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I run a webserver that I am currently having problems with. This is what starts it around once a day:

[Sun Sep 04 16:46:09 2011] [error] server reached MaxClients setting, consider raising    the MaxClients setting
[Sun Sep 04 16:46:10 2011] [error] [client 127.0.0.1] Directory index forbidden by        Options directive: /var/www/html/

Here is the apache config:

ServerTokens OS

ServerRoot "/etc/httpd"

PidFile run/httpd.pid

Timeout 120

KeepAlive Off

MaxKeepAliveRequests 100

KeepAliveTimeout 15

<IfModule prefork.c>
StartServers       1
MinSpareServers    1
MaxSpareServers    5
ServerLimit       10
MaxClients        10
MaxRequestsPerChild  4000
</IfModule>
<IfModule worker.c>
StartServers       1
MaxClients        20
MinSpareThreads    1
MaxSpareThreads    4
ThreadsPerChild     25
MaxRequestsPerChild  0
</IfModule>


Listen 80

LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule auth_digest_module modules/mod_auth_digest.so
LoadModule authn_file_module modules/mod_authn_file.so
LoadModule authn_alias_module modules/mod_authn_alias.so
LoadModule authn_anon_module modules/mod_authn_anon.so
LoadModule authn_dbm_module modules/mod_authn_dbm.so
LoadModule authn_default_module modules/mod_authn_default.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule authz_user_module modules/mod_authz_user.so
LoadModule authz_owner_module modules/mod_authz_owner.so
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
LoadModule authz_dbm_module modules/mod_authz_dbm.so
LoadModule authz_default_module modules/mod_authz_default.so
LoadModule ldap_module modules/mod_ldap.so
LoadModule authnz_ldap_module modules/mod_authnz_ldap.so
LoadModule include_module modules/mod_include.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule logio_module modules/mod_logio.so
LoadModule env_module modules/mod_env.so
LoadModule ext_filter_module modules/mod_ext_filter.so
LoadModule mime_magic_module modules/mod_mime_magic.so
LoadModule expires_module modules/mod_expires.so
LoadModule deflate_module modules/mod_deflate.so
LoadModule headers_module modules/mod_headers.so
LoadModule usertrack_module modules/mod_usertrack.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule mime_module modules/mod_mime.so
LoadModule dav_module modules/mod_dav.so
LoadModule status_module modules/mod_status.so
LoadModule autoindex_module modules/mod_autoindex.so
LoadModule info_module modules/mod_info.so
LoadModule dav_fs_module modules/mod_dav_fs.so
LoadModule vhost_alias_module modules/mod_vhost_alias.so
LoadModule negotiation_module modules/mod_negotiation.so
LoadModule dir_module modules/mod_dir.so
LoadModule actions_module modules/mod_actions.so
LoadModule speling_module modules/mod_speling.so
LoadModule userdir_module modules/mod_userdir.so
LoadModule alias_module modules/mod_alias.so
LoadModule rewrite_module modules/mod_rewrite.so
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
LoadModule proxy_ftp_module modules/mod_proxy_ftp.so
LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule proxy_connect_module modules/mod_proxy_connect.so
LoadModule cache_module modules/mod_cache.so
LoadModule suexec_module modules/mod_suexec.so
LoadModule disk_cache_module modules/mod_disk_cache.so
LoadModule file_cache_module modules/mod_file_cache.so
LoadModule mem_cache_module modules/mod_mem_cache.so
LoadModule cgi_module modules/mod_cgi.so
LoadModule version_module modules/mod_version.so

Include conf.d/*.conf

User apache
Group apache


ServerAdmin root@localhost

UseCanonicalName Off

DocumentRoot "/var/www/html"

<Directory />
    Options FollowSymLinks
    AllowOverride None
</Directory>

<Directory "/var/www/html">

    Options Indexes FollowSymLinks

    AllowOverride None

    Order allow,deny
    Allow from all

</Directory>


<IfModule mod_userdir.c>

    UserDir disable


</IfModule>


DirectoryIndex index.html index.html.var index.shtml index.cfm index.php index.htm

