mod_proxy_balancer.c

apache服务器源代码（版本号：2.2.2）

/* Copyright 1999-2005 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.
 */

/* Load balancer module for Apache proxy */

#define CORE_PRIVATE

#include "mod_proxy.h"
#include "ap_mpm.h"
#include "apr_version.h"
#include "apr_hooks.h"

module AP_MODULE_DECLARE_DATA proxy_balancer_module;

static int proxy_balancer_canon(request_rec *r, char *url)
{
    char *host, *path, *search;
    const char *err;
    apr_port_t port = 0;

    if (strncasecmp(url, "balancer:", 9) == 0) {
        url += 9;
    }
    else {
        return DECLINED;
    }

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
             "proxy: BALANCER: canonicalising URL %s", url);

    /* do syntatic check.
     * We break the URL into host, port, path, search
     */
    err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
    if (err) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
                      "error parsing URL %s: %s",
                      url, err);
        return HTTP_BAD_REQUEST;
    }
    /* now parse path/search args, according to rfc1738 */
    /* N.B. if this isn't a true proxy request, then the URL _path_
     * has already been decoded.  True proxy requests have r->uri
     * == r->unparsed_uri, and no others have that property.
     */
    if (r->uri == r->unparsed_uri) {
        search = strchr(url, '?');
        if (search != NULL)
            *(search++) = '\0';
    }
    else
        search = r->args;

    /* process path */
    path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0, r->proxyreq);
    if (path == NULL)
        return HTTP_BAD_REQUEST;

    r->filename = apr_pstrcat(r->pool, "proxy:balancer://", host,
            "/", path, (search) ? "?" : "", (search) ? search : "", NULL);
    return OK;
}

static int init_balancer_members(proxy_server_conf *conf, server_rec *s,
                                 proxy_balancer *balancer)
{
    int i;
    proxy_worker *workers;

    workers = (proxy_worker *)balancer->workers->elts;

    for (i = 0; i < balancer->workers->nelts; i++) {
        ap_proxy_initialize_worker_share(conf, workers, s);
        ap_proxy_initialize_worker(workers, s);
        ++workers;
    }

    workers = (proxy_worker *)balancer->workers->elts;
    for (i = 0; i < balancer->workers->nelts; i++) {
        /* Set to the original configuration */
        workers[i].s->lbstatus = workers[i].s->lbfactor =
          (workers[i].lbfactor ? workers[i].lbfactor : 1);
    }
    /* Set default number of attempts to the number of
     * workers.
     */
    if (!balancer->max_attempts_set && balancer->workers->nelts > 1) {
        balancer->max_attempts = balancer->workers->nelts - 1;
        balancer->max_attempts_set = 1;
    }
    return 0;
}

/* Retrieve the parameter with the given name
 * Something like 'JSESSIONID=12345...N'
 */
static char *get_path_param(apr_pool_t *pool, char *url,
                            const char *name)
{
    char *path = NULL;

    for (path = strstr(url, name); path; path = strstr(path + 1, name)) {
        path += strlen(name);
        if (*path == '=') {
            /*
             * Session path was found, get it's value
             */
            ++path;
            if (strlen(path)) {
                char *q;
                path = apr_pstrdup(pool, path);
                if ((q = strchr(path, '?')))
                    *q = '\0';
                return path;
            }
        }
    }
    return NULL;
}

static char *get_cookie_param(request_rec *r, const char *name)
{
    const char *cookies;
    const char *start_cookie;

    if ((cookies = apr_table_get(r->headers_in, "Cookie"))) {
        for (start_cookie = ap_strstr_c(cookies, name); start_cookie;
             start_cookie = ap_strstr_c(start_cookie + 1, name)) {
            if (start_cookie == cookies ||
                start_cookie[-1] == ';' ||
                start_cookie[-1] == ',' ||
                isspace(start_cookie[-1])) {

                start_cookie += strlen(name);
                while(*start_cookie && isspace(*start_cookie))
                    ++start_cookie;
                if (*start_cookie == '=' && start_cookie[1]) {
                    /*
                     * Session cookie was found, get it's value
                     */
                    char *end_cookie, *cookie;
                    ++start_cookie;
                    cookie = apr_pstrdup(r->pool, start_cookie);
                    if ((end_cookie = strchr(cookie, ';')) != NULL)
                        *end_cookie = '\0';
                    if((end_cookie = strchr(cookie, ',')) != NULL)
                        *end_cookie = '\0';
                    return cookie;
                }
            }
        }
    }
    return NULL;
}

