Skip to main content

capacity - Apache: "Server seems busy", but lots of idle processes



I should note that I'm not a sysadmin. You'll figure that out very shortly. :)



In a nutshell: Apache keeps taking a breather during heavy loads and all processes go idle. This is a polling server that is used by applications. The polls come from a lot of different endpoints. From time to time (every 4-5 minutes) if I'm watching top, HTTPD processes go idle all at the same time, stalling traffic for 10 seconds or so. It then recovers. The delay is problematic.





  • Server is serving a lot of traffic. These are application polls via HTTPS, not web pages (though I doubt Apache knows the difference)

  • The pauses noted above cause the traffic to become lopsided: after some time, I get a WHOLE BUNCH OF TRAFFIC, then a lull, then a WHOLE BUNCH OF TRAFFIC again

  • Each poll requires a small database dip



Apache logs



Sometimes, but not always (mostly after a restart), I get these messages in error_log. Most of the time when it happens, I see nothing in the error_log.





[Mon Jun 30 17:55:17 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 8 children, there are 31 idle, and 98 total children
[Mon Jun 30 17:55:18 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 16 children, there are 14 idle, and 98 total children
[Mon Jun 30 17:55:44 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 8 children, there are 74 idle, and 99 total children
[Mon Jun 30 17:55:54 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 8 children, there are 61 idle, and 99 total children
[Mon Jun 30 17:56:00 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 8 children, there are 0 idle, and 97 total children
[Mon Jun 30 17:56:02 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 16 children, there are 36 idle, and 99 total children
[Mon Jun 30 17:56:03 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 32 children, there are 39 idle, and 99 total children
[Mon Jun 30 18:08:17 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 8 children, there are 18 idle, and 99 total children
[Mon Jun 30 18:08:18 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 16 children, there are 63 idle, and 98 total children
[Mon Jun 30 18:08:19 2014] [info] server seems busy, (you may need to increase StartServers, or Min/MaxSpareServers), spawning 32 children, there are 74 idle, and 97 total children



Apache Config (old config commented out)



just showing config items that I suspect are relevant




#Timeout 60
Timeout 20
KeepAlive on

MaxKeepAliveRequests 1000
KeepAliveTimeout 2

IfModule prefork.c
        StartServers            85
        MinSpareServers         85
        MaxSpareServers         100
        ServerLimit             100
        MaxClients              100
        #StartServers       60

        #MinSpareServers    60
        #MaxSpareServers    85
        #ServerLimit        85
        #MaxClients         85
        MaxRequestsPerChild 1000
/IfModule



Note that there's no difference between old and new configs in behavior.




Environment
EC2, c1.medium, mod_perl, persistent database connections, separate RDS server, no errors showing in MySQL error logs and no errors showing in Apache logs



As an aside, I've seen suggestions to install mod-status, but i haven't figured out how to do so, and I don't know what to look for if I do.


Answer



Mystery solved.



In case this happens to anyone else:
The network connection (inside VPC via LAN interface) between Apache and database server was getting congested. Upgrading the database server to a larger instance solved the problem (for the time being).




Background: Amazon takes snapshots of your database every 5 minutes for its point-in-time restore feature. It downloads the binary log on your RDS instance to do so.



Every 5 minutes, the binary log gets transmitted (presumably to another EBS), and in my case that transmission congested the LAN interface. Apache stalls while it waited for the network connection every five minutes, and connections would pile up, with some ultimately aborting.


Comments

Post a Comment

Popular posts from this blog

iLO 3 Firmware Update (HP Proliant DL380 G7)

The iLO web interface allows me to upload a .bin file ( Obtain the firmware image (.bin) file from the Online ROM Flash Component for HP Integrated Lights-Out. ) The iLO web interface redirects me to a page in the HP support website ( http://www.hp.com/go/iLO ) where I am supposed to find this .bin firmware, but no luck for me. The support website is a mess and very slow, badly categorized and generally unusable. Where can I find this .bin file? The only related link I am able to find asks me about my server operating system (what does this have to do with the iLO?!) and lets me download an .iso with no .bin file And also a related question: what is the latest iLO 3 version? (for Proliant DL380 G7, not sure if the iLO is tied to the server model)
Post a Comment
Read more

linux - Awstats - outputting stats for merged Access_logs only producing stats for one server's log

I've been attempting this for two weeks and I've accessed countless number of sites on this issue and it seems there is something I'm not getting here and I'm at a lost. I manged to figure out how to merge logs from two servers together. (Taking care to only merge the matching domains together) The logs from the first server span from 15 Dec 2012 to 8 April 2014 The logs from the second server span from 2 Mar 2014 to 9 April 2014 I was able to successfully merge them using the logresolvemerge.pl script simply enermerating each log and > out_putting_it_to_file Looking at the two logs from each server the format seems exactly the same. The problem I'm having is producing the stats page for the logs. The command I've boiled it down to is /usr/share/awstats/tools/awstats_buildstaticpages.pl -configdir=/home/User/Documents/conf/ -config=example.com awstatsprog=/usr/share/awstats/wwwroot/cgi-bin/awstats.pl dir=/home/User/Documents/parced -month=all -year=all...
Post a Comment
Read more

linux - How can I get my mediawiki to stop thinking I have cookies disabled?

I've searched half a day for how to resolve this issue, and can't figure it out. Shortly after I made my wiki a simple private wiki according to the instructions at Mediawiki's website, it started giving me this weird login error message: Wiki uses cookies to log in users. You have cookies disabled. Please enable them and try again. If I remove those private wiki settings, the error disappears, even if I try logging in. But I need it to be a private wiki for only my team. So what do I do? Here's what I've done so far. Just to be safe, after ever change, I try rebooting Apache using: sudo /etc/init.d/apache2 restart In my php.ini file, I have the following set: session.save_path = "/var/lib/php5" session.cookie_secure = secure session.cookie_path = /tmp session.cookie_domain = my server's internal URL (should I even set this? this field was blank before, but not commented out) session.referer_check = Off I ran the following to ensure that the fold...
Post a Comment
Read more