mod_disk_cache.c

Apache官方在今天放出产品系列2.2的最新版本2.2.11的源码包 最流行的HTTP服务器软件之一

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 "mod_disk_cache.h"
#include "ap_provider.h"
#include "util_filter.h"
#include "util_script.h"
#include "util_charset.h"

/*
 * mod_disk_cache: Disk Based HTTP 1.1 Cache.
 *
 * Flow to Find the .data file:
 *   Incoming client requests URI /foo/bar/baz
 *   Generate <hash> off of /foo/bar/baz
 *   Open <hash>.header
 *   Read in <hash>.header file (may contain Format #1 or Format #2)
 *   If format #1 (Contains a list of Vary Headers):
 *      Use each header name (from .header) with our request values (headers_in) to
 *      regenerate <hash> using HeaderName+HeaderValue+.../foo/bar/baz
 *      re-read in <hash>.header (must be format #2)
 *   read in <hash>.data
 *
 * Format #1:
 *   apr_uint32_t format;
 *   apr_time_t expire;
 *   apr_array_t vary_headers (delimited by CRLF)
 *
 * Format #2:
 *   disk_cache_info_t (first sizeof(apr_uint32_t) bytes is the format)
 *   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
 */

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);
static apr_status_t read_array(request_rec *r, apr_array_header_t* arr,
                               apr_file_t *file);

/*
 * Local static functions
 */

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 = ap_cache_generate_name(p, conf->dirlevels,
                                                conf->dirlength, name);
    }

    if (dobj->prefix) {
        return apr_pstrcat(p, dobj->prefix, CACHE_VDIR_SUFFIX, "/",
                           dobj->hashfile, CACHE_HEADER_SUFFIX, NULL);
     }
     else {
        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 = ap_cache_generate_name(p, conf->dirlevels,
                                                conf->dirlength, name);
    }

    if (dobj->prefix) {
        return apr_pstrcat(p, dobj->prefix, CACHE_VDIR_SUFFIX, "/",
                           dobj->hashfile, CACHE_DATA_SUFFIX, NULL);
     }
     else {
        return apr_pstrcat(p, conf->cache_root, "/", dobj->hashfile,
                           CACHE_DATA_SUFFIX, NULL);
     }
}

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

    for (p = (char*)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;
    }
}

/* htcacheclean may remove directories underneath us.
 * So, we'll try renaming three times at a cost of 0.002 seconds.
 */
static apr_status_t safe_file_rename(disk_cache_conf *conf,
                                     const char *src, const char *dest,
                                     apr_pool_t *pool)
{
    apr_status_t rv;

    rv = apr_file_rename(src, dest, pool);

    if (rv != APR_SUCCESS) {
        int i;

        for (i = 0; i < 2 && rv != APR_SUCCESS; i++) {
            /* 1000 micro-seconds aka 0.001 seconds. */
            apr_sleep(1000);

            mkdir_structure(conf, dest, pool);

            rv = apr_file_rename(src, dest, pool);
        }
    }

    return rv;
}

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) {
            ap_log_error(APLOG_MARK, APLOG_WARNING, rv, r->server,
                         "disk_cache: rename tempfile to datafile failed:"
                         " %s -> %s", dobj->tempfile, dobj->datafile);
            apr_file_remove(dobj->tempfile, r->pool);
        }

        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;
    }

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

    info->status = disk_info.status;
    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;
}

static const char* regen_key(apr_pool_t *p, apr_table_t *headers,
                             apr_array_header_t *varray, const char *oldkey)
{
    struct iovec *iov;
    int i, k;
    int nvec;
    const char *header;
    const char **elts;

    nvec = (varray->nelts * 2) + 1;
    iov = apr_palloc(p, sizeof(struct iovec) * nvec);
    elts = (const char **) varray->elts;

    /* TODO:
     *    - Handle multiple-value headers better. (sort them?)
     *    - Handle Case in-sensitive Values better.
     *        This isn't the end of the world, since it just lowers the cache
     *        hit rate, but it would be nice to fix.
     *
     * The majority are case insenstive if they are values (encoding etc).
     * Most of rfc2616 is case insensitive on header contents.
     *
     * So the better solution may be to identify headers which should be
     * treated case-sensitive?
     *  HTTP URI's (3.2.3) [host and scheme are insensitive]
     *  HTTP method (5.1.1)
     *  HTTP-date values (3.3.1)
     *  3.7 Media Types [exerpt]
     *     The type, subtype, and parameter attribute names are case-
     *     insensitive. Parameter values might or might not be case-sensitive,
     *     depending on the semantics of the parameter name.
     *  4.20 Except [exerpt]
     *     Comparison of expectation values is case-insensitive for unquoted
     *     tokens (including the 100-continue token), and is case-sensitive for
     *     quoted-string expectation-extensions.
     */

    for(i=0, k=0; i < varray->nelts; i++) {
        header = apr_table_get(headers, elts[i]);
        if (!header) {
            header = "";
        }
        iov[k].iov_base = (char*) elts[i];
        iov[k].iov_len = strlen(elts[i]);
        k++;
        iov[k].iov_base = (char*) header;
        iov[k].iov_len = strlen(header);
        k++;
    }
    iov[k].iov_base = (char*) oldkey;
    iov[k].iov_len = strlen(oldkey);
    k++;

    return apr_pstrcatv(p, iov, k, NULL);
}

static int array_alphasort(const void *fn1, const void *fn2)
{
    return strcmp(*(char**)fn1, *(char**)fn2);
}

static void tokens_to_array(apr_pool_t *p, const char *data,
                            apr_array_header_t *arr)
{
    char *token;

    while ((token = ap_get_list_item(p, &data)) != NULL) {
        *((const char **) apr_array_push(arr)) = token;
    }

    /* Sort it so that "Vary: A, B" and "Vary: B, A" are stored the same. */
    qsort((void *) arr->elts, arr->nelts,
         sizeof(char *), array_alphasort);
}

/*
 * Hook and mod_cache callback functions
 */
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);
    cache_object_t *obj;
    disk_cache_object_t *dobj;

    if (conf->cache_root == NULL) {
        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);

    dobj->name = obj->key;
    dobj->prefix = NULL;
    /* Save the cache root */
    dobj->root = apr_pstrndup(r->pool, conf->cache_root, conf->cache_root_len);
    dobj->root_len = conf->cache_root_len;
    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_uint32_t format;
    apr_size_t len;
    const char *nkey;
    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,
                         "disk_cache: Cannot cache files to disk without a CacheRoot specified.");
        }
        return DECLINED;
    }

    /* Create and init the cache object */
    h->cache_obj = obj = apr_pcalloc(r->pool, sizeof(cache_object_t));
    obj->vobj = dobj = apr_pcalloc(r->pool, sizeof(disk_cache_object_t));

    info = &(obj->info);

    /* Open the headers file */
    dobj->prefix = NULL;

    /* Save the cache root */
    dobj->root = apr_pstrndup(r->pool, conf->cache_root, conf->cache_root_len);
    dobj->root_len = conf->cache_root_len;

    dobj->hdrsfile = header_file(r->pool, conf, dobj, key);
    flags = APR_READ|APR_BINARY|APR_BUFFERED;
    rc = apr_file_open(&dobj->hfd, dobj->hdrsfile, flags, 0, r->pool);
    if (rc != APR_SUCCESS) {
        return DECLINED;
    }

    /* read the format from the cache file */