Apache2 - Mod_bw v0.7

Author       : Ivan Barrera A. (Bruce)

HomePage     : Http://Ivn.cl/apache & http://bwmod.sf.net

Release Date : 01-09-2005

Status       : Functional. Tested under medium and heavy load.

License      : Licensed under the Apache Software License v2.0
               It must be included as LICENSE in this package.

Platform     : Linux/x86         (Tested with Fedora Core 4, Suse, etc)
               FreeBSD/x86       (Tested on 5.2)
               MacOS X/Ppc x86   (Tested on both platforms)
               Solaris 8/sparc   (Some notes on compile)
               Microsoft Windows (Win XP, Win2003. Others should work)

Notes        : This is a stable version of mod_bw. It works fine with
               almost any MPM (tested with WinNT/prefork/Worker MPM).

Limitations  : This mod doesn't know how fast is the client really 
               downloading a file, so it just divides the bw assigned
               between the users.
               MaxConnections works only for the given scope. (i.e , all 
               will limit maxconnections from all,not per ip or user)


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Contents :

1 .- Notices
 1.1 - Summer Of Code Program
 1.2 - ChangeLog and TODO

2 .- Installing
 2.1 - Windows
 2.2 - Linux

3 .- Getting it to Work, Directives
 3.1 - BandWidthModule
 3.2 - ForceBandWidthModule
 3.3 - BandWidth
 3.4 - MinBandWidth
 3.5 - LargeFileLimit
 3.6 - BandWidthPacket
 3.7 - BandWidthError
 3.8 - MaxConnection 

4 .- Examples
 4.1 - Misc Examples

5 .- FAQ

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1.- Notices

 1.1 - Summer Of Code Program :

   Google did Summer Of Code 2005 program, to motivate the development of
  open source software. Many students around the world signed on the program
  in differents areas/projects. 
   Mine has to do with Bandwidth limiting in current Apache webserver. The 
  main idea behind the program, is to incentivate the development of quality
  open source program.
   Mod Bw, participated, and completed the program.

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 1.2 - ChangeLog & TODO :

   This has been moved to the files ChangeLog and TODO. Available on the
  packages and CVS at SourceForge.

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2.- How To Install :

 2.1 - Windows

   In Windows, you have to download the binary dll from the site (or compile
  one yourself) that matches your apache version, and Install it under modules
  on your apache tree. Then edit httpd.conf, and add the LoadModule sentence.
  If there is no matching binary dll with your version of apache (the latest)
  you can ask me to compile it for you. Post a message in the home site as a
  feature request.

  Example :

    Download mod_bw-2.0.55.dll from the home site, to c:\apache2\modules
    Edit httpd.conf, and add LoadModule bw_module modules/mod_bw-2.0.54.dll
    Restart Apache.

 2.2 - Linux

   Well.. (under *nix) you *have* to compile it..
  It might sound scary, but it's easy. There is an easy way, and the hard way.
  If the easy way doesn't work for you, use the hard way.

  REQUIREMENTS :

   You will need apache2 headers in the include path. In redhat/suse or others
  this mean apache-devel or httpd-devel installed.
   You also need support for SHM in your OS. Usually you will have this.

 - Easy Way :

   For this to work, you MUST have apxs (or apxs2) installed. You might need
  to use it full path (i.e. /usr/sbin/apxs .....). Well, you have to do this :

   apxs -i -a -c mod_bw.c
   or
   apxs2 -i -a -c mod_bw.c

   This will bring out some stuff... nothing to worry (unless you see error)
  If it says ok, then you are ready. Restart apache (service apache restart on
  redhat, mandrake, and others... apachectl restart .. rcapache2 restart or... 
  well, you should know)

  Note On Solaris Users :

   If you got problems compiling it on Solaris, remember to check you have 
  libgcc correctly installed, and the ld_library_path set up correctly. 
   I didnt, so i compiled this way :

   export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
   apxs -i -a -c mod_bw.c -L/usr/local/lib -lgcc_s
               
   And then started apache, and everything worked fine.

