rest_client Module

Liviu Chircu

   OpenSIPS Solutions
   <liviu@opensips.org>

Edited by

Liviu Chircu

   Copyright © 2013 www.opensips-solutions.com
   Revision History
   Revision $Revision$ $Date$
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview
        1.2. Dependencies

              1.2.1. OpenSIPS Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. connection_timeout (integer)
              1.3.2. connect_poll_interval (integer)
              1.3.3. curl_timeout (integer)
              1.3.4. ssl_verifypeer (integer)
              1.3.5. ssl_verifyhost (integer)
              1.3.6. ssl_capath (integer)

        1.4. Exported Functions

              1.4.1. rest_get(url, body_pv[, [ctype_pv][,
                      [retcode_pv]]])

              1.4.2. rest_post(url, send_body_pv, [send_ctype_pv],
                      recv_body_pv[, [recv_ctype_pv][,
                      [retcode_pv]]])

              1.4.3. rest_append_hf(txt)

        1.5. Exported Asynchronous Functions

              1.5.1. rest_get(url, body_pv[, [ctype_pv][,
                      [retcode_pv]]])

              1.5.2. rest_post(url, send_body_pv, [send_ctype_pv],
                      recv_body_pv[, [recv_ctype_pv][,
                      [retcode_pv]]])

   List of Examples

   1.1. Setting the connection_timeout parameter
   1.2. Setting the connect_poll_interval parameter
   1.3. Setting the curl_timeout parameter
   1.4. Setting the ssl_verifypeer parameter
   1.5. Setting the ssl_verifyhost parameter
   1.6. Setting the ssl_capath parameter
   1.7. rest_get usage
   1.8. rest_post usage
   1.9. rest_append_hf usage
   1.10. async rest_get usage
   1.11. async rest_post usage

Chapter 1. Admin Guide

1.1. Overview

   The rest_client module provides a means of interacting with an
   HTTP server by doing RESTful queries, such as GET and POST.

1.2. Dependencies

1.2.1. OpenSIPS Modules

   The following modules must be loaded before this module:
     * No dependencies on other OpenSIPS modules..

1.2.2. External Libraries or Applications

   The following libraries or applications must be installed
   before running OpenSIPS with this module loaded:
     * libcurl.

1.3. Exported Parameters

1.3.1. connection_timeout (integer)

   Maximum time allowed to establish a connection with the server.

   Default value is “20” seconds.

   Example 1.1. Setting the connection_timeout parameter
...
modparam("rest_client", "connection_timeout", 300)
...

1.3.2. connect_poll_interval (integer)

   Allows complete control over how quickly we want to detect
   libcurl's completed TCP handshakes, so the transfers can be
   started. A lower "connect_poll_interval" will speed up all HTTP
   transfers, but will also increase CPU usage.

   Default value is “20” milliseconds.

   Example 1.2. Setting the connect_poll_interval parameter
...
modparam("rest_client", "connect_poll_interval", 2)
...

1.3.3. curl_timeout (integer)

   Maximum time allowed for the libcurl transfer to complete.

   Default value is “20” seconds.

   Example 1.3. Setting the curl_timeout parameter
...
modparam("rest_client", "curl_timeout", 300)
...

1.3.4. ssl_verifypeer (integer)

   Set this to 0 in order to disable the verification of the
   remote peer's certificate. Verification is done using a default
   bundle of CA certificates which come with libcurl.

   Default value is “1” (enabled).

   Example 1.4. Setting the ssl_verifypeer parameter
...
modparam("rest_client", "ssl_verifypeer", 0)
...

1.3.5. ssl_verifyhost (integer)

   Set this to 0 in order to disable the verification that the
   remote peer actually corresponds to the server listed in the
   certificate.

   Default value is “1” (enabled).

   Example 1.5. Setting the ssl_verifyhost parameter
...
modparam("rest_client", "ssl_verifyhost", 0)
...

1.3.6. ssl_capath (integer)

   An optional path for CA certificates to be used for host
   verifications.

   Example 1.6. Setting the ssl_capath parameter
...
modparam("rest_client", "ssl_capath", "/home/opensips/ca_certificates")
...

1.4. Exported Functions

1.4.1.  rest_get(url, body_pv[, [ctype_pv][, [retcode_pv]]])

   Issues an HTTP GET request to the given 'url', and returns a
   representation of the resource.

   The body_pv pseudo-var will hold the body of the HTTP response.

   The optional ctype_pv pseudo-var will contain the value of the
   "Content-Type:" header.

