mathie's tech+business bits

If you run “pecl install [something]” and get this error: “Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate xxx bytes)”, you want to change “/usr/bin/pecl” (or run “locate pecl” to see where it is) and specify a larger memory limit.

#!/bin/sh
exec /usr/bin/php -C -n -q -d include_path=/usr/share/pear \
    -d output_buffering=1 /usr/share/pear/peclcmd.php "$@"

becomes

#!/bin/sh
exec /usr/bin/php -C -n -q -d include_path=/usr/share/pear \
    -d memory_limit=16M -d output_buffering=1 /usr/share/pear/peclcmd.php "$@"

For busy servers, ip_conntrack can fill up quickly and must be monitored or you will get intermittent packet drops. Check var/log/messages for these error messages. Couple values can be adjusted to the kernel:

more /proc/sys/net/ipv4/netfilter/ip_conntrack_count
more /proc/sys/net/ipv4/netfilter/ip_conntrack_max
=> count should be less than max, if it's near the maximum value, increase max

more /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established
=> default 5 days, might want to lower it

echo 0 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_loose

Hmm, another day, another bug: #33499. This time it is mod_deflate and PHP don’t play well together. PHP makes a GIF/JPG file and yet mod_deflate still compress it. Solution: use mod_filter (which only available from 2.1), or disable Apache’s compression for PHP files and let PHP do the compression via ob_start(‘ob_gzhandler’);

This snippet displays Active, Passive and Established connections reported by “netstat –statistics” for saving into RRD or other monitoring tools.
<br /> <?php<br /> $vResult = shell_exec("cat /proc/net/snmp|grep Tcp:");<br /> $vTmp = explode("\n",$vResult);<br /> $vTmp = $vTmp[1];<br /> $vTmp = split(" +",$vTmp);<br /> return array($vTmp[5],$vTmp[6],$vTmp[9]);<br /> ?><br />

Both run on the same server: Apache/2.0.59 (port 80) & lighttpd 1.4.19 (port 8080). 2 tests: dynamic & static files. To make things a little realistic, it’s from a EU client to a US server.

Serving a dynamic file

eu$ ab -n 1000 -c 10 “http://us.server/run-some-sql.php”

Server Software:        Apache
Server Port:            80
Document Length:        824 bytes
Time taken for tests:   36.51463 seconds
Total transferred:      1213118 bytes
HTML transferred:       847886 bytes
Requests per second:    27.74 [#/sec] (mean)
Time per request:       360.515 [ms] (mean)
Time per request:       36.051 [ms] (mean, across all concurrent requests)
Transfer rate:          32.84 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      158  158   0.3    158     162
Processing:   174  200  26.4    191     340
Waiting:      173  199  26.3    191     340
Total:        332  358  26.4    349     498

Server Software:        lighttpd/1.4.19
Server Port:            8080
Document Length:        921 bytes
Time taken for tests:   35.406200 seconds
Total transferred:      1202655 bytes
HTML transferred:       857071 bytes
Requests per second:    28.24 [#/sec] (mean)
Time per request:       354.062 [ms] (mean)
Time per request:       35.406 [ms] (mean, across all concurrent requests)
Transfer rate:          33.16 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      158  158   0.6    158     167
Processing:   172  193  29.0    183     383
Waiting:      172  192  29.0    183     383
Total:        330  351  29.1    341     541

Apache: 27.74 requests/sec

Lighttpd 28.24 requests/sec

Serving a static file

eu$ ab -n 1000 -c 10 “http://us.server/img/some-image.gif”

Server Software:        Apache
Server Port:            80
Document Length:        14781 bytes
Time taken for tests:   63.858434 seconds
Total transferred:      15060000 bytes
HTML transferred:       14781000 bytes
Requests per second:    15.66 [#/sec] (mean)
Time per request:       638.584 [ms] (mean)
Time per request:       63.858 [ms] (mean, across all concurrent requests)
Transfer rate:          230.31 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      157  158   0.5    158     164
Processing:   476  478   4.6    478     549
Waiting:      158  159   4.0    159     228
Total:        634  636   4.6    636     707

Server Software:        lighttp/1.4.19
Server Port:            8080
Document Length:        14781 bytes
Time taken for tests:   63.736261 seconds
Total transferred:      14992000 bytes
HTML transferred:       14781000 bytes
Requests per second:    15.69 [#/sec] (mean)
Time per request:       637.363 [ms] (mean)
Time per request:       63.736 [ms] (mean, across all concurrent requests)
Transfer rate:          229.70 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      157  158   0.4    158     160
Processing:   476  478   2.2    478     491
Waiting:      158  158   1.5    159     166
Total:        634  636   2.3    636     649

Apache 15.66 requests/sec

Lighttpd 15.69 requests/sec

Apache is very decent when there is a low concurrency level (about 10-20). When taken into account the stability, features, modules, it’s an excellent choice. Lighttpd under high load although can perform very well, it does suffer from an issue with PHP (current with 1.4.19 and 5.1.6), its backend fast-cgi became overloaded and gave out 500 errors to clients. Bad lighty, or bad PHP! Hope they got it fixed in 1.5 or some future version of PHP

# netstat -tan | grep ':80 ' | awk '{print $6}' | sort | uniq -c
Sample Output:

     15 CLOSING
     26 ESTABLISHED
     31 FIN_WAIT1
      7 FIN_WAIT2
     14 LAST_ACK
      2 LISTEN
     24 SYN_RECV
   2428 TIME_WAIT