granicus.if.org Git - apache/blob - modules/proxy/mod_proxy_balancer.c

   1 /* Licensed to the Apache Software Foundation (ASF) under one or more
   2  * contributor license agreements.  See the NOTICE file distributed with
   3  * this work for additional information regarding copyright ownership.
   4  * The ASF licenses this file to You under the Apache License, Version 2.0
   5  * (the "License"); you may not use this file except in compliance with
   6  * the License.  You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /* Load balancer module for Apache proxy */
  18
  19 #include "mod_proxy.h"
  20 #include "scoreboard.h"
  21 #include "ap_mpm.h"
  22 #include "apr_version.h"
  23 #include "apr_hooks.h"
  24
  25 module AP_MODULE_DECLARE_DATA proxy_balancer_module;
  26
  27 static int proxy_balancer_canon(request_rec *r, char *url)
  28 {
  29     char *host, *path, *search;
  30     const char *err;
  31     apr_port_t port = 0;
  32
  33     if (strncasecmp(url, "balancer:", 9) == 0) {
  34         url += 9;
  35     }
  36     else {
  37         return DECLINED;
  38     }
  39
  40     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
  41              "proxy: BALANCER: canonicalising URL %s", url);
  42
  43     /* do syntatic check.
  44      * We break the URL into host, port, path, search
  45      */
  46     err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
  47     if (err) {
  48         ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
  49                       "error parsing URL %s: %s",
  50                       url, err);
  51         return HTTP_BAD_REQUEST;
  52     }
  53     /* now parse path/search args, according to rfc1738 */
  54     search = NULL;
  55
  56     /* process path */
  57     if (apr_table_get(r->notes, "proxy-nocanon")) {
  58         path = url;   /* this is the raw path */
  59     }
  60     else {
  61         path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0,
  62                                  r->proxyreq);
  63         search = r->args;
  64     }
  65     if (path == NULL)
  66         return HTTP_BAD_REQUEST;
  67
  68     r->filename = apr_pstrcat(r->pool, "proxy:balancer://", host,
  69             "/", path, (search) ? "?" : "", (search) ? search : "", NULL);
  70
  71     r->path_info = apr_pstrcat(r->pool, "/", path, NULL);
  72
  73     return OK;
  74 }
  75
  76 static int init_balancer_members(proxy_server_conf *conf, server_rec *s,
  77                                  proxy_balancer *balancer)
  78 {
  79     int i;
  80     proxy_worker *workers;
  81
  82     workers = (proxy_worker *)balancer->workers->elts;
  83
  84     for (i = 0; i < balancer->workers->nelts; i++) {
  85         int worker_is_initialized;
  86         worker_is_initialized = PROXY_WORKER_IS_INITIALIZED(workers);
  87         if (!worker_is_initialized) {
  88             proxy_worker_stat *slot;
  89             /*
  90              * If the worker is not initialized check whether its scoreboard
  91              * slot is already initialized.
  92              */
  93             slot = (proxy_worker_stat *) ap_get_scoreboard_lb(workers->id);
  94             if (slot) {
  95                 worker_is_initialized = slot->status & PROXY_WORKER_INITIALIZED;
  96             }
  97             else {
  98                 worker_is_initialized = 0;
  99             }
 100         }
 101         ap_proxy_initialize_worker_share(conf, workers, s);
 102         ap_proxy_initialize_worker(workers, s);
 103         if (!worker_is_initialized) {
 104             /* Set to the original configuration */
 105             workers->s->lbstatus = workers->s->lbfactor =
 106             (workers->lbfactor ? workers->lbfactor : 1);
 107             workers->s->lbset = workers->lbset;
 108         }
 109         ++workers;
 110     }
 111
 112     /* Set default number of attempts to the number of
 113      * workers.
 114      */
 115     if (!balancer->max_attempts_set && balancer->workers->nelts > 1) {
 116         balancer->max_attempts = balancer->workers->nelts - 1;
 117         balancer->max_attempts_set = 1;
 118     }
 119     return 0;
 120 }
 121
 122 /* Retrieve the parameter with the given name
 123  * Something like 'JSESSIONID=12345...N'
 124  */
 125 static char *get_path_param(apr_pool_t *pool, char *url,
 126                             const char *name)
 127 {
 128     char *path = NULL;
 129
 130     for (path = strstr(url, name); path; path = strstr(path + 1, name)) {
 131         path += strlen(name);
 132         if (*path == '=') {
 133             /*
 134              * Session path was found, get it's value
 135              */
 136             ++path;
 137             if (strlen(path)) {
 138                 char *q;
 139                 path = apr_strtok(apr_pstrdup(pool, path), "?&", &q);
 140                 return path;
 141             }
 142         }
 143     }
 144     return NULL;
 145 }
 146
 147 static char *get_cookie_param(request_rec *r, const char *name)
 148 {
 149     const char *cookies;
 150     const char *start_cookie;
 151
 152     if ((cookies = apr_table_get(r->headers_in, "Cookie"))) {
 153         for (start_cookie = ap_strstr_c(cookies, name); start_cookie;
 154              start_cookie = ap_strstr_c(start_cookie + 1, name)) {
 155             if (start_cookie == cookies ||
 156                 start_cookie[-1] == ';' ||
 157                 start_cookie[-1] == ',' ||
 158                 isspace(start_cookie[-1])) {
 159
 160                 start_cookie += strlen(name);
 161                 while(*start_cookie && isspace(*start_cookie))
 162                     ++start_cookie;
 163                 if (*start_cookie == '=' && start_cookie[1]) {
 164                     /*
 165                      * Session cookie was found, get it's value
 166                      */
 167                     char *end_cookie, *cookie;
 168                     ++start_cookie;
 169                     cookie = apr_pstrdup(r->pool, start_cookie);
 170                     if ((end_cookie = strchr(cookie, ';')) != NULL)
 171                         *end_cookie = '\0';
 172                     if((end_cookie = strchr(cookie, ',')) != NULL)
 173                         *end_cookie = '\0';
 174                     return cookie;
 175                 }
 176             }
 177         }
 178     }
 179     return NULL;
 180 }
 181
 182 /* Find the worker that has the 'route' defined
 183  */
 184 static proxy_worker *find_route_worker(proxy_balancer *balancer,
 185                                        const char *route, request_rec *r)
 186 {
 187     int i;
 188     int checking_standby;
 189     int checked_standby;
 190
 191     proxy_worker *worker;
 192
 193     checking_standby = checked_standby = 0;
 194     while (!checked_standby) {
 195         worker = (proxy_worker *)balancer->workers->elts;
 196         for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 197             if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
 198                 continue;
 199             if (*(worker->s->route) && strcmp(worker->s->route, route) == 0) {
 200                 if (worker && PROXY_WORKER_IS_USABLE(worker)) {
 201                     return worker;
 202                 } else {
 203                     /*
 204                      * If the worker is in error state run
 205                      * retry on that worker. It will be marked as
 206                      * operational if the retry timeout is elapsed.
