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/* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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/* Load balancer module for Apache proxy */
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#include "mod_proxy.h"
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#include "apr_version.h"
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#include "apr_hooks.h"
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module AP_MODULE_DECLARE_DATA proxy_balancer_module;
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static int proxy_balancer_canon(request_rec *r, char *url)
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char *host, *path, *search;
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if (strncasecmp(url, "balancer:", 9) == 0) {
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: BALANCER: canonicalising URL %s", url);
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* We break the URL into host, port, path, search
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err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
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ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
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"error parsing URL %s: %s",
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return HTTP_BAD_REQUEST;
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/* now parse path/search args, according to rfc1738 */
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/* N.B. if this isn't a true proxy request, then the URL _path_
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* has already been decoded. True proxy requests have r->uri
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* == r->unparsed_uri, and no others have that property.
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if (r->uri == r->unparsed_uri) {
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search = strchr(url, '?');
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path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0, r->proxyreq);
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return HTTP_BAD_REQUEST;
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r->filename = apr_pstrcat(r->pool, "proxy:balancer://", host,
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"/", path, (search) ? "?" : "", (search) ? search : "", NULL);
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static int init_balancer_members(proxy_server_conf *conf, server_rec *s,
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proxy_balancer *balancer)
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proxy_worker *workers;
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workers = (proxy_worker *)balancer->workers->elts;
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for (i = 0; i < balancer->workers->nelts; i++) {
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ap_proxy_initialize_worker_share(conf, workers, s);
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ap_proxy_initialize_worker(workers, s);
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workers = (proxy_worker *)balancer->workers->elts;
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for (i = 0; i < balancer->workers->nelts; i++) {
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/* Set to the original configuration */
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workers[i].s->lbstatus = workers[i].s->lbfactor =
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(workers[i].lbfactor ? workers[i].lbfactor : 1);
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/* Set default number of attempts to the number of
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if (!balancer->max_attempts_set && balancer->workers->nelts > 1) {
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balancer->max_attempts = balancer->workers->nelts - 1;
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balancer->max_attempts_set = 1;
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/* Retrieve the parameter with the given name
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* Something like 'JSESSIONID=12345...N'
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static char *get_path_param(apr_pool_t *pool, char *url,
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for (path = strstr(url, name); path; path = strstr(path + 1, name)) {
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path += strlen(name);
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* Session path was found, get it's value
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path = apr_pstrdup(pool, path);
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if ((q = strchr(path, '?')))
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static char *get_cookie_param(request_rec *r, const char *name)
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const char *start_cookie;
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if ((cookies = apr_table_get(r->headers_in, "Cookie"))) {
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for (start_cookie = ap_strstr_c(cookies, name); start_cookie;
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start_cookie = ap_strstr_c(start_cookie + 1, name)) {
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if (start_cookie == cookies ||
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start_cookie[-1] == ';' ||
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start_cookie[-1] == ',' ||
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isspace(start_cookie[-1])) {
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start_cookie += strlen(name);
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while(*start_cookie && isspace(*start_cookie))
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if (*start_cookie == '=' && start_cookie[1]) {
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* Session cookie was found, get it's value
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char *end_cookie, *cookie;
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cookie = apr_pstrdup(r->pool, start_cookie);
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if ((end_cookie = strchr(cookie, ';')) != NULL)
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if((end_cookie = strchr(cookie, ',')) != NULL)
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/* Find the worker that has the 'route' defined
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static proxy_worker *find_route_worker(proxy_balancer *balancer,
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proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
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for (i = 0; i < balancer->workers->nelts; i++) {
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if (*(worker->s->route) && strcmp(worker->s->route, route) == 0) {
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static proxy_worker *find_session_route(proxy_balancer *balancer,
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proxy_worker *worker = NULL;
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if (!balancer->sticky)
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/* Try to find the sticky route inside url */
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*route = get_path_param(r->pool, *url, balancer->sticky);
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*route = get_cookie_param(r, balancer->sticky);
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: BALANCER: Found value %s for "
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"stickysession %s", *route, balancer->sticky);
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* If we found a value for sticksession, find the first '.' within.
