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 #define CORE_PRIVATE
  20
  21 #include "mod_proxy.h"
  22 #include "scoreboard.h"
  23 #include "ap_mpm.h"
  24 #include "apr_version.h"
  25 #include "apr_hooks.h"
  26
  27 module AP_MODULE_DECLARE_DATA proxy_balancer_module;
  28
  29 static int proxy_balancer_canon(request_rec *r, char *url)
  30 {
  31     char *host, *path, *search;
  32     const char *err;
  33     apr_port_t port = 0;
  34
  35     if (strncasecmp(url, "balancer:", 9) == 0) {
  36         url += 9;
  37     }
  38     else {
  39         return DECLINED;
  40     }
  41
  42     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
  43              "proxy: BALANCER: canonicalising URL %s", url);
  44
  45     /* do syntatic check.
  46      * We break the URL into host, port, path, search
  47      */
  48     err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
  49     if (err) {
  50         ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
  51                       "error parsing URL %s: %s",
  52                       url, err);
  53         return HTTP_BAD_REQUEST;
  54     }
  55     /* now parse path/search args, according to rfc1738 */
  56     /* N.B. if this isn't a true proxy request, then the URL _path_
  57      * has already been decoded.  True proxy requests have r->uri
  58      * == r->unparsed_uri, and no others have that property.
  59      */
  60     if (r->uri == r->unparsed_uri) {
  61         search = strchr(url, '?');
  62         if (search != NULL)
  63             *(search++) = '\0';
  64     }
  65     else
  66         search = r->args;
  67
  68     /* process path */
  69     path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0, r->proxyreq);
  70     if (path == NULL)
  71         return HTTP_BAD_REQUEST;
  72
  73     r->filename = apr_pstrcat(r->pool, "proxy:balancer://", host,
  74             "/", path, (search) ? "?" : "", (search) ? search : "", NULL);
  75
  76     r->path_info = apr_pstrcat(r->pool, "/", path, NULL);
  77
  78     return OK;
  79 }
  80
  81 static int init_balancer_members(proxy_server_conf *conf, server_rec *s,
  82                                  proxy_balancer *balancer)
  83 {
  84     int i;
  85     proxy_worker *workers;
  86
  87     workers = (proxy_worker *)balancer->workers->elts;
  88
  89     for (i = 0; i < balancer->workers->nelts; i++) {
  90         int worker_is_initialized;
  91         worker_is_initialized = PROXY_WORKER_IS_INITIALIZED(workers);
  92         if (!worker_is_initialized) {
  93             proxy_worker_stat *slot;
  94             /*
  95              * If the worker is not initialized check whether its scoreboard
  96              * slot is already initialized.
  97              */
  98             slot = (proxy_worker_stat *) ap_get_scoreboard_lb(workers->id);
  99             if (slot) {
 100                 worker_is_initialized = slot->status & PROXY_WORKER_INITIALIZED;
 101             }
 102             else {
 103                 worker_is_initialized = 0;
 104             }
 105         }
 106         ap_proxy_initialize_worker_share(conf, workers, s);
 107         ap_proxy_initialize_worker(workers, s);
 108         if (!worker_is_initialized) {
 109             /* Set to the original configuration */
 110             workers->s->lbstatus = workers->s->lbfactor =
 111             (workers->lbfactor ? workers->lbfactor : 1);
 112             workers->s->lbset = workers->lbset;
 113         }
 114         ++workers;
 115     }
 116
 117     /* Set default number of attempts to the number of
 118      * workers.
 119      */
 120     if (!balancer->max_attempts_set && balancer->workers->nelts > 1) {
 121         balancer->max_attempts = balancer->workers->nelts - 1;
 122         balancer->max_attempts_set = 1;
 123     }
 124     return 0;
 125 }
 126
 127 /* Retrieve the parameter with the given name
 128  * Something like 'JSESSIONID=12345...N'
 129  */
 130 static char *get_path_param(apr_pool_t *pool, char *url,
 131                             const char *name)
 132 {
 133     char *path = NULL;
 134
 135     for (path = strstr(url, name); path; path = strstr(path + 1, name)) {
 136         path += strlen(name);
 137         if (*path == '=') {
 138             /*
 139              * Session path was found, get it's value
 140              */
 141             ++path;
 142             if (strlen(path)) {
 143                 char *q;
 144                 path = apr_strtok(apr_pstrdup(pool, path), "?&", &q);
 145                 return path;
 146             }
 147         }
 148     }
 149     return NULL;
 150 }
 151
 152 static char *get_cookie_param(request_rec *r, const char *name)
 153 {
 154     const char *cookies;
 155     const char *start_cookie;
 156
 157     if ((cookies = apr_table_get(r->headers_in, "Cookie"))) {
 158         for (start_cookie = ap_strstr_c(cookies, name); start_cookie;
 159              start_cookie = ap_strstr_c(start_cookie + 1, name)) {
 160             if (start_cookie == cookies ||
 161                 start_cookie[-1] == ';' ||
 162                 start_cookie[-1] == ',' ||
 163                 isspace(start_cookie[-1])) {
 164
 165                 start_cookie += strlen(name);
 166                 while(*start_cookie && isspace(*start_cookie))
 167                     ++start_cookie;
 168                 if (*start_cookie == '=' && start_cookie[1]) {
 169                     /*
 170                      * Session cookie was found, get it's value
 171                      */
 172                     char *end_cookie, *cookie;
 173                     ++start_cookie;
 174                     cookie = apr_pstrdup(r->pool, start_cookie);
 175                     if ((end_cookie = strchr(cookie, ';')) != NULL)
 176                         *end_cookie = '\0';
 177                     if((end_cookie = strchr(cookie, ',')) != NULL)
 178                         *end_cookie = '\0';
 179                     return cookie;
 180                 }
 181             }
 182         }
 183     }
 184     return NULL;
 185 }
 186
 187 /* Find the worker that has the 'route' defined
 188  */
 189 static proxy_worker *find_route_worker(proxy_balancer *balancer,
 190                                        const char *route, request_rec *r)
 191 {
 192     int i;
 193     int checking_standby;
 194     int checked_standby;
 195
 196     proxy_worker *worker;
 197
 198     checking_standby = checked_standby = 0;
 199     while (!checked_standby) {
 200         worker = (proxy_worker *)balancer->workers->elts;
 201         for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 202             if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
 203                 continue;
 204             if (*(worker->s->route) && strcmp(worker->s->route, route) == 0) {
 205                 if (worker && PROXY_WORKER_IS_USABLE(worker)) {
 206                     return worker;
 207                 } else {
 208                     /*
 209                      * If the worker is in error state run
 210                      * retry on that worker. It will be marked as
 211                      * operational if the retry timeout is elapsed.
