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