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* Everything after '.' (if present) is our route.
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if ((*route) && ((*route = strchr(*route, '.')) != NULL ))
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if ((*route) && (**route)) {
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: BALANCER: Found route %s", *route);
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/* We have a route in path or in cookie
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* Find the worker that has this route defined.
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worker = find_route_worker(balancer, *route);
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if (worker && !PROXY_WORKER_IS_USABLE(worker)) {
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/* We have a worker that is unusable.
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* It can be in error or disabled, but in case
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* it has a redirection set use that redirection worker.
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* This enables to safely remove the member from the
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* balancer. Of course you will need a some kind of
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* session replication between those two remote.
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if (*worker->s->redirect)
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worker = find_route_worker(balancer, worker->s->redirect);
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/* Check if the redirect worker is usable */
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if (worker && !PROXY_WORKER_IS_USABLE(worker))
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static proxy_worker *find_best_worker(proxy_balancer *balancer,
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proxy_worker *candidate = NULL;
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if (PROXY_THREAD_LOCK(balancer) != APR_SUCCESS)
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candidate = (*balancer->lbmethod->finder)(balancer, r);
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PROXY_THREAD_UNLOCK(balancer);
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PROXY_THREAD_UNLOCK(balancer);
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if (candidate == NULL) {
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/* All the workers are in error state or disabled.
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* If the balancer has a timeout sleep for a while
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* and try again to find the worker. The chances are
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* that some other thread will release a connection.
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* By default the timeout is not set, and the server
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* returns SERVER_BUSY.
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if (balancer->timeout) {
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/* XXX: This can perhaps be build using some
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* smarter mechanism, like tread_cond.
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* But since the statuses can came from
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* different childs, use the provided algo.
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apr_interval_time_t timeout = balancer->timeout;
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apr_interval_time_t step, tval = 0;
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/* Set the timeout to 0 so that we don't
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* end in infinite loop
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balancer->timeout = 0;
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step = timeout / 100;
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while (tval < timeout) {
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if ((candidate = find_best_worker(balancer, r)))
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/* restore the timeout */
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balancer->timeout = timeout;
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static int rewrite_url(request_rec *r, proxy_worker *worker,
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const char *scheme = strstr(*url, "://");
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const char *path = NULL;
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path = ap_strchr_c(scheme + 3, '/');
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/* we break the URL into host, port, uri */
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return ap_proxyerror(r, HTTP_BAD_REQUEST, apr_pstrcat(r->pool,
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"missing worker. URI cannot be parsed: ", *url,
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*url = apr_pstrcat(r->pool, worker->name, path, NULL);
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static int proxy_balancer_pre_request(proxy_worker **worker,
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proxy_balancer **balancer,
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proxy_server_conf *conf, char **url)
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proxy_worker *runtime;
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/* Step 1: check if the url is for us
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* The url we can handle starts with 'balancer://'
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* If balancer is already provided skip the search
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* for balancer, because this is failover attempt.
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!(*balancer = ap_proxy_get_balancer(r->pool, conf, *url)))
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/* Step 2: find the session route */
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runtime = find_session_route(*balancer, r, &route, url);
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/* Lock the LoadBalancer
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* XXX: perhaps we need the process lock here
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if ((rv = PROXY_THREAD_LOCK(*balancer)) != APR_SUCCESS) {
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ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
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"proxy: BALANCER: lock");
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int i, total_factor = 0;
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proxy_worker *workers;
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/* We have a sticky load balancer
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* Update the workers status
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* so that even session routes get
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workers = (proxy_worker *)(*balancer)->workers->elts;
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for (i = 0; i < (*balancer)->workers->nelts; i++) {
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/* Take into calculation only the workers that are
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* not in error state or not disabled.
