cache.c

harvest是一个下载html网页得机器人

static char rcsid[] = "$Id: cache.c,v 2.1 1997/03/21 18:01:13 sxw Exp $";
/*
 *  cache.c - Simple, local disk cache for liburl.
 *  Uses a GDBM file to map URLs to the cached files.  Uses links to copy
 *  files.  Locks out other processes that might make modifications to the
 *  cache by using the mutual exclusion protection of GDBM.  Maintains a
 *  Cache.size file that has the number of bytes in the cache.
 *
 *  DEBUG: section  22, level 1         Common liburl disk cache routines
 *  AUTHOR: Harvest derived
 *
 *  Harvest Indexer http://harvest.sourceforge.net/
 *  -----------------------------------------------
 *
 *  The Harvest Indexer is a continued development of code developed by
 *  the Harvest Project. Development is carried out by numerous individuals
 *  in the Internet community, and is not officially connected with the
 *  original Harvest Project or its funding sources.
 *
 *  Please mail [e-mail] if you are interested in participating
 *  in the development effort.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
/*
 *  ----------------------------------------------------------------------
 *  Copyright (c) 1994, 1995.  All rights reserved.
 *
 *    The Harvest software was developed by the Internet Research Task
 *    Force Research Group on Resource Discovery (IRTF-RD):
 *
 *          Mic Bowman of Transarc Corporation.
 *          Peter Danzig of the University of Southern California.
 *          Darren R. Hardy of the University of Colorado at Boulder.
 *          Udi Manber of the University of Arizona.
 *          Michael F. Schwartz of the University of Colorado at Boulder.
 *          Duane Wessels of the University of Colorado at Boulder.
 *
 *    This copyright notice applies to software in the Harvest
 *    ``src/'' directory only.  Users should consult the individual
 *    copyright notices in the ``components/'' subdirectories for
 *    copyright information about other software bundled with the
 *    Harvest source code distribution.
 *
 *  TERMS OF USE
 *
 *    The Harvest software may be used and re-distributed without
 *    charge, provided that the software origin and research team are
 *    cited in any use of the system.  Most commonly this is
 *    accomplished by including a link to the Harvest Home Page
 *    (http://harvest.cs.colorado.edu/) from the query page of any
 *    Broker you deploy, as well as in the query result pages.  These
 *    links are generated automatically by the standard Broker
 *    software distribution.
 *
 *    The Harvest software is provided ``as is'', without express or
 *    implied warranty, and with no support nor obligation to assist
 *    in its use, correction, modification or enhancement.  We assume
 *    no liability with respect to the infringement of copyrights,
 *    trade secrets, or any patents, and are not responsible for
 *    consequential damages.  Proper use of the Harvest software is
 *    entirely the responsibility of the user.
 *
 *  DERIVATIVE WORKS
 *
 *    Users may make derivative works from the Harvest software, subject
 *    to the following constraints:
 *
 *      - You must include the above copyright notice and these
 *        accompanying paragraphs in all forms of derivative works,
 *        and any documentation and other materials related to such
 *        distribution and use acknowledge that the software was
 *        developed at the above institutions.
 *
 *      - You must notify IRTF-RD regarding your distribution of
 *        the derivative work.
 *
 *      - You must clearly notify users that your are distributing
 *        a modified version and not the original Harvest software.
 *
 *      - Any derivative product is also subject to these copyright
 *        and use restrictions.
 *
 *    Note that the Harvest software is NOT in the public domain.  We
 *    retain copyright, as specified above.
 *
 *  HISTORY OF FREE SOFTWARE STATUS
 *
 *    Originally we required sites to license the software in cases
 *    where they were going to build commercial products/services
 *    around Harvest.  In June 1995 we changed this policy.  We now
 *    allow people to use the core Harvest software (the code found in
 *    the Harvest ``src/'' directory) for free.  We made this change
 *    in the interest of encouraging the widest possible deployment of
 *    the technology.  The Harvest software is really a reference
 *    implementation of a set of protocols and formats, some of which
 *    we intend to standardize.  We encourage commercial
 *    re-implementations of code complying to this set of standards.
 *
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <time.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <gdbm.h>
#include "util.h"
#include "url.h"