 212                      * The worker might still be unusable, but we try
 213                      * anyway.
 214                      */
 215                     ap_proxy_retry_worker("BALANCER", worker, r->server);
 216                     if (PROXY_WORKER_IS_USABLE(worker)) {
 217                             return worker;
 218                     } else {
 219                         /*
 220                          * We have a worker that is unusable.
 221                          * It can be in error or disabled, but in case
 222                          * it has a redirection set use that redirection worker.
 223                          * This enables to safely remove the member from the
 224                          * balancer. Of course you will need some kind of
 225                          * session replication between those two remote.
 226                          */
 227                         if (*worker->s->redirect) {
 228                             proxy_worker *rworker = NULL;
 229                             rworker = find_route_worker(balancer, worker->s->redirect, r);
 230                             /* Check if the redirect worker is usable */
 231                             if (rworker && !PROXY_WORKER_IS_USABLE(rworker)) {
 232                                 /*
 233                                  * If the worker is in error state run
 234                                  * retry on that worker. It will be marked as
 235                                  * operational if the retry timeout is elapsed.
 236                                  * The worker might still be unusable, but we try
 237                                  * anyway.
 238                                  */
 239                                 ap_proxy_retry_worker("BALANCER", rworker, r->server);
 240                             }
 241                             if (rworker && PROXY_WORKER_IS_USABLE(rworker))
 242                                 return rworker;
 243                         }
 244                     }
 245                 }
 246             }
 247         }
 248         checked_standby = checking_standby++;
 249     }
 250     return NULL;
 251 }
 252
 253 static proxy_worker *find_session_route(proxy_balancer *balancer,
 254                                         request_rec *r,
 255                                         char **route,
 256                                         const char **sticky_used,
 257                                         char **url)
 258 {
 259     proxy_worker *worker = NULL;
 260
 261     if (!balancer->sticky)
 262         return NULL;
 263     /* Try to find the sticky route inside url */
 264     *route = get_path_param(r->pool, *url, balancer->sticky_path);
 265     if (*route) {
 266         ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 267                      "proxy: BALANCER: Found value %s for "
 268                      "stickysession %s", *route, balancer->sticky_path);
 269         *sticky_used =  balancer->sticky_path;
 270     }
 271     else {
 272         *route = get_cookie_param(r, balancer->sticky);
 273         if (*route) {
 274             *sticky_used =  balancer->sticky;
 275             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 276                          "proxy: BALANCER: Found value %s for "
 277                          "stickysession %s", *route, balancer->sticky);
 278         }
 279     }
 280     /*
 281      * If we found a value for sticksession, find the first '.' within.
 282      * Everything after '.' (if present) is our route.
 283      */
 284     if ((*route) && ((*route = strchr(*route, '.')) != NULL ))
 285         (*route)++;
 286     if ((*route) && (**route)) {
 287         ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 288                                   "proxy: BALANCER: Found route %s", *route);
 289         /* We have a route in path or in cookie
 290          * Find the worker that has this route defined.
 291          */
 292         worker = find_route_worker(balancer, *route, r);
 293         if (worker && strcmp(*route, worker->s->route)) {
 294             /*
 295              * Notice that the route of the worker chosen is different from
 296              * the route supplied by the client.
 297              */
 298             apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
 299             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 300                          "proxy: BALANCER: Route changed from %s to %s",
 301                          *route, worker->s->route);
 302         }
 303         return worker;
 304     }
 305     else
 306         return NULL;
 307 }
 308
 309 static proxy_worker *find_best_worker(proxy_balancer *balancer,
 310                                       request_rec *r)
 311 {
 312     proxy_worker *candidate = NULL;
 313     apr_status_t rv;
 314
 315     if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {
 316         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 317         "proxy: BALANCER: (%s). Lock failed for find_best_worker()", balancer->name);
 318         return NULL;
 319     }
 320
 321     candidate = (*balancer->lbmethod->finder)(balancer, r);
 322
 323     if (candidate)
 324         candidate->s->elected++;
 325
 326 /*
 327         PROXY_THREAD_UNLOCK(balancer);
 328         return NULL;
 329 */
 330
 331     if ((rv = PROXY_THREAD_UNLOCK(balancer)) != APR_SUCCESS) {
 332         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 333         "proxy: BALANCER: (%s). Unlock failed for find_best_worker()", balancer->name);
 334     }
 335
 336     if (candidate == NULL) {
 337         /* All the workers are in error state or disabled.
