mod_mem_cache.c

apache服务器源代码（版本号：2.2.2）

    int eos = 0;

    if (mobj->type == CACHE_TYPE_FILE) {
        apr_file_t *file = NULL;
        int fd = 0;
        int other = 0;

        /* We can cache an open file descriptor if:
         * - the brigade contains one and only one file_bucket &&
         * - the brigade is complete &&
         * - the file_bucket is the last data bucket in the brigade
         */
        for (e = APR_BRIGADE_FIRST(b);
             e != APR_BRIGADE_SENTINEL(b);
             e = APR_BUCKET_NEXT(e))
        {
            if (APR_BUCKET_IS_EOS(e)) {
                eos = 1;
            }
            else if (APR_BUCKET_IS_FILE(e)) {
                apr_bucket_file *a = e->data;
                fd++;
                file = a->fd;
            }
            else {
                other++;
            }
        }
        if (fd == 1 && !other && eos) {
            apr_file_t *tmpfile;
            const char *name;
            /* Open a new XTHREAD handle to the file */
            apr_file_name_get(&name, file);
            mobj->flags = ((APR_SENDFILE_ENABLED & apr_file_flags_get(file))
                           | APR_READ | APR_BINARY | APR_XTHREAD | APR_FILE_NOCLEANUP);
            rv = apr_file_open(&tmpfile, name, mobj->flags,
                               APR_OS_DEFAULT, r->pool);
            if (rv != APR_SUCCESS) {
                return rv;
            }
            apr_file_inherit_unset(tmpfile);
            apr_os_file_get(&(mobj->fd), tmpfile);

            /* Open for business */
            ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
                         "mem_cache: Cached file: %s with key: %s", name, obj->key);
            obj->complete = 1;
            return APR_SUCCESS;
        }

        /* Content not suitable for fd caching. Cache in-memory instead. */
        mobj->type = CACHE_TYPE_HEAP;
    }

    /*
     * FD cacheing is not enabled or the content was not
     * suitable for fd caching.
     */
    if (mobj->m == NULL) {
        mobj->m = malloc(mobj->m_len);
        if (mobj->m == NULL) {
            return APR_ENOMEM;
        }
        obj->count = 0;
    }
    cur = (char*) mobj->m + obj->count;

    /* Iterate accross the brigade and populate the cache storage */
    for (e = APR_BRIGADE_FIRST(b);
         e != APR_BRIGADE_SENTINEL(b);
         e = APR_BUCKET_NEXT(e))
    {
        const char *s;
        apr_size_t len;

        if (APR_BUCKET_IS_EOS(e)) {
            if (mobj->m_len > obj->count) {
                /* Caching a streamed response. Reallocate a buffer of the
                 * correct size and copy the streamed response into that
                 * buffer */
                char *buf = malloc(obj->count);
                if (!buf) {
                    return APR_ENOMEM;
                }
                memcpy(buf, mobj->m, obj->count);
                free(mobj->m);
                mobj->m = buf;

                /* Now comes the crufty part... there is no way to tell the
                 * cache that the size of the object has changed. We need
                 * to remove the object, update the size and re-add the
                 * object, all under protection of the lock.
                 */
                if (sconf->lock) {
                    apr_thread_mutex_lock(sconf->lock);
                }
                /* Has the object been ejected from the cache?
                 */
                tobj = (cache_object_t *) cache_find(sconf->cache_cache, obj->key);
                if (tobj == obj) {
                    /* Object is still in the cache, remove it, update the len field then
                     * replace it under protection of sconf->lock.
                     */
                    cache_remove(sconf->cache_cache, obj);
                    /* For illustration, cache no longer has reference to the object
                     * so decrement the refcount
                     * apr_atomic_dec32(&obj->refcount);
                     */
                    mobj->m_len = obj->count;

                    cache_insert(sconf->cache_cache, obj);
                    /* For illustration, cache now has reference to the object, so
                     * increment the refcount
                     * apr_atomic_inc32(&obj->refcount);
                     */
                }
                else if (tobj) {
                    /* Different object with the same key found in the cache. Doing nothing
                     * here will cause the object refcount to drop to 0 in decrement_refcount
                     * and the object will be cleaned up.
                     */

