workflow/tutorial/tutorial-15-name_service.cc

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <string>
#include "workflow/WFGlobal.h"
#include "workflow/WFNameService.h"
#include "workflow/WFTaskFactory.h"
#include "workflow/WFFacilities.h"
#include "workflow/HttpUtil.h"

// The example domonstrate the simplest user defined naming policy.

/* 'MyNSPolicy' is a naming policy, which use local file for naming.
 * The format of naming file is similar to 'hosts' file, but we allow
 * domain name and IP address as destination. For example:
 *
 * 127.0.0.1 localhost
 * 127.0.0.1 mydomain  # another alias for 127.0.0.1
 * www.sogou.com sogou # sogou -> www.sogou.com
 */
class MyNSPolicy : public WFNSPolicy
{
public:
	WFRouterTask *create_router_task(const struct WFNSParams *params,
									 router_callback_t callback) override;

private:
	std::string path;

private:
	std::string read_from_fp(FILE *fp, const char *name);
	std::string parse_line(char *p, const char *name);

public:
	MyNSPolicy(const char *naming_file) : path(naming_file) { }
};

std::string MyNSPolicy::parse_line(char *p, const char *name)
{
	const char *dest = NULL;
	char *start;

	start = p;
	while (*start != '\0' && *start != '#')
		start++;
	*start = '\0';

	while (1)
	{
		while (isspace(*p))
			p++;

		start = p;
		while (*p != '\0' && !isspace(*p))
			p++;

		if (start == p)
			break;

		if (*p != '\0')
			*p++ = '\0';

		if (dest == NULL)
		{
			dest = start;
			continue;
		}

		if (strcasecmp(name, start) == 0)
			return std::string(dest);
	}

	return std::string();
}

std::string MyNSPolicy::read_from_fp(FILE *fp, const char *name)
{
	char *line = NULL;
	size_t bufsize = 0;
	std::string result;

	while (getline(&line, &bufsize, fp) > 0)
	{
		result = this->parse_line(line, name);
		if (result.size() > 0)
			break;
	}

	free(line);
	return result;
}

WFRouterTask *MyNSPolicy::create_router_task(const struct WFNSParams *params,
											 router_callback_t callback)
{
	WFDnsResolver *dns_resolver = WFGlobal::get_dns_resolver();

	if (params->uri.host)
	{
		FILE *fp = fopen(this->path.c_str(), "r");
		if (fp)
		{
			std::string dest = this->read_from_fp(fp, params->uri.host);
			if (dest.size() > 0)
			{
				/* Update the uri structure's 'host' field directly.
				 * You can also update the 'port' field if needed. */
				free(params->uri.host);
				params->uri.host = strdup(dest.c_str());
			}

			fclose(fp);
		}
	}

	/* Simply, use the global dns resolver to create a router task. */
	return dns_resolver->create_router_task(params, std::move(callback));
}

int main(int argc, char *argv[])
{
	if (argc != 3)
	{
		fprintf(stderr, "USAGE: %s <http url> <naming file>\n", argv[0]);
		exit(1);
	}

	ParsedURI uri;
	URIParser::parse(argv[1], uri);
	char *name = uri.host;
	if (name == NULL)
	{
		fprintf(stderr, "Invalid http URI\n");
		exit(1);
	}

	/* Create an naming policy. */
	MyNSPolicy *policy = new MyNSPolicy(argv[2]);

	/* Get the global name service object.*/
	WFNameService *ns = WFGlobal::get_name_service();

	/* Add the our name with policy to global name service.
	 * You can add mutilply names with one policy object. */
	ns->add_policy(name, policy);

	WFFacilities::WaitGroup wg(1);
	WFHttpTask *task = WFTaskFactory::create_http_task(argv[1], 2, 3,
		[&wg](WFHttpTask *task) {
			int state = task->get_state();
			int error = task->get_error();
			if (state != WFT_STATE_SUCCESS)
			{
				fprintf(stderr, "error: %s\n",
						WFGlobal::get_error_string(state, error));
			}
			else
			{
				auto *r = task->get_resp();
				std::string body = protocol::HttpUtil::decode_chunked_body(r);
				fwrite(body.c_str(), 1, body.size(), stdout);
			}
			wg.done();
		});

	task->start();
	wg.wait();

	/* clean up */
	ns->del_policy(name);
	delete policy;
	return 0;
}