mod_proxy_balancer.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.
 */

/* Load balancer module for Apache proxy */

#define CORE_PRIVATE

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

module AP_MODULE_DECLARE_DATA proxy_balancer_module;

static char balancer_nonce[APR_UUID_FORMATTED_LENGTH + 1];

static int proxy_balancer_canon(request_rec *r, char *url)
{
    char *host, *path;
    char *search = NULL;
    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:
     * process the path. With proxy-noncanon set (by
     * mod_proxy) we use the raw, unparsed uri
     */
    if (apr_table_get(r->notes, "proxy-nocanon")) {
        path = url;   /* this is the raw path */
    }
    else {
        path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0,
                                 r->proxyreq);
        search = r->args;
    }
    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;
    int worker_is_initialized;
    proxy_worker_stat *slot;

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

    for (i = 0; i < balancer->workers->nelts; i++) {
        worker_is_initialized = PROXY_WORKER_IS_INITIALIZED(workers);
        if (!worker_is_initialized) {
            /*
             * If the worker is not initialized check whether its scoreboard
             * slot is already initialized.
             */
            slot = (proxy_worker_stat *) ap_get_scoreboard_lb(workers->id);
            if (slot) {
                worker_is_initialized = slot->status & PROXY_WORKER_INITIALIZED;
            }
            else {
                worker_is_initialized = 0;
            }
        }
        ap_proxy_initialize_worker_share(conf, workers, s);
        ap_proxy_initialize_worker(workers, s);
        if (!worker_is_initialized) {
            /* Set to the original configuration */
            workers->s->lbstatus = workers->s->lbfactor =
            (workers->lbfactor ? workers->lbfactor : 1);
            workers->s->lbset = workers->lbset;
        }
        ++workers;
    }

    /* 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, int scolon_sep)
{
    char *path = NULL;
    char *pathdelims = "?&";

    if (scolon_sep) {
        pathdelims = ";?&";
    }
    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_strtok(apr_pstrdup(pool, path), pathdelims, &q);
                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, request_rec *r)
{
    int i;
    int checking_standby;
    int checked_standby;
    
    proxy_worker *worker;

    checking_standby = checked_standby = 0;
    while (!checked_standby) {
        worker = (proxy_worker *)balancer->workers->elts;
        for (i = 0; i < balancer->workers->nelts; i++, worker++) {
            if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
                continue;
            if (*(worker->s->route) && strcmp(worker->s->route, route) == 0) {
                if (worker && PROXY_WORKER_IS_USABLE(worker)) {
                    return worker;
                } else {
                    /*
                     * If the worker is in error state run
                     * retry on that worker. It will be marked as
                     * operational if the retry timeout is elapsed.
                     * The worker might still be unusable, but we try
                     * anyway.
                     */
                    ap_proxy_retry_worker("BALANCER", worker, r->server);
                    if (PROXY_WORKER_IS_USABLE(worker)) {
                            return worker;
                    } else {
                        /*
                         * 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 some kind of
                         * session replication between those two remote.
                         */
                        if (*worker->s->redirect) {
                            proxy_worker *rworker = NULL;
                            rworker = find_route_worker(balancer, worker->s->redirect, r);
                            /* Check if the redirect worker is usable */
                            if (rworker && !PROXY_WORKER_IS_USABLE(rworker)) {
                                /*
                                 * If the worker is in error state run
                                 * retry on that worker. It will be marked as
                                 * operational if the retry timeout is elapsed.
                                 * The worker might still be unusable, but we try
                                 * anyway.
                                 */
                                ap_proxy_retry_worker("BALANCER", rworker, r->server);
                            }
                            if (rworker && PROXY_WORKER_IS_USABLE(rworker))
                                return rworker;
                        }
                    }
                }
            }
        }
        checked_standby = checking_standby++;
    }
    return NULL;
}

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

    if (!balancer->sticky)
        return NULL;
    sticky = sticky_path = apr_pstrdup(r->pool, balancer->sticky);
    if ((path = strchr(sticky, '|'))) {
        *path++ = '\0';
         sticky_path = path;
    }
    
    /* Try to find the sticky route inside url */
    *sticky_used = sticky_path;
    *route = get_path_param(r->pool, *url, sticky_path, balancer->scolonsep);
    if (!*route) {
        *route = get_cookie_param(r, sticky);
        *sticky_used = 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, r);
        if (worker && strcmp(*route, worker->s->route)) {
            /*
             * Notice that the route of the worker chosen is different from
             * the route supplied by the client.
             */
            apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
            ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                         "proxy: BALANCER: Route changed from %s to %s",
                         *route, worker->s->route);
        }
        return worker;
    }
    else
        return NULL;
}

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

    if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {