Mod python
From FreeSWITCH Wiki
mod_python has been rewritten and the documentation below is pending a re-write. See migrate mod python 8998 for changes you will need to make to scripts.
Getting Started
Building mod_python
Install python-dev package
On Debian/Ubuntu:
apt-get install python2.5 python2.5-dev
Be careful not to have a previously installed version of python (like python2.4). Otherwise it will try to compile with this version, and you will need either to remove python2.4 package, or install the development header for it.
Enable compilation in modules.conf
- edit modules.conf and uncomment languages/mod_python
- make installall
Notes regarding Configure Script
The configure script will try to detect your existing python, if it cannot find it or it does not support multi-threading, it will print a warning. Otherwise, it will write a Makefile that uses the detected version.
You can specify arguments to configure to make it use a particular version (you really only need to manually specify them if the default doesn't work for you). Both args need to be given:
- --with-python (eg, --with-python=/usr/bin/python-2.5)
- --with-python-config (eg, --with-python-config=/usr/bin/python-config-2.5)
NOTE: if you use custom locations you have to make sure python and python-config are from the same version
NOTE #2: As of svn revision 8455 / 1.0_rc6 --with-python-config has been removed!
NOTE #3 - Make current auto fixes the makefile in case it doesn't get generated (correctly, or at all). make python-reconf to regenerate it.
Enabling mod_python
Open up conf/autoload_configs/modules.conf.xml and add an entry
<load module="mod_python"/>
PYTHONPATH
There are two different ways to tell the python interpreter how to find python modules. If you don't do either of these, the embedded python interpreter will have no way to find your python scripts.
Assuming you have
<action application="python" data="foo.bar"/>
This is telling python to load the bar module that lives in the foo package.
Copy or Symlink to site-packages directory
If the source file is in /usr/src/foo/bar.py:
cd /path/to/python/site-packages ln -s /usr/src/foo .
The same can be done via copying. Don't forget, the foo package directory will need an __init__.py.
Adding to PYTHONPATH environment variable
If the file is in /usr/src/foo/bar.py, add the following to your system environment startup
export PYTHONPATH=$PYTHONPATH:/usr/src
Don't forget, the foo package directory will need an __init__.py.
In the shell where freeswitch is started, this environment variable will need to be defined.
Invoking mod_python applications
To call a Python application from dialplan, you should probably be familiar with the Dialplan. You simply call it as an application similar to:
<action application="python" data="foo.bar"/>
The module is bar, in the foo package. See the Finding python modules section to tell the embedded python interpreter how to find this module.
If your module (say, test.py) is not in any package directory, then you would instead use:
<action application="python" data="test"/>
In both cases, you need to leave off the .py file extension otherwise it will not work. It expects a fully qualified module name only.
You would put this in your 'dialplan' if using the XML dialplan module with freeswitch. Don't forget your 'condition' tags and all that goodness.
Its posible to call python script from CLI with following format:
freeswitch> python foo.bar
NOTE: if you invoke it this way, your python handler() function will be called with no arguments.
Python module specification
Your python module must define a function called handler that takes two arguments:
- session
- args
Eg, def handler(session, args).
The session is the main interface to freeswitch, which wraps a freeswitch session, and the args are any args passed to the handler script.
API
Supports the same API as Mod_lua
Sample Python Scripts
Hello World via call
In the case that an extension has been mapped to the python module in the dialplan, here is what bar.py should look like:
import os
from freeswitch import *
# HANGUP HOOK
#
# session is a session object
# what is "hangup" or "transfer"
# if you pass an extra arg to setInputCallback then append 'arg' to get that value
#
# WARNING: known bugs with hangup hooks, use with extreme caution
def hangup_hook(session, what):
consoleLog("info","hangup hook for %s!!\n\n" % what)
return
# INPUT CALLBACK
#
# session is a session object
# what is "dtmf" or "event"
# obj is a dtmf object or an event object depending on the 'what' var.
# if you pass an extra arg to setInputCallback then append 'arg' to get that value
# def input_callback(session, what, obj, arg):
def input_callback(session, what, obj):
if (what == "dtmf"):
consoleLog("info", what + " " + obj.digit + "\n")
else:
consoleLog("info", what + " " + obj.serialize() + "\n")
return "pause"
# APPLICATION
#
# default name for apps is "handler" it can be overridden with <modname>::<function>
# session is a session object
# args is all the args passed after the module name
def handler(session, args):
session.answer()
session.setHangupHook(hangup_hook)
session.setInputCallback(input_callback)
session.execute("playback", session.getVariable("hold_music"))
EDIT: Notice the input_callback will never be called even if you press digit during the music on hold. Because playback return only at call end. If you want to catch DTMF, use session.streamFile(session.getVariable("hold_music")) for example. Took me a few hour to understand that. Hope it help.