 338          * If the balancer has a timeout sleep for a while
 339          * and try again to find the worker. The chances are
 340          * that some other thread will release a connection.
 341          * By default the timeout is not set, and the server
 342          * returns SERVER_BUSY.
 343          */
 344 #if APR_HAS_THREADS
 345         if (balancer->timeout) {
 346             /* XXX: This can perhaps be build using some
 347              * smarter mechanism, like tread_cond.
 348              * But since the statuses can came from
 349              * different childs, use the provided algo.
 350              */
 351             apr_interval_time_t timeout = balancer->timeout;
 352             apr_interval_time_t step, tval = 0;
 353             /* Set the timeout to 0 so that we don't
 354              * end in infinite loop
 355              */
 356             balancer->timeout = 0;
 357             step = timeout / 100;
 358             while (tval < timeout) {
 359                 apr_sleep(step);
 360                 /* Try again */
 361                 if ((candidate = find_best_worker(balancer, r)))
 362                     break;
 363                 tval += step;
 364             }
 365             /* restore the timeout */
 366             balancer->timeout = timeout;
 367         }
 368 #endif
 369     }
 370     return candidate;
 371 }
 372
 373 static int rewrite_url(request_rec *r, proxy_worker *worker,
 374                         char **url)
 375 {
 376     const char *scheme = strstr(*url, "://");
 377     const char *path = NULL;
 378
 379     if (scheme)
 380         path = ap_strchr_c(scheme + 3, '/');
 381
 382     /* we break the URL into host, port, uri */
 383     if (!worker) {
 384         return ap_proxyerror(r, HTTP_BAD_REQUEST, apr_pstrcat(r->pool,
 385                              "missing worker. URI cannot be parsed: ", *url,
 386                              NULL));
 387     }
 388
 389     *url = apr_pstrcat(r->pool, worker->name, path, NULL);
 390
 391     return OK;
 392 }
 393
 394 static void force_recovery(proxy_balancer *balancer, server_rec *s)
 395 {
 396     int i;
 397     int ok = 0;
 398     proxy_worker *worker;
 399
 400     worker = (proxy_worker *)balancer->workers->elts;
 401     for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 402         if (!(worker->s->status & PROXY_WORKER_IN_ERROR)) {
 403             ok = 1;
 404             break;
 405         }
 406     }
 407     if (!ok) {
 408         /* If all workers are in error state force the recovery.
 409          */
 410         worker = (proxy_worker *)balancer->workers->elts;
 411         for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 412             ++worker->s->retries;
 413             worker->s->status &= ~PROXY_WORKER_IN_ERROR;
 414             ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s,
 415                          "proxy: BALANCER: (%s). Forcing recovery for worker (%s)",
 416                          balancer->name, worker->hostname);
 417         }
 418     }
 419 }
 420
 421 static int proxy_balancer_pre_request(proxy_worker **worker,
 422                                       proxy_balancer **balancer,
 423                                       request_rec *r,
 424                                       proxy_server_conf *conf, char **url)
 425 {
 426     int access_status;
 427     proxy_worker *runtime;
 428     char *route = NULL;
 429     const char *sticky = NULL;
 430     apr_status_t rv;
 431
 432     *worker = NULL;
 433     /* Step 1: check if the url is for us
 434      * The url we can handle starts with 'balancer://'
 435      * If balancer is already provided skip the search
 436      * for balancer, because this is failover attempt.
 437      */
 438     if (!*balancer &&
 439         !(*balancer = ap_proxy_get_balancer(r->pool, conf, *url)))
 440         return DECLINED;
 441
 442     /* Step 2: Lock the LoadBalancer
 443      * XXX: perhaps we need the process lock here
 444      */
 445     if ((rv = PROXY_THREAD_LOCK(*balancer)) != APR_SUCCESS) {
 446         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 447                      "proxy: BALANCER: (%s). Lock failed for pre_request",
 448                      (*balancer)->name);
 449         return DECLINED;
 450     }
 451
 452     /* Step 3: force recovery */
 453     force_recovery(*balancer, r->server);
 454
 455     /* Step 4: find the session route */
 456     runtime = find_session_route(*balancer, r, &route, &sticky, url);
 457     if (runtime) {
 458         int i, total_factor = 0;
 459         proxy_worker *workers;
 460         /* We have a sticky load balancer
 461          * Update the workers status
 462          * so that even session routes get
 463          * into account.
 464          */
 465         workers = (proxy_worker *)(*balancer)->workers->elts;
 466         for (i = 0; i < (*balancer)->workers->nelts; i++) {
 467             /* Take into calculation only the workers that are
 468              * not in error state or not disabled.