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if (PROXY_WORKER_IS_USABLE(workers)) {
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workers->s->lbstatus += workers->s->lbfactor;
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total_factor += workers->s->lbfactor;
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runtime->s->lbstatus -= total_factor;
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runtime->s->elected++;
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else if (route && (*balancer)->sticky_force) {
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ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
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"proxy: BALANCER: (%s). All workers are in error state for route (%s)",
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(*balancer)->name, route);
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PROXY_THREAD_UNLOCK(*balancer);
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return HTTP_SERVICE_UNAVAILABLE;
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PROXY_THREAD_UNLOCK(*balancer);
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runtime = find_best_worker(*balancer, r);
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ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
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"proxy: BALANCER: (%s). All workers are in error state",
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return HTTP_SERVICE_UNAVAILABLE;
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/* Rewrite the url from 'balancer://url'
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* to the 'worker_scheme://worker_hostname[:worker_port]/url'
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* This replaces the balancers fictional name with the
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* real hostname of the elected worker.
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access_status = rewrite_url(r, *worker, url);
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/* Add the session route to request notes if present */
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apr_table_setn(r->notes, "session-sticky", (*balancer)->sticky);
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apr_table_setn(r->notes, "session-route", route);
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: BALANCER (%s) worker (%s) rewritten to %s",
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(*balancer)->name, (*worker)->name, *url);
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return access_status;
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static int proxy_balancer_post_request(proxy_worker *worker,
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proxy_balancer *balancer,
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proxy_server_conf *conf)
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if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {
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ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
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"proxy: BALANCER: lock");
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return HTTP_INTERNAL_SERVER_ERROR;
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/* TODO: calculate the bytes transferred
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* This will enable to elect the worker that has
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* The bytes transferred depends on the protocol
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* used, so each protocol handler should keep the
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PROXY_THREAD_UNLOCK(balancer);
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy_balancer_post_request for (%s)", balancer->name);
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static void recalc_factors(proxy_balancer *balancer)
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proxy_worker *workers;
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/* Recalculate lbfactors */
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workers = (proxy_worker *)balancer->workers->elts;
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/* Special case if there is only one worker it's
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* load factor will always be 1
441
if (balancer->workers->nelts == 1) {
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workers->s->lbstatus = workers->s->lbfactor = 1;
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for (i = 0; i < balancer->workers->nelts; i++) {
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/* Update the status entries */
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workers[i].s->lbstatus = workers[i].s->lbfactor;
