Libevent http server that acts like a middle man between a client and http server. (A quick example, just to try and clear a few libevent related things up. Pretty sure it could have been done better.)

gistfile1.cpp

#include <iostream>

#include <event.h>
#include <evhttp.h>
#include <event2/event.h>
#include <event2/http.h>
#include <event2/buffer.h>  
#include <sys/queue.h>
#include <cstdlib>

#include <string.h>

using namespace std;

static void final_reply_cb(struct evhttp_request *req, void *arg) {
	string body;
	struct evhttp_request* r = (evhttp_request*)arg;

	// Prepare things for an outgoing response
	struct evbuffer *output_buffer;
	output_buffer = evbuffer_new();

	struct evkeyvalq *output_headers = evhttp_request_get_output_headers(r);
	evhttp_add_header(output_headers, "Content-Type", "text/plain");

	string response = "";

	// Parse the incoming response body
	int len = evbuffer_get_length(req->input_buffer);
	void *buf = malloc(len);
	evbuffer_copyout(req->input_buffer, buf, len);

	body = string(static_cast<char*>(buf), len);

	// Send the outgoing response
	evbuffer_add_printf(output_buffer, "%s", body.c_str());
	evhttp_send_reply(r, HTTP_OK, "OK", output_buffer);
	evbuffer_free(output_buffer);
}

void request_to_endpoint_cb(struct evhttp_request *r, void *arg) {
	// Parse the URI parameters
	struct evkeyvalq* args = new evkeyvalq;
	const char *uri = evhttp_request_get_uri(r);
	const char *query_part;

	struct evhttp_uri* parsed_uri = NULL;
	parsed_uri = evhttp_uri_parse(uri);

	if (parsed_uri != NULL) query_part = evhttp_uri_get_query(parsed_uri);
	else query_part = uri;

	string type = "";
 	evhttp_parse_query_str(query_part,args);
	struct evkeyval *param;
	TAILQ_FOREACH(param, args,next) {
		if (strcmp(param->key,"type") == 0) {
			type = param->value;
			break;
		}
	}

	string url = "";
	string host = "";
	string host_ip = "";
	
	if (type == "1") {
		url = "http://www.google.com/robots.txt";
		host = "google.com";
		host_ip = "173.194.70.113";
	} else {
		url = "http://localhost/sleep10"; // nginx set to wait 10 sec before replying
		host = "localhost";
		host_ip = "192.168.2.15";
	}

	// Create new connection to server
	const char *addr = host_ip.c_str();
	unsigned int port = 80;
	struct evhttp_connection *connection = evhttp_connection_new(addr, port);
	evhttp_connection_set_timeout(connection, 15);

	// Create the http request
	struct evhttp_request *request = evhttp_request_new(final_reply_cb, r);
	evhttp_add_header(request->output_headers, "Host", host.c_str());
	evhttp_add_header(request->output_headers, "Content-Length", "0");

	cout << "(proxy) Making a request to endpoint (" << url << ")." << endl;
	evhttp_make_request(connection, request, EVHTTP_REQ_GET, url.c_str());
	cout << "(proxy) Request to endpoint made (" << url << "), waiting for a reply." << endl;
}

int main(int argc, char* argv[]) {
	cout << "Starting test http server" << endl;
	
	// Setup evhttp server
	struct event_base *libeventbase = event_init();
	struct evhttp *metrics_server;
	metrics_server = evhttp_new(libeventbase);

	evhttp_bind_socket(metrics_server, "0.0.0.0", 8080);
	evhttp_set_cb(metrics_server, "/test", request_to_endpoint_cb, libeventbase);
	
	event_dispatch();

	event_base_free(libeventbase);

	return 0;
}