So, you use Asterisk professionally, for fun, or both, and you want to know how to optimize the shit out of your Asterisk platform? No problem, I've got you covered.

Grab a beer, free up the next 2 hours of your time, and let's get to it!

Why Do This?

To speed up your Asterisk platform. Asterisk is a large and complex PBX system with hundreds of features, commands, and various components. Each component that is in use adds additional overhead to your Asterisk system in the form of RAM, CPU, and sometimes disk space.

To make your Asterisk PBX perform at its best, it is useful to strip out everything you don't need, and force your Asterisk system to perform its best.

Preparation

To make this quick, you should already have a box with Asterisk up and running, ideally with some working call routing code of some sort. If you manage an Asterisk server at work, that will do just fine.

WARNING: Don't attempt this stuff live on production servers unless you really like abuse.

Approach

The approach I like to take with my Asterisk slimming, streamlining, or whatever you want to call it, is to install Asterisk initially with as many features as possible, disable everything, then selectively enable the features I need, one at a time.

This is called a 'whitelisting` approach, as you block everything by default, and then manually allow only certain features (think network security).

This method requires more effort to setup and maintain, but leads to the best possible performance.

Install Asterisk

If you are familiar with Asterisk installation, you can go ahead and skip to the next section. Good work, smart guy!

If you've never installed Asterisk before, read my guide.

If you installed Asterisk from your distro's package manager (yum, apt, etc.), then you can also skip this section.

So, I guess you installed Asterisk from source. Nice. That's the best way (but you already know that). Anyway, as I mentioned in the previous section, I like to install Asterisk with as many features enabled as possible. This way, if I ever need to get some extra functionality, I can simply enable it, and not have to completely re-install Asterisk from source.

If you aren't sure of how to selectively choose which features are installed when you are compiling Asterisk, all you have to do is run make menuselect in the Asterisk source directory (this also applies to asterisk-addons), after running ./configure, but before running make.

While installing Asterisk, you might run the following commands:

cd asterisk-latest
./configure
make menuselect
make
sudo make install

When you run make menuselect, you'll see an ncurses based GUI window, that lets you use the arrow keys, enter, and tab to navigate around and choose which components to install. You should choose as many as possible.

Figure Out Which Features You're Using

This step is important. You need to figure out what parts of Asterisk you need in order to do what you're doing before you can even think about removing unnecessary junk.

Here are some helpful tips for figuring out what parts of Asterisk you need:

  • Read this page on voip-info. It has a pretty good list of module and configuration file dependencies.

  • Look at all of your code in extensions.conf, and write down all of the application names you use. This would be stuff like Plaback, Monitor, etc.

  • Which sort of protocols does your system support? SIP? IAX? DAHDI? ZAPTEL?

  • What sort of call codecs do you support? ULAW, G729, etc.?

  • Which configuration files have you explicitly put code into? indications.conf? smdi.conf? etc.?

I suggest writing these all down somewhere. It's not critical to have all of them perfectly figured out at the start, you can always figure it out later via trial-and-error.

Get a List of All Modules

We now need to get a list of all the Asterisk modules that are currently available on your system. If you compiled Asterisk from scratch, and read my 'Installing Asterisk' section, you should have a ton.

On most linux systems, you can get a list of all your Asterisk modules by running the following command: ls /usr/lib/asterisk/modules/. This may be different for you, depending on what operating system you're using.

Disable Everything

Before enabling the modules we need, we're going to disable everything. This is part of our 'whitelisting' approach to Asterisk slimming.

To do this, open up your modules.conf file (usually located in /etc/asterisk/). Your file should look something like:

;
; Asterisk configuration file
;
; Module Loader configuration file
;
 
[modules]
autoload=yes
;
; Any modules that need to be loaded before the Asterisk core has been
; initialized (just after the logger has been initialized) can be loaded
; using 'preload'. This will frequently be needed if you wish to map all
; module configuration files into Realtime storage, since the Realtime
; driver will need to be loaded before the modules using those 
; configuration files are initialized.
;
; An example of loading ODBC support would be:
;preload => res_odbc.so
;preload => res_config_odbc.so
;
; res_phoneprov requires func_strings.so to be loaded:
preload => func_strings.so
;
; Uncomment the following if you wish to use the Speech Recognition API
;preload => res_speech.so
;
; If you want, load the GTK console right away.
;
noload => pbx_gtkconsole.so
;load => pbx_gtkconsole.so
;
load => res_musiconhold.so
;
; Load one of: chan_oss, alsa, or console (portaudio).
; By default, load chan_oss only (automatically).
;
noload => chan_alsa.so
;noload => chan_oss.so
noload => chan_console.so
;

Change the line that says autoload=yes to autoload=no. This will prevent Asterisk from automatically loading modules.

The next thing you need to do is preload any required modules. As shown in the sample config above, if you need odbc support, you should put preload => res_odbc.so directly below your autoload=yes line.

After you've gotten all the preloads finished, delete everything else in the file. Seriously. You won't need it anymore :)

Enable Only What You Need

You should still be in your modules.conf file. Now, remember before when you got a list of all the Asterisk modules available on your system (ls /usr/lib/asterisk/modules/)? Do the following:

  1. Below all of your preload lines in modules.conf, insert load => module_name.so for each module that starts with res_, ex:

    ;load => res_adsi.so
;load => res_agi.so
;load => res_clioriginate.so
;load => res_config_curl.so
;load => res_convert.so
;load => res_curl.so
;load => res_crypto.so
;load => res_indications.so
;load => res_limit.so
;load => res_monitor.so
;load => res_musiconhold.so
;load => res_phoneprov.so
;load => res_smdi.so
;load => res_timing_dahdi.so
;load => res_timing_pthread.so

    Wondering why you need to do all of the modules with 'res' first? Because these modules are special, they are 'resources'. Resource modules need to be loaded before any other modules as they often satisfy dependency issues.