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/* Manages the loadfactors and member status
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static int balancer_handler(request_rec *r)
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void *sconf = r->server->module_config;
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proxy_server_conf *conf = (proxy_server_conf *)
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ap_get_module_config(sconf, &proxy_module);
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proxy_balancer *balancer, *bsel = NULL;
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proxy_worker *worker, *wsel = NULL;
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apr_table_t *params = apr_table_make(r->pool, 10);
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/* is this for us? */
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if (strcmp(r->handler, "balancer-manager"))
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r->allowed = (AP_METHOD_BIT << M_GET);
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if (r->method_number != M_GET)
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char *args = apr_pstrdup(r->pool, r->args);
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while (args && *args) {
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if ((val = ap_strchr(args, '='))) {
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if ((tok = ap_strchr(val, '&')))
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* Special case: workers are allowed path information
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if ((access_status = ap_unescape_url(val)) != OK)
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if (strcmp(args, "w") || (access_status != HTTP_NOT_FOUND))
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return access_status;
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apr_table_setn(params, args, val);
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return HTTP_BAD_REQUEST;
493
if ((name = apr_table_get(params, "b")))
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bsel = ap_proxy_get_balancer(r->pool, conf,
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apr_pstrcat(r->pool, "balancer://", name, NULL));
496
if ((name = apr_table_get(params, "w"))) {
499
ws = ap_proxy_get_worker(r->pool, conf, name);
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worker = (proxy_worker *)bsel->workers->elts;
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for (n = 0; n < bsel->workers->nelts; n++) {
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if (strcasecmp(worker->name, ws->name) == 0) {
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/* First set the params */
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if ((val = apr_table_get(params, "ss"))) {
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bsel->sticky = apr_pstrdup(conf->pool, val);
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if ((val = apr_table_get(params, "tm"))) {
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int ival = atoi(val);
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bsel->timeout = apr_time_from_sec(ival);
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if ((val = apr_table_get(params, "fa"))) {
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int ival = atoi(val);
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bsel->max_attempts = ival;
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bsel->max_attempts_set = 1;
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if ((val = apr_table_get(params, "lm"))) {
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proxy_balancer_method *provider;
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provider = ap_lookup_provider(PROXY_LBMETHOD, val, "0");
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bsel->lbmethod = provider;
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if ((val = apr_table_get(params, "lf"))) {
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int ival = atoi(val);
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if (ival >= 1 && ival <= 100) {
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wsel->s->lbfactor = ival;
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recalc_factors(bsel);
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if ((val = apr_table_get(params, "wr"))) {
550
if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
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strcpy(wsel->s->route, val);
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*wsel->s->route = '\0';
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if ((val = apr_table_get(params, "rr"))) {
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if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
