bouquins-bchs/db.c

/*	$Id$ */
/*
 * Copyright (c) 2016 Kristaps Dzonsons <kristaps@bsd.lv>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <kcgi.h>
#include <kcgijson.h>
#include <sqlite3.h>

#include "extern.h"

/*
 * When the database is busy or locked, sleep for a random amount of
 * time before continuing.
 * We could put all sorts of heuristics in here to back off, but we do
 * something really simple.
 */
static void
db_sleep(size_t attempt)
{

	if (attempt < 10)
		usleep(arc4random_uniform(100000));
	else
		usleep(arc4random_uniform(500000));
}

/*
 * Open the database and stash the resulting handle in the kreq
 */
int
db_open(struct kreq *r, const char *file)
{
	size_t	 attempt;
	sqlite3	*db;
	int	 rc;

	attempt = 0;
  // TODO max attempt, return 0
again:
  // TODO open readonly
	rc = sqlite3_open(file, &db);
	if (SQLITE_BUSY == rc) {
		db_sleep(attempt++);
		goto again;
	} else if (SQLITE_LOCKED == rc) {
		fprintf(stderr, "sqlite3_open: %s\n", 
			sqlite3_errmsg(db));
		db_sleep(attempt++);
		goto again;
	} else if (SQLITE_PROTOCOL == rc) {
		fprintf(stderr, "sqlite3_open: %s\n", 
			sqlite3_errmsg(db));
		db_sleep(attempt++);
		goto again;
	} else if (SQLITE_OK == rc) {
		sqlite3_busy_timeout(db, 500);
    r->arg = db;
    return(1);
	} 
  return(0);
}

/*
 * Close the database stashed in the kreq's argument.
 */
void
db_close(struct kreq *r)
{
	if (SQLITE_OK == sqlite3_close(r->arg)) {
    r->arg = NULL;
		return;
  }
	fprintf(stderr, "sqlite3_close: %s\n", sqlite3_errmsg(r->arg));
}