  Note On SuSe Users :

   You NEED to have installed apache2 header files (apache2-devel rpm).
  Otherwise you'll get lots of include files error.

 - Hard Way

   If using the easy way, you turned to have some .o files.. you are almost
  done... skip to the part of installing the module.
   Back to the hard way..... you might notice that you dont have apxs,
  dont know why (maybe the dog ate it). Well. try the following (and please
  do it on a newly-fresh created directory for this purpose) :
  (this does not necessarily work on all cases)

    libtool --silent --mode=compile gcc  -g -O2 -pthread    -DLINUX=2 \
        -D_REENTRANT -D_XOPEN_SOURCE=500 -D_BSD_SOURCE -D_SVID_SOURCE \
        -I/usr/include/httpd \
        -I/usr/include/apr-0 -Wall -g\
        -prefer-pic -c mod_bw.c && touch mod_bw.slo


    libtool --silent --mode=link gcc  -g -O2 -pthread    -DLINUX=2 \
        -D_REENTRANT -D_XOPEN_SOURCE=500 -D_BSD_SOURCE -D_SVID_SOURCE \
        -D_GNU_SOURCE -DAP_HAVE_DESIGNATED_INITIALIZER \
        -I/usr/include/httpd \
        -I/usr/include/apr-0 -Wall -g\
        -export-dynamic -o mod_bw.la  -rpath /usr/lib/httpd/modules \
        -module -avoid-version  mod_bw.lo

    (this cleans some unneeded files)
    rm -rf *.a *.la *.lo *.slo *.o *.loT
    mv .libs/*.so .
    rm -rf .libs

    Note that you need to know where are your httpd and apr includes.
    (dont ask me where they are.. you are supossed to know)
    If this worked... we are good to install the module.

   * Installing the module (hey.. this is part of the hard way)

    Ok, either if the easy way didnt install the mod, or if you did the
   hard way, now you must install the module by hand.
    Is easy as copying the file (usually mod_bw.so) to the apache
   modules directory (usually /etc/httpd/modules or 
   /usr/local/libexec/apache2/) and then adding the following line at
   httpd.conf (better of if you add it at the last part of all LoadModule
   sentences) :

    LoadModule bw_module mod_bw.so

    Please, take a look at the other LoadModule sentences. You may need
   to add a path before the .so file. 
   (i.e LoadModule bw_module libexec/apache2/mod_bw.so)



  If you didn't manage to get it installed, drop me a letter. But please
 be sure you tried everything. Sometimes the simplest way, is the better.
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3.- Getting it to Work :


  Ok.. this is the most confusing part. (yeh, most of us think the installing
 part is the hardest xD )

  This mod, is able to limit bandwidth usage on every virtual host or
 directory. htaccess files are not supported yet, cause i've been having some
 serious segfaults when implementing it.

 * Configuration Directives
 *****************************************************************************

 3.1 - BandWidthModule [On|Off]

    You need to set this to On, for the mod to work.. By default, the mod is
   disabled, and wont limit anything.

   Example :
              BandWidthModule On

 3.2 - ForceBandWidthModule [On|Off]
 
    By default, the mod wont catch every request.
    If you enable it, every request will be processed by the mod.
   
   Example :
              (normal use)
              AddOutputFilterByType MOD_BW text/html text/plain

              (enabling Force)
              ForceBandWidthModule On
 

 3.3 - BandWidth [From] [bytes/s]

    This takes 2 parameters. From is the origin of the connections. It could
   be a full host, part of a domain, an ip address, a network mask (i.e
   192.168.0.0/24 or 192.168.0.0/255.255.255.0) or all.
    The second parameter indicates the total speed available to the Origin.
    If speed is 0, there is no limit.