/*
 *  Try HAVE_SRAND48, then try HAVE_SRANDOM, otherwise assume HAVE_SRAND
 */

/*
 *  CACHE_TTL - number of seconds that makes cached files invalid
 */
#ifndef CACHE_TTL
#define CACHE_TTL		(1 * 7 * 24 * 60 * 60)	/* 1 week */
#endif

/*
 *  USE_CACHE_TMPDIR is the default temporary directory of where to
 *  place the cache, or the environment variable TMPDIR is used.
 *  This directory MUST be on the same partition as TMPDIR, since we
 *  use link(2) for copying.
 */
#ifndef USE_CACHE_TMPDIR
#define USE_CACHE_TMPDIR	"/tmp"
#endif

/* Local variables */
static char cachedir[BUFSIZ];
static char cachetable[BUFSIZ];
static char cachesize[BUFSIZ];
static time_t watermark;
static GDBM_FILE dbf = NULL;
static int max_cache_size = (32 * 1024 * 1024);		/* 32 MBs */
static int cache_ttl = CACHE_TTL;

static GDBM_FILE lm_dbf = NULL;
static char lmttable[BUFSIZ];

/* Local functions */
static void delete_cache_entry();
static void get_access();
static void release_access();
static void die();
static int get_cachesize();
static void change_cachesize();
static void delete_cache_url();
static char *next_filename();
static void init_next_filename();

static void die()
{
	if (lm_dbf != NULL)
		gdbm_close(lm_dbf);
	lm_dbf = NULL;
	if (dbf != NULL)
		gdbm_close(dbf);
	dbf = NULL;
	exit(1);
}

/*
 *  finish_cache() - Cleanup the cache.
 */
void finish_cache()
{
	if (lm_dbf != NULL)
		gdbm_close(lm_dbf);
	lm_dbf = NULL;
	if (dbf != NULL)
		gdbm_close(dbf);
	dbf = NULL;
}

/*
 *  init_cache() - Startup the cache
 */
void init_cache()
{
	char *s = getenv("TMPDIR");
	struct stat sb;

	/* Create a directory in which to cache the files */
	sprintf(cachedir, "%s/cache-liburl", s ? s : USE_CACHE_TMPDIR);
	(void) mkdir(cachedir, 0755);
	if (access(cachedir, W_OK)) {
		errorlog("Cannot use %s\n", cachedir);
		die();
	}
	init_next_filename(cachedir);
	sprintf(cachetable, "%s/Cache.gdbm", cachedir);
	sprintf(cachesize, "%s/Cache.size", cachedir);
	if (access(cachetable, F_OK)) {
		dbf = gdbm_open(cachetable, 0, GDBM_NEWDB, 0664, NULL);
		if (dbf == NULL) {
			if ((gdbm_errno != GDBM_CANT_BE_WRITER) &&
			    (gdbm_errno != GDBM_CANT_BE_READER)) {
				errorlog("GDBM ERROR: gdbm_open: %s: %s\n",
				    cachetable, gdbm_strerror(gdbm_errno));
				die();
			}
		} else
			gdbm_close(dbf);
	}
	dbf = NULL;
	/*
	 * watermark was used for comparing cached object time with time on
	 * GDBM file.  Now we use the the current time instead so this could
	 * go away -DW
	 */
	if (stat(cachetable, &sb) < 0) {
		log_errno(cachetable);
		watermark = 0;
	} else {
		watermark = sb.st_mtime;
	}
	watermark = watermark > 0 ? watermark : 0;
	sprintf(lmttable, "%s/LMT.gdbm", cachedir);
	if (access(lmttable, F_OK)) {
		lm_dbf = gdbm_open(lmttable, 0, GDBM_NEWDB, 0664, NULL);
		if (lm_dbf == NULL) {
			if ((gdbm_errno != GDBM_CANT_BE_WRITER) &&
			    (gdbm_errno != GDBM_CANT_BE_READER)) {
				errorlog("GDBM ERROR: gdbm_open: %s: %s\n",
				    lmttable, gdbm_strerror(gdbm_errno));
				die();
			}
		} else
			gdbm_close(lm_dbf);
	}
	lm_dbf = NULL;

