[ACCEPTED]-Failed requests by length in my ApacheBench load test result-apachebench

Accepted answer
Score: 20

Run ab with the -v 2 parameter, meaning verbosity 14 level 2. This will dump the response headers. If 13 your requests are not using chunked encoding, you 12 will see a "Content-Length" header indicating 11 the size of each response.

gw:~$ ab -n 1 -v 2 "http://whatever.com/"


LOG: header received:
HTTP/1.0 200 OK
Content-Length: 1568399

If your responses 10 use chunked encoding, then the length is 9 not known until the transfer ends. Usually 8 chunked encoding is only used for compressed 7 responses, and ApacheBench doesn't do compression 6 by default.

If it is compressing the responses 5 for whatever reason that might explain it; the 4 compressed length depends on the content.

You 3 can also use curl -i and the --compress option to see the 2 response headers to a single request with 1 and without compression.

Score: 4

Use tcpdump

Open qty 2 terminal/shell windows or just 8 use screen.

In the first window, use tcpdump 7 to capture transmission data from/to your 6 NIC (eth0) to a file:

sudo tcpdump -s 9999 -i eth0 -w myfile.txt

In the second window, fire 5 off your ab command:

ab -n 500 -c 200 http://domain.com/test/index.php

When that's all done, parse 4 the file with strings and grep:

strings myfile2.txt | grep -C 3 "200 OK"

You should 3 be able to monitor all the data segments 2 from there by eyeballing or grep'ing the 1 results.

Score: 3

ab assumes that all responses are the same. It 6 looks at the content-length of the first 5 response, and then compares others to that.

From 4 the man page:

Document Length
  This is the size in bytes of the first successfully returned document. 
  If the document length changes during  testing,  the  response  is 
  considered an error.

So if your first request contains 3 following data:


And the next one is:


ab will 2 fail with a Length error, since the output 1 is one character longer.

Score: 0

This is an issue with dynamic pages, it 3 happens because the Content-Length HTTP header can vary 2 between the requests. When using ab with such 1 pages you need to use the -l option.

-l              Accept variable document length (use this for dynamic pages)

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