I have created a web app where the client polls the server every 1-2 seconds for a small bit of information. I have configured a Ubuntu 12.04 droplet with Varnish as a frontend to Apache.

Here’s a real URL that I’m serving:

http://lafayettecc.org/lcc_live/event/132/progress

You can see that it returns only a single integer

If I log into my server and run apachebench I get astounding results:

====================================== $ ab -n 200 -c 200 http://lafayettecc.org/lcc_live/event/132/progress This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/

[TRIMMED]

Document Path: /lcc_live/event/132/progress Document Length: 2 bytes

Concurrency Level: 200 Time taken for tests: 0.087 seconds Complete requests: 200 Failed requests: 0 Write errors: 0 Total transferred: 67589 bytes HTML transferred: 400 bytes Requests per second: 2289.88 [#/sec] (mean) Time per request: 87.341 [ms] (mean) Time per request: 0.437 [ms] (mean, across all concurrent requests) Transfer rate: 755.71 [Kbytes/sec] received

However, after doing some minor testing from my local machine, I am now getting this:

$ ab -n 100 -c 20 http://lafayettecc.org/lcc_live/event/132/progress This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking lafayettecc.org (be patient)…Send request failed! Send request failed! Send request failed! apr_socket_recv: Connection reset by peer (54) Total of 43 requests completed

Running it again, I get this:

$ ab -n 100 -c 20 http://lafayettecc.org/lcc_live/event/132/progress This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking lafayettecc.org (be patient)…done

Server Software: Apache/2.2.22 Server Hostname: lafayettecc.org Server Port: 80

Document Path: /lcc_live/event/132/progress Document Length: 2 bytes

Concurrency Level: 20 Time taken for tests: 0.605 seconds Complete requests: 100 Failed requests: 0 Write errors: 0 Total transferred: 33789 bytes HTML transferred: 200 bytes Requests per second: 165.39 [#/sec] (mean) Time per request: 120.928 [ms] (mean) Time per request: 6.046 [ms] (mean, across all concurrent requests) Transfer rate: 54.57 [Kbytes/sec] received

The performance is way worse, but that’s okay since I have to consider my own network lag to the droplet.

However, if I up the concurrency just to 50 I get this:

$ ab -n 100 -c 50 http://lafayettecc.org/lcc_live/event/132/progress This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking lafayettecc.org (be patient)…apr_socket_recv: Operation timed out (60)

So, is there some reason why my droplet can handle massively concurrent requests locally, but times out when they come from the network?