 469              *
 470              * TODO: Abstract the below, since this is dependent
 471              *       on the LB implementation
 472              */
 473             if (PROXY_WORKER_IS_USABLE(workers)) {
 474                 workers->s->lbstatus += workers->s->lbfactor;
 475                 total_factor += workers->s->lbfactor;
 476             }
 477             workers++;
 478         }
 479         runtime->s->lbstatus -= total_factor;
 480         runtime->s->elected++;
 481
 482         *worker = runtime;
 483     }
 484     else if (route && (*balancer)->sticky_force) {
 485         int i, member_of = 0;
 486         proxy_worker *workers;
 487         /*
 488          * We have a route provided that doesn't match the
 489          * balancer name. See if the provider route is the
 490          * member of the same balancer in which case return 503
 491          */
 492         workers = (proxy_worker *)(*balancer)->workers->elts;
 493         for (i = 0; i < (*balancer)->workers->nelts; i++) {
 494             if (*(workers->s->route) && strcmp(workers->s->route, route) == 0) {
 495                 member_of = 1;
 496                 break;
 497             }
 498             workers++;
 499         }
 500         if (member_of) {
 501             ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
 502                          "proxy: BALANCER: (%s). All workers are in error state for route (%s)",
 503                          (*balancer)->name, route);
 504             if ((rv = PROXY_THREAD_UNLOCK(*balancer)) != APR_SUCCESS) {
 505                 ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 506                              "proxy: BALANCER: (%s). Unlock failed for pre_request",
 507                              (*balancer)->name);
 508             }
 509             return HTTP_SERVICE_UNAVAILABLE;
 510         }
 511     }
 512
 513     if ((rv = PROXY_THREAD_UNLOCK(*balancer)) != APR_SUCCESS) {
 514         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 515                      "proxy: BALANCER: (%s). Unlock failed for pre_request",
 516                      (*balancer)->name);
 517     }
 518     if (!*worker) {
 519         runtime = find_best_worker(*balancer, r);
 520         if (!runtime) {
 521             ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
 522                          "proxy: BALANCER: (%s). All workers are in error state",
 523                          (*balancer)->name);
 524
 525             return HTTP_SERVICE_UNAVAILABLE;
 526         }
 527         if ((*balancer)->sticky && runtime) {
 528             /*
 529              * This balancer has sticky sessions and the client either has not
 530              * supplied any routing information or all workers for this route
 531              * including possible redirect and hotstandby workers are in error
 532              * state, but we have found another working worker for this
 533              * balancer where we can send the request. Thus notice that we have
 534              * changed the route to the backend.
 535              */
 536             apr_table_setn(r->subprocess_env, "BALANCER_ROUTE_CHANGED", "1");
 537         }
 538         *worker = runtime;
 539     }
 540
 541     /* Add balancer/worker info to env. */
 542     apr_table_setn(r->subprocess_env,
 543                    "BALANCER_NAME", (*balancer)->name);
 544     apr_table_setn(r->subprocess_env,
 545                    "BALANCER_WORKER_NAME", (*worker)->name);
 546     apr_table_setn(r->subprocess_env,
 547                    "BALANCER_WORKER_ROUTE", (*worker)->s->route);
 548
 549     /* Rewrite the url from 'balancer://url'
 550      * to the 'worker_scheme://worker_hostname[:worker_port]/url'
 551      * This replaces the balancers fictional name with the
 552      * real hostname of the elected worker.
 553      */
 554     access_status = rewrite_url(r, *worker, url);
 555     /* Add the session route to request notes if present */
 556     if (route) {
 557         apr_table_setn(r->notes, "session-sticky", sticky);
 558         apr_table_setn(r->notes, "session-route", route);
 559
 560         /* Add session info to env. */
 561         apr_table_setn(r->subprocess_env,
 562                        "BALANCER_SESSION_STICKY", sticky);
 563         apr_table_setn(r->subprocess_env,
 564                        "BALANCER_SESSION_ROUTE", route);
 565     }
 566     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 567                  "proxy: BALANCER (%s) worker (%s) rewritten to %s",
 568                  (*balancer)->name, (*worker)->name, *url);
 569
 570     return access_status;
 571 }
 572
 573 static int proxy_balancer_post_request(proxy_worker *worker,
 574                                        proxy_balancer *balancer,
 575                                        request_rec *r,
 576                                        proxy_server_conf *conf)
 577 {
 578
 579 #if 0
 580     apr_status_t rv;
 581
 582     if ((rv = PROXY_THREAD_LOCK(balancer)) != APR_SUCCESS) {
 583         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 584             "proxy: BALANCER: (%s). Lock failed for post_request",
 585             balancer->name);
 586         return HTTP_INTERNAL_SERVER_ERROR;
 587     }
 588     /* TODO: placeholder for post_request actions
 589      */
 590
 591     if ((rv = PROXY_THREAD_UNLOCK(balancer)) != APR_SUCCESS) {
 592         ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
 593             "proxy: BALANCER: (%s). Unlock failed for post_request",
 594             balancer->name);
 595     }