Hello World via cmd line
Hello World - Dialplan API
<action application="set"
data="foo=${python(my_script)}"/>
So foo channel variable is set to the output of the my_script python script.
The script will be called with a magic object called "stream" which has the method write, and the anything written to this method will be the script's output. So for example
def fsapi(session, stream, env, args):
stream.write("hello")
will cause the foo variable to be set to "hello".
Run something in a thread using API
Usage of the API in Python is conceptually identical to usage in other supported languages.
The example scripts below employ the API, along with the 'runtime' function described in python_example.py to run a job in a thread.
This approach provides a means of implementing non-blocking code without employing mod_event_socket and may be suitable/useful for cleanup or post-processing.
This example includes two modules. The first module is a virtual copy of the default example script with a couple of notable differences.
import os
from freeswitch import *
# WARNING: known bugs with hangup hooks, use with extreme caution
def hangup_hook(session, what):
consoleLog("info","hangup hook for %s!!\n\n" % what)
return
def input_callback(session, what, obj):
if (what == "dtmf"):
consoleLog("info", what + " " + obj.digit + "\n")
else:
consoleLog("info", what + " " + obj.serialize() + "\n")
return "pause"
def handler(session, args):
session.answer()
session.setHangupHook(hangup_hook)
session.setInputCallback(input_callback)
session.streamFile("/my/test/audio.wav")
session.hangup() #hangup the call
#Now run another python script in a thread. If we
# don't do it this way all subsequent work will block
# the hangup message from being sent to the client
new_api_obj = API()
new_api_obj.executeString( \
"pyrun foo.postprocessing " + \
session.getVariable('caller_id_number') )
The second module, "postprocessing", handles our post-processing needs and for convenience resides in the same package, "foo":
import os, sys, time
from freeswitch import *
# everything after the command (in this case pyrun) and
# the module name (in this case foo.postprocessing) will
# be interpreted as a string and handed to our 'runtime'
# function where it will be accessible via the argument 'arg1'
def runtime(arg1):
time.sleep(10) #this is just to test that we are actually
# running in a separate thread.
consoleLog( "info", "Caller: %s hung up 10s ago!\n" % arg1 )
When running the above example, the client should receive a hangup immediately after streamFile returns. 10 seconds later the "Caller: xxxx hung up 10s ago!" message should be printed to the console.
More samples
Fetch Effective Caller Name from CSV file using Python
The purpose of this script is simply to associate foreign caller-id without caller_id_name to a static caller_id_name using a csv file, and at the same time it shows how to work with Python and CSV files inside FreeSWITCH
First you must add something like that to the generic dialplan for your local extensions (personally i use Local_Extension in dialplan/default.xml:
<action application="set" data="caller=${caller_id_number}"/>
<action application="python" data="setCallerName"/>
It's pretty self-explanatory, it create a variable which will be used in the python script that we call on the second line. setCallerName is the name of your script in ${FS_ROOT}/scripts/
Here the code in ${FS_ROOT}/scripts/setCallerName.py :
import csv
from freeswitch import *
def handler(session,args):
caller = session.getVariable("caller") # We use the variable we set previously in our Dialplan
csv_reader = csv.reader(open("<filepath>","rb")) # <filepath> must be replace with the path of the .csv file (watch out for relative path, if not sure use full path ie. /opt/freeswitch/file.csv)
portfolio_list = []
portfolio_list.extend(csv_reader)
for data in portfolio_list:
if (data[0] == caller): # We compare first column to the variable
session.execute("set","effective_caller_id_name="+data[1]) # If equal, then set the session variable to second column
The CSV should look something like this :
"7001","Remote User" "7002","Remote User2"
FAQ
Does each script spawn a python interpreter?
No. A single python interpreter is spawned at module startup and used for the lifetime of the freeswitch process.
Are there thread safety issues?
Each thread swaps in its "thread state" before executing python code and then swaps it out when finished. Also during blocking calls into freeswitch, a thread will swap out its thread state in order to not block other threads, and then swap it in after the blocking call to freeswitch has finished.
I changed a module I'm importing, and nothing happened
Answer: assume you are importing a module called baz, change your entry point module to:
import baz reload(baz)
How do I pass arguments to the script?
This is possible using channel variables. In the dialplan:
<extension name="foo">
<condition field="destination_number" expression="^123$">
<action application="set" data="foo=bar"/>
<action application="python" data="mypackage.myscript"/>
</condition>
</extension>
and in the python script:
foo = session.getVariable("foo")
console_log("info", "\n\\n foo: %s\n\n" % foo)
Can I test scripts using python shell?
