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 #include "apr_uuid.h"
  25
  26 module AP_MODULE_DECLARE_DATA proxy_balancer_module;
  27
  28 static char balancer_nonce[APR_UUID_FORMATTED_LENGTH + 1];
  29
  30 static int proxy_balancer_canon(request_rec *r, char *url)
  31 {
  32     char *host, *path;
  33     char *search = NULL;
  34     const char *err;
  35     apr_port_t port = 0;
  36
  37     if (strncasecmp(url, "balancer:", 9) == 0) {
  38         url += 9;
  39     }
  40     else {
  41         return DECLINED;
  42     }
  43
  44     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
  45              "proxy: BALANCER: canonicalising URL %s", url);
  46
  47     /* do syntatic check.
  48      * We break the URL into host, port, path, search
  49      */
  50     err = ap_proxy_canon_netloc(r->pool, &url, NULL, NULL, &host, &port);
  51     if (err) {
  52         ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
  53                       "error parsing URL %s: %s",
  54                       url, err);
  55         return HTTP_BAD_REQUEST;
  56     }
  57     /*
  58      * now parse path/search args, according to rfc1738:
  59      * process the path. With proxy-noncanon set (by
  60      * mod_proxy) we use the raw, unparsed uri
  61      */
  62     if (apr_table_get(r->notes, "proxy-nocanon")) {
  63         path = url;   /* this is the raw path */
  64     }
  65     else {
  66         path = ap_proxy_canonenc(r->pool, url, strlen(url), enc_path, 0,
  67                                  r->proxyreq);
  68         search = r->args;
  69     }
  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 /* post_config hook: */
 626 static int balancer_init(apr_pool_t *p, apr_pool_t *plog,
 627                          apr_pool_t *ptemp, server_rec *s)
 628 {
 629     void *data;
 630     const char *userdata_key = "mod_proxy_balancer_init";
 631     apr_uuid_t uuid;
 632
 633     /* balancer_init() will be called twice during startup.  So, only
 634      * set up the static data the second time through. */
 635     apr_pool_userdata_get(&data, userdata_key, s->process->pool);
 636     if (!data) {
 637         apr_pool_userdata_set((const void *)1, userdata_key,
 638                                apr_pool_cleanup_null, s->process->pool);
 639         return OK;
 640     }
 641
 642     /* Retrieve a UUID and store the nonce for the lifetime of
 643      * the process. */
 644     apr_uuid_get(&uuid);
 645     apr_uuid_format(balancer_nonce, &uuid);
 646
 647     return OK;
 648 }
 649
 650 /* Manages the loadfactors and member status
 651  */
 652 static int balancer_handler(request_rec *r)
 653 {
 654     void *sconf = r->server->module_config;
 655     proxy_server_conf *conf = (proxy_server_conf *)
 656         ap_get_module_config(sconf, &proxy_module);
 657     proxy_balancer *balancer, *bsel = NULL;
 658     proxy_worker *worker, *wsel = NULL;
 659     apr_table_t *params = apr_table_make(r->pool, 10);
 660     int access_status;
 661     int i, n;
 662     const char *name;
 663
 664     /* is this for us? */
 665     if (strcmp(r->handler, "balancer-manager"))
 666         return DECLINED;
 667     r->allowed = (AP_METHOD_BIT << M_GET);
 668     if (r->method_number != M_GET)
 669         return DECLINED;
 670
 671     if (r->args) {
 672         char *args = apr_pstrdup(r->pool, r->args);
 673         char *tok, *val;
 674         while (args && *args) {
 675             if ((val = ap_strchr(args, '='))) {
 676                 *val++ = '\0';
 677                 if ((tok = ap_strchr(val, '&')))
 678                     *tok++ = '\0';
 679                 /*
 680                  * Special case: workers are allowed path information
 681                  */
 682                 if ((access_status = ap_unescape_url(val)) != OK)
 683                     if (strcmp(args, "w") || (access_status !=  HTTP_NOT_FOUND))
 684                         return access_status;
 685                 apr_table_setn(params, args, val);
 686                 args = tok;
 687             }
 688             else
 689                 return HTTP_BAD_REQUEST;
 690         }
 691     }
 692
 693     /* Check that the supplied nonce matches this server's nonce;
 694      * otherwise ignore all parameters, to prevent a CSRF attack. */
 695     if ((name = apr_table_get(params, "nonce")) == NULL
 696         || strcmp(balancer_nonce, name) != 0) {
 697         apr_table_clear(params);
 698     }
 699
 700     if ((name = apr_table_get(params, "b")))
 701         bsel = ap_proxy_get_balancer(r->pool, conf,
 702             apr_pstrcat(r->pool, "balancer://", name, NULL));
 703     if ((name = apr_table_get(params, "w"))) {
 704         proxy_worker *ws;
 705
 706         ws = ap_proxy_get_worker(r->pool, conf, name);
 707         if (bsel && ws) {
 708             worker = (proxy_worker *)bsel->workers->elts;
 709             for (n = 0; n < bsel->workers->nelts; n++) {
 710                 if (strcasecmp(worker->name, ws->name) == 0) {
 711                     wsel = worker;
 712                     break;
 713                 }
 714                 ++worker;
 715             }
 716         }
 717     }
 718     /* First set the params */
 719     /*
 720      * Note that it is not possible set the proxy_balancer because it is not
 721      * in shared memory.
