Re: [AOLSERVER] Problem with Apache Bench: 2c-1 requests

[patrick o'leary]

apache bench mark will dispatch requests up until it's received -n number of responses. e.g. with concurrency of 3 (c1, c2, c3), and -n 3 requests c1 -> send request 1 c2 -> send request 2 c3 -> send request 3 c1 <- response 1      # of responses < 3        c1 -> send request 4 c2 <- response 2     # of responses < 3        c2 -> send request 5 c3 <- response 3     # of responses > 3         wait for clients to end and report Hopefully if the above makes sense, you should see that ab will continue to dispatch requests until it gets all the necessary responses back. Since ab 1.3 it's acted like this, same sort of thing with microsoft stress tool, JMeter is probably the only thing I've found accurate enough for precision testing rather than capacity testing. HTH P Tom Jackson wrote: When I run apache bench like this: $ ab -n 3 -c 3 http://192.168.1.102:8000/bgwrite/sns-thumb.jpg I expect that it will send exactly three requests using three different connections. In fact, the summary tells me exactly that: -------------- Server Software: AOLserver/4.5.0 Server Hostname: 192.168.1.102 Server Port: 8000 Document Path: /bgwrite/sns-thumb.jpg Document Length: 28672 bytes Concurrency Level: 3 Time taken for tests: 6.21440 seconds Complete requests: 3 Failed requests: 0 Write errors: 0 Total transferred: 86658 bytes HTML transferred: 86016 bytes Requests per second: 0.50 [#/sec] (mean) Time per request: 6021.440 [ms] (mean) Time per request: 2007.147 [ms] (mean, across all concurrent requests) Transfer rate: 13.95 [Kbytes/sec] received --------------------- But last week I noticed something weird, then forgot about it. If the concurrency was 'c', I would get 'c-1' extra requests. These were logged in the defective prequeue filter in the driver thread before being queued. The access log also recorded extra hits. For instance, the above command to ab will produce exactly 5 access.log entries. I noticed this again today when I did 50 requests with concurrency=50. I got 99 requests logged, but apache bench checked out early and did the report after 50. I only noticed this because I had only one thread configured and there was a 0-5 second delay for each request. Long after the report showed up, AOLserver was chugging away logging what it was doing, and the access log did the same. So I thought either AOLserver is duplicating this stuff or Apache Bench is doing it. I guess if I had considered the fact that AOLserver has no idea what the concurrency is, it would have been obvious. I then used netstat to show if there were actually 5 connections or just three: Prior to running ab: Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 1 0 192.168.1.101:33180 207.228.252.10:80 CLOSE_WAIT tcp 0 0 127.0.0.1:9997 127.0.0.1:56705 ESTABLISHED tcp 0 0 127.0.0.1:56705 127.0.0.1:9997 ESTABLISHED tcp 0 0 192.168.1.101:45825 216.211.130.179:110 TIME_WAIT Just after running ab: Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 1 0 192.168.1.101:33180 207.228.252.10:80 CLOSE_WAIT tcp 1 0 192.168.1.102:8000 192.168.1.102:49737 CLOSE_WAIT tcp 1 0 192.168.1.102:8000 192.168.1.102:49736 CLOSE_WAIT tcp 0 0 192.168.1.102:8000 192.168.1.102:49735 TIME_WAIT tcp 0 0 192.168.1.102:8000 192.168.1.102:49734 TIME_WAIT tcp 0 0 192.168.1.102:8000 192.168.1.102:49733 TIME_WAIT tcp 0 0 192.168.1.102:49737 192.168.1.102:8000 FIN_WAIT2 tcp 0 0 192.168.1.102:49736 192.168.1.102:8000 FIN_WAIT2 tcp 0 0 192.168.1.102:49738 192.168.1.102:8000 TIME_WAIT ... The extra two are in CLOSE_WAIT, from ports 49736-7 I'm not sure what the exact significance of this is, but we are benchmarking stuff which we are not sure is working. It appears that the tool I am using is somewhat broken itself. I wonder if this analysis is correct, and if so, are there other benchmarking tools we could use? tom jackson -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to <[EMAIL PROTECTED]> with the body of "SIGNOFF AOLSERVER" in the email message. You can leave the Subject: field of your email blank. -- Patrick O'Leary You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat. - Albert Einstein View Patrick O Leary's profile -- AOLserver - http://www.aolserver.com/ To Remove yourself from this list, simply send an email to <[EMAIL PROTECTED]> with the body of "SIGNOFF AOLSERVER" in the email message. You can leave the Subject: field of your email blank.