 596     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 597                  "proxy_balancer_post_request for (%s)", balancer->name);
 598
 599 #endif
 600
 601     return OK;
 602 }
 603
 604 static void recalc_factors(proxy_balancer *balancer)
 605 {
 606     int i;
 607     proxy_worker *workers;
 608
 609
 610     /* Recalculate lbfactors */
 611     workers = (proxy_worker *)balancer->workers->elts;
 612     /* Special case if there is only one worker it's
 613      * load factor will always be 1
 614      */
 615     if (balancer->workers->nelts == 1) {
 616         workers->s->lbstatus = workers->s->lbfactor = 1;
 617         return;
 618     }
 619     for (i = 0; i < balancer->workers->nelts; i++) {
 620         /* Update the status entries */
 621         workers[i].s->lbstatus = workers[i].s->lbfactor;
 622     }
 623 }
 624
 625 /* Manages the loadfactors and member status
 626  */
 627 static int balancer_handler(request_rec *r)
 628 {
 629     void *sconf = r->server->module_config;
 630     proxy_server_conf *conf = (proxy_server_conf *)
 631         ap_get_module_config(sconf, &proxy_module);
 632     proxy_balancer *balancer, *bsel = NULL;
 633     proxy_worker *worker, *wsel = NULL;
 634     apr_table_t *params = apr_table_make(r->pool, 10);
 635     int access_status;
 636     int i, n;
 637     const char *name;
 638
 639     /* is this for us? */
 640     if (strcmp(r->handler, "balancer-manager"))
 641         return DECLINED;
 642     r->allowed = (AP_METHOD_BIT << M_GET);
 643     if (r->method_number != M_GET)
 644         return DECLINED;
 645
 646     if (r->args) {
 647         char *args = apr_pstrdup(r->pool, r->args);
 648         char *tok, *val;
 649         while (args && *args) {
 650             if ((val = ap_strchr(args, '='))) {
 651                 *val++ = '\0';
 652                 if ((tok = ap_strchr(val, '&')))
 653                     *tok++ = '\0';
 654                 /*
 655                  * Special case: workers are allowed path information
 656                  */
 657                 if ((access_status = ap_unescape_url(val)) != OK)
 658                     if (strcmp(args, "w") || (access_status !=  HTTP_NOT_FOUND))
 659                         return access_status;
 660                 apr_table_setn(params, args, val);
 661                 args = tok;
 662             }
 663             else
 664                 return HTTP_BAD_REQUEST;
 665         }
 666     }
 667     if ((name = apr_table_get(params, "b")))
 668         bsel = ap_proxy_get_balancer(r->pool, conf,
 669             apr_pstrcat(r->pool, "balancer://", name, NULL));
 670     if ((name = apr_table_get(params, "w"))) {
 671         proxy_worker *ws;
 672
 673         ws = ap_proxy_get_worker(r->pool, conf, name);
 674         if (bsel && ws) {
 675             worker = (proxy_worker *)bsel->workers->elts;
 676             for (n = 0; n < bsel->workers->nelts; n++) {
 677                 if (strcasecmp(worker->name, ws->name) == 0) {
 678                     wsel = worker;
 679                     break;
 680                 }
 681                 ++worker;
 682             }
 683         }
 684     }
 685     /* First set the params */
 686     /*
 687      * Note that it is not possible set the proxy_balancer because it is not
 688      * in shared memory.
 689      */
 690     if (wsel) {
 691         const char *val;
 692         if ((val = apr_table_get(params, "lf"))) {
 693             int ival = atoi(val);
 694             if (ival >= 1 && ival <= 100) {
 695                 wsel->s->lbfactor = ival;
 696                 if (bsel)
 697                     recalc_factors(bsel);
 698             }
 699         }
 700         if ((val = apr_table_get(params, "wr"))) {
 701             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 702                 strcpy(wsel->s->route, val);
 703             else
 704                 *wsel->s->route = '\0';
 705         }
 706         if ((val = apr_table_get(params, "rr"))) {
 707             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 708                 strcpy(wsel->s->redirect, val);
 709             else
 710                 *wsel->s->redirect = '\0';
 711         }
 712         if ((val = apr_table_get(params, "dw"))) {
 713             if (!strcasecmp(val, "Disable"))
 714                 wsel->s->status |= PROXY_WORKER_DISABLED;
 715             else if (!strcasecmp(val, "Enable"))
 716                 wsel->s->status &= ~PROXY_WORKER_DISABLED;
 717         }
 718         if ((val = apr_table_get(params, "ls"))) {
 719             int ival = atoi(val);
 720             if (ival >= 0 && ival <= 99) {
 721                 wsel->s->lbset = ival;
 722              }
 723         }
 724
 725     }
 726     if (apr_table_get(params, "xml")) {
 727         ap_set_content_type(r, "text/xml");
 728         ap_rputs("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n", r);
 729         ap_rputs("<httpd:manager xmlns:httpd=\"http://httpd.apache.org\">\n", r);
 730         ap_rputs("  <httpd:balancers>\n", r);
 731         balancer = (proxy_balancer *)conf->balancers->elts;
 732         for (i = 0; i < conf->balancers->nelts; i++) {
 733             ap_rputs("    <httpd:balancer>\n", r);
 734             ap_rvputs(r, "      <httpd:name>", balancer->name, "</httpd:name>\n", NULL);
 735             ap_rputs("      <httpd:workers>\n", r);
 736             worker = (proxy_worker *)balancer->workers->elts;
 737             for (n = 0; n < balancer->workers->nelts; n++) {
 738                 ap_rputs("        <httpd:worker>\n", r);
 739                 ap_rvputs(r, "          <httpd:scheme>", worker->scheme,
