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I have a CentOS 5.5 Final with Apache 2.2.3 and checking if there are some misconfigurations I settled up server-status page and querying a certain page I obtained this result:

Apache Server Status for 192.168.3.23

Server Version: Apache/2.2.3 (CentOS)
Server Built: Aug 30 2010 12:32:08

Current Time: Tuesday, 07-Aug-2012 16:27:17 CEST
Restart Time: Tuesday, 07-Aug-2012 15:35:02 CEST
Parent Server Generation: 0
Server uptime: 52 minutes 14 seconds
Total accesses: 6263 - Total Traffic: 12.2 MB
CPU Usage: u1.85 s.77 cu0 cs0 - .0836% CPU load
2 requests/sec - 4083 B/second - 2043 B/request
1 requests currently being processed, 4 idle workers

_..__W_.........................................................
................................................................
................................................................
................................................................

Scoreboard Key:
"_" Waiting for Connection, "S" Starting up, "R" Reading Request,
"W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup,
"C" Closing connection, "L" Logging, "G" Gracefully finishing,
"I" Idle cleanup of worker, "." Open slot with no current process

Srv PID     Acc         M   CPU     SS    Req   Conn    Child   Slot    Client          VHost       Request
0-0 29399   0/14/875    _   0.03    1     27    0.0     0.03    1.58    X.X.X.X         127.0.0.1   GET /messaggi_xml.php?id_srv=2381&id_dev=1233&last_event=1&i
1-0 -       0/0/908     .   0.40    43    25    0.0     0.00    1.81    X.X.X.X         127.0.0.1   GET /messaggi_xml.php?id_srv=2381&id_dev=1233&last_event=1&i
2-0 -       0/0/859     .   0.45    3     23    0.0     0.00    1.67    X.X.X.X         127.0.0.1   GET /messaggi_xml.php?id_srv=2381&id_dev=1233&last_event=1&i
3-0 29379   0/160/857   _   0.34    0     25    0.0     0.30    1.68    X.X.X.X         127.0.0.1   GET /messaggi_xml.php?id_srv=2381&id_dev=1233&last_event=1&i
4-0 29380   0/132/804   _   0.31    1     15    0.0     0.27    1.61    X.X.X.X         127.0.0.1   GET /check_realtime.php?id_srv=2381&id_dev=1233 HTTP/1.1
5-0 29383   0/116/851   W   0.24    0     0     0.0     0.27    1.68    X.X.X.X         127.0.0.1   GET /server-status HTTP/1.1
6-0 29385   0/114/751   _   0.23    0     16    0.0     0.17    1.32    X.X.X.X         127.0.0.1   GET /check_realtime.php?id_srv=2381&id_dev=1233 HTTP/1.1
7-0 -       0/0/178     .   0.26    2410  22    0.0     0.00    0.48    X.X.X.X         127.0.0.1   GET /messaggi_xml.php?id_srv=2381&id_dev=1233&last_event=1&i
8-0 -       0/0/180     .   0.36    2362  12    0.0     0.00    0.38    X.X.X.X         127.0.0.1   GET /check_realtime.php?id_srv=2381&id_dev=1233 HTTP/1.1

Since I see an open slot with no current process associated with some pages, would that mean there is misconfiguration in Apache and do you have an hint to check a possible parameter to avoid that? If you need more infos, like configurations, I can provide... Plus I have to say I don't see any errors in /var/log/messages or /var/log/httpd/error_log or /var/log/httpd/ssl_error_log and neither in /tmp/php_error_log... plus if I do ps aux I don't see those open slot listed...

Cheers, Luigi

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1 Answer 1

The open slots with no current processes are just display place holders for future threads. On lightly used systems, you won't see all of the slots being used by threads. Compare your output with this user's scoreboard. Almost all of their slots are in a waiting for connection state.

Try using one of these HTTP Benchmark tools and watch how your scoreboard changes.

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Hello skohrs... first thank you for reply.. but I would say open slots with no current processes remains hanged also for over 10000 seconds without freeing memory...and after getting plenty of them the webserver slows a lot.. in fact doing this command "netstat -an|awk '/tcp/ {print $6}'|sort|uniq -c"I see I got 228 TIME_WAITs which I don't understand why they keep hanging since I enabled in freetds.conf "timeout = 10" and "connect timeout = 10" in freetds.conf... do you have any hint I should check?.. thanks in advance. Cheers. –  Luigino Aug 8 '12 at 8:51
    
I have a better understanding now, but unfortunately I can't think of anything to recommend. I'm not familiar with FreeTDS. Good luck. –  skohrs Aug 8 '12 at 13:07

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