mod_disk_cache.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * 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.
 */

#include "apr_file_io.h"
#include "apr_strings.h"
#include "mod_cache.h"
#include "ap_provider.h"
#include "util_filter.h"
#include "util_script.h"

#if APR_HAVE_UNISTD_H
#include <unistd.h> /* needed for unlink/link */
#endif

/* Our on-disk header format is:
 *
 * disk_cache_info_t
 * entity name (dobj->name) [length is in disk_cache_info_t->name_len]
 * r->headers_out (delimited by CRLF)
 * CRLF
 * r->headers_in (delimited by CRLF)
 * CRLF
 */
#define DISK_FORMAT_VERSION 0
typedef struct {
    /* Indicates the format of the header struct stored on-disk. */
    int format;
    /* The HTTP status code returned for this response.  */
    int status;
    /* The size of the entity name that follows. */
    apr_size_t name_len;
    /* The number of times we've cached this entity. */
    apr_size_t entity_version;
    /* Miscellaneous time values. */
    apr_time_t date;
    apr_time_t expire;
    apr_time_t request_time;
    apr_time_t response_time;
} disk_cache_info_t;

/*
 * disk_cache_object_t
 * Pointed to by cache_object_t::vobj
 */
typedef struct disk_cache_object {
    const char *root;        /* the location of the cache directory */
    char *tempfile;          /* temp file tohold the content */
#if 0
    int dirlevels;              /* Number of levels of subdirectories */
    int dirlength;            /* Length of subdirectory names */
#endif
    char *datafile;          /* name of file where the data will go */
    char *hdrsfile;          /* name of file where the hdrs will go */
    char *hashfile;          /* Computed hash key for this URI */
    char *name;
    apr_file_t *fd;          /* data file */
    apr_file_t *hfd;         /* headers file */
    apr_file_t *tfd;         /* temporary file for data */
    apr_off_t file_size;     /*  File size of the cached data file  */
    disk_cache_info_t disk_info; /* Header information. */
} disk_cache_object_t;


/*
 * mod_disk_cache configuration
 */
/* TODO: Make defaults OS specific */
#define CACHEFILE_LEN 20        /* must be less than HASH_LEN/2 */
#define DEFAULT_DIRLEVELS 3
#define DEFAULT_DIRLENGTH 2
#define DEFAULT_MIN_FILE_SIZE 1
#define DEFAULT_MAX_FILE_SIZE 1000000
#define DEFAULT_CACHE_SIZE 1000000

typedef struct {
    const char* cache_root;
    apr_size_t cache_root_len;
    off_t space;                 /* Maximum cache size (in 1024 bytes) */
    apr_time_t maxexpire;        /* Maximum time to keep cached files in msecs */
    apr_time_t defaultexpire;    /* default time to keep cached file in msecs */
    double lmfactor;             /* factor for estimating expires date */
    apr_time_t gcinterval;       /* garbage collection interval, in msec */
    int dirlevels;               /* Number of levels of subdirectories */
    int dirlength;               /* Length of subdirectory names */
    int        expirychk;               /* true if expiry time is observed for cached files */
    apr_size_t minfs;            /* minumum file size for cached files */
    apr_size_t maxfs;            /* maximum file size for cached files */
    apr_time_t mintm;            /* minimum time margin for caching files */
    /* dgc_time_t gcdt;            time of day for daily garbage collection */
    apr_array_header_t *gcclnun; /* gc_retain_t entries for unused files */
    apr_array_header_t *gcclean; /* gc_retain_t entries for all files */
    int maxgcmem;                /* maximum memory used by garbage collection */
} disk_cache_conf;

module AP_MODULE_DECLARE_DATA disk_cache_module;

/* Forward declarations */
static int remove_entity(cache_handle_t *h);
static apr_status_t store_headers(cache_handle_t *h, request_rec *r, cache_info *i);
static apr_status_t store_body(cache_handle_t *h, request_rec *r, apr_bucket_brigade *b);
static apr_status_t recall_headers(cache_handle_t *h, request_rec *r);
static apr_status_t recall_body(cache_handle_t *h, apr_pool_t *p, apr_bucket_brigade *bb);

/*
 * Local static functions
 */
#define CACHE_HEADER_SUFFIX ".header"
#define CACHE_DATA_SUFFIX   ".data"
static char *header_file(apr_pool_t *p, disk_cache_conf *conf,
                         disk_cache_object_t *dobj, const char *name)
{
    if (!dobj->hashfile) {
        dobj->hashfile = generate_name(p, conf->dirlevels, conf->dirlength,
                                       name);
    }
    return apr_pstrcat(p, conf->cache_root, "/", dobj->hashfile,
                       CACHE_HEADER_SUFFIX, NULL);
}

static char *data_file(apr_pool_t *p, disk_cache_conf *conf,
                       disk_cache_object_t *dobj, const char *name)
{
    if (!dobj->hashfile) {
        dobj->hashfile = generate_name(p, conf->dirlevels, conf->dirlength,
                                       name);
    }
    return apr_pstrcat(p, conf->cache_root, "/", dobj->hashfile,
                       CACHE_DATA_SUFFIX, NULL);
}

static void mkdir_structure(disk_cache_conf *conf, char *file, apr_pool_t *pool)
{
    apr_status_t rv;
    char *p;

    for (p = file + conf->cache_root_len + 1;;) {
        p = strchr(p, '/');
        if (!p)
            break;
        *p = '\0';

        rv = apr_dir_make(file,
                          APR_UREAD|APR_UWRITE|APR_UEXECUTE, pool);
        if (rv != APR_SUCCESS && !APR_STATUS_IS_EEXIST(rv)) {
            /* XXX */
        }
        *p = '/';
        ++p;
    }
}

static apr_status_t file_cache_el_final(disk_cache_object_t *dobj,
                                        request_rec *r)
{
    /* move the data over */
    if (dobj->tfd) {
        apr_status_t rv;

        apr_file_close(dobj->tfd);

