Comments to @dmoreno_cb. http://blog.coralbits.com.

gistfile1.c

// Compile it with: 
//   $ gcc -o bench bench.c -lonion -Wall -O2 -lsqlite3
//   $ export ONION_LOG=noinfo  # To properly test, you may need some control over logging. Here almost disabled. 
//   $ ./bench
// It listens to localhost:8080, known addresses: http://localhost:8080/ , http://localhost:8080/db , http://localhost:8080/db20
// Test it with ab:
//   $ ab -k -t 10 -c 20 http://localhost:8080/
// It gave me (Intel(R) Core(TM) i7-2677M CPU @ 1.80GHz):
//   Requests per second:    58288.10 [#/sec] (mean)

// Done in response of http://www.techempower.com/blog/2013/03/28/framework-benchmarks/
// Although onion is not a framework.

// Copyright (c) 2013, David Moreno
// Under BSD license

// All rights reserved. 
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met: 
// 
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer. 
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// 
// The views and conclusions contained in the software and documentation are those
// of the authors and should not be interpreted as representing official policies, 
// either expressed or implied, of the FreeBSD Project.



#include <onion/onion.h>
#include <onion/handler.h>
#include <onion/dict.h>
#include <onion/block.h>
#include <onion/log.h>
#include <string.h>
#include <sqlite3.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>

/// Gets the dict and converts it to JSON and writes it into the response
onion_connection_status return_json(onion_dict *json, onion_request *req, onion_response *res){
	onion_block *bl=onion_dict_to_json(json);
	size_t size=onion_block_size(bl);
	onion_response_set_header(res, "Content-Type","application/json");
	onion_response_set_length(res, size);
	onion_response_write(res, onion_block_data(bl), size);
	onion_block_free(bl);
	return OCS_PROCESSED;
}

/// Adds the answer to the dict
static int return_db_1_callback(onion_dict *d, int argc, char **argv, char **azColName){
	int i;
	for(i=0;i<argc;i++){
		onion_dict_add(d, azColName[i], argv[i], OD_DUP_ALL);
	}
	return 0;
}

/// Do one sqlite petition
onion_connection_status return_db_1(sqlite3 *db, onion_request *req, onion_response *res){
	char query[256];
	char *error;
	onion_dict *d=onion_dict_new();
	snprintf(query,sizeof(query), "SELECT * FROM World WHERE id = %d", rand()%100);
	int rc = sqlite3_exec(db, query, (void*)&return_db_1_callback, d, &error);
	if (rc<0){
		ONION_ERROR("Error on query: %s",error);
		return OCS_INTERNAL_ERROR;
	}
	
	onion_block *bl=onion_dict_to_json(d);
	onion_response_set_header(res,"Content-Type","application/json");
	int size=onion_block_size(bl);
	onion_response_set_length(res, size);
	onion_response_write(res, onion_block_data(bl), size);
	onion_block_free(bl);
	onion_dict_free(d);
	return OCS_PROCESSED;
}

// Do 20 sqlite petitions. 
onion_connection_status return_db_20(sqlite3 *db, onion_request *req, onion_response *res){
	char query[256];
	char *error;
	onion_dict *d=onion_dict_new();
	int i;
	for (i=0;i<20;i++){
		snprintf(query,sizeof(query), "SELECT * FROM World WHERE id = %d", rand()%100);
		int rc = sqlite3_exec(db, query, (void*)&return_db_1_callback, d, &error);
		if (rc<0){
			ONION_ERROR("Error on query: %s",error);
			return OCS_INTERNAL_ERROR;
		}
	}
	
	onion_block *bl=onion_dict_to_json(d);
	onion_response_set_header(res,"Content-Type","application/json");
	int size=onion_block_size(bl);
	onion_response_set_length(res, size);
	onion_response_write(res, onion_block_data(bl), size);
	onion_block_free(bl);
	onion_dict_free(d);
	return OCS_PROCESSED;
}


// Some data needed by the handler
struct test_data{
	onion_dict *hello;
	sqlite3 *db[10];
};
#define NCONN 10

/// Multiplexes to the proper handler depending on the path.
/// As there is no proper database connection pool, take one connection randomly, and uses it.
onion_connection_status muxer(struct test_data *data, onion_request *req, onion_response *res){
	const char *path=onion_request_get_path(req);
	if (strcmp(path, "")==0)
		return return_json(data->hello, req, res);
	if (strcmp(path, "db")==0)
		return return_db_1(data->db[rand()%NCONN], req, res);
	if (strcmp(path, "db20")==0)
		return return_db_20(data->db[rand()%NCONN], req, res);
	
	return OCS_INTERNAL_ERROR;
}

/// Creates the onion http server, creates some server data, creates the handler, listens.
int main(void){
	onion *o=onion_new(O_POOL);
	
	struct test_data data;
	data.hello=onion_dict_new();
	
	int i;
	for (i=0;i<NCONN;i++){
		int rc=sqlite3_open("hello.sqlite", &data.db[i]);
		if (rc<0){
			perror("Cant open hello.sqlite");
			return 1;
		}
	}
	
	onion_dict_add(data.hello,"message","Hello, world", 0);

	onion_set_root_handler(o, onion_handler_new((void*)&muxer, (void*)&data, NULL));

	printf("Listening at http://localhost:8080/\n");
	onion_listen(o);
	
	onion_dict_free(data.hello);
	for (i=0;i<NCONN;i++){
		sqlite3_close(data.db[i]);
	}
	return 0;
}