[Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

Sirish Masur Mohan Sirish.MasurMohan at oa.com.au
Wed Jan 2 04:28:52 MSK 2013 

Hi Michael,

I have modified my implementation to use hash, as recommended. I now use a Lua script which will

*         hash selects to read the port status & previous timestamp of each port

*         decide on the port to be used based on the oldest time stamp - hash insert the status of this port to busy
On hang-up, I have another Lua script which would hash insert the status of this port back to idle, and hash insert the latest timestamp

If I were to have two or more incoming calls at the same time, and the answering Lua script were to get executed at the same time for these calls, I am still worried about the concurrency factor - wouldn't the Lua script hash select and return the same port? If yes, how do I 'protect' this script to handle concurrency?

Thanks!

With regards,
Sirish

From: freeswitch-users-bounces at lists.freeswitch.org [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Michael Collins
Sent: Saturday, 22 December 2012 4:32 AM
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

Agreed, the hash/db options are safe and effective. You don't need global variables. I highly recommend that you look at the default.xml dialplan file and look at the places where "hash" occurs. In Local_Extension a lot of items are written to the local database with hash "inserts" and elsewhere you'll see hash "selects" and the occasional hash "delete". Use the hash_dump command to see what's in the database. Make a few test calls and do a hash_dump before, during, and after the call. You'll quickly see what you can do with the hash command and storing information. Just store information for each of your ports and use a Lua script to read and/or write as needed.

-MC
On Thu, Dec 20, 2012 at 6:32 PM, Steven Ayre <steveayre at gmail.com<mailto:steveayre at gmail.com>> wrote:
If I remember correctly when when anthm added the option by request, global_setvar is NOT safe for setting concurrently. Very occasionally should be ok for config changes without a restart, but it is not safe to use from call dial plans where calls are running alongside each other.

You should look at using mod_hash or mod_db, which are much safer

Sent from my iPad

On 20 Dec 2012, at 23:23, Sirish Masur Mohan <Sirish.MasurMohan at oa.com.au<mailto:Sirish.MasurMohan at oa.com.au>> wrote:
Hi Michael,

Thanks for the reply, and the suggestions.

My current implementation is a similar to what you have suggested, i.e.:

1.       I have defined 4 sets of global variables in vars.xml, where each set keeps a track of port's status and last used timestamp

2.       In the dialplan, I execute a simple Lua script which 'chooses' the line based on global variables status and timestamp (using "global_getvar") and update the status of the line to be used (using "global_setvar")

3.       Bridge to the line returned by the above script

4.       Execute another Lua script on hang-up, which updates the global variables (status and timestamp)

If I were to implement the hash way, I would have to probably do the following:

1.       In the dialplan, I execute a simple Lua script which 'chooses' the line by reading the hash values of the line status and timestamp and update the hash status of the line to be used

2.       Bridge to the line returned by the above script

3.       Execute another Lua script on hang-up, which updates the hash values (status and timestamp)

But I am still not clear on the concurrency question - if FreeSWITCH has received 2 calls at the same time on the E1 line, should I be worried about protecting the script that gets executed to access the hash, decide on the line to be used, and then update the hash?

Thanks again!

With regards,
Sirish

From: freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org> [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Michael Collins
Sent: Friday, 21 December 2012 3:42 AM
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

Sirish,

Since you're using an E1 to connect to the PBX then really all you need to do is keep track of the last time each port was hung up and whether or not a given port is currently in use. I would use api_on_answer to launch a simple script to set a flag to say that a particular port is in use and then use the api_hangup_hook to launch another script when the call ends.

The channel variables page on the wiki has some examples of how to use these. I recommend that you write simple Lua scripts that use the "hash" API to store information in the local database. Also, check out the "hash_dump" API as it is a useful way to quickly see what all is stored there.

For an example of how to add, remove, and read information from the local database using the "hash" API please see conf/dialplan/default.xml. Search for "hash" and you'll see all sorts of examples of how the example dialplan uses the local database to store useful information that allows us to implement features like call return, call intercept, etc.

-MC
On Tue, Dec 18, 2012 at 7:39 PM, Sirish Masur Mohan <Sirish.MasurMohan at oa.com.au<mailto:Sirish.MasurMohan at oa.com.au>> wrote:
Hi Michael,

>> How are you physically connecting from FreeSWITCH to the PBX?

I connect this via E1 link - I have a Sangoma card installed on the FreeSWITCH machine.

