Getting failed requests with apache benchmark on a load balanced Tornado site but none logged

Question

Perhaps this is a question about ab rather than about Tornado but something doesn't make sense.

I run the benchmark like this:

$ ab -n 100 http://localdomainname/ # 2 tornados being 1 nginx
 ...
Concurrency Level:      1
Time taken for tests:   0.162 seconds
Complete requests:      100
Failed requests:        17
   (Connect: 0, Receive: 0, Length: 17, Exceptions: 0)
Write errors:           0

So according to that 17 of 100 requests failed.

Prior to running the benchamark I reset the log files and look at them again:

$ wc -l /tmp/gkc.access.log 
100 /tmp/gkc.access.log
$ cat /tmp/gkc.access.log | grep ' 200 ' | wc -l
100

So, according to Nginx no requests failed! Why is ab saying 17 of 100 failed?

(By the way, 17 out of 100 was just one example. it goes up and down but never 0 which I'd expect)

UPDATE

Having tested with httperf without touching the Tornado+Nginx setup I get 0 failed requests.

Tried this with a simple app, couldn't reproduce - bizarrely, I get connection reset errors with httperf, but only when I hit the file descriptor limit. — Cole Maclean, Jun 08 '11 at 21:32
I can reproduce the problem with Tornado´s `Hello world` example (412 of 10,000 requests failed, using ab, no nginx or other frontend). — jholster, Sep 01 '11 at 11:10

score 14 · Answer 1 · edited May 23 '17 at 12:13

14

You get the "length" failed requests, which does not mean that the response code was not 200. It just means that the length of response across requests was different (it remembers the length of the first one).

In detail this issue has been discussed in this question: Load Testing with AB ... fake failed requests (length)

edited May 23 '17 at 12:13

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answered Nov 06 '11 at 16:41

Ivan Blinkov

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Getting failed requests with apache benchmark on a load balanced Tornado site but none logged

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