AccessFileName .htaccess

<Files ~ "^\.ht">
    Order allow,deny
    Deny from all
</Files>

TypesConfig /etc/mime.types

DefaultType text/plain

<IfModule mod_mime_magic.c>
    MIMEMagicFile conf/magic
</IfModule>

HostnameLookups Off

ErrorLog logs/error_log

LogLevel warn

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

CustomLog logs/access_log combined

ServerSignature On

Alias /icons/ "/var/www/icons/"

<Directory "/var/www/icons">
    Options Indexes MultiViews
    AllowOverride None
    Order allow,deny
    Allow from all
</Directory>

<IfModule mod_dav_fs.c>
    # Location of the WebDAV lock database.
    DAVLockDB /var/lib/dav/lockdb
</IfModule>

ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

<Directory "/var/www/cgi-bin">
    AllowOverride None
    Options None
    Order allow,deny
    Allow from all
</Directory>

IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable

AddIconByEncoding (CMP,/icons/compressed.gif) x-compress x-gzip

AddIconByType (TXT,/icons/text.gif) text/*
AddIconByType (IMG,/icons/image2.gif) image/*
AddIconByType (SND,/icons/sound2.gif) audio/*
AddIconByType (VID,/icons/movie.gif) video/*

AddIcon /icons/binary.gif .bin .exe
AddIcon /icons/binhex.gif .hqx
AddIcon /icons/tar.gif .tar
AddIcon /icons/world2.gif .wrl .wrl.gz .vrml .vrm .iv
AddIcon /icons/compressed.gif .Z .z .tgz .gz .zip
AddIcon /icons/a.gif .ps .ai .eps
AddIcon /icons/layout.gif .html .shtml .htm .pdf
AddIcon /icons/text.gif .txt
AddIcon /icons/c.gif .c
AddIcon /icons/p.gif .pl .py
AddIcon /icons/f.gif .for
AddIcon /icons/dvi.gif .dvi
AddIcon /icons/uuencoded.gif .uu
AddIcon /icons/script.gif .conf .sh .shar .csh .ksh .tcl
AddIcon /icons/tex.gif .tex
AddIcon /icons/bomb.gif core

AddIcon /icons/back.gif ..
AddIcon /icons/hand.right.gif README
AddIcon /icons/folder.gif ^^DIRECTORY^^
AddIcon /icons/blank.gif ^^BLANKICON^^

DefaultIcon /icons/unknown.gif


ReadmeName README.html
HeaderName HEADER.html

IndexIgnore .??* *~ *# HEADER* README* RCS CVS *,v *,t

AddLanguage ca .ca
AddLanguage cs .cz .cs
AddLanguage da .dk
AddLanguage de .de
AddLanguage el .el
AddLanguage en .en
AddLanguage eo .eo
AddLanguage es .es
AddLanguage et .et
AddLanguage fr .fr
AddLanguage he .he
AddLanguage hr .hr
AddLanguage it .it
AddLanguage ja .ja
AddLanguage ko .ko
AddLanguage ltz .ltz
AddLanguage nl .nl
AddLanguage nn .nn
AddLanguage no .no
AddLanguage pl .po
AddLanguage pt .pt
AddLanguage pt-BR .pt-br
AddLanguage ru .ru
AddLanguage sv .sv
AddLanguage zh-CN .zh-cn
AddLanguage zh-TW .zh-tw



</IfModule>
</IfModule>


BrowserMatch "Mozilla/2" nokeepalive
BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0
BrowserMatch "RealPlayer 4\.0" force-response-1.0
BrowserMatch "Java/1\.0" force-response-1.0
BrowserMatch "JDK/1\.0" force-response-1.0

BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-carefully
BrowserMatch "MS FrontPage" redirect-carefully
BrowserMatch "^WebDrive" redirect-carefully
BrowserMatch "^WebDAVFS/1.[0123]" redirect-carefully
BrowserMatch "^gnome-vfs/1.0" redirect-carefully
BrowserMatch "^XML Spy" redirect-carefully
BrowserMatch "^Dreamweaver-WebDAV-SCM1" redirect-carefully


AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
share|improve this question
    
Thank you for editing my post. I was having difficulty getting the code tags to work. –  Richardp Sep 4 '11 at 22:32
    
which is the issue, maxclients or the directory forbidden? –  Sean Kimball Sep 4 '11 at 22:54
    
The directory forbidden occurs for around half an hour whenever apache reaches it's max clients. I know how to increase the max clients. But, I am just wondering if it is causing the directory forbidden error. If so, would increasing the max clients eliminate the directory error? –  Richardp Sep 4 '11 at 23:12
    
If you are hitting the maxclients regularly enough to be a problem, you should increase it anyway, as for if it is actually causing the Directory Forbidden - sorry, I'm not sure. –  Sean Kimball Sep 4 '11 at 23:38
    
Okay, do you know how to fix the Directory Forbidden error? –  Richardp Sep 4 '11 at 23:49
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2 Answers

up vote 1 down vote accepted

It looks like the forbidden message is a side effect of reaching your MaxClients limit. Your best option is increase your MaxClients, but first you need to determine the following:

  • How much memory does each client consumes. Depending on type of site and the number of modules, it could be as much as 20 megabytes.

  • Once you determine how much memory each client has consumed, you will need to determine the total amount of memory that Apache consumes when it hit it MaxClient limits. Also, I strongly recommend that you (if you haven't already done so) start tracking the amount of memory that Apache uses throughout the day, either writing to a simple text file that you can graph in your spreadsheet or via a rrdtool (using a monitoring tool like cacti for ease of use). There is a very good chance that the forbidden message will correlate strongly with high memory usage by Apache.

    • With both pieces of information in mind, you next take a look at how much physical memory that you have available plus swap. Since you don't want to use swap if it can be helped, you would use your Physical RAM as your limit, subtract the maximum amount of memory that Apache uses at its peak, then subtract the amount of memory that your other applications use. At that point, with what is left, you would probably aside a certain amount for file buffers/emergencies/day to day operations and uses the rest for Apache. Then, you would increase your MaxClient settings.

So in this case with a MaxClient setting of 10 (and assuming that each client consumes about 10 megabytes of data), you would need at least 100 megabytes of physical RAM. If your clients uses about 100 megabytes of data and you have about 512 megabytes of RAM, you have 312 megabytes left. At that point, if you set aside about 112 megabytes, you have about 200 megabytes you can use, which means you can increase your Maxclients from 10 to 30.

  • However, if you are in the situation where you don't have enough physical RAM and it is not possible to add additional RAM anytime soon, you'll need to look into streamlining your Apache config, disabling any Apache modules that are no longer necessary. Alternatively (or concurrently), if you are running a server side application (Java/PHP/RoR), you may also need to investigate to see if the application is using more memory than necessary (intentionally or not). This will involve either rewriting the code to make it more memory efficient or patching it or the supporting libraries if it was written by a third-party. Worse case, you may need to swap to disk for the time being, which, depending on your i/o subsystem, will result in noticeable performance degradation.

So in short:

  • Measure your daily memory usage with Apache.
  • Increase MaxClient if there is available Physical memory for use.
  • Streamline Apache configs and review/update application code.

Of course, MaxClient is not the only setting you may need to change. You probably need to review your other Apache settings as well, adjusting them as necessary to support your site within the physical constraints of your server. This resource at the O'Reilly Site may be of help in this case.

share|improve this answer
    
Thank you for the perfect in depth answer. –  Richardp Sep 5 '11 at 1:06
    
Sure. I will add that you probably need to review the site link I provided. Tuning Apache can be a bit of an art, so you will probably need to start making changes to the rest of the Apache conf file before you come to an optimal configuration –  Rilindo Sep 5 '11 at 1:10
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Change this:

<Directory />
    Options FollowSymLinks
    AllowOverride None
</Directory>

to this:

<Directory />
    Options FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all
</Directory>

And then report your status.

share|improve this answer
    
It is tough to report my status. The problem occurs at random times daily and lasts for around half an hour. But, I will keep you informed. –  Richardp Sep 5 '11 at 0:19
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