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strcpy(wsel->s->redirect, val);
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*wsel->s->redirect = '\0';
561
if ((val = apr_table_get(params, "dw"))) {
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if (!strcasecmp(val, "Disable"))
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wsel->s->status |= PROXY_WORKER_DISABLED;
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else if (!strcasecmp(val, "Enable"))
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wsel->s->status &= ~PROXY_WORKER_DISABLED;
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if (apr_table_get(params, "xml")) {
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ap_set_content_type(r, "text/xml");
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ap_rputs("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n", r);
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ap_rputs("<httpd:manager xmlns:httpd=\"http://httpd.apache.org\">\n", r);
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ap_rputs(" <httpd:balancers>\n", r);
574
balancer = (proxy_balancer *)conf->balancers->elts;
575
for (i = 0; i < conf->balancers->nelts; i++) {
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ap_rputs(" <httpd:balancer>\n", r);
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ap_rvputs(r, " <httpd:name>", balancer->name, "</httpd:name>\n", NULL);
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ap_rputs(" <httpd:workers>\n", r);
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worker = (proxy_worker *)balancer->workers->elts;
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for (n = 0; n < balancer->workers->nelts; n++) {
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ap_rputs(" <httpd:worker>\n", r);
582
ap_rvputs(r, " <httpd:scheme>", worker->scheme,
583
"</httpd:scheme>\n", NULL);
584
ap_rvputs(r, " <httpd:hostname>", worker->hostname,
585
"</httpd:hostname>\n", NULL);
586
ap_rprintf(r, " <httpd:loadfactor>%d</httpd:loadfactor>\n",
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worker->s->lbfactor);
588
ap_rputs(" </httpd:worker>\n", r);
591
ap_rputs(" </httpd:workers>\n", r);
592
ap_rputs(" </httpd:balancer>\n", r);
595
ap_rputs(" </httpd:balancers>\n", r);
596
ap_rputs("</httpd:manager>", r);
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ap_set_content_type(r, "text/html");
600
ap_rputs(DOCTYPE_HTML_3_2
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"<html><head><title>Balancer Manager</title></head>\n", r);
602
ap_rputs("<body><h1>Load Balancer Manager for ", r);
603
ap_rvputs(r, ap_get_server_name(r), "</h1>\n\n", NULL);
604
ap_rvputs(r, "<dl><dt>Server Version: ",
605
ap_get_server_version(), "</dt>\n", NULL);
606
ap_rvputs(r, "<dt>Server Built: ",
607
ap_get_server_built(), "\n</dt></dl>\n", NULL);
608
balancer = (proxy_balancer *)conf->balancers->elts;
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for (i = 0; i < conf->balancers->nelts; i++) {
611
ap_rputs("<hr />\n<h3>LoadBalancer Status for ", r);
612
ap_rvputs(r, "<a href=\"", r->uri, "?b=",
613
balancer->name + sizeof("balancer://") - 1,
615
ap_rvputs(r, balancer->name, "</a></h3>\n\n", NULL);
616
ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
617
"<th>StickySession</th><th>Timeout</th><th>FailoverAttempts</th><th>Method</th>"
619
ap_rvputs(r, "<td>", balancer->sticky, NULL);
620
ap_rprintf(r, "</td><td>%" APR_TIME_T_FMT "</td>",
621
apr_time_sec(balancer->timeout));
622
ap_rprintf(r, "<td>%d</td>\n", balancer->max_attempts);
623
ap_rprintf(r, "<td>%s</td>\n",
624
balancer->lbmethod->name);
625
ap_rputs("</table>\n<br />", r);
626
ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
627
"<th>Worker URL</th>"
628
"<th>Route</th><th>RouteRedir</th>"
629
"<th>Factor</th><th>Status</th>"
632
worker = (proxy_worker *)balancer->workers->elts;
633
for (n = 0; n < balancer->workers->nelts; n++) {
635
ap_rvputs(r, "<tr>\n<td><a href=\"", r->uri, "?b=",
636
balancer->name + sizeof("balancer://") - 1, "&w=",
637
ap_escape_uri(r->pool, worker->name),
639
ap_rvputs(r, worker->name, "</a></td>", NULL);
640
ap_rvputs(r, "<td>", worker->s->route, NULL);
641
ap_rvputs(r, "</td><td>", worker->s->redirect, NULL);
642
ap_rprintf(r, "</td><td>%d</td><td>", worker->s->lbfactor);
643
if (worker->s->status & PROXY_WORKER_DISABLED)
645
else if (worker->s->status & PROXY_WORKER_IN_ERROR)
647
else if (worker->s->status & PROXY_WORKER_INITIALIZED)
651
ap_rputs("</td></tr>\n", r);
655
ap_rputs("</table>\n", r);
658
ap_rputs("<hr />\n", r);
660
ap_rputs("<h3>Edit worker settings for ", r);
661
ap_rvputs(r, wsel->name, "</h3>\n", NULL);
662
ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
663
ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
664
ap_rputs("<table><tr><td>Load factor:</td><td><input name=\"lf\" type=text ", r);