With regards,
Sirish

From: freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org> [mailto:freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org>] On Behalf Of Michael Collins
Sent: Wednesday, 19 December 2012 1:31 PM
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

To trigger SIP registrations you'd need the PBX to have a SIP client. I'm assuming this is possible, but maybe that's a false assumption. How are you physically connecting from FreeSWITCH to the PBX?

-MC
On Tue, Dec 18, 2012 at 2:36 PM, Sirish Masur Mohan <Sirish.MasurMohan at oa.com.au<mailto:Sirish.MasurMohan at oa.com.au>> wrote:
Hey Guys,

Would really appreciate if you could help me out here - isn't there a way to handle concurrent calls in the dial plan, especially when Lua scripts, accessing global variables, are executed on receiving calls?

Is mod_fifo the closest I could get to handle concurrency (as Michael has explained)? If yes, how do I trigger SIP registrations, especially working with a PBX which I don't have full control of?

With regards,
Sirish

From: Sirish Masur Mohan
Sent: Tuesday, 18 December 2012 1:02 PM
To: FreeSWITCH Users Help
Subject: RE: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

Hi Michael,

Thanks for the reply.

>> You would need a SIP registration from the PBX to FreeSWITCH for each of the modem extensions
I am seen SIP clients such as X-Lite sending out the SIP registrations, but could you please clarify as to how this can be achieved in the PBX? The final production environment would be out in the customer's PBX, which I may not have complete control of..

>> What application are you building?
I may not be able to provide the details because of the NDA with customer, but what I am trying to achieve is, to replace an existing IVR with FreeSWITCH in an old existing setup of the customer - that's the reason why we continue working with dialup modems!

With regards,
Sirish

From: freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org> [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Michael Collins
Sent: Tuesday, 18 December 2012 6:23 AM
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

You don't have to have actual human agents for mod_fifo. You could define a user for each modem and then manually "log in" those "agents" on the command line using the fifo_member API command. Something like this:

fifo_member add fifo_name {fifo_member_wait=nowait}user/1234

Where 1234 is the user id of one of the modems. You would need a SIP registration from the PBX to FreeSWITCH for each of the modem extensions.

Having modems go through a VoIP system sounds a bit scary. What application are you building?
-MC
On Sun, Dec 16, 2012 at 5:41 PM, Sirish Masur Mohan <Sirish.MasurMohan at oa.com.au<mailto:Sirish.MasurMohan at oa.com.au>> wrote:
Hi William,

Thanks for the reply.

My setup is as follows:
Client(Caller)->dialup modem->PBX->FreeSWITCH->PBX-> 4 dialup modems->Server(Receiver)

I basically need FreeSWITCH to bridge the incoming call to the best external destination (out of the 4 available), so that the modem training, connection etc can take place smoothly, before exchange of data. I am not sure if mod_fifo would help me in this scenario, as, I would require an agent to dial in and read the fifo. Could you please clarify?

Thanks!

With regards,
Sirish

-----Original Message-----
From: freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org> [mailto:freeswitch-users-bounces at lists.freeswitch.org<mailto:freeswitch-users-bounces at lists.freeswitch.org>] On Behalf Of William King
Sent: Monday, 17 December 2012 10:47 AM
To: freeswitch-users at lists.freeswitch.org<mailto:freeswitch-users at lists.freeswitch.org>
Subject: Re: [Freeswitch-users] Newbie question: Executing Lua scripts for incoming calls, how concurrency is to be handled?

Sounds like you want to take a look into mod_fifo.

William King
Senior Engineer
Quentus Technologies, INC
1037 NE 65th St Suite 273
Seattle, WA 98115
Main:   (877) 211-9337<tel:%28877%29%20211-9337>
Office: (206) 388-4772<tel:%28206%29%20388-4772>
Cell:   (253) 686-5518<tel:%28253%29%20686-5518>
william.king at quentustech.com<mailto:william.king at quentustech.com>
_________________________________________________________________________
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_________________________________________________________________________
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Michael S Collins
Twitter: @mercutioviz
http://www.FreeSWITCH.org
http://www.ClueCon.com
http://www.OSTAG.org

_________________________________________________________________________
Professional FreeSWITCH Consulting Services:
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--
Michael S Collins
Twitter: @mercutioviz
http://www.FreeSWITCH.org
http://www.ClueCon.com
http://www.OSTAG.org
_________________________________________________________________________
Professional FreeSWITCH Consulting Services:
consulting at freeswitch.org<mailto:consulting at freeswitch.org>
http://www.freeswitchsolutions.com




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