JSONRPCC (jsonrpc client) Module

Matthew Williams

Edited by

Jordan Levy

Table of Contents

1. Admin Guide
1. Overview
2. Dependencies
2.1. Kamailio Modules
2.2. External Libraries or Applications
3. Parameters
3.1. servers (string)
3.2. max_conn_attempts (int)
4. Functions
4.1. jsonrpc_notification(method, parameters)
4.2. jsonrpc_request(method, parameters, return_route, error_route, result_var)

List of Examples

1.1. Set servers parameter
1.2. Set max_conn_attempts parameter
1.3. jsonrpc_notification usage
1.4. jsonrpc_request usage

Chapter 1. Admin Guide

1. Overview

This module provides access to json-rpc services (operating over TCP/Netstrings).

This module uses t_suspend() and t_continue() from the TM module.

Note that after invoking an asyncronous operation, the processing will continue later, in another application process. Therefore, do not rely on variables stored in private memory, use shared memory if you want to get values after the processing is resumend (e.g., $shv(...) or htable $sht(...)).

2. Dependencies

2.1. Kamailio Modules

The following modules must be loaded before this module:

  • tm - transaction management.

2.2. External Libraries or Applications

Note: this module uses Linux specific API, part of glibc library, it might not compile on other types of operating systems.

The following libraries or applications must be installed before running Kamailio with this module loaded:

  • libjson (https://github.com/json-c/json-c/wiki)

  • libevent - http://libevent.org/

  • glibc - http://www.gnu.org/software/libc/ (v2.8 or higher)

3. Parameters

3.1. servers (string)

The servers providing the remote jsonrpc service. Format is "host1:port1,priority1 host2:port2,priority2". Requests to servers of the same priority will be distributed evenly (round robin). Server groups with higher priority are used first.

Example 1.1. Set servers parameter

modparam("jsonrpcc", "servers", "localhost:9999,2,2 backup.server:9999,1")

3.2. max_conn_attempts (int)

Max number of connection attempts for a server. -1 will keep reconnecting forever, 0 will skip any attempt to reconnect.

Example 1.2. Set max_conn_attempts parameter

modparam("jsonrpcc", "max_conn_attempts", 10)

4. Functions

4.1.  jsonrpc_notification(method, parameters)

Invokes the remote 'method' with the given 'parameters' as a notification. Unlike jsonrpc_request (below), notifications do not receive a response. Script processing continues in the usual fashion as soon as the notification has been sent.

The method and parameters can be a static string or dynamic string value with config variables.

Example 1.3. jsonrpc_notification usage

jsonrpc_notification("update_user", "{'id': 1234, 'name': 'Petros'}")

4.2.  jsonrpc_request(method, parameters, return_route, error_route, result_var)

Invokes the remote 'method' with the given 'parameters'. When the response is received, continues processing of the SIP request with the route[return_route]. If a timeout occurs, no servers can be reached, or a jsonrpc error message is received, continues process at route[error_route]. In this case, the result_var will contain one of "timeout", "failure", or the error message received back from the jsonrpc server.

The method, parameters, return_route, and error_route can be a static string or a dynamic string value with config variables.

Since the SIP request handling is resumed in another process, the config file execution is lost. As mentioned above, only shared variables ($shv, etc) should be used for any value that will be needed when the script is resumed.

The result is stored in the pseudo-variable 'result_var'. Since this variable is set after the response is received, it is possible to use a $var for this parameter.

Example 1.4. jsonrpc_request usage

jsonrpc_request("get_user", "{'id': 1234}", "RESPONSE", "ERROR", "$var(result)");
route[RESPONSE] {
	xlog("Result received: $var(result)");
route[ERROR] {
	xlog("Error received: $var(result)");