#if   defined(HAVE_SRAND48)
	(void) srand48((long) time(NULL));
#elif defined(HAVE_SRANDOM)
	(void) srandom((unsigned) time(NULL));
#else
	(void) srand(time(NULL));
#endif

	max_cache_size = 32;
	if ((s = getenv("HARVEST_MAX_LOCAL_CACHE")) != NULL)
		max_cache_size = atoi(s);
	if (max_cache_size < 0)
		max_cache_size = 32;
	max_cache_size *= 1024 * 1024;

	cache_ttl = CACHE_TTL;
	if ((s = getenv("GATHERER_CACHE_TTL")) != NULL)
		cache_ttl = atoi(s);
	if (cache_ttl < 0)
		cache_ttl = CACHE_TTL;
}


/*
 *  get_access() - Obtains access to GDBM database table.  Blocks until
 *  it can obtain access.  Locks all other liburl's from the cache table.
 */
static void get_access(flag)
     int flag;
{
	while (1) {
		dbf = gdbm_open(cachetable, 0, flag, 0664, NULL);
		if (dbf != NULL)
			break;
		if ((gdbm_errno != GDBM_CANT_BE_WRITER) &&
		    (gdbm_errno != GDBM_CANT_BE_READER)) {
			errorlog("GDBM ERROR: gdbm_open: %s: %s\n",
			    cachetable, gdbm_strerror(gdbm_errno));
			die();
		}
#ifdef HAVE_USLEEP
#if   defined(HAVE_SRAND48)
		(void) usleep((lrand48() % 200) + 10);	/* wait a random amount */
#elif defined(HAVE_SRANDOM)
		(void) usleep((random() % 200) + 10);	/* wait a random amount */
#else
		(void) usleep((rand() % 200) + 10);	/* wait a random amount */
#endif
#else
		{
			struct timeval sleep;
			sleep.tv_sec = 0;
#if   defined(HAVE_SRAND48)
			sleep.tv_usec = (lrand48() % 200) + 10;
#elif defined(HAVE_SRANDOM)
			sleep.tv_usec = (random() % 200) + 10;
#else
			sleep.tv_usec = (rand() % 200) + 10;
#endif

#ifndef _HARVEST_HPUX_
			select(0, (fd_set *) 0, (fd_set *) 0, (fd_set *) 0, &sleep);
#else /* _HARVEST_HPUX_ */
			select(0, (int *) 0, (int *) 0, (int *) 0, &sleep);
#endif /* _HARVEST_HPUX_ */
		}
#endif
	}

	/*
	 * this should be safe.  Only open this DB after the other has
	 * been opened.
	 */
	lm_dbf = gdbm_open(lmttable, 0, flag, 0664, NULL);
	if (lm_dbf == NULL) {
		errorlog("GDBM ERROR: gdbm_open: %s: %s\n",
		    lmttable, gdbm_strerror(gdbm_errno));
		die();
	}
}

/*
 *  release_access() - Releases access to the GDBM database.
 */
static void release_access()
{
	if (lm_dbf != NULL)
		gdbm_close(lm_dbf);
	lm_dbf = NULL;
	if (dbf != NULL)
		gdbm_close(dbf);
	dbf = NULL;
}

/*
 *  get_cache_filename() - Generates a unique filename to store in the cache
 */
static char *get_cache_filename()
{
	static char *s;

	while (1) {
		if ((s = next_filename()) == NULL)
			return (NULL);
		if (access(s, F_OK))
			return (s);
		xfree(s);
	}
	return (NULL);
}

/*
 *  add_cache() - Add the URL,filename to the cache.
 */
void add_cache(url, filename, lmt)
     char *url;
     char *filename;
     time_t lmt;
{
	datum k, d;
	char *cfile;
	struct stat sb;
	int ndeletes = 0, current_size;
	int status;

	/* Find out some more about the file */
	if (lstat(filename, &sb) < 0) {
		log_errno(filename);
		return;
	}
	if (!S_ISREG(sb.st_mode))
		return;

	get_access(GDBM_WRCREAT);	/* LOCK */