 722      */
 723     if (wsel) {
 724         const char *val;
 725         if ((val = apr_table_get(params, "lf"))) {
 726             int ival = atoi(val);
 727             if (ival >= 1 && ival <= 100) {
 728                 wsel->s->lbfactor = ival;
 729                 if (bsel)
 730                     recalc_factors(bsel);
 731             }
 732         }
 733         if ((val = apr_table_get(params, "wr"))) {
 734             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 735                 strcpy(wsel->s->route, val);
 736             else
 737                 *wsel->s->route = '\0';
 738         }
 739         if ((val = apr_table_get(params, "rr"))) {
 740             if (strlen(val) && strlen(val) < PROXY_WORKER_MAX_ROUTE_SIZ)
 741                 strcpy(wsel->s->redirect, val);
 742             else
 743                 *wsel->s->redirect = '\0';
 744         }
 745         if ((val = apr_table_get(params, "dw"))) {
 746             if (!strcasecmp(val, "Disable"))
 747                 wsel->s->status |= PROXY_WORKER_DISABLED;
 748             else if (!strcasecmp(val, "Enable"))
 749                 wsel->s->status &= ~PROXY_WORKER_DISABLED;
 750         }
 751         if ((val = apr_table_get(params, "ls"))) {
 752             int ival = atoi(val);
 753             if (ival >= 0 && ival <= 99) {
 754                 wsel->s->lbset = ival;
 755              }
 756         }
 757
 758     }
 759     if (apr_table_get(params, "xml")) {
 760         ap_set_content_type(r, "text/xml");
 761         ap_rputs("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\n", r);
 762         ap_rputs("<httpd:manager xmlns:httpd=\"http://httpd.apache.org\">\n", r);
 763         ap_rputs("  <httpd:balancers>\n", r);
 764         balancer = (proxy_balancer *)conf->balancers->elts;
 765         for (i = 0; i < conf->balancers->nelts; i++) {
 766             ap_rputs("    <httpd:balancer>\n", r);
 767             ap_rvputs(r, "      <httpd:name>", balancer->name, "</httpd:name>\n", NULL);
 768             ap_rputs("      <httpd:workers>\n", r);
 769             worker = (proxy_worker *)balancer->workers->elts;
 770             for (n = 0; n < balancer->workers->nelts; n++) {
 771                 ap_rputs("        <httpd:worker>\n", r);
 772                 ap_rvputs(r, "          <httpd:scheme>", worker->scheme,
 773                           "</httpd:scheme>\n", NULL);
 774                 ap_rvputs(r, "          <httpd:hostname>", worker->hostname,
 775                           "</httpd:hostname>\n", NULL);
 776                ap_rprintf(r, "          <httpd:loadfactor>%d</httpd:loadfactor>\n",
 777                           worker->s->lbfactor);
 778                 ap_rputs("        </httpd:worker>\n", r);
 779                 ++worker;
 780             }
 781             ap_rputs("      </httpd:workers>\n", r);
 782             ap_rputs("    </httpd:balancer>\n", r);
 783             ++balancer;
 784         }
 785         ap_rputs("  </httpd:balancers>\n", r);
 786         ap_rputs("</httpd:manager>", r);
 787     }
 788     else {
 789         ap_set_content_type(r, "text/html; charset=ISO-8859-1");
 790         ap_rputs(DOCTYPE_HTML_3_2
 791                  "<html><head><title>Balancer Manager</title></head>\n", r);
 792         ap_rputs("<body><h1>Load Balancer Manager for ", r);
 793         ap_rvputs(r, ap_get_server_name(r), "</h1>\n\n", NULL);
 794         ap_rvputs(r, "<dl><dt>Server Version: ",
 795                   ap_get_server_description(), "</dt>\n", NULL);
 796         ap_rvputs(r, "<dt>Server Built: ",