665
ap_rprintf(r, "value=\"%d\"></td><tr>\n", wsel->s->lbfactor);
666
ap_rputs("<tr><td>Route:</td><td><input name=\"wr\" type=text ", r);
667
ap_rvputs(r, "value=\"", wsel->route, NULL);
668
ap_rputs("\"></td><tr>\n", r);
669
ap_rputs("<tr><td>Route Redirect:</td><td><input name=\"rr\" type=text ", r);
670
ap_rvputs(r, "value=\"", wsel->redirect, NULL);
671
ap_rputs("\"></td><tr>\n", r);
672
ap_rputs("<tr><td>Status:</td><td>Disabled: <input name=\"dw\" value=\"Disable\" type=radio", r);
673
if (wsel->s->status & PROXY_WORKER_DISABLED)
674
ap_rputs(" checked", r);
675
ap_rputs("> | Enabled: <input name=\"dw\" value=\"Enable\" type=radio", r);
676
if (!(wsel->s->status & PROXY_WORKER_DISABLED))
677
ap_rputs(" checked", r);
678
ap_rputs("></td><tr>\n", r);
679
ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
680
ap_rvputs(r, "</table>\n<input type=hidden name=\"w\" ", NULL);
681
ap_rvputs(r, "value=\"", ap_escape_uri(r->pool, wsel->name), "\">\n", NULL);
682
ap_rvputs(r, "<input type=hidden name=\"b\" ", NULL);
683
ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
684
"\">\n</form>\n", NULL);
685
ap_rputs("<hr />\n", r);
688
ap_rputs("<h3>Edit balancer settings for ", r);
689
ap_rvputs(r, bsel->name, "</h3>\n", NULL);
690
ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
691
ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
692
ap_rputs("<table><tr><td>StickySession Identifier:</td><td><input name=\"ss\" type=text ", r);
694
ap_rvputs(r, "value=\"", bsel->sticky, "\"", NULL);
695
ap_rputs("></td><tr>\n<tr><td>Timeout:</td><td><input name=\"tm\" type=text ", r);
696
ap_rprintf(r, "value=\"%" APR_TIME_T_FMT "\"></td></tr>\n",
697
apr_time_sec(bsel->timeout));
698
ap_rputs("<tr><td>Failover Attempts:</td><td><input name=\"fa\" type=text ", r);
699
ap_rprintf(r, "value=\"%d\"></td></tr>\n",
701
ap_rputs("<tr><td>LB Method:</td><td><select name=\"lm\">", r);
703
apr_array_header_t *methods;
704
ap_list_provider_names_t *method;
706
methods = ap_list_provider_names(r->pool, PROXY_LBMETHOD, "0");
707
method = (ap_list_provider_names_t *)methods->elts;
708
for (i = 0; i < methods->nelts; i++) {
709
ap_rprintf(r, "<option value=\"%s\" %s>%s</option>", method->provider_name,
710
(!strcasecmp(bsel->lbmethod->name, method->provider_name)) ? "selected" : "",
711
method->provider_name);
715
ap_rputs("</select></td></tr>\n", r);
716
ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
717
ap_rvputs(r, "</table>\n<input type=hidden name=\"b\" ", NULL);
718
ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
719
"\">\n</form>\n", NULL);
720
ap_rputs("<hr />\n", r);
722
ap_rputs(ap_psignature("",r), r);
723
ap_rputs("</body></html>\n", r);
728
static void child_init(apr_pool_t *p, server_rec *s)
731
void *sconf = s->module_config;
732
proxy_server_conf *conf;
733
proxy_balancer *balancer;
735
conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
737
/* Initialize shared scoreboard data */
738
balancer = (proxy_balancer *)conf->balancers->elts;
739
for (i = 0; i < conf->balancers->nelts; i++) {
740
init_balancer_members(conf, s, balancer);
749
* The idea behind the find_best_byrequests scheduler is the following:
751
* lbfactor is "how much we expect this worker to work", or "the worker's
752
* normalized work quota".
754
* lbstatus is "how urgent this worker has to work to fulfill its quota
757
* We distribute each worker's work quota to the worker, and then look
758
* which of them needs to work most urgently (biggest lbstatus). This
759
* worker is then selected for work, and its lbstatus reduced by the
760
* total work quota we distributed to all workers. Thus the sum of all
761
* lbstatus does not change.(*)
763
* If some workers are disabled, the others will
764
* still be scheduled correctly.
766
* If a balancer is configured as follows:
769
* lbfactor 25 25 25 25
771
* And b gets disabled, the following schedule is produced:
773
* a c d a c d a c d ...
775
* Note that the above lbfactor setting is the *exact* same as:
780
* Asymmetric configurations work as one would expect. For
786
* would have a, b and c all handling about the same
787
* amount of load with d handling twice what a or b
788
* or c handles individually. So we could see:
790
* b a d c d a c d b d ...
794
static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
798
int total_factor = 0;
799
proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
800
proxy_worker *mycandidate = NULL;
803
ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
804
"proxy: Entering byrequests for BALANCER (%s)",
807
/* First try to see if we have available candidate */
808
for (i = 0; i < balancer->workers->nelts; i++) {
809
/* If the worker is in error state run
810
* retry on that worker. It will be marked as
811
* operational if the retry timeout is elapsed.
