Mod_bandwidth documentation

ftp://ftp.cohprog.com/pub/apache/module/1.3.0/mod_bandwidth.c

 

Installation :

WARNING: It is very important to give the lowest priority to mod_bandwidth so other modules will have the time to do their job before the documents are transmited ! For that reason, it is important to follow those steps :

1. APACI installation
   
   • Copy the file mod_bandwidth.c to your Apache source directory.
     
   • Run the ./configure script with the following directives : --add-module=mod_bandwidth.c /
     --permute-module=BEGIN:bandwidth
     
   • Compile and install Apache.

   APXS installation
   
   • Compile the module with :
     /path_to_apache/bin/apxs -c /path/mod_bandwidth.c -o /path_to_apache/libexec/mod_bandwidth.so
     
   • Add the following lines to your httpd.conf file :
     LoadModule bandwidth_module libexec/mod_bandwidth.so
     AddModule mod_bandwidth.c

     Those directives should be placed at the begining of the list so that the module will be given the lowest priority and be executed after others modules.

   Manual installation
   
   • Copy the file mod_bandwidth.c to the "src/modules/extra" directory of your Apache sources.
     
   • Copy the "src/Configuration.tmpl" file to "src/Configuration"
     
   • Edit the "src/Configuration" file and add near the begining :
     AddModule modules/extra/mod_bandwidth.o
     (This is the reverse of old Apache versions)
     
   • Run the "./Configure" script
     
   • Compile and install Apache

2. Create the needed directories and make sure that they are "read/write/execute" for the user under which Apache run. By default, mod_bandwidth use the following directories but they can be changed using the BandWidthDataDir configuration directive:

   /tmp/apachebw
   /tmp/apachebw/link
   /tmp/apachebw/master

   Note that if any of those directories doesn't exist, or if they can't be accessed by the server, the module is totaly disabled except for logging an error message in the logfile.

   Be careful that on some systems the content of the /tmp directory is deleted at boot time or every so often by a cronjob. If that the case, either disable this feature or change the location of the directories used by the module using the BandWidthDataDir configuration directive.

Global configuration directives :

• BandWidthDataDir
  Syntax : BandWidthDataDir <directory>
  Default : "/tmp/apachebw"
  Context : server config

  Sets the name of the root directory used by mod_bandwidth to store its internal temporary information. Don't forget to create the needed directories : <directory>/master and <directory>/link

• BandWidthModule
  Syntax : BandWidthModule <On|Off>
  Default : Off
  Context : per server config

  Enable or disable totaly the whole module. By default, the module is disable so it is safe to compile it in the server anyway.

  PLEASE, NOTE THAT IF YOU SET A BANDWIDTH LIMIT INSIDE A VIRTUALHOST BLOCK, YOU ALSO __NEED__ TO PUT THE "BandWidthModule On" DIRECTIVE INSIDE THAT VIRTUALHOST BLOCK !

  IF YOU SET BANDWIDTH LIMITS INSIDE DIRECTORY BLOCKS (OUTSIDE OF ANY VIRTUALHOST BLOCK), YOU ONLY NEED TO PUT THE "BandWidthModule On" DIRECTIVE ONCE, OUTSIDE OF ANY VIRTUALHOST OR DIRECTORY BLOCK.

• BandWidthPulse
  Syntax : BandWidthPulse <microseconds>
  Default :
  Context : per server config

  Change the algorithm used to calculate bandwidth and transmit data. In normal mode (old mode), the module try to transmit data in packets of 1KB. That mean that if the bandwidth available is of 512B, the module will transmit 1KB, wait 2 seconds, transmit another 1KB and so one.

  Seting a value with "BandWidthPulse", will change the algorithm so that the server will always wait the same amount of time between sending packets but the size of the packets will change. The value is in microseconds. For example, if you set "BandWidthPulse 1000000" (1 sec) and the bandwidth available is of 512B, the sever will transmit 512B, wait 1 second, transmit 512B and so on.

  The advantage is a smother flow of data. The disadvantage is a bigger overhead of data transmited for packet header. Setting too small a value (bellow 1/5 of a sec) is not realy useful and will put more load on the system and generate more traffic for packet header.

  Note also that the operating system may do some buffering on it's own and so defeat the purpose of setting small values.

  This may be very useful on especialy crowded network connection : In normal mode, several seconds may happen between the sending of a full packet. This may lead to timeout or people may believe that the connection is hanging. Seting a value of 1000000 (1 sec) would guarantee that some data are sent every seconds...