 207                      * The worker might still be unusable, but we try
 208                      * anyway.
 209                      */
 210                     ap_proxy_retry_worker("BALANCER", worker, r->server);
 211                     if (PROXY_WORKER_IS_USABLE(worker)) {
 212                             return worker;
 213                     } else {
 214                         /*
 215                          * We have a worker that is unusable.
 216                          * It can be in error or disabled, but in case
 217                          * it has a redirection set use that redirection worker.
 218                          * This enables to safely remove the member from the
 219                          * balancer. Of course you will need some kind of
 220                          * session replication between those two remote.
 221                          */
 222                         if (*worker->s->redirect) {
 223                             proxy_worker *rworker = NULL;
 224                             rworker = find_route_worker(balancer, worker->s->redirect, r);
 225                             /* Check if the redirect worker is usable */
 226                             if (rworker && !PROXY_WORKER_IS_USABLE(rworker)) {
 227                                 /*
 228                                  * If the worker is in error state run
 229                                  * retry on that worker. It will be marked as
 230                                  * operational if the retry timeout is elapsed.
 231                                  * The worker might still be unusable, but we try
 232                                  * anyway.
 233                                  */
 234                                 ap_proxy_retry_worker("BALANCER", rworker, r->server);
 235                             }
 236                             if (rworker && PROXY_WORKER_IS_USABLE(rworker))
 237                                 return rworker;
 238                         }
 239                     }
 240                 }
 241             }
 242         }
 243         checked_standby = checking_standby++;
 244     }
 245     return NULL;
 246 }
 247
 248 static proxy_worker *find_session_route(proxy_balancer *balancer,
 249                                         request_rec *r,
 250                                         char **route,
 251                                         const char **sticky_used,
 252                                         char **url)
 253 {
 254     proxy_worker *worker = NULL;
 255
 256     if (!balancer->sticky)
 257         return NULL;
 258     /* Try to find the sticky route inside url */
 259     *route = get_path_param(r->pool, *url, balancer->sticky_path);
 260     if (*route) {
 261         ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 262                      "proxy: BALANCER: Found value %s for "
 263                      "stickysession %s", *route, balancer->sticky_path);
 264         *sticky_used =  balancer->sticky_path;
 265     }
 266     else {
 267         *route = get_cookie_param(r, balancer->sticky);
 268         if (*route) {
 269             *sticky_used =  balancer->sticky;
 270             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 271                          "proxy: BALANCER: Found value %s for "
 272                          "stickysession %s", *route, balancer->sticky);
 273         }
 274     }
 275     /*
 276      * If we found a value for sticksession, find the first '.' within.
 277      * Everything after '.' (if present) is our route.
 278      */
 279     if ((*route) && ((*route = strchr(*route, '.')) != NULL ))
 280         (*route)++;
 281     if ((*route) && (**route)) {
 282         ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 283                                   "proxy: BALANCER: Found route %s", *route);
 284         /* We have a route in path or in cookie
 285          * Find the worker that has this route defined.
 286          */
 287         worker = find_route_worker(balancer, *route, r);
 288         if (worker && strcmp(*route, worker->s->route)) {
 289             /*
 290              * Notice that the route of the worker chosen is different from
 291              * the route supplied by the client.