No, it will fail as follows when you try to import the python module:
>>> from freeswitch import *
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "/usr/lib/python2.4/site-packages/freeswitch.py", line 7, in ?
import _freeswitch
ImportError: No module named _freeswitch
Can it serve configuration (like Lua)?
Yes, this has been added but not documented. The default hook for serving a config is xml_fetch as stated in the python_example.py script. However, the interpreter complains with a 'takes exactly 1 argument (2 given)' message if xml_fetch is defined to accept only one param. Altering the definition to accept 2 params solves the problem. However, consoleLog invariably shows param2 to contain nothing...
from freeswitch import *
def xml_fetch( param1, param2 ):
xml = '''
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<document type="freeswitch/xml">
<section name="dialplan" description="RE Dial Plan For FreeSWITCH">
<context name="default">
<extension name="generated">
<condition field="destination_number" expression="^9992$">>
<action application="answer"/>
<action application="playback" data="${hold_music}"/>
</condition>
</extension>
</context>
</section>
</document>
'''
return xml
and you will need to create/edit a python.conf.xml to be something like:
<configuration name="python.conf" description="Python Configuration">
<settings>
<param name="xml-handler-script" value="mypackage.mymodule"/>
<param name="xml-handler-bindings" value="dialplan"/>
</settings>
</configuration>
Gotchas
String Substitution in Functions
The session function recordFile cannot contain anything but strings in the <filename> parameter. Attempting to use sql rows or other tuples as part of a string substitution will give you a
NotImplementedError: Wrong number of arguments for overloaded function 'CoreSession_recordFile'.
For example
record_file = row[0] + '-' + row[1] + '.wav' session.recordFile(record_file,120,500,2)
will throw the error mentioned above even though when printing the variable record_file will result in the expected value. Instead the values row[0] and row[1] need to be wrapped in the str() function when assigning a value to record_file.
first_name = str(row[0]) last_name = str(row[1]) record_file = first_name + '-' + last_name + '.wav' session.recordFile(record_file,120,500,2)
should give proper behavior.
Troubleshooting
Script fails but I don't see a stack trace
Are you connecting to freeswitch via fs_cli? If so, that is probably why you don't see the stack trace. The stack trace (unfortunately) only shows up when you are on the actual freeswitch console, not when you are connected via sockets as is done with fs_cli.
Error:TypeError: CoreSession_playAndGetDigits() takes exactly 9 arguments (10 given)
You need to update your scripts for this change
Cannot import FreeSWITCH
Copy freeswitch.py from the python directory installed by freeswitch to /usr/lib/python2.5/site-packages
NOTE: if you are getting this error trying to test on the python shell .. you will never get past it. The only way to test python IVR scripts is to define the script in the dialplan and call the number. There is no way to currently do any testing with mod_python scripts outside the context of an IVR running in freeswitch.
Cannot import time
This indicates a problem where lib-dynload is pointing to the wrong place. Try printing out "sys.path" from your python script and look for a situation where you have /opt/freeswitch-trunk/lib/python2.5/site-packages and /usr/lib/python2.5/lib-dynload but not /opt/freeswitch-trunk/lib/python2.5/lib-dynload
Workaround
Change your $PATH environment variable so it sees the python installed by freeswitch before the system python, eg, PATH=/opt/fs/bin:$PATH. More info
Workaround #2
You can try modifying the Makefile so that it uses the python already on your system.
CoreSession_setDTMFCallback() takes exactly 4 arguments ..
If you see:
TypeError: CoreSession_setDTMFCallback() takes exactly 4 arguments (2 given)
Indicates you are running an older release and need to update if you want this to work.
Message: 'module' object has no attribute 'EventConsumer_node_set'
If you see:
Message: 'module' object has no attribute 'EventConsumer_node_set'
You upgraded your freeswitch but obviously you forgot to update freeswitch.py within the /usr/lib/pythonX.Y/site-packages/ (X and Y are the python's version)
CoreSession_streamfile() takes exactly 3 arguments (4 given)
If you see
TypeError: CoreSession_streamfile() takes exactly 3 arguments (4 given)
it could mean that you are trying to use a dtmf callback that is a bound method of an object -- don't do that! The dtmf callback function should always be at the module scope and not take ("self") as an argument.
Error calling DTMF callback - wrong # of arguments
You may be trying to use a bound instance method to a class. (eg, takes self as first argument). This will not work. Instead what you can do is to have a nested method for your dtmf handler that can access instance's self name.
'console_log', argument 2 of type 'char *'
If you see error messages:
TypeError: in method 'console_log', argument 2 of type 'char *'
You just need to call str() on the variable before passing to console_log, which cannot deal with Unicode strings at the present time.