Directory / VirtualServer configuration directives

• BandWidth
  Syntax : BandWidth <domain|ip|all> <rate>
  Default : none
  Context : per directory, .htaccess

  Limit the bandwidth for files in this directory and sub-directories based on the remote host <domain> or <ip> address or for <all> remote hosts.

  Ip addresses may now be specified in the network/mask format. (Ie: 192.168.0.0/21 )

  The <rate> is in Bytes/second. A <rate> of "0" means no bandwidth limit.

  Several BandWidth limits can be set for the same directory to set different limits for different hosts. In this case, the order of the "BandWidth" keywords is important as the module will take the first entry which matches the client address.

  Example :
  <Directory /home/www>
  BandWidth ecp.fr 0
  BandWidth 138.195 0
  BandWidth all 1024
  </Directory>

  This will limit the bandwith for directory /home/www and all it's subdirectories to 1024Bytes/sec, except for .ecp.fr or 138.195..where no limit is set.

• LargeFileLimit
  Syntax : LargeFileLimit <filesize> <rate>
  Default : none
  Context : per directory, .htaccess

  Set a maximal <rate> (in bytes/sec) to use when transfering a file of <filesize> KBytes or more.

  Several "LargeFileLimit" can be set for various files sizes to create range. The rate used for a given file size will be the one of the matching range.

  A <rate> of "0" mean that there isn't any limit based on the size.

  A <rate> of "-1" mean that there isn't any limit for that type of file. It's override even a BandWidth limit. I found this usefull to give priority to very small files (html pages, very small pictures) while seting limits for larger files... (users with their video files can go to hell ! :)

  Example :
  If the following limits are set :
  LargeFileLimit 200 3072
  LargeFileLimit 1024 2048

  That's mean that a file of less than 200KBytes won't be limited based on his size. A file with a size between 200KBytes (included) and 1023Kbytes (included) will be limited to 3072Bytes/sec and a file of 1024Kbytes or more will be limited to 2048Bytes/sec.

• MaxConnection
  Syntax : MaxConnection <connections>
  Default : 0 (illimited)
  Context : per directory, .htaccess

  Restrict the number of maximum simultanous connections. If the limit is reached, new connections will be rejected. A value of 0 mean that there isn't any limits.

• MinBandWidth
  Syntax : MinBandWidth <domain|ip|all> <rate>
  Default : all 256
  Context : per directory, .htaccess

  Set a minimal bandwidth to use for transfering data. This over-ride both BandWidth and LargeFileLimit rules as well as the calculated rate based on the number of connections.

  The first argument is used in the same way as the first argument of BandWidth.

  <rate> is in bytes per second.

  A rate of "0" explicitly means to use the default minimal value (256 Bytes/sec).

  A rate of "-1" means that the minimal rate is equal to the actual rate defined by BandWidth and LargeFileLimit. In fact, that means that the final rate won't depend of the number of connections but only on what was defined.

  Example :
  If BandWidth is set to "3072" (3KBytes/sec) and MinBandWidth is set to "1024" (1KBytes/sec) that means :
  - if there is one connection, the file will be transfered at 3072 Bytes/sec.
  - if there is two connections, each files will be transfered at 1536 Bytes/sec.
  - if there is three or more connections, each files will be transfered at 1024 Bytes/sec. (Minimal of 1024 Bytes/sec).

  If MinBandWidth is set to "-1" that means :
  - if there is one connection, the file will be transfered at 3072 Bytes/sec.
  - if there is two or more connections, each files will be transfered at 3072 Bytes/sec. In effect, the rate doesn't depend anymore on the number of connections but only on the configuration values.

  Note that the total transfer rate will never exceed your physical bandwidth limitation.

  Note : If both a "BandWidth" and a "LargeFileLimit" limit apply, the lowest one will be used. (But never lower than the "MinBandWidth" rate)

  If both a virtual server limit is defined and another apply for a directory under this virtual server, the directory limit will over-ride it.

  If a limit is defined outside a Directory or VirtualHost directive, it will act as default on a per virtual server basis. (Ie: each virtual server will have that limit, _independantly_ of the other servers)

Runing Apache with mod_bandwidth :

For correct results, it is important that there isn't any "dead" links in the "link" directory of mod_bandwidth when you start the server.

It may be a good idee to run the "cleanlink.pl" script we provide to automaticaly remove dead links