 292              */
 293             apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
 294             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 295                          "proxy: BALANCER: Route changed from %s to %s",
 296                          *route, worker->s->route);
 297         }
 298         return worker;
 299     }
 300     else
 301         return NULL;
 302 }
 303
 304 static proxy_worker *find_best_worker(proxy_balancer *balancer,
 305                                       request_rec *r)
 306 {
 307     proxy_worker *candidate = NULL;
 308     apr_status_t rv;
 309
 310     if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {
 311         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 312         "proxy: BALANCER: (%s). Lock failed for find_best_worker()", balancer->name);
 313         return NULL;
 314     }
 315
 316     candidate = (*balancer->lbmethod->finder)(balancer, r);
 317
 318     if (candidate)
 319         candidate->s->elected++;
 320
 321 /*
 322         PROXY_THREAD_UNLOCK(balancer);
 323         return NULL;
 324 */
 325
 326     if ((rv = PROXY_THREAD_UNLOCK(balancer)) != APR_SUCCESS) {
 327         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 328         "proxy: BALANCER: (%s). Unlock failed for find_best_worker()", balancer->name);
 329     }
 330
 331     if (candidate == NULL) {
 332         /* All the workers are in error state or disabled.
 333          * If the balancer has a timeout sleep for a while
 334          * and try again to find the worker. The chances are
 335          * that some other thread will release a connection.
 336          * By default the timeout is not set, and the server
 337          * returns SERVER_BUSY.
 338          */
 339 #if APR_HAS_THREADS
 340         if (balancer->timeout) {
 341             /* XXX: This can perhaps be build using some
 342              * smarter mechanism, like tread_cond.
 343              * But since the statuses can came from
 344              * different childs, use the provided algo.
 345              */
 346             apr_interval_time_t timeout = balancer->timeout;
 347             apr_interval_time_t step, tval = 0;
 348             /* Set the timeout to 0 so that we don't
 349              * end in infinite loop
 350              */
 351             balancer->timeout = 0;
 352             step = timeout / 100;
 353             while (tval < timeout) {
 354                 apr_sleep(step);
 355                 /* Try again */
 356                 if ((candidate = find_best_worker(balancer, r)))
 357                     break;
 358                 tval += step;
 359             }
 360             /* restore the timeout */
 361             balancer->timeout = timeout;
 362         }
 363 #endif
 364     }
 365     return candidate;
 366 }
 367
 368 static int rewrite_url(request_rec *r, proxy_worker *worker,
 369                         char **url)
 370 {
 371     const char *scheme = strstr(*url, "://");
 372     const char *path = NULL;
 373
 374     if (scheme)
 375         path = ap_strchr_c(scheme + 3, '/');
 376
 377     /* we break the URL into host, port, uri */
 378     if (!worker) {
 379         return ap_proxyerror(r, HTTP_BAD_REQUEST, apr_pstrcat(r->pool,
 380                              "missing worker. URI cannot be parsed: ", *url,
 381                              NULL));
 382     }
 383
 384     *url = apr_pstrcat(r->pool, worker->name, path, NULL);
 385
 386     return OK;
 387 }
 388
 389 static void force_recovery(proxy_balancer *balancer, server_rec *s)
 390 {
 391     int i;
 392     int ok = 0;
 393     proxy_worker *worker;
 394
 395     worker = (proxy_worker *)balancer->workers->elts;
 396     for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 397         if (!(worker->s->status & PROXY_WORKER_IN_ERROR)) {
 398             ok = 1;
 399             break;
 400         }
 401     }
 402     if (!ok) {
 403         /* If all workers are in error state force the recovery.
 404          */
 405         worker = (proxy_worker *)balancer->workers->elts;
 406         for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 407             ++worker->s->retries;
 408             worker->s->status &= ~PROXY_WORKER_IN_ERROR;
 409             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s,
 410                          "proxy: BALANCER: (%s). Forcing recovery for worker (%s)",
 411                          balancer->name, worker->hostname);
 412         }
 413     }
 414 }
 415
 416 static int proxy_balancer_pre_request(proxy_worker **worker,
 417                                       proxy_balancer **balancer,
 418                                       request_rec *r,
 419                                       proxy_server_conf *conf, char **url)
 420 {
 421     int access_status;
 422     proxy_worker *runtime;
 423     char *route = NULL;
 424     const char *sticky = NULL;
 425     apr_status_t rv;
 426
 427     *worker = NULL;
 428     /* Step 1: check if the url is for us
 429      * The url we can handle starts with 'balancer://'
 430      * If balancer is already provided skip the search
 431      * for balancer, because this is failover attempt.
 432      */
 433     if (!*balancer &&
 434         !(*balancer = ap_proxy_get_balancer(r->pool, conf, *url)))
 435         return DECLINED;
 436
 437     /* Step 2: Lock the LoadBalancer
 438      * XXX: perhaps we need the process lock here
 439      */
 440     if ((rv = PROXY_THREAD_LOCK(*balancer)) != APR_SUCCESS) {
 441         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 442                      "proxy: BALANCER: (%s). Lock failed for pre_request",
 443                      (*balancer)->name);
 444         return DECLINED;
 445     }
 446
 447     /* Step 3: force recovery */
 448     force_recovery(*balancer, r->server);
 449
 450     /* Step 4: find the session route */
 451     runtime = find_session_route(*balancer, r, &route, &sticky, url);
 452     if (runtime) {
 453         int i, total_factor = 0;
 454         proxy_worker *workers;
 455         /* We have a sticky load balancer
 456          * Update the workers status
 457          * so that even session routes get
 458          * into account.
 459          */
 460         workers = (proxy_worker *)(*balancer)->workers->elts;
 461         for (i = 0; i < (*balancer)->workers->nelts; i++) {
 462             /* Take into calculation only the workers that are
 463              * not in error state or not disabled.
