### Description Hello,

When there is an error in my ruby script, app_ruby prints exception message without a stack trace, like this: ``` Dec 14 16:25:17 servername /usr/sbin/kamailio[24313]: ERROR: app_ruby [app_ruby_api.c:105]: app_ruby_print_last_exception(): exception: wrong number of arguments (1 for 2..3) Dec 14 16:25:17 servername /usr/sbin/kamailio[24313]: ERROR: app_ruby [app_ruby_api.c:1078]: app_ruby_run_ex(): ruby exception (6) on callback for: ksr_request_route (res type: 17) ```

Altough this message tells what is the error, it doesn't tell **where** the error happened, so it's hard to find the source of the problem.

In ruby, exceptions have _backtrace()_ method returning stack trace as an array of strings. It would be really helpful if app_ruby also call this method and append its result to error message.

### Reproduction in kamailio.cfg ``` loadmodule "app_ruby.so" modparam("app_ruby", "load", "/etc/kamailio/ruby/routes.rb") cfgengine "ruby" ```

in /etc/kamailio/ruby/routes.rb ``` def some_method(param1, param2) end

def ksr_request_route some_method(1) end ```

### Expected behavior ``` Dec 14 16:46:24 servername /usr/sbin/kamailio[24314]: ERROR: <core> [core/kemi.c:87]: sr_kemi_core_err(): wrong number of arguments (1 for 2): /etc/kamailio/ruby/routes.rb:1:in `some_method' /etc/kamailio/ruby/routes.rb:4:in `ksr_request_route' ``` #### Actual observed behavior ``` Dec 14 16:45:42 servername /usr/sbin/kamailio[24311]: ERROR: app_ruby [app_ruby_api.c:105]: app_ruby_print_last_exception(): exception: wrong number of arguments (1 for 2) ``` ### Possible Solutions

Relevant code seem to be here: https://github.com/kamailio/kamailio/blob/master/src/modules/app_ruby/app_ru...

I found example C code to print stack trace here but couldn't figure out how to integrate to app_ruby: http://zoo-project.org/svn/trunk/zoo-project/zoo-kernel/service_internal_rub...

Equivalent ruby code would be (this code is not idiomatic, my aim is to provide C-like ruby code): ``` def some_error_generating_method method_taking_two_params(1) rescue => exception message = exception.to_s() + "\n" stack_trace = exception.backtrace() for line in stack_trace message = message + line + "\n" end print(message) end ```

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 5.2.0 (x86_64/linux) 535e13 flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144 MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: 535e13 compiled on 10:26:34 Nov 28 2018 with gcc 4.8.5 ```

* **Operating System**:

Centos 7.2 64bit

``` Linux servername 3.10.0-327.28.2.el7.x86_64 #1 SMP Wed Aug 3 11:11:39 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

```