 740                           "</httpd:scheme>\n", NULL);
 741                 ap_rvputs(r, "          <httpd:hostname>", worker->hostname,
 742                           "</httpd:hostname>\n", NULL);
 743                ap_rprintf(r, "          <httpd:loadfactor>%d</httpd:loadfactor>\n",
 744                           worker->s->lbfactor);
 745                 ap_rputs("        </httpd:worker>\n", r);
 746                 ++worker;
 747             }
 748             ap_rputs("      </httpd:workers>\n", r);
 749             ap_rputs("    </httpd:balancer>\n", r);
 750             ++balancer;
 751         }
 752         ap_rputs("  </httpd:balancers>\n", r);
 753         ap_rputs("</httpd:manager>", r);
 754     }
 755     else {
 756         ap_set_content_type(r, "text/html; charset=ISO-8859-1");
 757         ap_rputs(DOCTYPE_HTML_3_2
 758                  "<html><head><title>Balancer Manager</title></head>\n", r);
 759         ap_rputs("<body><h1>Load Balancer Manager for ", r);
 760         ap_rvputs(r, ap_get_server_name(r), "</h1>\n\n", NULL);
 761         ap_rvputs(r, "<dl><dt>Server Version: ",
 762                   ap_get_server_description(), "</dt>\n", NULL);
 763         ap_rvputs(r, "<dt>Server Built: ",
 764                   ap_get_server_built(), "\n</dt></dl>\n", NULL);
 765         balancer = (proxy_balancer *)conf->balancers->elts;
 766         for (i = 0; i < conf->balancers->nelts; i++) {
 767
 768             ap_rputs("<hr />\n<h3>LoadBalancer Status for ", r);
 769             ap_rvputs(r, balancer->name, "</h3>\n\n", NULL);
 770             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 771                 "<th>StickySession</th><th>Timeout</th><th>FailoverAttempts</th><th>Method</th>"
 772                 "</tr>\n<tr>", r);
 773             if (balancer->sticky) {
 774                 if (strcmp(balancer->sticky, balancer->sticky_path)) {
 775                     ap_rvputs(r, "<td>", balancer->sticky, " | ",
 776                               balancer->sticky_path, NULL);
 777                 }
 778                 else {
 779                     ap_rvputs(r, "<td>", balancer->sticky, NULL);
 780                 }
 781             }
 782             else {
 783                 ap_rputs("<td> - ", r);
 784             }
 785             ap_rprintf(r, "</td><td>%" APR_TIME_T_FMT "</td>",
 786                 apr_time_sec(balancer->timeout));
 787             ap_rprintf(r, "<td>%d</td>\n", balancer->max_attempts);
 788             ap_rprintf(r, "<td>%s</td>\n",
 789                        balancer->lbmethod->name);
 790             ap_rputs("</table>\n<br />", r);
 791             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 792                 "<th>Worker URL</th>"
 793                 "<th>Route</th><th>RouteRedir</th>"
 794                 "<th>Factor</th><th>Set</th><th>Status</th>"
 795                 "<th>Elected</th><th>To</th><th>From</th>"
 796                 "</tr>\n", r);
 797
 798             worker = (proxy_worker *)balancer->workers->elts;
 799             for (n = 0; n < balancer->workers->nelts; n++) {
 800                 char fbuf[50];
 801                 ap_rvputs(r, "<tr>\n<td><a href=\"", r->uri, "?b=",
 802                           balancer->name + sizeof("balancer://") - 1, "&w=",
 803                           ap_escape_uri(r->pool, worker->name),
 804                           "\">", NULL);
 805                 ap_rvputs(r, worker->name, "</a></td>", NULL);
 806                 ap_rvputs(r, "<td>", worker->s->route, NULL);
 807                 ap_rvputs(r, "</td><td>", worker->s->redirect, NULL);
 808                 ap_rprintf(r, "</td><td>%d</td>", worker->s->lbfactor);
 809                 ap_rprintf(r, "<td>%d</td><td>", worker->s->lbset);
 810                 if (worker->s->status & PROXY_WORKER_DISABLED)
 811                    ap_rputs("Dis ", r);
 812                 if (worker->s->status & PROXY_WORKER_IN_ERROR)
 813                    ap_rputs("Err ", r);
 814                 if (worker->s->status & PROXY_WORKER_STOPPED)
 815                    ap_rputs("Stop ", r);
 816                 if (worker->s->status & PROXY_WORKER_HOT_STANDBY)
 817                    ap_rputs("Stby ", r);
 818                 if (PROXY_WORKER_IS_USABLE(worker))
 819                     ap_rputs("Ok", r);
 820                 if (!PROXY_WORKER_IS_INITIALIZED(worker))
 821                     ap_rputs("-", r);
 822                 ap_rputs("</td>", r);
 823                 ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td><td>", worker->s->elected);
 824                 ap_rputs(apr_strfsize(worker->s->transferred, fbuf), r);
 825                 ap_rputs("</td><td>", r);
 826                 ap_rputs(apr_strfsize(worker->s->read, fbuf), r);
 827                 ap_rputs("</td></tr>\n", r);
 828
 829                 ++worker;
 830             }
 831             ap_rputs("</table>\n", r);
 832             ++balancer;
 833         }
 834         ap_rputs("<hr />\n", r);
 835         if (wsel && bsel) {
 836             ap_rputs("<h3>Edit worker settings for ", r);
 837             ap_rvputs(r, wsel->name, "</h3>\n", NULL);
 838             ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
 839             ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
 840             ap_rputs("<table><tr><td>Load factor:</td><td><input name=\"lf\" type=text ", r);
 841             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbfactor);
 842             ap_rputs("<tr><td>LB Set:</td><td><input name=\"ls\" type=text ", r);