   Example :
            BandWidth localhost 10240
            BandWidth 192.168.218.5 0

            ( Order is relevant. First entries have precedence )

 3.4 - MinBandWidth [From] [bytes/s]

    This takes 2 parameters. From is the origin of the connections. It could
   be a full host, part of a domain, an ip address, a network mask (i.e
   192.168.0.0/24 or 192.168.0.0/255.255.255.0) or all.
    The second parameter indicates the minimun speed each client will have.
   What does this mean ? If you have a total of 100kbytes speed, and you put
   MinBandWidth at 50kbytes, it doesnt matter how many clients you have, all
   of them will have at minimun 50kbytes of total speed to download.
    If speed is 0, you will be using the default minimun (256 bytes/s).
    There is a special value of -1. This value means that each client, will
   have a top speed determined by the BandWidth directive. See the examples.

   Examples :
              BandWidth    all 102400
              MinBandWidth all 50000
 
             The example above, will have a top speed of 100kb for the 1º
            client. If more clients come, it will be splitted accordingly but
            everyone will have at least 50kb (even if you have 50 clients)

              BandWidth    all 50000
              MinBandWidth all -1

             This example, makes everyone have 50kb as top speed.

 3.5 - LargeFileLimit [Type] [Minimum Size] [bytes/s]

    Type, is the last part of a file, or * for all. You can use .tgz to match 
   only tar-compressed files, .avi to match video files, or * to match all.
    Minimum Size, is the size (in kbytes) of the file, to be matched. That way
   you can match huge video files that hog your bandwidth.
    The last parameter... is obvious. The speed allowed.

   Example :
             LargeFileLimit .avi 500 10240

             This limits .avi files over (or equal to) 500kb to 10kbytes/s

 3.6 - BandWidthPacket [Size]

    Probably you never need to touch this. It defaults to 8192 which is good
   for almost any speed.
    It must be a size between 1024 and 131072. A Small packet will cause the
   top speed to be lower, and the mod using more time splitting. If you use
   a Size too big, the mod will adjust it to lower speeds.

 3.7 - BandWidthError [Error]

    This directives is useful to deliver a personalized error code.
    At default, when maxconnections is reached, the mod will issue a 503 
   HTTP_SERVICE_UNAVAILABLE code. For some users, it is annoying to have an
   error message, and dont knowing why. You could use an ErrorDocument to 
   point error 503 to a page explaining that you are under a heavy load of
   connections, but sometimes 503 isn't issued by the mod.
    So, with this directive, you can set the error code to return when
   maxconnections is reached. You can use any error code between 300 and 599.
   Please note, that some of the error codes are already used, so before using
   any number, take a look to a list of the codes (search for http error codes
   in google). 
    When testing, i've used the error code 510, which hasn't been defined yet.

    And Example, with Personalized Error Page :

      ErrorDocument 510 /errors/maxconexceeded.html
      BandWidthError 510

    Note : Sometimes, the personalized page didn't appear. I'm not sure, but
          in many cases, it got fixed, by making the page size over 1024bytes.
           Anyways, if you need help using ErrorDocument, refer to the apache
          Documentation.
 
 3.8 - MaxConnection [From] [Max]

    This takes 2 parameters. From is the origin of the connections. It could
   be a full host, part of a domain, an ip address, a network mask (i.e
   192.168.0.0/24 or 192.168.0.0/255.255.255.0) or all.
    The second parameter, is the max connections allowed from the origin. Any
   connection over Max, will get a 503 Service Temporarily Unavailable

    There is a catch. You NEED to have a BandWidth limit for the same origin.
   It doesnt need to be a low limit. You can use an unlimited setting.
    You might wonder why. It's because im using them same memory space of the
   bandwidth limit, to count the connections, so i can save memory space.
    If you dont put a BandWidth using the same origin, MaxConnections will be
   ignored.

   Example :
              BandWidth all 0
              MaxConnection all 20
    or
              BandWidth all 0
              BandWidth 192.168.0.0/24 10240
              MaxConnection all 20
              MaxConnection 192.168.0.0/24 5


  Please, rememeber that every speed, will depend mostly on your connection.
 You cant get more speed if you dont have it.

  Remember also.. if you dont follow the instructions, and get some weird 
 results, recheck your config before sending me an email.