 464              *
 465              * TODO: Abstract the below, since this is dependent
 466              *       on the LB implementation
 467              */
 468             if (PROXY_WORKER_IS_USABLE(workers)) {
 469                 workers->s->lbstatus += workers->s->lbfactor;
 470                 total_factor += workers->s->lbfactor;
 471             }
 472             workers++;
 473         }
 474         runtime->s->lbstatus -= total_factor;
 475         runtime->s->elected++;
 476
 477         *worker = runtime;
 478     }
 479     else if (route && (*balancer)->sticky_force) {
 480         int i, member_of = 0;
 481         proxy_worker *workers;
 482         /*
 483          * We have a route provided that doesn't match the
 484          * balancer name. See if the provider route is the
 485          * member of the same balancer in which case return 503
 486          */
 487         workers = (proxy_worker *)(*balancer)->workers->elts;
 488         for (i = 0; i < (*balancer)->workers->nelts; i++) {
 489             if (*(workers->s->route) && strcmp(workers->s->route, route) == 0) {
 490                 member_of = 1;
 491                 break;
 492             }
 493             workers++;
 494         }
 495         if (member_of) {
 496             ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
 497                          "proxy: BALANCER: (%s). All workers are in error state for route (%s)",
 498                          (*balancer)->name, route);
 499             if ((rv = PROXY_THREAD_UNLOCK(*balancer)) != APR_SUCCESS) {
 500                 ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 501                              "proxy: BALANCER: (%s). Unlock failed for pre_request",
 502                              (*balancer)->name);
 503             }
 504             return HTTP_SERVICE_UNAVAILABLE;
 505         }
 506     }
 507
 508     if ((rv = PROXY_THREAD_UNLOCK(*balancer)) != APR_SUCCESS) {
 509         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 510                      "proxy: BALANCER: (%s). Unlock failed for pre_request",
 511                      (*balancer)->name);
 512     }
 513     if (!*worker) {
 514         runtime = find_best_worker(*balancer, r);
 515         if (!runtime) {
 516             ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
 517                          "proxy: BALANCER: (%s). All workers are in error state",
 518                          (*balancer)->name);
 519
 520             return HTTP_SERVICE_UNAVAILABLE;
 521         }
 522         if ((*balancer)->sticky && runtime) {
 523             /*
 524              * This balancer has sticky sessions and the client either has not
 525              * supplied any routing information or all workers for this route
 526              * including possible redirect and hotstandby workers are in error
 527              * state, but we have found another working worker for this
 528              * balancer where we can send the request. Thus notice that we have
 529              * changed the route to the backend.
 530              */
 531             apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
 532         }
 533         *worker = runtime;
 534     }
 535
 536     /* Add balancer/worker info to env. */
 537     apr_table_setn(r->subprocess_env,
 538                    "BALANCER_NAME", (*balancer)->name);
 539     apr_table_setn(r->subprocess_env,
 540                    "BALANCER_WORKER_NAME", (*worker)->name);
 541     apr_table_setn(r->subprocess_env,
 542                    "BALANCER_WORKER_ROUTE", (*worker)->s->route);
 543
 544     /* Rewrite the url from 'balancer://url'
 545      * to the 'worker_scheme://worker_hostname[:worker_port]/url'
 546      * This replaces the balancers fictional name with the
 547      * real hostname of the elected worker.
 548      */
 549     access_status = rewrite_url(r, *worker, url);
 550     /* Add the session route to request notes if present */
 551     if (route) {
 552         apr_table_setn(r->notes, "session-sticky", sticky);
 553         apr_table_setn(r->notes, "session-route", route);
 554
 555         /* Add session info to env. */
 556         apr_table_setn(r->subprocess_env,
 557                        "BALANCER_SESSION_STICKY", sticky);
 558         apr_table_setn(r->subprocess_env,
 559                        "BALANCER_SESSION_ROUTE", route);
 560     }
 561     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 562                  "proxy: BALANCER (%s) worker (%s) rewritten to %s",
 563                  (*balancer)->name, (*worker)->name, *url);
 564
 565     return access_status;
 566 }
 567
 568 static int proxy_balancer_post_request(proxy_worker *worker,
 569                                        proxy_balancer *balancer,
 570                                        request_rec *r,
 571                                        proxy_server_conf *conf)
 572 {
 573
 574 #if 0
 575     apr_status_t rv;
 576
 577     if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {
 578         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 579             "proxy: BALANCER: (%s). Lock failed for post_request",
 580             balancer->name);
 581         return HTTP_INTERNAL_SERVER_ERROR;
 582     }
 583     /* TODO: placeholder for post_request actions
 584      */
 585
 586     if ((rv = PROXY_THREAD_UNLOCK(balancer)) != APR_SUCCESS) {
 587         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 588             "proxy: BALANCER: (%s). Unlock failed for post_request",
 589             balancer->name);
 590     }
 591     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 592                  "proxy_balancer_post_request for (%s)", balancer->name);