  2. Now, feel free to insert load => module_name.so lines for your remaining modules that don't start with res_, ex:

    ;load => app_addon_sql_mysql.so
;load => app_adsiprog.so
;load => app_alarmreceiver.so
;load => app_amd.so
;load => app_authenticate.so
;load => app_cdr.so
;load => app_chanisavail.so
;load => app_channelredirect.so
;load => app_chanspy.so
;load => app_controlplayback.so
;load => app_dahdibarge.so
;load => app_dahdiras.so
;load => app_dahdiscan.so
;load => app_db.so
;load => app_dial.so
;load => app_dictate.so
;load => app_directed_pickup.so
;load => app_directory.so
;load => app_disa.so
;load => app_dumpchan.so
;load => app_echo.so
;load => app_exec.so
;load => app_externalivr.so
;load => app_festival.so
;load => app_flash.so
;load => app_followme.so
;load => app_forkcdr.so
;load => app_getcpeid.so
;load => app_ices.so
;load => app_image.so
;load => app_macro.so
;load => app_meetme.so
;load => app_milliwatt.so
;load => app_minivm.so
;load => app_mixmonitor.so
;load => app_morsecode.so
;load => app_mp3.so
;load => app_nbscat.so
;load => app_page.so
;load => app_parkandannounce.so
;load => app_playback.so
;load => app_privacy.so
;load => app_queue.so
;load => app_read.so
;load => app_readexten.so
;load => app_readfile.so
;load => app_record.so
;load => app_saycountpl.so
;load => app_sayunixtime.so
;load => app_senddtmf.so
;load => app_sendtext.so
;load => app_setcallerid.so
;load => app_sms.so
;load => app_softhangup.so
;load => app_speech_utils.so
;load => app_stack.so
;load => app_system.so
;load => app_talkdetect.so
;load => app_test.so
;load => app_transfer.so
;load => app_url.so
;load => app_userevent.so
;load => app_verbose.so
;load => app_voicemail.so
;load => app_waitforring.so
;load => app_waitforsilence.so
;load => app_while.so
;load => app_zapateller.so
 
;load => cdr_addon_mysql.so
 
;load => chan_agent.so
;load => chan_dahdi.so
;load => chan_iax2.so
;load => chan_local.so
;load => chan_mgcp.so
;load => chan_ooh323.so
;load => chan_oss.so
;load => chan_phone.so
;load => chan_sip.so
;load => codec_adpcm.so
;load => codec_alaw.so
;load => codec_dahdi.so
;load => codec_g726.so
;load => codec_gsm.so
;load => codec_lpc10.so
;load => codec_ulaw.so
 
;load => format_g723.so
;load => format_g726.so
;load => format_g729.so
;load => format_gsm.so
;load => format_h263.so
;load => format_h264.so
;load => format_jpeg.so
;load => format_mp3.so
;load => format_pcm.so
;load => format_sln.so
;load => format_sln16.so
;load => format_vox.so
;load => format_wav.so
;load => format_wav_gsm.so
 
;load => func_audiohookinherit.so
;load => func_base64.so
;load => func_blacklist.so
;load => func_callerid.so
;load => func_cdr.so
;load => func_channel.so
;load => func_curl.so
;load => func_cut.so
;load => func_db.so
;load => func_enum.so
;load => func_env.so
;load => func_extstate.so
;load => func_global.so
;load => func_groupcount.so
;load => func_iconv.so
;load => func_lock.so
;load => func_logic.so
;load => func_math.so
;load => func_md5.so
 
;load => func_module.so
;load => func_rand.so
;load => func_realtime.so
;load => func_sha1.so
;load => func_shell.so
;load => func_strings.so
;load => func_sysinfo.so
;load => func_timeout.so
;load => func_uri.so
;load => func_version.so
;load => func_vmcount.so
;load => func_volume.so
 
;load => pbx_config.so
;load => pbx_loopback.so
;load => pbx_spool.so

  3. Now, go through the list of modules you have in your modules.conf, and uncomment the ones that you absolutely can't live without.

I realize that the above steps aren't exactly super descriptive, so keep reading. The next section will give you some additional pointers.

Tips for Slimming

At some point during this article, you've probably thought to yourself, "How do I know which modules are absolutely essential to my setup?".

If you aren't able to figure it out, there's one foolproof way to figure it out: trial-and-error.

Don't feel bad about doing trial-and-error here either, Asterisk can be complex.

  1. Configure your logger.conf to output with maximum verbosity to the full logfile. Your logger.conf file should have a line that looks like: full => notice,warning,error,debug,verbose.

  2. Try to restart Asterisk: /etc/init.d/asterisk restart. Then check your full logfile: tail /var/log/asterisk/full, and look for lines that contain WARNING or ERROR. Asterisk provides great error messages. So if you aren't loading a necessary module, it will tell you.

  3. Load the modules you were missing, and go back to step 1.

You know you're done when you've gone through every single module on your system, and know exactly which ones you need to have enabled to make your system run.

Results

Streamlining your Asterisk installs has great benefits. Not only will your system run much faster, and more efficently than before, but you'll also know a lot more about Asterisk, how it works, and how to modify its behavior.

One of the great strengths of Asterisk is its module system, which is extremely dynamic and provides a great interface for developers to add functionality.

Got any questions? Post a comment and I'll try to help.