 797                   ap_get_server_built(), "\n</dt></dl>\n", NULL);
 798         balancer = (proxy_balancer *)conf->balancers->elts;
 799         for (i = 0; i < conf->balancers->nelts; i++) {
 800
 801             ap_rputs("<hr />\n<h3>LoadBalancer Status for ", r);
 802             ap_rvputs(r, balancer->name, "</h3>\n\n", NULL);
 803             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 804                 "<th>StickySession</th><th>Timeout</th><th>FailoverAttempts</th><th>Method</th>"
 805                 "</tr>\n<tr>", r);
 806             if (balancer->sticky) {
 807                 if (strcmp(balancer->sticky, balancer->sticky_path)) {
 808                     ap_rvputs(r, "<td>", balancer->sticky, " | ",
 809                               balancer->sticky_path, NULL);
 810                 }
 811                 else {
 812                     ap_rvputs(r, "<td>", balancer->sticky, NULL);
 813                 }
 814             }
 815             else {
 816                 ap_rputs("<td> - ", r);
 817             }
 818             ap_rprintf(r, "</td><td>%" APR_TIME_T_FMT "</td>",
 819                 apr_time_sec(balancer->timeout));
 820             ap_rprintf(r, "<td>%d</td>\n", balancer->max_attempts);
 821             ap_rprintf(r, "<td>%s</td>\n",
 822                        balancer->lbmethod->name);
 823             ap_rputs("</table>\n<br />", r);
 824             ap_rputs("\n\n<table border=\"0\" style=\"text-align: left;\"><tr>"
 825                 "<th>Worker URL</th>"
 826                 "<th>Route</th><th>RouteRedir</th>"
 827                 "<th>Factor</th><th>Set</th><th>Status</th>"
 828                 "<th>Elected</th><th>To</th><th>From</th>"
 829                 "</tr>\n", r);
 830
 831             worker = (proxy_worker *)balancer->workers->elts;
 832             for (n = 0; n < balancer->workers->nelts; n++) {
 833                 char fbuf[50];
 834                 ap_rvputs(r, "<tr>\n<td><a href=\"", r->uri, "?b=",
 835                           balancer->name + sizeof("balancer://") - 1, "&w=",
 836                           ap_escape_uri(r->pool, worker->name),
 837                           "&nonce=", balancer_nonce,
 838                           "\">", NULL);
 839                 ap_rvputs(r, worker->name, "</a></td>", NULL);
 840                 ap_rvputs(r, "<td>", ap_escape_html(r->pool, worker->s->route),
 841                           NULL);
 842                 ap_rvputs(r, "</td><td>",
 843                           ap_escape_html(r->pool, worker->s->redirect), NULL);
 844                 ap_rprintf(r, "</td><td>%d</td>", worker->s->lbfactor);
 845                 ap_rprintf(r, "<td>%d</td><td>", worker->s->lbset);
 846                 if (worker->s->status & PROXY_WORKER_DISABLED)
 847                    ap_rputs("Dis ", r);
 848                 if (worker->s->status & PROXY_WORKER_IN_ERROR)
 849                    ap_rputs("Err ", r);
 850                 if (worker->s->status & PROXY_WORKER_STOPPED)
 851                    ap_rputs("Stop ", r);
 852                 if (worker->s->status & PROXY_WORKER_HOT_STANDBY)
 853                    ap_rputs("Stby ", r);
 854                 if (PROXY_WORKER_IS_USABLE(worker))
 855                     ap_rputs("Ok", r);
 856                 if (!PROXY_WORKER_IS_INITIALIZED(worker))
 857                     ap_rputs("-", r);
 858                 ap_rputs("</td>", r);
 859                 ap_rprintf(r, "<td>%" APR_SIZE_T_FMT "</td><td>", worker->s->elected);
 860                 ap_rputs(apr_strfsize(worker->s->transferred, fbuf), r);