 593
 594 #endif
 595
 596     return OK;
 597 }
 598
 599 static void recalc_factors(proxy_balancer *balancer)
 600 {
 601     int i;
 602     proxy_worker *workers;
 603
 604
 605     /* Recalculate lbfactors */
 606     workers = (proxy_worker *)balancer->workers->elts;
 607     /* Special case if there is only one worker it's
 608      * load factor will always be 1
 609      */
 610     if (balancer->workers->nelts == 1) {
 611         workers->s->lbstatus = workers->s->lbfactor = 1;
 612         return;
 613     }
 614     for (i = 0; i < balancer->workers->nelts; i++) {
 615         /* Update the status entries */
 616         workers[i].s->lbstatus = workers[i].s->lbfactor;
 617     }
 618 }
 619
 620 /* Manages the loadfactors and member status
 621  */
 622 static int balancer_handler(request_rec *r)
 623 {
 624     void *sconf = r->server->module_config;
 625     proxy_server_conf *conf = (proxy_server_conf *)
 626         ap_get_module_config(sconf, &proxy_module);
 627     proxy_balancer *balancer, *bsel = NULL;
 628     proxy_worker *worker, *wsel = NULL;
 629     apr_table_t *params = apr_table_make(r->pool, 10);
 630     int access_status;
 631     int i, n;
 632     const char *name;
 633
 634     /* is this for us? */
 635     if (strcmp(r->handler, "balancer-manager"))
 636         return DECLINED;
 637     r->allowed = (AP_METHOD_BIT << M_GET);
 638     if (r->method_number != M_GET)
 639         return DECLINED;
 640
 641     if (r->args) {
 642         char *args = apr_pstrdup(r->pool, r->args);
 643         char *tok, *val;
 644         while (args && *args) {
 645             if ((val = ap_strchr(args, '='))) {
 646                 *val++ = '\0';
 647                 if ((tok = ap_strchr(val, '&')))
 648                     *tok++ = '\0';
 649                 /*
 650                  * Special case: workers are allowed path information
 651                  */
 652                 if ((access_status = ap_unescape_url(val)) != OK)
 653                     if (strcmp(args, "w") || (access_status !=  HTTP_NOT_FOUND))
 654                         return access_status;
 655                 apr_table_setn(params, args, val);
 656                 args = tok;
 657             }
 658             else
 659                 return HTTP_BAD_REQUEST;
 660         }
 661     }
 662     if ((name = apr_table_get(params, "b")))
 663         bsel = ap_proxy_get_balancer(r->pool, conf,
 664             apr_pstrcat(r->pool, "balancer://", name, NULL));
 665     if ((name = apr_table_get(params, "w"))) {
 666         proxy_worker *ws;
 667
 668         ws = ap_proxy_get_worker(r->pool, conf, name);
 669         if (bsel && ws) {
 670             worker = (proxy_worker *)bsel->workers->elts;
 671             for (n = 0; n < bsel->workers->nelts; n++) {
 672                 if (strcasecmp(worker->name, ws->name) == 0) {
 673                     wsel = worker;
 674                     break;
 675                 }
 676                 ++worker;
 677             }
 678         }
 679     }
 680     /* First set the params */
 681     /*
 682      * Note that it is not possible set the proxy_balancer because it is not
 683      * in shared memory.
 684      */
 685     if (wsel) {
 686         const char *val;
 687         if ((val = apr_table_get(params, "lf"))) {
 688             int ival = atoi(val);
 689             if (ival >= 1 && ival <= 100) {
 690                 wsel->s->lbfactor = ival;
 691                 if (bsel)
 692                     recalc_factors(bsel);
 693             }
 694         }
 695         if ((val = apr_table_get(params, "wr"))) {
 696             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 697                 strcpy(wsel->s->route, val);
 698             else
 699                 *wsel->s->route = '\0';
 700         }
 701         if ((val = apr_table_get(params, "rr"))) {
 702             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 703                 strcpy(wsel->s->redirect, val);
 704             else
 705                 *wsel->s->redirect = '\0';
 706         }
 707         if ((val = apr_table_get(params, "dw"))) {
 708             if (!strcasecmp(val, "Disable"))
 709                 wsel->s->status |= PROXY_WORKER_DISABLED;
 710             else if (!strcasecmp(val, "Enable"))
 711                 wsel->s->status &= ~PROXY_WORKER_DISABLED;
 712         }
 713         if ((val = apr_table_get(params, "ls"))) {
 714             int ival = atoi(val);
 715             if (ival >= 0 && ival <= 99) {
 716                 wsel->s->lbset = ival;
 717              }
 718         }
 719
 720     }
 721     if (apr_table_get(params, "xml")) {
 722         ap_set_content_type(r, "text/xml");
 723         ap_rputs("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n", r);
 724         ap_rputs("<httpd:manager xmlns:httpd=\"http://httpd.apache.org\">\n", r);
 725         ap_rputs("  <httpd:balancers>\n", r);
 726         balancer = (proxy_balancer *)conf->balancers->elts;
 727         for (i = 0; i < conf->balancers->nelts; i++) {
 728             ap_rputs("    <httpd:balancer>\n", r);
 729             ap_rvputs(r, "      <httpd:name>", balancer->name, "</httpd:name>\n", NULL);
 730             ap_rputs("      <httpd:workers>\n", r);
 731             worker = (proxy_worker *)balancer->workers->elts;
 732             for (n = 0; n < balancer->workers->nelts; n++) {
 733                 ap_rputs("        <httpd:worker>\n", r);
 734                 ap_rvputs(r, "          <httpd:scheme>", worker->scheme,
 735                           "</httpd:scheme>\n", NULL);
