq=1602 Ack=208150 Win=257760 Len=0
    890 8.549451    203.81.29.137     192.168.1.61      TCP      http > 14020 [FIN, ACK] Seq=208150 Ack=1603 Win=17280 Len=0
    892 8.566246    192.168.1.61      203.81.29.137     TCP      14022 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    893 8.601893    203.81.29.137     192.168.1.61      TCP      http > 14022 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    899 8.702628    192.168.1.61      203.81.29.137     TCP      14023 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    904 8.741807    203.81.29.137     192.168.1.61      TCP      http > 14023 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
   1298 11.809456   192.168.1.61      203.81.29.137     TCP      14022 > http [FIN, ACK] Seq=1550 Ack=159770 Win=257484 Len=0
   1310 11.878665   203.81.29.137     192.168.1.61      TCP      http > 14022 [FIN, ACK] Seq=159770 Ack=1551 Win=17280 Len=0
   1341 12.771707   192.168.1.61      203.81.29.137     TCP      14026 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
   1348 12.813950   203.81.29.137     192.168.1.61      TCP      http > 14026 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
   1759 16.032952   192.168.1.61      203.81.29.137     TCP      14023 > http [FIN, ACK] Seq=3151 Ack=367918 Win=257484 Len=0
   1761 16.068296   203.81.29.137     192.168.1.61      TCP      http > 14023 [FIN, ACK] Seq=367918 Ack=3152 Win=17280 Len=0
   1779 16.983042   192.168.1.61      203.81.29.137     TCP      14026 > http [FIN, ACK] Seq=1602 Ack=208150 Win=257760 Len=0
   1781 17.016836   203.81.29.137     192.168.1.61      TCP      http > 14026 [FIN, ACK] Seq=208150 Ack=1603 Win=17280 Len=0

　　

In this case, the number of data packets is very large and there are many connections. Because the cache function is not available, you need to download all the resource files every time you open the page.

　　4.Select Ade

Result: A total of 525 data packets are obtained, 3 connections are established, and 3 are disconnected (no longer identified, SYN is the connection request, and fin is the disconnection request)

No.     Time        Source            Destination       Protocol Info
      1 0.000000    192.168.1.61      203.81.29.137     TCP      14189 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      2 0.033657    203.81.29.137     192.168.1.61      TCP      http > 14189 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
      6 0.100636    192.168.1.61      203.81.29.137     TCP      14190 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      9 0.133703    203.81.29.137     192.168.1.61      TCP      http > 14190 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    429 3.383748    192.168.1.61      203.81.29.137     TCP      14190 > http [FIN, ACK] Seq=1852 Ack=150284 Win=257484 Len=0
    431 3.418556    203.81.29.137     192.168.1.61      TCP      http > 14190 [FIN, ACK] Seq=150284 Ack=1853 Win=16998 Len=0
    471 4.352071    192.168.1.61      203.81.29.137     TCP      14189 > http [FIN, ACK] Seq=1504 Ack=235576 Win=257760 Len=0
    472 4.380312    192.168.1.61      203.81.29.137     TCP      14192 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    474 4.389778    203.81.29.137     192.168.1.61      TCP      http > 14189 [FIN, ACK] Seq=235576 Ack=1505 Win=17280 Len=0
    476 4.413220    203.81.29.137     192.168.1.61      TCP      http > 14192 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    522 5.078068    192.168.1.61      203.81.29.137     TCP      14192 > http [FIN, ACK] Seq=409 Ack=35882 Win=257760 Len=0
524 5.115099    203.81.29.137     192.168.1.61      TCP      http > 14192 [FIN, ACK] Seq=35882 Ack=410 Win=16872 Len=0

In this case, the cache plays a role, and data packets are greatly reduced compared to the third case, which is almost equal to the data volume (449 data packets) on the homepage once ), you only need to download the complete page (including resource files) when you open the page for the first time. You only need to download the HTML page (excluding resource files) when you open the page for the next three times ).