 861                 ap_rputs("</td><td>", r);
 862                 ap_rputs(apr_strfsize(worker->s->read, fbuf), r);
 863                 ap_rputs("</td></tr>\n", r);
 864
 865                 ++worker;
 866             }
 867             ap_rputs("</table>\n", r);
 868             ++balancer;
 869         }
 870         ap_rputs("<hr />\n", r);
 871         if (wsel && bsel) {
 872             ap_rputs("<h3>Edit worker settings for ", r);
 873             ap_rvputs(r, wsel->name, "</h3>\n", NULL);
 874             ap_rvputs(r, "<form method=\"GET\" action=\"", NULL);
 875             ap_rvputs(r, r->uri, "\">\n<dl>", NULL);
 876             ap_rputs("<table><tr><td>Load factor:</td><td><input name=\"lf\" type=text ", r);
 877             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbfactor);
 878             ap_rputs("<tr><td>LB Set:</td><td><input name=\"ls\" type=text ", r);
 879             ap_rprintf(r, "value=\"%d\"></td></tr>\n", wsel->s->lbset);
 880             ap_rputs("<tr><td>Route:</td><td><input name=\"wr\" type=text ", r);
 881             ap_rvputs(r, "value=\"", ap_escape_html(r->pool, wsel->s->route),
 882                       NULL);
 883             ap_rputs("\"></td></tr>\n", r);
 884             ap_rputs("<tr><td>Route Redirect:</td><td><input name=\"rr\" type=text ", r);
 885             ap_rvputs(r, "value=\"", ap_escape_html(r->pool, wsel->s->redirect),
 886                       NULL);
 887             ap_rputs("\"></td></tr>\n", r);
 888             ap_rputs("<tr><td>Status:</td><td>Disabled: <input name=\"dw\" value=\"Disable\" type=radio", r);
 889             if (wsel->s->status & PROXY_WORKER_DISABLED)
 890                 ap_rputs(" checked", r);
 891             ap_rputs("> | Enabled: <input name=\"dw\" value=\"Enable\" type=radio", r);
 892             if (!(wsel->s->status & PROXY_WORKER_DISABLED))
 893                 ap_rputs(" checked", r);
 894             ap_rputs("></td></tr>\n", r);
 895             ap_rputs("<tr><td colspan=2><input type=submit value=\"Submit\"></td></tr>\n", r);
 896             ap_rvputs(r, "</table>\n<input type=hidden name=\"w\" ",  NULL);
 897             ap_rvputs(r, "value=\"", ap_escape_uri(r->pool, wsel->name), "\">\n", NULL);
 898             ap_rvputs(r, "<input type=hidden name=\"b\" ", NULL);
 899             ap_rvputs(r, "value=\"", bsel->name + sizeof("balancer://") - 1,
 900                       "\">\n</form>\n", NULL);
 901             ap_rvputs(r, "<input type=hidden name=\"nonce\" value=\"",
 902                       balancer_nonce, "\">\n", NULL);
 903             ap_rputs("<hr />\n", r);
 904         }
 905         ap_rputs(ap_psignature("",r), r);
 906         ap_rputs("</body></html>\n", r);
 907     }
 908     return OK;
 909 }
 910
 911 static void child_init(apr_pool_t *p, server_rec *s)
 912 {
 913     while (s) {
 914         void *sconf = s->module_config;
 915         proxy_server_conf *conf;
 916         proxy_balancer *balancer;
 917         int i;
 918         conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
 919
 920         /* Initialize shared scoreboard data */
 921         balancer = (proxy_balancer *)conf->balancers->elts;
 922         for (i = 0; i < conf->balancers->nelts; i++) {
 923             init_balancer_members(conf, s, balancer);
 924             balancer++;
 925         }
 926         s = s->next;
 927     }
 928
 929 }
 930
 931 /*
 932  * The idea behind the find_best_byrequests scheduler is the following:
 933  *
 934  * lbfactor is "how much we expect this worker to work", or "the worker's
 935  * normalized work quota".