 736                 ap_rvputs(r, "          <httpd:hostname>", worker->hostname,
 737                           "</httpd:hostname>\n", NULL);
 738                ap_rprintf(r, "          <httpd:loadfactor>%d</httpd:loadfactor>\n",
 739                           worker->s->lbfactor);
 740                 ap_rputs("        </httpd:worker>\n", r);
 741                 ++worker;
 742             }
 743             ap_rputs("      </httpd:workers>\n", r);
 744             ap_rputs("    </httpd:balancer>\n", r);
 745             ++balancer;
 746         }
 747         ap_rputs("  </httpd:balancers>\n", r);
 748         ap_rputs("</httpd:manager>", r);
 749     }
 750     else {
 751         ap_set_content_type(r, "text/html; charset=ISO-8859-1");
 752         ap_rputs(DOCTYPE_HTML_3_2
 753                  "<html><head><title>Balancer Manager</title></head>\n", r);
 754         ap_rputs("<body><h1>Load Balancer Manager for ", r);
 755         ap_rvputs(r, ap_get_server_name(r), "</h1>\n\n", NULL);
 756         ap_rvputs(r, "<dl><dt>Server Version: ",
 757                   ap_get_server_description(), "</dt>\n", NULL);
 758         ap_rvputs(r, "<dt>Server Built: ",
 759                   ap_get_server_built(), "\n</dt></dl>\n", NULL);
 760         balancer = (proxy_balancer *)conf->balancers->elts;
 761         for (i = 0; i < conf->balancers->nelts; i++) {
 762
 763             ap_rputs("<hr />\n<h3>LoadBalancer Status for ", r);
 764             ap_rvputs(r, balancer->name, "</h3>\n\n", NULL);
 765             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 766                 "<th>StickySession</th><th>Timeout</th><th>FailoverAttempts</th><th>Method</th>"
 767                 "</tr>\n<tr>", r);
 768             if (balancer->sticky) {
 769                 if (strcmp(balancer->sticky, balancer->sticky_path)) {
 770                     ap_rvputs(r, "<td>", balancer->sticky, " | ",
 771                               balancer->sticky_path, NULL);
 772                 }
 773                 else {
 774                     ap_rvputs(r, "<td>", balancer->sticky, NULL);
 775                 }
 776             }
 777             else {
 778                 ap_rputs("<td> - ", r);
 779             }
 780             ap_rprintf(r, "</td><td>%" APR_TIME_T_FMT "</td>",
 781                 apr_time_sec(balancer->timeout));
 782             ap_rprintf(r, "<td>%d</td>\n", balancer->max_attempts);
 783             ap_rprintf(r, "<td>%s</td>\n",
 784                        balancer->lbmethod->name);
 785             ap_rputs("</table>\n<br />", r);
 786             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 787                 "<th>Worker URL</th>"
 788                 "<th>Route</th><th>RouteRedir</th>"
 789                 "<th>Factor</th><th>Set</th><th>Status</th>"
 790                 "<th>Elected</th><th>To</th><th>From</th>"
 791                 "</tr>\n", r);
 792
 793             worker = (proxy_worker *)balancer->workers->elts;
 794             for (n = 0; n < balancer->workers->nelts; n++) {
 795                 char fbuf[50];
 796                 ap_rvputs(r, "<tr>\n<td><a href=\"", r->uri, "?b=",
 797                           balancer->name + sizeof("balancer://") - 1, "&w=",
 798                           ap_escape_uri(r->pool, worker->name),
 799                           "\">", NULL);
 800                 ap_rvputs(r, worker->name, "</a></td>", NULL);
 801                 ap_rvputs(r, "<td>", ap_escape_html(r->pool, worker->s->route),
 802                           NULL);
 803                 ap_rvputs(r, "</td><td>",
 804                           ap_escape_html(r->pool, worker->s->redirect), NULL);
 805                 ap_rprintf(r, "</td><td>%d</td>", worker->s->lbfactor);
 806                 ap_rprintf(r, "<td>%d</td><td>", worker->s->lbset);
 807                 if (worker->s->status & PROXY_WORKER_DISABLED)
 808                    ap_rputs("Dis ", r);
 809                 if (worker->s->status & PROXY_WORKER_IN_ERROR)
 810                    ap_rputs("Err ", r);
 811                 if (worker->s->status & PROXY_WORKER_STOPPED)
 812                    ap_rputs("Stop ", r);
 813                 if (worker->s->status & PROXY_WORKER_HOT_STANDBY)
 814                    ap_rputs("Stby ", r);
 815                 if (PROXY_WORKER_IS_USABLE(worker))
 816                     ap_rputs("Ok", r);
 817                 if (!PROXY_WORKER_IS_INITIALIZED(worker))
 818                     ap_rputs("-", r);
 819                 ap_rputs("</td>", r);
 820                 ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td><td>", worker->s->elected);
 821                 ap_rputs(apr_strfsize(worker->s->transferred, fbuf), r);
 822                 ap_rputs("</td><td>", r);
 823                 ap_rputs(apr_strfsize(worker->s->read, fbuf), r);
 824                 ap_rputs("</td></tr>\n", r);
 825
 826                 ++worker;
 827             }
 828             ap_rputs("</table>\n", r);
 829             ++balancer;
 830         }
 831         ap_rputs("<hr />\n", r);
 832         if (wsel && bsel) {
 833             ap_rputs("<h3>Edit worker settings for ", r);
 834             ap_rvputs(r, wsel->name, "</h3>\n", NULL);
 835             ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
 836             ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
 837             ap_rputs("<table><tr><td>Load factor:</td><td><input name=\"lf\" type=text ", r);
 838             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbfactor);
 839             ap_rputs("<tr><td>LB Set:</td><td><input name=\"ls\" type=text ", r);
 840             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbset);