                } else {
                    /* Object has been ejected from the cache, add it back to the cache */
                    mobj->m_len = obj->count;
                    cache_insert(sconf->cache_cache, obj);
                    apr_atomic_inc32(&obj->refcount);
                }

                if (sconf->lock) {
                    apr_thread_mutex_unlock(sconf->lock);
                }
            }
            /* Open for business */
            ap_log_error(APLOG_MARK, APLOG_INFO, 0, r->server,
                         "mem_cache: Cached url: %s", obj->key);
            obj->complete = 1;
            break;
        }
        rv = apr_bucket_read(e, &s, &len, eblock);
        if (rv != APR_SUCCESS) {
            return rv;
        }
        if (len) {
            /* Check for buffer overflow */
           if ((obj->count + len) > mobj->m_len) {
               return APR_ENOMEM;
           }
           else {
               memcpy(cur, s, len);
               cur+=len;
               obj->count+=len;
           }
        }
        /* This should not fail, but if it does, we are in BIG trouble
         * cause we just stomped all over the heap.
         */
        AP_DEBUG_ASSERT(obj->count <= mobj->m_len);
    }
    return APR_SUCCESS;
}
/**
 * Configuration and start-up
 */
static int mem_cache_post_config(apr_pool_t *p, apr_pool_t *plog,
                                 apr_pool_t *ptemp, server_rec *s)
{
    int threaded_mpm;

    /* Sanity check the cache configuration */
    if (sconf->min_cache_object_size >= sconf->max_cache_object_size) {
        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s,
                     "MCacheMaxObjectSize must be greater than MCacheMinObjectSize");
        return DONE;
    }
    if (sconf->max_cache_object_size >= sconf->max_cache_size) {
        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s,
                     "MCacheSize must be greater than MCacheMaxObjectSize");
        return DONE;
    }
    if (sconf->max_streaming_buffer_size > sconf->max_cache_object_size) {
        /* Issue a notice only if something other than the default config
         * is being used */
        if (sconf->max_streaming_buffer_size != DEFAULT_MAX_STREAMING_BUFFER_SIZE &&
            sconf->max_cache_object_size != DEFAULT_MAX_CACHE_OBJECT_SIZE) {
            ap_log_error(APLOG_MARK, APLOG_NOTICE, 0, s,
                         "MCacheMaxStreamingBuffer must be less than or equal to MCacheMaxObjectSize. "
                         "Resetting MCacheMaxStreamingBuffer to MCacheMaxObjectSize.");
        }
        sconf->max_streaming_buffer_size = sconf->max_cache_object_size;
    }
    if (sconf->max_streaming_buffer_size < sconf->min_cache_object_size) {
        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, s,
                     "MCacheMaxStreamingBuffer must be greater than or equal to MCacheMinObjectSize. "
                     "Resetting MCacheMaxStreamingBuffer to MCacheMinObjectSize.");
        sconf->max_streaming_buffer_size = sconf->min_cache_object_size;
    }
    ap_mpm_query(AP_MPMQ_IS_THREADED, &threaded_mpm);
    if (threaded_mpm) {
        apr_thread_mutex_create(&sconf->lock, APR_THREAD_MUTEX_DEFAULT, p);
    }

    sconf->cache_cache = cache_init(sconf->max_object_cnt,
                                    sconf->max_cache_size,
                                    memcache_get_priority,
                                    sconf->cache_remove_algorithm,
                                    memcache_get_pos,
                                    memcache_set_pos,
                                    memcache_inc_frequency,
                                    memcache_cache_get_size,
                                    memcache_cache_get_key,
                                    memcache_cache_free);
    apr_pool_cleanup_register(p, sconf, cleanup_cache_mem, apr_pool_cleanup_null);

    if (sconf->cache_cache)
        return OK;

    return -1;

}

static const char
*set_max_cache_size(cmd_parms *parms, void *in_struct_ptr, const char *arg)
{
    apr_size_t val;

    if (sscanf(arg, "%" APR_SIZE_T_FMT, &val) != 1) {
        return "MCacheSize argument must be an integer representing the max cache size in KBytes.";
    }
    sconf->max_cache_size = val*1024;
    return NULL;
}
static const char
*set_min_cache_object_size(cmd_parms *parms, void *in_struct_ptr, const char *arg)
{
    apr_size_t val;

    if (sscanf(arg, "%" APR_SIZE_T_FMT, &val) != 1) {
        return "MCacheMinObjectSize value must be an integer (bytes)";
    }
    sconf->min_cache_object_size = val;
    return NULL;
}
static const char
*set_max_cache_object_size(cmd_parms *parms, void *in_struct_ptr, const char *arg)
{
    apr_size_t val;