 936  *
 937  * lbstatus is "how urgent this worker has to work to fulfill its quota
 938  * of work".
 939  *
 940  * We distribute each worker's work quota to the worker, and then look
 941  * which of them needs to work most urgently (biggest lbstatus).  This
 942  * worker is then selected for work, and its lbstatus reduced by the
 943  * total work quota we distributed to all workers.  Thus the sum of all
 944  * lbstatus does not change.(*)
 945  *
 946  * If some workers are disabled, the others will
 947  * still be scheduled correctly.
 948  *
 949  * If a balancer is configured as follows:
 950  *
 951  * worker     a    b    c    d
 952  * lbfactor  25   25   25   25
 953  *
 954  * And b gets disabled, the following schedule is produced:
 955  *
 956  *    a c d a c d a c d ...
 957  *
 958  * Note that the above lbfactor setting is the *exact* same as:
 959  *
 960  * worker     a    b    c    d
 961  * lbfactor   1    1    1    1
 962  *
 963  * Asymmetric configurations work as one would expect. For
 964  * example:
 965  *
 966  * worker     a    b    c    d
 967  * lbfactor   1    1    1    2
 968  *
 969  * would have a, b and c all handling about the same
 970  * amount of load with d handling twice what a or b
 971  * or c handles individually. So we could see:
 972  *
 973  *   b a d c d a c d b d ...
 974  *
 975  */
 976
 977 static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
 978                                 request_rec *r)
 979 {
 980     int i;
 981     int total_factor = 0;
 982     proxy_worker *worker;
 983     proxy_worker *mycandidate = NULL;
 984     int cur_lbset = 0;
 985     int max_lbset = 0;
 986     int checking_standby;
 987     int checked_standby;
 988
 989     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
 990                  "proxy: Entering byrequests for BALANCER (%s)",
 991                  balancer->name);
 992
 993     /* First try to see if we have available candidate */
 994     do {
 995         checking_standby = checked_standby = 0;
 996         while (!mycandidate && !checked_standby) {
 997             worker = (proxy_worker *)balancer->workers->elts;
 998             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
 999                 if (!checking_standby) {    /* first time through */
1000                     if (worker->s->lbset > max_lbset)
1001                         max_lbset = worker->s->lbset;
1002                 }
1003                 if (worker->s->lbset > cur_lbset)
1004                     continue;
1005                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
1006                     continue;
1007                 /* If the worker is in error state run
1008                  * retry on that worker. It will be marked as
1009                  * operational if the retry timeout is elapsed.
1010                  * The worker might still be unusable, but we try
1011                  * anyway.
1012                  */
1013                 if (!PROXY_WORKER_IS_USABLE(worker))
1014                     ap_proxy_retry_worker("BALANCER", worker, r->server);
1015                 /* Take into calculation only the workers that are
1016                  * not in error state or not disabled.
1017                  */
1018                 if (PROXY_WORKER_IS_USABLE(worker)) {
1019                     worker->s->lbstatus += worker->s->lbfactor;
1020                     total_factor += worker->s->lbfactor;
1021                     if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
1022                         mycandidate = worker;
1023                 }
1024             }
1025             checked_standby = checking_standby++;
1026         }
1027         cur_lbset++;
1028     } while (cur_lbset <= max_lbset && !mycandidate);
1029
1030     if (mycandidate) {
1031         mycandidate->s->lbstatus -= total_factor;
1032     }
1033
1034     return mycandidate;
1035 }
1036
1037 /*
1038  * The idea behind the find_best_bytraffic scheduler is the following:
1039  *
1040  * We know the amount of traffic (bytes in and out) handled by each
1041  * worker. We normalize that traffic by each workers' weight. So assuming
1042  * a setup as below:
1043  *
1044  * worker     a    b    c
1045  * lbfactor   1    1    3
1046  *
1047  * the scheduler will allow worker c to handle 3 times the
1048  * traffic of a and b. If each request/response results in the
1049  * same amount of traffic, then c would be accessed 3 times as
1050  * often as a or b. If, for example, a handled a request that
1051  * resulted in a large i/o bytecount, then b and c would be
1052  * chosen more often, to even things out.
