| /* Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "mod_proxy.h" |
| #include "scoreboard.h" |
| #include "ap_mpm.h" |
| #include "apr_version.h" |
| #include "ap_hooks.h" |
| |
| module AP_MODULE_DECLARE_DATA lbmethod_byrequests_module; |
| |
| static APR_OPTIONAL_FN_TYPE(proxy_balancer_get_best_worker) |
| *ap_proxy_balancer_get_best_worker_fn = NULL; |
| |
| static int is_best_byrequests(proxy_worker *current, proxy_worker *prev_best, void *baton) |
| { |
| int *total_factor = (int *)baton; |
| |
| current->s->lbstatus += current->s->lbfactor; |
| *total_factor += current->s->lbfactor; |
| |
| return (!prev_best || (current->s->lbstatus > prev_best->s->lbstatus)); |
| } |
| |
| /* |
| * The idea behind the find_best_byrequests scheduler is the following: |
| * |
| * lbfactor is "how much we expect this worker to work", or "the worker's |
| * normalized work quota". |
| * |
| * lbstatus is "how urgent this worker has to work to fulfill its quota |
| * of work". |
| * |
| * We distribute each worker's work quota to the worker, and then look |
| * which of them needs to work most urgently (biggest lbstatus). This |
| * worker is then selected for work, and its lbstatus reduced by the |
| * total work quota we distributed to all workers. Thus the sum of all |
| * lbstatus does not change.(*) |
| * |
| * If some workers are disabled, the others will |
| * still be scheduled correctly. |
| * |
| * If a balancer is configured as follows: |
| * |
| * worker a b c d |
| * lbfactor 25 25 25 25 |
| * |
| * And b gets disabled, the following schedule is produced: |
| * |
| * a c d a c d a c d ... |
| * |
| * Note that the above lbfactor setting is the *exact* same as: |
| * |
| * worker a b c d |
| * lbfactor 1 1 1 1 |
| * |
| * Asymmetric configurations work as one would expect. For |
| * example: |
| * |
| * worker a b c d |
| * lbfactor 1 1 1 2 |
| * |
| * would have a, b and c all handling about the same |
| * amount of load with d handling twice what a or b |
| * or c handles individually. So we could see: |
| * |
| * b a d c d a c d b d ... |
| * |
| */ |
| static proxy_worker *find_best_byrequests(proxy_balancer *balancer, |
| request_rec *r) |
| { |
| int total_factor = 0; |
| proxy_worker *worker = ap_proxy_balancer_get_best_worker_fn(balancer, r, is_best_byrequests, &total_factor); |
| |
| if (worker) { |
| worker->s->lbstatus -= total_factor; |
| } |
| |
| return worker; |
| } |
| |
| /* assumed to be mutex protected by caller */ |
| static apr_status_t reset(proxy_balancer *balancer, server_rec *s) |
| { |
| int i; |
| proxy_worker **worker; |
| worker = (proxy_worker **)balancer->workers->elts; |
| for (i = 0; i < balancer->workers->nelts; i++, worker++) { |
| (*worker)->s->lbstatus = 0; |
| } |
| return APR_SUCCESS; |
| } |
| |
| static apr_status_t age(proxy_balancer *balancer, server_rec *s) |
| { |
| return APR_SUCCESS; |
| } |
| |
| /* |
| * How to add additional lbmethods: |
| * 1. Create func which determines "best" candidate worker |
| * (eg: find_best_bytraffic, above) |
| * 2. Register it as a provider. |
| */ |
| static const proxy_balancer_method byrequests = |
| { |
| "byrequests", |
| &find_best_byrequests, |
| NULL, |
| &reset, |
| &age, |
| NULL |
| }; |
| |
| /* post_config hook: */ |
| static int lbmethod_byrequests_post_config(apr_pool_t *pconf, apr_pool_t *plog, |
| apr_pool_t *ptemp, server_rec *s) |
| { |
| |
| /* lbmethod_byrequests_post_config() will be called twice during startup. So, don't |
| * set up the static data the 1st time through. */ |
| if (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_CREATE_PRE_CONFIG) { |
| return OK; |
| } |
| |
| ap_proxy_balancer_get_best_worker_fn = |
| APR_RETRIEVE_OPTIONAL_FN(proxy_balancer_get_best_worker); |
| if (!ap_proxy_balancer_get_best_worker_fn) { |
| ap_log_error(APLOG_MARK, APLOG_EMERG, 0, s, APLOGNO(10152) |
| "mod_proxy must be loaded for mod_lbmethod_byrequests"); |
| return !OK; |
| } |
| |
| return OK; |
| } |
| |
| static void register_hook(apr_pool_t *p) |
| { |
| ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests); |
| ap_hook_post_config(lbmethod_byrequests_post_config, NULL, NULL, APR_HOOK_MIDDLE); |
| } |
| |
| AP_DECLARE_MODULE(lbmethod_byrequests) = { |
| STANDARD20_MODULE_STUFF, |
| NULL, /* create per-directory config structure */ |
| NULL, /* merge per-directory config structures */ |
| NULL, /* create per-server config structure */ |
| NULL, /* merge per-server config structures */ |
| NULL, /* command apr_table_t */ |
| register_hook /* register hooks */ |
| }; |