   The optional retcode_pv pseudo-var is used to retain the HTTP
   status code of the response message. Since the module is based
   on libcurl, a 0 value means no HTTP reply arrived at all.

   Possible parameter types
     * url - String, pseudo-variable, or a String which includes
       pseudo-variables. (useful for specifying additional
       attribute-value fields in the URL)
     * body_pv, ctype_pv, retcode_pv - pseudo-variables

   This function can be used from the startup, branch, failure,
   request and timer routes.

   Example 1.7. rest_get usage
...
# Example of querying a REST service to get the credit of an account

if (!rest_get("http://getcredit.org/?ruri=$fU", "$var(credit)", "$var(ct
)", "$var(rcode)")) {
        xlog("Error code $var(rcode) in HTTP GET!\n");
        send_reply("403", "Not registered");
        exit;
}
...

1.4.2.  rest_post(url, send_body_pv, [send_ctype_pv], recv_body_pv[,
[recv_ctype_pv][, [retcode_pv]]])

   Issues an HTTP POST request to the specified url. The request
   body will be copied from the send_body_pv pseudo-variable. The
   MIME Content-Type header for the request will be taken from
   send_ctype_pv (default is "application/x-www-form-urlencoded")

   The mandatory recv_body_pv pseudo-var will hold the body of the
   HTTP response.

   The optional recv_ctype_pv parameter will contain the value of
   the "Content-Type" header of the response message.

   The optional retcode_pv pseudo-var parameter can be given in
   order to retrieve the HTTP status code of the response message.
   Since the module based on libcurl, a 0 value means no HTTP
   reply arrived at all.

   Possible parameter types
     * url, send_body_pv, send_type_pv - String, pseudo-variable,
       or a String which includes pseudo-variables.
     * recv_body_pv, recv_ctype_pv, retcode_pv - pseudo-variables

   This function can be used from the startup, branch, failure,
   request and timer routes.

   Example 1.8. rest_post usage
...
# Storing data using a RESTful service with an HTTP POST request

if (!rest_post("http://myserver.org/register_user", "$fU", , "$var(body)
", "$var(ct)", "$var(rcode)")) {
        xlog("Error code $var(rcode) in HTTP POST!\n");
        send_reply("403", "POST Forbidden");
        exit;
}
...

1.4.3.  rest_append_hf(txt)

   Appends 'txt' to the HTTP headers of the subsequent request.
   Multiple headers can be appended by making multiple calls
   before executing a request.

   The contents of txt should adhere to the specification for HTTP
   headers (ex. Field: Value)

   Parameter types
     * txt - String, pseudo-variable, or a String which includes
       pseudo-variables. (useful for specifying additional
       attribute-value fields in the URL)

   This function can be used from the startup, branch, failure,
   request and timer routes.

   Example 1.9. rest_append_hf usage
...
# Example of querying a REST service requiring additional headers

rest_append_hf("Authorization: Bearer mF_9.B5f-4.1JqM");
if (!rest_get("http://getcredit.org/?ruri=$fU", "$var(credit)")) {
                                ...
}
...

1.5. Exported Asynchronous Functions

1.5.1.  rest_get(url, body_pv[, [ctype_pv][, [retcode_pv]]])

   Sends a GET HTTP request. This function behaves exactly the
   same as rest_get (in terms of input, output and processing),
   but in an asynchronous way. Script execution is suspended until
   the entire content of the HTTP response if available.

   Example 1.10. async rest_get usage
route {
        ...
        async(rest_get("http://getcredit.org/?ruri=$fU", "$var(credit)",
 , "$var(rcode)"), resume);
}

route [resume]
{
        if ($rc < 0) {
                xlog("Error code $var(rcode) in HTTP GET!\n");
                send_reply("403", "GET Forbidden");
                exit;
        }
        ......
}

1.5.2.  rest_post(url, send_body_pv, [send_ctype_pv], recv_body_pv[,
[recv_ctype_pv][, [retcode_pv]]])

   Sends a POST HTTP request. This function behaves exactly the
   same as rest_post (in terms of input, output and processing),
   but in an asynchronous way. Script execution is suspended until
   the entire content of the HTTP response if available.

   Example 1.11. async rest_post usage
route {
        ...
        async(rest_post("http://myserver.org/register_user", "$fU", , "$
var(body)", "$var(ct)", "$var(rcode)"), resume);
}

route [resume]
{
        if ($rc < 0) {
                xlog("Error code $var(rcode) in HTTP POST!\n");
                send_reply("403", "POST Forbidden");
                exit;
        }
        ......
}