1053  */
1054 static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
1055                                          request_rec *r)
1056 {
1057     int i;
1058     apr_off_t mytraffic = 0;
1059     apr_off_t curmin = 0;
1060     proxy_worker *worker;
1061     proxy_worker *mycandidate = NULL;
1062     int cur_lbset = 0;
1063     int max_lbset = 0;
1064     int checking_standby;
1065     int checked_standby;
1066
1067     ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
1068                  "proxy: Entering bytraffic for BALANCER (%s)",
1069                  balancer->name);
1070
1071     /* First try to see if we have available candidate */
1072     do {
1073         checking_standby = checked_standby = 0;
1074         while (!mycandidate && !checked_standby) {
1075             worker = (proxy_worker *)balancer->workers->elts;
1076             for (i = 0; i < balancer->workers->nelts; i++, worker++) {
1077                 if (!checking_standby) {    /* first time through */
1078                     if (worker->s->lbset > max_lbset)
1079                         max_lbset = worker->s->lbset;
1080                 }
1081                 if (worker->s->lbset > cur_lbset)
1082                     continue;
1083                 if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
1084                     continue;
1085                 /* If the worker is in error state run
1086                  * retry on that worker. It will be marked as
1087                  * operational if the retry timeout is elapsed.
1088                  * The worker might still be unusable, but we try
1089                  * anyway.
1090                  */
1091                 if (!PROXY_WORKER_IS_USABLE(worker))
1092                     ap_proxy_retry_worker("BALANCER", worker, r->server);
1093                 /* Take into calculation only the workers that are
1094                  * not in error state or not disabled.
1095                  */
1096                 if (PROXY_WORKER_IS_USABLE(worker)) {
1097                     mytraffic = (worker->s->transferred/worker->s->lbfactor) +
1098                                 (worker->s->read/worker->s->lbfactor);
1099                     if (!mycandidate || mytraffic < curmin) {
1100                         mycandidate = worker;
1101                         curmin = mytraffic;
1102                     }
1103                 }
1104             }
1105             checked_standby = checking_standby++;
1106         }
1107         cur_lbset++;
1108     } while (cur_lbset <= max_lbset && !mycandidate);
1109
1110     return mycandidate;
1111 }
1112
1113 /*
1114  * How to add additional lbmethods:
1115  *   1. Create func which determines "best" candidate worker
1116  *      (eg: find_best_bytraffic, above)
1117  *   2. Register it as a provider.
1118  */
1119 static const proxy_balancer_method byrequests =
1120 {
1121     "byrequests",
1122     &find_best_byrequests,
1123     NULL
1124 };
1125
1126 static const proxy_balancer_method bytraffic =
1127 {
1128     "bytraffic",
1129     &find_best_bytraffic,
1130     NULL
1131 };
1132
1133 static void ap_proxy_balancer_register_hook(apr_pool_t *p)
1134 {
1135     /* Only the mpm_winnt has child init hook handler.
1136      * make sure that we are called after the mpm
1137      * initializes and after the mod_proxy
1138      */
1139     static const char *const aszPred[] = { "mpm_winnt.c", "mod_proxy.c", NULL};
1140      /* manager handler */
1141     ap_hook_post_config(balancer_init, NULL, NULL, APR_HOOK_MIDDLE);
1142     ap_hook_handler(balancer_handler, NULL, NULL, APR_HOOK_FIRST);
1143     ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
1144     proxy_hook_pre_request(proxy_balancer_pre_request, NULL, NULL, APR_HOOK_FIRST);
1145     proxy_hook_post_request(proxy_balancer_post_request, NULL, NULL, APR_HOOK_FIRST);
1146     proxy_hook_canon_handler(proxy_balancer_canon, NULL, NULL, APR_HOOK_FIRST);
1147     ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
1148     ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
1149 }
1150
1151 module AP_MODULE_DECLARE_DATA proxy_balancer_module = {
1152     STANDARD20_MODULE_STUFF,
1153     NULL,       /* create per-directory config structure */
1154     NULL,       /* merge per-directory config structures */
1155     NULL,       /* create per-server config structure */
1156     NULL,       /* merge per-server config structures */
1157     NULL,       /* command apr_table_t */
1158     ap_proxy_balancer_register_hook /* register hooks */
1159 };