 841             ap_rputs("<tr><td>Route:</td><td><input name=\"wr\" type=text ", r);
 842             ap_rvputs(r, "value=\"", ap_escape_html(r->pool, wsel->s->route),
 843                       NULL);
 844             ap_rputs("\"></td></tr>\n", r);
 845             ap_rputs("<tr><td>Route Redirect:</td><td><input name=\"rr\" type=text ", r);
 846             ap_rvputs(r, "value=\"", ap_escape_html(r->pool, wsel->s->redirect),
 847                       NULL);
 848             ap_rputs("\"></td></tr>\n", r);
 849             ap_rputs("<tr><td>Status:</td><td>Disabled: <input name=\"dw\" value=\"Disable\" type=radio", r);
 850             if (wsel->s->status & PROXY_WORKER_DISABLED)
 851                 ap_rputs(" checked", r);
 852             ap_rputs("> | Enabled: <input name=\"dw\" value=\"Enable\" type=radio", r);
 853             if (!(wsel->s->status & PROXY_WORKER_DISABLED))
 854                 ap_rputs(" checked", r);
 855             ap_rputs("></td></tr>\n", r);
 856             ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
 857             ap_rvputs(r, "</table>\n<input type=hidden name=\"w\" ",  NULL);
 858             ap_rvputs(r, "value=\"", ap_escape_uri(r->pool, wsel->name), "\">\n", NULL);
 859             ap_rvputs(r, "<input type=hidden name=\"b\" ", NULL);
 860             ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
 861                       "\">\n</form>\n", NULL);
 862             ap_rputs("<hr />\n", r);
 863         }
 864         ap_rputs(ap_psignature("",r), r);
 865         ap_rputs("</body></html>\n", r);
 866     }
 867     return OK;
 868 }
 869
 870 static void child_init(apr_pool_t *p, server_rec *s)
 871 {
 872     while (s) {
 873         void *sconf = s->module_config;
 874         proxy_server_conf *conf;
 875         proxy_balancer *balancer;
 876         int i;
 877         conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
 878
 879         /* Initialize shared scoreboard data */
 880         balancer = (proxy_balancer *)conf->balancers->elts;
 881         for (i = 0; i < conf->balancers->nelts; i++) {
 882             init_balancer_members(conf, s, balancer);
 883             balancer++;
 884         }
 885         s = s->next;
 886     }
 887
 888 }
 889
 890 /*
 891  * The idea behind the find_best_byrequests scheduler is the following:
 892  *
 893  * lbfactor is "how much we expect this worker to work", or "the worker's
 894  * normalized work quota".
 895  *
 896  * lbstatus is "how urgent this worker has to work to fulfill its quota
 897  * of work".
 898  *
 899  * We distribute each worker's work quota to the worker, and then look
 900  * which of them needs to work most urgently (biggest lbstatus).  This
 901  * worker is then selected for work, and its lbstatus reduced by the
 902  * total work quota we distributed to all workers.  Thus the sum of all
 903  * lbstatus does not change.(*)
 904  *
 905  * If some workers are disabled, the others will
 906  * still be scheduled correctly.
 907  *
 908  * If a balancer is configured as follows:
 909  *
 910  * worker     a    b    c    d
 911  * lbfactor  25   25   25   25
 912  *
 913  * And b gets disabled, the following schedule is produced:
 914  *
 915  *    a c d a c d a c d ...
 916  *
 917  * Note that the above lbfactor setting is the *exact* same as:
 918  *
 919  * worker     a    b    c    d
 920  * lbfactor   1    1    1    1
 921  *
 922  * Asymmetric configurations work as one would expect. For
 923  * example:
 924  *
 925  * worker     a    b    c    d
 926  * lbfactor   1    1    1    2
 927  *
 928  * would have a, b and c all handling about the same
 929  * amount of load with d handling twice what a or b
 930  * or c handles individually. So we could see:
 931  *
 932  *   b a d c d a c d b d ...
 933  *
 934  */
 935
 936 static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
 937                                 request_rec *r)
 938 {
 939     int i;
 940     int total_factor = 0;
 941     proxy_worker *worker;
 942     proxy_worker *mycandidate = NULL;
 943     int cur_lbset = 0;
 944     int max_lbset = 0;
 945     int checking_standby;
 946     int checked_standby;
 947
 948     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 949                  "proxy: Entering byrequests for BALANCER (%s)",
 950                  balancer->name);
 951
 952     /* First try to see if we have available candidate */
 953     do {
 954         checking_standby = checked_standby = 0;
 955         while (!mycandidate && !checked_standby) {
 956             worker = (proxy_worker *)balancer->workers->elts;
 957             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 958                 if (!checking_standby) {    /* first time through */
 959                     if (worker->s->lbset > max_lbset)
 960                         max_lbset = worker->s->lbset;
 961                 }
 962                 if (worker->s->lbset > cur_lbset)
 963                     continue;
 964                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
 965                     continue;
 966                 /* If the worker is in error state run
 967                  * retry on that worker. It will be marked as
 968                  * operational if the retry timeout is elapsed.
 969                  * The worker might still be unusable, but we try
 970                  * anyway.
 971                  */
 972                 if (!PROXY_WORKER_IS_USABLE(worker))
 973                     ap_proxy_retry_worker("BALANCER", worker, r->server);
 974                 /* Take into calculation only the workers that are
 975                  * not in error state or not disabled.
