[Freeswitch-users] Lua Dialplan Application to turn down FS

Bernhard Wendel bernhard at sessionbird.com
Sun Oct 12 14:45:26 MSD 2014


I'm using the following Lua-Script to check whether a conference exists 
and only let a caller join if so.
The script is called via the following dialplan /<action 
application="lua" data="/path/to/script.lua $1" />///, where $1 is the 
destination number.

 1. -- Connect to a database
 2. local dbh = freeswitch.Dbh("pgsql://hostaddr=
    dbname=database user=username password='password'
 3. assert(dbh:connected());
 4. -- Execute SQL
 5. dbh:query(string.format("SELECT COUNT(*) as \"MyCount\" FROM
    \"MyTable\" WHERE ColA = '%s'", argv[1]), function(row)
 6.      --freeswitch.consoleLog("INFO", "Results: " .. row.MyCount)
 8.      dbh:release()
10.      if (row.MyCount== '1') then
11.          freeswitch.consoleLog("INFO", "User is joining conference
    at " .. argv[1])
13.          session:answer()
14.          session:execute("conference", argv[1] .. "@wideband")
15.      end
16.      session:hangup()
17. end)

Line 8 instructs FS to return the postgres-Connection back to the pool - 
which is as expected. When a user now leaves the conference, FS throws 
this errors:

2014-10-12 10:32:30.065924 [DEBUG] switch_cpp.cpp:694 CoreSession::hangup
2014-10-12 10:32:30.065924 [CRIT] switch_pgsql.c:368 An error occurred 
trying to consume input for query (200): connection pointer is NULL
2014-10-12 10:32:30.065924 [CRIT] switch_pgsql.c:122 No DB Connection
2014-10-12 10:32:30.065924 [ERR] switch_core_sqldb.c:1177 ERR: [SELECT 
COUNT(*) as "MyCount" FROM "MyTable" WHERE ColA = 
'conf-1234'][connection pointer is NULL]
2014-10-12 10:32:30.065924 [ERR] freeswitch_lua.cpp:446 DBH NOT Connected.
2014-10-12 10:32:30.065924 [DEBUG] switch_cpp.cpp:1075 
sofia/internal/Alice at my.pbx.com destroy/unlink session from object

Now, I could live with that. BUT: The problem is, that sometimes, when a 
user leaves the conference, FS crashes.
I've narrowed down the main cause to the above lua script. If I comment 
line 8 out, FS stops crashing. This will also stop FS from reusing 

Now my questions:

 1. I don't use `dbh` after line 8. So where does the error come from?
 2. How can I stop the error?
 3. How can I rewrite the lua script to have both a) non-crashing FS and
    b) reusing of connection?


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