 843             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbset);
 844             ap_rputs("<tr><td>Route:</td><td><input name=\"wr\" type=text ", r);
 845             ap_rvputs(r, "value=\"", wsel->s->route, NULL);
 846             ap_rputs("\"></td></tr>\n", r);
 847             ap_rputs("<tr><td>Route Redirect:</td><td><input name=\"rr\" type=text ", r);
 848             ap_rvputs(r, "value=\"", wsel->s->redirect, NULL);
 849             ap_rputs("\"></td></tr>\n", r);
 850             ap_rputs("<tr><td>Status:</td><td>Disabled: <input name=\"dw\" value=\"Disable\" type=radio", r);
 851             if (wsel->s->status & PROXY_WORKER_DISABLED)
 852                 ap_rputs(" checked", r);
 853             ap_rputs("> | Enabled: <input name=\"dw\" value=\"Enable\" type=radio", r);
 854             if (!(wsel->s->status & PROXY_WORKER_DISABLED))
 855                 ap_rputs(" checked", r);
 856             ap_rputs("></td></tr>\n", r);
 857             ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
 858             ap_rvputs(r, "</table>\n<input type=hidden name=\"w\" ",  NULL);
 859             ap_rvputs(r, "value=\"", ap_escape_uri(r->pool, wsel->name), "\">\n", NULL);
 860             ap_rvputs(r, "<input type=hidden name=\"b\" ", NULL);
 861             ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
 862                       "\">\n</form>\n", NULL);
 863             ap_rputs("<hr />\n", r);
 864         }
 865         ap_rputs(ap_psignature("",r), r);
 866         ap_rputs("</body></html>\n", r);
 867     }
 868     return OK;
 869 }
 870
 871 static void child_init(apr_pool_t *p, server_rec *s)
 872 {
 873     while (s) {
 874         void *sconf = s->module_config;
 875         proxy_server_conf *conf;
 876         proxy_balancer *balancer;
 877         int i;
 878         conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
 879
 880         /* Initialize shared scoreboard data */
 881         balancer = (proxy_balancer *)conf->balancers->elts;
 882         for (i = 0; i < conf->balancers->nelts; i++) {
 883             init_balancer_members(conf, s, balancer);
 884             balancer++;
 885         }
 886         s = s->next;
 887     }
 888
 889 }
 890
 891 /*
 892  * The idea behind the find_best_byrequests scheduler is the following:
 893  *
 894  * lbfactor is "how much we expect this worker to work", or "the worker's
 895  * normalized work quota".
 896  *
 897  * lbstatus is "how urgent this worker has to work to fulfill its quota
 898  * of work".
 899  *
 900  * We distribute each worker's work quota to the worker, and then look
 901  * which of them needs to work most urgently (biggest lbstatus).  This
 902  * worker is then selected for work, and its lbstatus reduced by the
 903  * total work quota we distributed to all workers.  Thus the sum of all
 904  * lbstatus does not change.(*)
 905  *
 906  * If some workers are disabled, the others will
 907  * still be scheduled correctly.
 908  *
 909  * If a balancer is configured as follows:
 910  *
 911  * worker     a    b    c    d
 912  * lbfactor  25   25   25   25
 913  *
 914  * And b gets disabled, the following schedule is produced:
 915  *
 916  *    a c d a c d a c d ...
 917  *
 918  * Note that the above lbfactor setting is the *exact* same as:
 919  *
 920  * worker     a    b    c    d
 921  * lbfactor   1    1    1    1
 922  *
 923  * Asymmetric configurations work as one would expect. For
 924  * example:
 925  *
 926  * worker     a    b    c    d
 927  * lbfactor   1    1    1    2
 928  *
 929  * would have a, b and c all handling about the same
 930  * amount of load with d handling twice what a or b
 931  * or c handles individually. So we could see:
 932  *
 933  *   b a d c d a c d b d ...
 934  *
 935  */
 936
 937 static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
 938                                 request_rec *r)
 939 {
 940     int i;
 941     int total_factor = 0;
 942     proxy_worker *worker;
 943     proxy_worker *mycandidate = NULL;
 944     int cur_lbset = 0;
 945     int max_lbset = 0;
 946     int checking_standby;
 947     int checked_standby;
 948
 949     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 950                  "proxy: Entering byrequests for BALANCER (%s)",
 951                  balancer->name);
 952
 953     /* First try to see if we have available candidate */
 954     do {
 955         checking_standby = checked_standby = 0;
 956         while (!mycandidate && !checked_standby) {
 957             worker = (proxy_worker *)balancer->workers->elts;
 958             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 959                 if (!checking_standby) {    /* first time through */
 960                     if (worker->s->lbset > max_lbset)
 961                         max_lbset = worker->s->lbset;
 962                 }
 963                 if (worker->s->lbset > cur_lbset)
 964                     continue;
 965                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
 966                     continue;
 967                 /* If the worker is in error state run
 968                  * retry on that worker. It will be marked as
 969                  * operational if the retry timeout is elapsed.
 970                  * The worker might still be unusable, but we try
 971                  * anyway.
 972                  */
 973                 if (!PROXY_WORKER_IS_USABLE(worker))
 974                     ap_proxy_retry_worker("BALANCER", worker, r->server);
 975                 /* Take into calculation only the workers that are
 976                  * not in error state or not disabled.