    if (sscanf(arg, "%" APR_SIZE_T_FMT, &val) != 1) {
        return "MCacheMaxObjectSize value must be an integer (bytes)";
    }
    sconf->max_cache_object_size = val;
    return NULL;
}
static const char
*set_max_object_count(cmd_parms *parms, void *in_struct_ptr, const char *arg)
{
    apr_size_t val;

    if (sscanf(arg, "%" APR_SIZE_T_FMT, &val) != 1) {
        return "MCacheMaxObjectCount value must be an integer";
    }
    sconf->max_object_cnt = val;
    return NULL;
}

static const char
*set_cache_removal_algorithm(cmd_parms *parms, void *name, const char *arg)
{
    if (strcasecmp("LRU", arg)) {
        sconf->cache_remove_algorithm = memcache_lru_algorithm;
    }
    else {
        if (strcasecmp("GDSF", arg)) {
            sconf->cache_remove_algorithm = memcache_gdsf_algorithm;
        }
        else {
            return "currently implemented algorithms are LRU and GDSF";
        }
    }
    return NULL;
}

static const char *set_max_streaming_buffer(cmd_parms *parms, void *dummy,
                                            const char *arg)
{
    char *err;
    if (apr_strtoff(&sconf->max_streaming_buffer_size, arg, &err, 10) || *err) {
        return "MCacheMaxStreamingBuffer value must be a number";
    }

    return NULL;
}

static const command_rec cache_cmds[] =
{
    AP_INIT_TAKE1("MCacheSize", set_max_cache_size, NULL, RSRC_CONF,
     "The maximum amount of memory used by the cache in KBytes"),
    AP_INIT_TAKE1("MCacheMaxObjectCount", set_max_object_count, NULL, RSRC_CONF,
     "The maximum number of objects allowed to be placed in the cache"),
    AP_INIT_TAKE1("MCacheMinObjectSize", set_min_cache_object_size, NULL, RSRC_CONF,
     "The minimum size (in bytes) of an object to be placed in the cache"),
    AP_INIT_TAKE1("MCacheMaxObjectSize", set_max_cache_object_size, NULL, RSRC_CONF,
     "The maximum size (in bytes) of an object to be placed in the cache"),
    AP_INIT_TAKE1("MCacheRemovalAlgorithm", set_cache_removal_algorithm, NULL, RSRC_CONF,
     "The algorithm used to remove entries from the cache (default: GDSF)"),
    AP_INIT_TAKE1("MCacheMaxStreamingBuffer", set_max_streaming_buffer, NULL, RSRC_CONF,
     "Maximum number of bytes of content to buffer for a streamed response"),
    {NULL}
};

static const cache_provider cache_mem_provider =
{
    &remove_entity,
    &store_headers,
    &store_body,
    &recall_headers,
    &recall_body,
    &create_mem_entity,
    &open_entity,
    &remove_url,
};

static const cache_provider cache_fd_provider =
{
    &remove_entity,
    &store_headers,
    &store_body,
    &recall_headers,
    &recall_body,
    &create_fd_entity,
    &open_entity,
    &remove_url,
};

static void register_hooks(apr_pool_t *p)
{
    ap_hook_post_config(mem_cache_post_config, NULL, NULL, APR_HOOK_MIDDLE);
    /* cache initializer */
    /* cache_hook_init(cache_mem_init, NULL, NULL, APR_HOOK_MIDDLE);  */
    /*
    cache_hook_create_entity(create_entity, NULL, NULL, APR_HOOK_MIDDLE);
    cache_hook_open_entity(open_entity,  NULL, NULL, APR_HOOK_MIDDLE);
    cache_hook_remove_url(remove_url, NULL, NULL, APR_HOOK_MIDDLE);
    */
    ap_register_provider(p, CACHE_PROVIDER_GROUP, "mem", "0",
                         &cache_mem_provider);
    ap_register_provider(p, CACHE_PROVIDER_GROUP, "fd", "0",
                         &cache_fd_provider);
}

module AP_MODULE_DECLARE_DATA mem_cache_module =
{
    STANDARD20_MODULE_STUFF,
    NULL,                    /* create per-directory config structure */
    NULL,                    /* merge per-directory config structures */
    create_cache_config,     /* create per-server config structure */
    NULL,                    /* merge per-server config structures */
    cache_cmds,              /* command apr_table_t */
    register_hooks
};