# &adminguide;

## 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 asynchronous 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 resumed (e.g., $shv(...) or htable $sht(...)).

## Dependencies

### &kamailio; Modules

The following modules must be loaded before this module:

- tm - transaction management.

### 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)

## Parameters

### `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.

#### Set `servers` parameter

    ...
    modparam("jsonrpcc", "servers", "localhost:9999,2 10.10.0.1:9999,2 backup.server:9999,1")
    ...

### `max_conn_attempts` (int)

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

#### Set `max_conn_attempts` parameter

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

## Functions

### `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.

#### `jsonrpc_notification` usage

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

### `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.

#### `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)");
    	...
    }
    ...