 976                  */
 977                 if (PROXY_WORKER_IS_USABLE(worker)) {
 978                     worker->s->lbstatus += worker->s->lbfactor;
 979                     total_factor += worker->s->lbfactor;
 980                     if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
 981                         mycandidate = worker;
 982                 }
 983             }
 984             checked_standby = checking_standby++;
 985         }
 986         cur_lbset++;
 987     } while (cur_lbset <= max_lbset && !mycandidate);
 988
 989     if (mycandidate) {
 990         mycandidate->s->lbstatus -= total_factor;
 991     }
 992
 993     return mycandidate;
 994 }
 995
 996 /*
 997  * The idea behind the find_best_bytraffic scheduler is the following:
 998  *
 999  * We know the amount of traffic (bytes in and out) handled by each
1000  * worker. We normalize that traffic by each workers' weight. So assuming
1001  * a setup as below:
1002  *
1003  * worker     a    b    c
1004  * lbfactor   1    1    3
1005  *
1006  * the scheduler will allow worker c to handle 3 times the
1007  * traffic of a and b. If each request/response results in the
1008  * same amount of traffic, then c would be accessed 3 times as
1009  * often as a or b. If, for example, a handled a request that
1010  * resulted in a large i/o bytecount, then b and c would be
1011  * chosen more often, to even things out.
1012  */
1013 static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
1014                                          request_rec *r)
1015 {
1016     int i;
1017     apr_off_t mytraffic = 0;
1018     apr_off_t curmin = 0;
1019     proxy_worker *worker;
1020     proxy_worker *mycandidate = NULL;
1021     int cur_lbset = 0;
1022     int max_lbset = 0;
1023     int checking_standby;
1024     int checked_standby;
1025
1026     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
1027                  "proxy: Entering bytraffic for BALANCER (%s)",
1028                  balancer->name);
1029
1030     /* First try to see if we have available candidate */
1031     do {
1032         checking_standby = checked_standby = 0;
1033         while (!mycandidate && !checked_standby) {
1034             worker = (proxy_worker *)balancer->workers->elts;
1035             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
1036                 if (!checking_standby) {    /* first time through */
1037                     if (worker->s->lbset > max_lbset)
1038                         max_lbset = worker->s->lbset;
1039                 }
1040                 if (worker->s->lbset > cur_lbset)
1041                     continue;
1042                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
1043                     continue;
1044                 /* If the worker is in error state run
1045                  * retry on that worker. It will be marked as
1046                  * operational if the retry timeout is elapsed.
1047                  * The worker might still be unusable, but we try
1048                  * anyway.
1049                  */
1050                 if (!PROXY_WORKER_IS_USABLE(worker))
1051                     ap_proxy_retry_worker("BALANCER", worker, r->server);
1052                 /* Take into calculation only the workers that are
1053                  * not in error state or not disabled.
1054                  */
1055                 if (PROXY_WORKER_IS_USABLE(worker)) {
1056                     mytraffic = (worker->s->transferred/worker->s->lbfactor) +
1057                                 (worker->s->read/worker->s->lbfactor);
1058                     if (!mycandidate || mytraffic < curmin) {
1059                         mycandidate = worker;
1060                         curmin = mytraffic;
1061                     }
1062                 }
1063             }
1064             checked_standby = checking_standby++;
1065         }
1066         cur_lbset++;
1067     } while (cur_lbset <= max_lbset && !mycandidate);
1068
1069     return mycandidate;
1070 }
1071
1072 /*
1073  * How to add additional lbmethods:
1074  *   1. Create func which determines "best" candidate worker
1075  *      (eg: find_best_bytraffic, above)
1076  *   2. Register it as a provider.
1077  */
1078 static const proxy_balancer_method byrequests =
1079 {
1080     "byrequests",
1081     &find_best_byrequests,
1082     NULL
1083 };
1084
1085 static const proxy_balancer_method bytraffic =
1086 {
1087     "bytraffic",
1088     &find_best_bytraffic,
1089     NULL
1090 };
1091
1092 static void ap_proxy_balancer_register_hook(apr_pool_t *p)
1093 {
1094     /* Only the mpm_winnt has child init hook handler.
1095      * make sure that we are called after the mpm
1096      * initializes and after the mod_proxy
1097      */
1098     static const char *const aszPred[] = { "mpm_winnt.c", "mod_proxy.c", NULL};
1099      /* manager handler */
1100     ap_hook_handler(balancer_handler, NULL, NULL, APR_HOOK_FIRST);
1101     ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
1102     proxy_hook_pre_request(proxy_balancer_pre_request, NULL, NULL, APR_HOOK_FIRST);
1103     proxy_hook_post_request(proxy_balancer_post_request, NULL, NULL, APR_HOOK_FIRST);
1104     proxy_hook_canon_handler(proxy_balancer_canon, NULL, NULL, APR_HOOK_FIRST);
1105     ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
1106     ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
1107 }
1108
1109 module AP_MODULE_DECLARE_DATA proxy_balancer_module = {
1110     STANDARD20_MODULE_STUFF,
1111     NULL,       /* create per-directory config structure */
1112     NULL,       /* merge per-directory config structures */
1113     NULL,       /* create per-server config structure */
1114     NULL,       /* merge per-server config structures */
1115     NULL,       /* command apr_table_t */
1116     ap_proxy_balancer_register_hook /* register hooks */
1117 };