Channels are not being cleaned up
This should not happen, if it does please report a bug with detailed instructions on how to reproduce. This has surfaced and been fixed a few times.
Avoid module-level global variables
If you find yourself using the globals keyword -- redesign your script. Concurrent calls will also be looking at the same variables, and things might not work as you expected. (These aren't "thread safety" issues, per se, since the Python GIL insures only one thread can run python code at any given time, but just be aware that multiple threads can see/access these variables).
Build error: Python.h: No such file or directory
If you see
In file included from freeswitch_python.cpp:3: freeswitch_python.h:5:20: error: Python.h: No such file or directory
You need to install the python-dev package. You should also double-check the src/mod/languages/mod_python/Makefile to make sure it's using the version of python you are expecting. If not you can edit the Makefile manually.
Build error: /usr/bin/ld: cannot find -lpython2.5
This can happen due to missing symlinks. Try running "locate libpython", here is some example output:
# locate libpython /usr/lib/libpython2.4.so /usr/lib/libpython2.4.so.1 /usr/lib/libpython2.4.so.1.0 /usr/lib/libpython2.5.so.1 /usr/lib/libpython2.5.so.1.0 /usr/lib/python2.4/config/libpython2.4.a /usr/lib/python2.4/config/libpython2.4-pic.a /usr/lib/python2.4/config/libpython2.4.so /usr/lib/python2.5/config/libpython2.5.a
Note that there is no libpython2.5.so -> libpython2.5.so.1 symlink. in /usr/lib or /usr/lib/python2.4/config/
ImportError: /../datetime.so: undefined symbol: PyExc_IOError
This error and the Py_ZeroStruct error (below) have been resolved as of subversion revision 11560. A build from the most recent code should resolve the problem.
If you see something like this on your freeswitch console:
freeswitch Traceback (most recent call last):
File "/path/to/myscript.py", line 5, in module
import datetime
ImportError: /usr/lib/python2.5/lib-dynload/datetime.so: undefined symbol: PyExc_IOError
FreeSWITCH does not use global name space in their shared objects. This has
a side effect on modules who in turn try to load it's own shared objects
because they too inherit the non-global namespace param.
Solution:
Add an attribute to the modues.conf to ask it to load with global name space
<load module="mod_foo" global="true"/>
Workaround:
This will also fix the problem, but is not the recommended approach.
export LD_PRELOAD=/usr/lib/libpython2.5.so ./freeswitch
Dev Note:
mod_python should be modified to add the param SMODF_GLOBAL_SYMBOLS to the SWITCH_MODULE_DEFINITION macro (See mod_cepstral at the top). Also, try changing the module definition to use global symbols the same way it is done in mod_lua, see if that resolves the issue.
ImportError: /usr/lib/../datetime.so: undefinedsymbol: _Py_ZeroStruct
This error, and the PyExec_IOError have been fixed as of revision 11560 in subversion. A build from the latest code should resolve this problem.
Known Bugs
Hangup hook + SQLAlchemy crashes switch
It's not clear if it only happens in conjunction with SQLAlchemy, but removing the hangup hook definitely fixed the problem. Hangup hooks are buggy, please avoid or use with extreme caution.
Makefile deploys to /usr/lib/python2.4/site-packages even if python 2.5
The configure script detects the latest python version installed on the system and generates the Makefile accordingly. However if it detects 2.5 it still tries to deploy the freeswitch.py to /usr/lib/python2.4/site-packages.
read() function might have problems
See mailing list thread. The bug caused concurrent calls to block eachother when calling the read() function.
Fixed in svn 12958
Description of fix: the first call to read() called a blocking freeswitch API call without releasing the GIL by calling begin_allow_threads(), and so basically everything else in the python VM is just blocked after that since it cannot not get the GIL. The fix was to add a call to begin_allow_threads() before calling the freeswitch API call, and its counterpart end_allow_threads() after the API call.
FIXED: Django database connections are not cleaned up
When using Django with mod_python, database connections are left open and will accumulate.
UPDATE: Fixed in revision 8193
NEEDS RETESTING: python IVR's that execute nested python applications crash
See old mod python for details, not retested after re-write
NEEDS RETESTING:transferring to an extension that runs a python IVR hangs
See old mod python for details, not retested after re-write
NEEDS RETESTING:Using originate() and bridge() results in the audio only flowing one direction
See old mod python for details, not retested after re-write
NEEDS RETESTING:Strange errors on shutdown
See old mod python for details, not retested after re-write
NEEDS RETESTING:Unloading and reloading the module does not seem to work
See Also
Check mod python dev for more info.