5.Select adef

After selecting F, let's look at the result: a total of 942 data packets are obtained, 4 are established, and 4 are disconnected.

No.     Time        Source            Destination       Protocol Info
      1 0.000000    192.168.1.61      203.81.29.137     TCP      14292 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      2 0.034524    203.81.29.137     192.168.1.61      TCP      http > 14292 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
      6 0.102314    192.168.1.61      203.81.29.137     TCP      14294 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
      9 0.139752    203.81.29.137     192.168.1.61      TCP      http > 14294 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    426 3.791111    192.168.1.61      203.81.29.137     TCP      14294 > http [FIN, ACK] Seq=1852 Ack=150284 Win=257484 Len=0
    428 3.824970    203.81.29.137     192.168.1.61      TCP      http > 14294 [FIN, ACK] Seq=150284 Ack=1853 Win=16998 Len=0
    468 6.213276    192.168.1.61      203.81.29.137     TCP      14292 > http [FIN, ACK] Seq=1504 Ack=235576 Win=257760 Len=0
    469 6.244052    192.168.1.61      203.81.29.137     TCP      14297 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    471 6.249564    203.81.29.137     192.168.1.61      TCP      http > 14292 [FIN, ACK] Seq=235576 Ack=1505 Win=17280 Len=0
    473 6.279647    203.81.29.137     192.168.1.61      TCP      http > 14297 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    479 6.374967    192.168.1.61      203.81.29.137     TCP      14298 > http [SYN] Seq=0 Len=0 MSS=1460 WS=2
    484 6.419597    203.81.29.137     192.168.1.61      TCP      http > 14298 [SYN, ACK] Seq=0 Ack=1 Win=17280 Len=0 MSS=1440 WS=0
    897 9.858493    192.168.1.61      203.81.29.137     TCP      14297 > http [FIN, ACK] Seq=1550 Ack=159770 Win=257484 Len=0
    899 9.895188    203.81.29.137     192.168.1.61      TCP      http > 14297 [FIN, ACK] Seq=159770 Ack=1551 Win=17280 Len=0
    939 12.840029   192.168.1.61      203.81.29.137     TCP      14298 > http [FIN, ACK] Seq=1806 Ack=226090 Win=257760 Len=0
    941 12.876120   203.81.29.137     192.168.1.61      TCP      http > 14298 [FIN, ACK] Seq=226090 Ack=1807 Win=17076 Len=0

In this case, because f is selected and the cache is cleared during iteration, the resource file needs to be re-downloaded for each iteration. A data packet is about half of the third case, which is about the data volume of the home page opened twice (449x2 data packets ).

　　6.About BCOption

　　C(Check for newer versions of stored pages every visit to the page)

C is easy to understand. It is similar to the check in IE settings. If C is not set, LR will not send a new request to the server for cached files. If C is selected, you can find a lot of 304 information in the data packet.

　　B(Cache URLs requiring content (htmls))

LR does not actually cache resource files in the memory or on the disk. This option indicates that the page resolution content is actually cached in the memory for some associations, verifications, and page resolutions that need to be used, reduce repetitive work on the client.

Of course, if you want to cache the GIF to the memory, you can set it in advanced, select specify URL requiring content in addition to HTML pages, add the entry image/GIF, and select. When vuseris running, you can compare the memory consumption of the mongommdrv.exe process (more memory usage ).

　　Iv. Conclusion

Through the test analysis above, we probably know the true meaning of each option. You need to select the appropriate settings based on your testing purpose:

1. for a specific application test, the front-end web server cannot be ignored. The default settings are very suitable and do not need to be adjusted (sometimes you need to consider selecting C)

Note: many users are used to storing the login operation in vuser_init when recording the script. At this time, the default setting may cause an error. We recommend that you include all these operations in the action.

2. If you are more concerned about the performance of the backend application server or do some architecture Verification and analysis, then your default settings are not suitable for you. You need to cancel all settings.

Of course, you can also make different adjustments based on your actual situation, but you must understand the specific meaning of these options to avoid making mistakes.