        /* This assumes that the tempfile is on the same file system
         * as the cache_root. If not, then we need a file copy/move
         * rather than a rename.
         */
        rv = apr_file_rename(dobj->tempfile, dobj->datafile, r->pool);
        if (rv != APR_SUCCESS) {
            /* XXX log */
        }

        dobj->tfd = NULL;
    }

    return APR_SUCCESS;
}

static apr_status_t file_cache_errorcleanup(disk_cache_object_t *dobj, request_rec *r)
{
    /* Remove the header file and the body file. */
    apr_file_remove(dobj->hdrsfile, r->pool);
    apr_file_remove(dobj->datafile, r->pool);

    /* If we opened the temporary data file, close and remove it. */
    if (dobj->tfd) {
        apr_file_close(dobj->tfd);
        apr_file_remove(dobj->tempfile, r->pool);
        dobj->tfd = NULL;
    }

    return APR_SUCCESS;
}


/* These two functions get and put state information into the data
 * file for an ap_cache_el, this state information will be read
 * and written transparent to clients of this module
 */
static int file_cache_recall_mydata(apr_file_t *fd, cache_info *info,
                                    disk_cache_object_t *dobj, request_rec *r)
{
    apr_status_t rv;
    char *urlbuff;
    disk_cache_info_t disk_info;
    apr_size_t len;

    /* read the data from the cache file */
    len = sizeof(disk_cache_info_t);
    rv = apr_file_read_full(fd, &disk_info, len, &len);
    if (rv != APR_SUCCESS) {
        return rv;
    }

    if (disk_info.format != DISK_FORMAT_VERSION) {
        ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
                     "cache_disk: URL %s had a on-disk version mismatch",
                     r->uri);
        return APR_EGENERAL;
    }

    /* Store it away so we can get it later. */
    dobj->disk_info = disk_info;

    info->date = disk_info.date;
    info->expire = disk_info.expire;
    info->request_time = disk_info.request_time;
    info->response_time = disk_info.response_time;

    /* Note that we could optimize this by conditionally doing the palloc
     * depending upon the size. */
    urlbuff = apr_palloc(r->pool, disk_info.name_len + 1);
    len = disk_info.name_len;
    rv = apr_file_read_full(fd, urlbuff, len, &len);
    if (rv != APR_SUCCESS) {
        return rv;
    }
    urlbuff[disk_info.name_len] = '\0';

    /* check that we have the same URL */
    /* Would strncmp be correct? */
    if (strcmp(urlbuff, dobj->name) != 0) {
        return APR_EGENERAL;
    }

    return APR_SUCCESS;
}

/*
 * Hook and mod_cache callback functions
 */
#define AP_TEMPFILE "/aptmpXXXXXX"
static int create_entity(cache_handle_t *h, request_rec *r,
                         const char *key,
                         apr_off_t len)
{
    disk_cache_conf *conf = ap_get_module_config(r->server->module_config,
                                                 &disk_cache_module);
    apr_status_t rv;
    cache_object_t *obj;
    disk_cache_object_t *dobj;
    apr_file_t *tmpfile;

    if (conf->cache_root == NULL) {
        return DECLINED;
    }

    /* If the Content-Length is still unknown, cache anyway */
    if (len != -1 && (len < conf->minfs || len > conf->maxfs)) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                     "cache_disk: URL %s failed the size check, "
                     "or is incomplete",
                     key);
        return DECLINED;
    }

    /* Allocate and initialize cache_object_t and disk_cache_object_t */
    h->cache_obj = obj = apr_pcalloc(r->pool, sizeof(*obj));
    obj->vobj = dobj = apr_pcalloc(r->pool, sizeof(*dobj));

    obj->key = apr_pstrdup(r->pool, key);
    /* XXX Bad Temporary Cast - see cache_object_t notes */
    obj->info.len = (apr_size_t) len;
    obj->complete = 0;   /* Cache object is not complete */

    dobj->name = obj->key;
    dobj->datafile = data_file(r->pool, conf, dobj, key);
    dobj->hdrsfile = header_file(r->pool, conf, dobj, key);
    dobj->tempfile = apr_pstrcat(r->pool, conf->cache_root, AP_TEMPFILE, NULL);

    return OK;
}

static int open_entity(cache_handle_t *h, request_rec *r, const char *key)
{
    apr_status_t rc;
    static int error_logged = 0;
    disk_cache_conf *conf = ap_get_module_config(r->server->module_config,
                                                 &disk_cache_module);
    apr_finfo_t finfo;
    cache_object_t *obj;
    cache_info *info;
    disk_cache_object_t *dobj;
    int flags;

    h->cache_obj = NULL;

    /* Look up entity keyed to 'url' */
    if (conf->cache_root == NULL) {
        if (!error_logged) {
            error_logged = 1;
            ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,