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4.- Examples

  4.1 - Misc examples

    Limit every user to a max of 10Kb/s on a vhost :

    <Virtualhost *>
      BandwidthModule On
      ForceBandWidthModule On
      Bandwidth all 10240
      MinBandwidth all -1
      Servername www.example.com
    </Virtualhost>


    Limit al internal users (lan) to 1000 kb/s with a minimum of 50kb/s , and 
  files greater than 500kb to 50kb/s.

    <Virtualhost *>
      BandwidthModule On
      ForceBandWidthModule On
      Bandwidth all 1024000
      MinBandwidth all 50000
      LargeFileLimit * 500 50000
      Servername www.example.com
    </Virtualhost>


    Limit avi and mpg extensions to 20kb/s.

    <Virtualhost *>
      BandwidthModule On
      ForceBandWidthModule On
      LargeFileLimit .avi 1 20000
      LargeFileLimit .mpg 1 20000
      Servername www.example.com
    </Virtualhost>


    Using it the "right" way, with output filter by mime type (for text) 
  to 5kb/s:
    
    <Virtualhost *>
      BandwidthModule On
      AddOutputFilterByType MOD_BW text/html text/plain
      Bandwidth all 5000
      Servername www.example.com 
    </Virtualhost>


    If you need help on doing more complex setup, you could post it in sf.net 
  forums.

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5.- FAQ

(No particular order)

1.- Why should i use mod_bw ?

    If you want to restrict the top speed a site is able to use, or limit the
  max connections allowed per site, or just to try the mod.
    Some people told me, they use it primarily to stop small sites hogging 
  all the bandwidth when serving video, images, or other content.

2.- How do i ... ?

    First, read the documentation. it is pretty straightforward to use.
  If you can't make it work, or if you want to ask for a feature, visit the
  home site, and post a request. Remember to read the documentation and the
  faq. If the request is already posted, i'll just delete the duplicates.

3.- What's the difference with mod_bwshare, mod_throttle, etc ?

    The main difference, is that this mod, is aimed to the Apache 2 API.
  Some other differences, is, how this mod works, and the directives it 
  implements.
    I took some ideas from other mods, as the shared memory implementation
  (mod_bandwidth2 from Tim Verhoeven). Most of the directives, are in origin
  from mod_bandiwdth for apache 1.

4.- How does it works ?

    The mod, will set a shared memory holding all of the configuration you
  make. In this space, it will also, keep a "count" of the info currently
  using (as current connections, bw used, time, and bytes sent).
    When you assign a bw limit, the mod will "split" the data, and will send
  it piece by piece, with a small delay between pieces. The delay will be
  adjusted so at least 1 piece is sent in a second, thus eviting browser
  timeout.
    If there are two or more clients downloading from the same vhost, the
  limit will be "splitted" too. So, if you have a bw limit of 16Kb and two
  clients, each one will have 8Kb to download. You can also set a fixed 
  download rate, so each client will have a fixed maximun download rate.
    This is a simple explanation of how this works. Take a look at the code
  if you want to know more about it.

5.- Can you make it do ... ? 

    Post a request for a feature in the home site. I'll respond there.

6.- Can you make mod_bw work for ... ?

    See question 5. Anyways, if i dont own (or have access) to the hardware
  needed, i won't be able to help you.

7.- I'm having some trouble in windows ... 

    I cannot support windows in an official way. I do not own a licensed copy
  of Windows, or Visual C.
    Anyways, post your problem in the home site. 

8.- The mod is not limiting certain Directory

    Ok... first, read the documentation. Then the FAQ. If it isn't working,
  then look if you have defined correctly the limits within that directory.
    If you have a limit in a vhost, and inside the vhost, a directory with
  another limit, a new context with the configs of the directory is created,
  and only have the configurations you added there. 

  In example :

  <VirtualHost *>
    BandWidthModule On
    BandWidth all 16384
    LargeFileLimit * 500 4096
    <Directory />
      LargeFileLimit * 100 1024
    </Directory>

  This wont limit Directory / to 16384. The Directory wont "inherit" the
 settings from the vhost if you use some of the mod's directives.


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 Ivan Barrera A. 
 Ivn Systems Software                                      -(Bruce@Ivn.cl)-