/* Find the worker that has the 'route' defined
 */
static proxy_worker *find_route_worker(proxy_balancer *balancer,
                                       const char *route)
{
    int i;
    proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
    for (i = 0; i < balancer->workers->nelts; i++) {
        if (*(worker->s->route) && strcmp(worker->s->route, route) == 0) {
            return worker;
        }
        worker++;
    }
    return NULL;
}

static proxy_worker *find_session_route(proxy_balancer *balancer,
                                        request_rec *r,
                                        char **route,
                                        char **url)
{
    proxy_worker *worker = NULL;

    if (!balancer->sticky)
        return NULL;
    /* Try to find the sticky route inside url */
    *route = get_path_param(r->pool, *url, balancer->sticky);
    if (!*route)
        *route = get_cookie_param(r, balancer->sticky);
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                            "proxy: BALANCER: Found value %s for "
                            "stickysession %s", *route, balancer->sticky);
    /*
     * If we found a value for sticksession, find the first '.' within.
     * Everything after '.' (if present) is our route.
     */
    if ((*route) && ((*route = strchr(*route, '.')) != NULL ))
        (*route)++;
    if ((*route) && (**route)) {
        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                                  "proxy: BALANCER: Found route %s", *route);
        /* We have a route in path or in cookie
         * Find the worker that has this route defined.
         */
        worker = find_route_worker(balancer, *route);
        if (worker && !PROXY_WORKER_IS_USABLE(worker)) {
            /* We have a worker that is unusable.
             * It can be in error or disabled, but in case
             * it has a redirection set use that redirection worker.
             * This enables to safely remove the member from the
             * balancer. Of course you will need a some kind of
             * session replication between those two remote.
             */
            if (*worker->s->redirect)
                worker = find_route_worker(balancer, worker->s->redirect);
            /* Check if the redirect worker is usable */
            if (worker && !PROXY_WORKER_IS_USABLE(worker))
                worker = NULL;
        }
        return worker;
    }
    else
        return NULL;
}

static proxy_worker *find_best_worker(proxy_balancer *balancer,
                                      request_rec *r)
{
    proxy_worker *candidate = NULL;

    if (PROXY_THREAD_LOCK(balancer) != APR_SUCCESS)
        return NULL;

    candidate = (*balancer->lbmethod->finder)(balancer, r);

/*
        PROXY_THREAD_UNLOCK(balancer);
        return NULL;
*/

    PROXY_THREAD_UNLOCK(balancer);

    if (candidate == NULL) {
        /* All the workers are in error state or disabled.
         * If the balancer has a timeout sleep for a while
         * and try again to find the worker. The chances are
         * that some other thread will release a connection.
         * By default the timeout is not set, and the server
         * returns SERVER_BUSY.
         */
#if APR_HAS_THREADS
        if (balancer->timeout) {
            /* XXX: This can perhaps be build using some
             * smarter mechanism, like tread_cond.
             * But since the statuses can came from
             * different childs, use the provided algo.
             */
            apr_interval_time_t timeout = balancer->timeout;
            apr_interval_time_t step, tval = 0;
            /* Set the timeout to 0 so that we don't
             * end in infinite loop
             */
            balancer->timeout = 0;
            step = timeout / 100;
            while (tval < timeout) {
                apr_sleep(step);
                /* Try again */
                if ((candidate = find_best_worker(balancer, r)))
                    break;
                tval += step;
            }
            /* restore the timeout */
            balancer->timeout = timeout;
        }
#endif
    }
    return candidate;
}

static int rewrite_url(request_rec *r, proxy_worker *worker,
                        char **url)
{
    const char *scheme = strstr(*url, "://");
    const char *path = NULL;

    if (scheme)
        path = ap_strchr_c(scheme + 3, '/');

    /* we break the URL into host, port, uri */
    if (!worker) {
        return ap_proxyerror(r, HTTP_BAD_REQUEST, apr_pstrcat(r->pool,
                             "missing worker. URI cannot be parsed: ", *url,
                             NULL));
    }

    *url = apr_pstrcat(r->pool, worker->name, path, NULL);

    return OK;
}

static int proxy_balancer_pre_request(proxy_worker **worker,
                                      proxy_balancer **balancer,
                                      request_rec *r,
                                      proxy_server_conf *conf, char **url)
{
    int access_status;
    proxy_worker *runtime;