812
* The worker might still be unusable, but we try
815
if (!PROXY_WORKER_IS_USABLE(worker))
816
ap_proxy_retry_worker("BALANCER", worker, r->server);
817
/* Take into calculation only the workers that are
818
* not in error state or not disabled.
820
if (PROXY_WORKER_IS_USABLE(worker)) {
821
worker->s->lbstatus += worker->s->lbfactor;
822
total_factor += worker->s->lbfactor;
823
if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
824
mycandidate = worker;
830
mycandidate->s->lbstatus -= total_factor;
831
mycandidate->s->elected++;
838
* The idea behind the find_best_bytraffic scheduler is the following:
840
* We know the amount of traffic (bytes in and out) handled by each
841
* worker. We normalize that traffic by each workers' weight. So assuming
847
* the scheduler will allow worker c to handle 3 times the
848
* traffic of a and b. If each request/response results in the
849
* same amount of traffic, then c would be accessed 3 times as
850
* often as a or b. If, for example, a handled a request that
851
* resulted in a large i/o bytecount, then b and c would be
852
* chosen more often, to even things out.
854
static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
858
apr_off_t mytraffic = 0;
859
apr_off_t curmin = 0;
860
proxy_worker *worker = (proxy_worker *)balancer->workers->elts;
861
proxy_worker *mycandidate = NULL;
863
ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
864
"proxy: Entering bytraffic for BALANCER (%s)",
867
/* First try to see if we have available candidate */
868
for (i = 0; i < balancer->workers->nelts; i++) {
869
/* If the worker is in error state run
870
* retry on that worker. It will be marked as
871
* operational if the retry timeout is elapsed.
872
* The worker might still be unusable, but we try
875
if (!PROXY_WORKER_IS_USABLE(worker))
876
ap_proxy_retry_worker("BALANCER", worker, r->server);
877
/* Take into calculation only the workers that are
878
* not in error state or not disabled.
880
if (PROXY_WORKER_IS_USABLE(worker)) {
881
mytraffic = (worker->s->transferred/worker->s->lbfactor) +
882
(worker->s->read/worker->s->lbfactor);
883
if (!mycandidate || mytraffic < curmin) {
884
mycandidate = worker;
892
mycandidate->s->elected++;
899
* How to add additional lbmethods:
900
* 1. Create func which determines "best" candidate worker
901
* (eg: find_best_bytraffic, above)
902
* 2. Register it as a provider.
904
static const proxy_balancer_method byrequests =
907
&find_best_byrequests,
911
static const proxy_balancer_method bytraffic =
914
&find_best_bytraffic,
918
static void ap_proxy_balancer_register_hook(apr_pool_t *p)
920
/* Only the mpm_winnt has child init hook handler.
921
* make sure that we are called after the mpm
922
* initializes and after the mod_proxy
924
static const char *const aszPred[] = { "mpm_winnt.c", "mod_proxy.c", NULL};
925
/* manager handler */
926
ap_hook_handler(balancer_handler, NULL, NULL, APR_HOOK_FIRST);
927
ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
928
proxy_hook_pre_request(proxy_balancer_pre_request, NULL, NULL, APR_HOOK_FIRST);
929
proxy_hook_post_request(proxy_balancer_post_request, NULL, NULL, APR_HOOK_FIRST);
930
proxy_hook_canon_handler(proxy_balancer_canon, NULL, NULL, APR_HOOK_FIRST);
931
ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
932
ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
935
module AP_MODULE_DECLARE_DATA proxy_balancer_module = {
936
STANDARD20_MODULE_STUFF,
937
NULL, /* create per-directory config structure */
938
NULL, /* merge per-directory config structures */
939
NULL, /* create per-server config structure */
940
NULL, /* merge per-server config structures */
941
NULL, /* command apr_table_t */
942
ap_proxy_balancer_register_hook /* register hooks */
added
removed
modules/proxy/mod_proxy_balancer.c
