workflow
/
tutorial
/
tutorial-05-http_proxy.cc

/*
  Copyright (c) 2019 Sogou, Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

  Author: Xie Han (xiehan@sogou-inc.com;63350856@qq.com)
*/

#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <utility>
#include "workflow/Workflow.h"
#include "workflow/HttpMessage.h"
#include "workflow/HttpUtil.h"
#include "workflow/WFHttpServer.h"
#include "workflow/WFFacilities.h"

struct tutorial_series_context
{
	std::string url;
	WFHttpTask *proxy_task;
	bool is_keep_alive;
};

void reply_callback(WFHttpTask *proxy_task)
{
	SeriesWork *series = series_of(proxy_task);
	tutorial_series_context *context =
		(tutorial_series_context *)series->get_context();
	auto *proxy_resp = proxy_task->get_resp();
	size_t size = proxy_resp->get_output_body_size();

	if (proxy_task->get_state() == WFT_STATE_SUCCESS)
		fprintf(stderr, "%s: Success. Http Status: %s, BodyLength: %zu\n",
				context->url.c_str(), proxy_resp->get_status_code(), size);
	else /* WFT_STATE_SYS_ERROR*/
		fprintf(stderr, "%s: Reply failed: %s, BodyLength: %zu\n",
				context->url.c_str(), strerror(proxy_task->get_error()), size);
}

void http_callback(WFHttpTask *task)
{
	int state = task->get_state();
	int error = task->get_error();
	auto *resp = task->get_resp();
	SeriesWork *series = series_of(task);
	tutorial_series_context *context =
		(tutorial_series_context *)series->get_context();
	auto *proxy_resp = context->proxy_task->get_resp();

	/* Some servers may close the socket as the end of http response. */
	if (state == WFT_STATE_SYS_ERROR && error == ECONNRESET)
		state = WFT_STATE_SUCCESS;

	if (state == WFT_STATE_SUCCESS)
	{
		const void *body;
		size_t len;

		/* set a callback for getting reply status. */
		context->proxy_task->set_callback(reply_callback);

		/* Copy the remote webserver's response, to proxy response. */
		if (resp->get_parsed_body(&body, &len))
			resp->append_output_body_nocopy(body, len);
		*proxy_resp = std::move(*resp);
		if (!context->is_keep_alive)
			proxy_resp->set_header_pair("Connection", "close");
	}
	else
	{
		const char *err_string;
		int error = task->get_error();

		if (state == WFT_STATE_SYS_ERROR)
			err_string = strerror(error);
		else if (state == WFT_STATE_DNS_ERROR)
			err_string = gai_strerror(error);
		else if (state == WFT_STATE_SSL_ERROR)
			err_string = "SSL error";
		else /* if (state == WFT_STATE_TASK_ERROR) */
			err_string = "URL error (Cannot be a HTTPS proxy)";

		fprintf(stderr, "%s: Fetch failed. state = %d, error = %d: %s\n",
				context->url.c_str(), state, task->get_error(),
				err_string);

		/* As a tutorial, make it simple. And ignore reply status. */
		proxy_resp->set_status_code("404");
		proxy_resp->append_output_body_nocopy(
							"<html>404 Not Found.</html>", 27);
	}
}

void process(WFHttpTask *proxy_task)
{
	auto *req = proxy_task->get_req();
	SeriesWork *series = series_of(proxy_task);
	WFHttpTask *http_task; /* for requesting remote webserver. */

	tutorial_series_context *context = new tutorial_series_context;
	context->url = req->get_request_uri();
	context->proxy_task = proxy_task;

	series->set_context(context);
	series->set_callback([](const SeriesWork *series) {
		delete (tutorial_series_context *)series->get_context();
	});

	context->is_keep_alive = req->is_keep_alive();
	http_task = WFTaskFactory::create_http_task(req->get_request_uri(), 0, 0,
												http_callback);

	const void *body;
	size_t len;

	/* Copy user's request to the new task's reuqest using std::move() */
	req->set_request_uri(http_task->get_req()->get_request_uri());
	req->get_parsed_body(&body, &len);
	req->append_output_body_nocopy(body, len);
	*http_task->get_req() = std::move(*req);

	/* also, limit the remote webserver response size. */
	http_task->get_resp()->set_size_limit(200 * 1024 * 1024);

	*series << http_task;
}

static WFFacilities::WaitGroup wait_group(1);

void sig_handler(int signo)
{
	wait_group.done();
}

int main(int argc, char *argv[])
{
	unsigned short port;

	if (argc != 2)
	{
		fprintf(stderr, "USAGE: %s <port>\n", argv[0]);
		exit(1);
	}

	port = atoi(argv[1]);
	signal(SIGINT, sig_handler);

	struct WFServerParams params = HTTP_SERVER_PARAMS_DEFAULT;
	/* for safety, limit request size to 8MB. */
	params.request_size_limit = 8 * 1024 * 1024;

	WFHttpServer server(&params, process);

	if (server.start(port) == 0)
	{
		wait_group.wait();
		server.stop();
	}
	else
	{
		perror("Cannot start server");
		exit(1);
	}

	return 0;
}