 977                  */
 978                 if (PROXY_WORKER_IS_USABLE(worker)) {
 979                     worker->s->lbstatus += worker->s->lbfactor;
 980                     total_factor += worker->s->lbfactor;
 981                     if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
 982                         mycandidate = worker;
 983                 }
 984             }
 985             checked_standby = checking_standby++;
 986         }
 987         cur_lbset++;
 988     } while (cur_lbset <= max_lbset && !mycandidate);
 989
 990     if (mycandidate) {
 991         mycandidate->s->lbstatus -= total_factor;
 992     }
 993
 994     return mycandidate;
 995 }
 996
 997 /*
 998  * The idea behind the find_best_bytraffic scheduler is the following:
 999  *
1000  * We know the amount of traffic (bytes in and out) handled by each
1001  * worker. We normalize that traffic by each workers' weight. So assuming
1002  * a setup as below:
1003  *
1004  * worker     a    b    c
1005  * lbfactor   1    1    3
1006  *
1007  * the scheduler will allow worker c to handle 3 times the
1008  * traffic of a and b. If each request/response results in the
1009  * same amount of traffic, then c would be accessed 3 times as
1010  * often as a or b. If, for example, a handled a request that
1011  * resulted in a large i/o bytecount, then b and c would be
1012  * chosen more often, to even things out.
1013  */
1014 static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
1015                                          request_rec *r)
1016 {
1017     int i;
1018     apr_off_t mytraffic = 0;
1019     apr_off_t curmin = 0;
1020     proxy_worker *worker;
1021     proxy_worker *mycandidate = NULL;
1022     int cur_lbset = 0;
1023     int max_lbset = 0;
1024     int checking_standby;
1025     int checked_standby;
1026
1027     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
1028                  "proxy: Entering bytraffic for BALANCER (%s)",
1029                  balancer->name);
1030
1031     /* First try to see if we have available candidate */
1032     do {
1033         checking_standby = checked_standby = 0;
1034         while (!mycandidate && !checked_standby) {
1035             worker = (proxy_worker *)balancer->workers->elts;
1036             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
1037                 if (!checking_standby) {    /* first time through */
1038                     if (worker->s->lbset > max_lbset)
1039                         max_lbset = worker->s->lbset;
1040                 }
1041                 if (worker->s->lbset > cur_lbset)
1042                     continue;
1043                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
1044                     continue;
1045                 /* If the worker is in error state run
1046                  * retry on that worker. It will be marked as
1047                  * operational if the retry timeout is elapsed.
1048                  * The worker might still be unusable, but we try
1049                  * anyway.
1050                  */
1051                 if (!PROXY_WORKER_IS_USABLE(worker))
1052                     ap_proxy_retry_worker("BALANCER", worker, r->server);
1053                 /* Take into calculation only the workers that are
1054                  * not in error state or not disabled.
1055                  */
1056                 if (PROXY_WORKER_IS_USABLE(worker)) {
1057                     mytraffic = (worker->s->transferred/worker->s->lbfactor) +
1058                                 (worker->s->read/worker->s->lbfactor);
1059                     if (!mycandidate || mytraffic < curmin) {
1060                         mycandidate = worker;
1061                         curmin = mytraffic;
1062                     }
1063                 }
1064             }
1065             checked_standby = checking_standby++;
1066         }
1067         cur_lbset++;
1068     } while (cur_lbset <= max_lbset && !mycandidate);
1069
1070     return mycandidate;
1071 }
1072
1073 /*
1074  * How to add additional lbmethods:
1075  *   1. Create func which determines "best" candidate worker
1076  *      (eg: find_best_bytraffic, above)
1077  *   2. Register it as a provider.
1078  */
1079 static const proxy_balancer_method byrequests =
1080 {
1081     "byrequests",
1082     &find_best_byrequests,
1083     NULL
1084 };
1085
1086 static const proxy_balancer_method bytraffic =
1087 {
1088     "bytraffic",
1089     &find_best_bytraffic,
1090     NULL
1091 };
1092
1093 static void ap_proxy_balancer_register_hook(apr_pool_t *p)
1094 {
1095     /* Only the mpm_winnt has child init hook handler.
1096      * make sure that we are called after the mpm
1097      * initializes and after the mod_proxy
1098      */
1099     static const char *const aszPred[] = { "mpm_winnt.c", "mod_proxy.c", NULL};
1100      /* manager handler */
1101     ap_hook_handler(balancer_handler, NULL, NULL, APR_HOOK_FIRST);
1102     ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
1103     proxy_hook_pre_request(proxy_balancer_pre_request, NULL, NULL, APR_HOOK_FIRST);
1104     proxy_hook_post_request(proxy_balancer_post_request, NULL, NULL, APR_HOOK_FIRST);
1105     proxy_hook_canon_handler(proxy_balancer_canon, NULL, NULL, APR_HOOK_FIRST);
1106     ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
1107     ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
1108 }
1109
1110 module AP_MODULE_DECLARE_DATA proxy_balancer_module = {
1111     STANDARD20_MODULE_STUFF,
1112     NULL,       /* create per-directory config structure */
1113     NULL,       /* merge per-directory config structures */
1114     NULL,       /* create per-server config structure */
1115     NULL,       /* merge per-server config structures */
1116     NULL,       /* command apr_table_t */
1117     ap_proxy_balancer_register_hook /* register hooks */
1118 };