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