| /* 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 int (*ap_proxy_retry_worker_fn)(const char *proxy_function, |
| proxy_worker *worker, server_rec *s) = NULL; |
| |
| /* |
| * 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 i; |
| int total_factor = 0; |
| proxy_worker **worker; |
| proxy_worker *mycandidate = NULL; |
| int cur_lbset = 0; |
| int max_lbset = 0; |
| int checking_standby; |
| int checked_standby; |
| |
| if (!ap_proxy_retry_worker_fn) { |
| ap_proxy_retry_worker_fn = |
| APR_RETRIEVE_OPTIONAL_FN(ap_proxy_retry_worker); |
| if (!ap_proxy_retry_worker_fn) { |
| /* can only happen if mod_proxy isn't loaded */ |
| return NULL; |
| } |
| } |
| |
| ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server, APLOGNO(01207) |
| "proxy: Entering byrequests for BALANCER (%s)", |
| balancer->s->name); |
| |
| /* First try to see if we have available candidate */ |
| do { |
| checking_standby = checked_standby = 0; |
| while (!mycandidate && !checked_standby) { |
| worker = (proxy_worker **)balancer->workers->elts; |
| for (i = 0; i < balancer->workers->nelts; i++, worker++) { |
| if (!checking_standby) { /* first time through */ |
| if ((*worker)->s->lbset > max_lbset) |
| max_lbset = (*worker)->s->lbset; |
| } |
| if ( |
| ((*worker)->s->lbset != cur_lbset) || |
| (checking_standby ? !PROXY_WORKER_IS_STANDBY(*worker) : PROXY_WORKER_IS_STANDBY(*worker)) || |
| (PROXY_WORKER_IS_DRAINING(*worker)) |
| ) { |
| continue; |
| } |
| |
| /* If the worker is in error state run |
| * retry on that worker. It will be marked as |
| * operational if the retry timeout is elapsed. |
| * The worker might still be unusable, but we try |
| * anyway. |
| */ |
| if (!PROXY_WORKER_IS_USABLE(*worker)) |
| ap_proxy_retry_worker_fn("BALANCER", *worker, r->server); |
| /* Take into calculation only the workers that are |
| * not in error state or not disabled. |
| */ |
| if (PROXY_WORKER_IS_USABLE(*worker)) { |
| (*worker)->s->lbstatus += (*worker)->s->lbfactor; |
| total_factor += (*worker)->s->lbfactor; |
| if (!mycandidate || (*worker)->s->lbstatus > mycandidate->s->lbstatus) |
| mycandidate = *worker; |
| } |
| } |
| checked_standby = checking_standby++; |
| } |
| cur_lbset++; |
| } while (cur_lbset <= max_lbset && !mycandidate); |
| |
| if (mycandidate) { |
| mycandidate->s->lbstatus -= total_factor; |
| ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server, APLOGNO(01208) |
| "proxy: byrequests selected worker \"%s\" : busy %" APR_SIZE_T_FMT " : lbstatus %d", |
| mycandidate->s->name, mycandidate->s->busy, mycandidate->s->lbstatus); |
| |
| } |
| |
| return mycandidate; |
| } |
| |
| /* 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 |
| }; |
| |
| static void register_hook(apr_pool_t *p) |
| { |
| /* Only the mpm_winnt has child init hook handler. |
| * make sure that we are called after the mpm |
| * initializes and after the mod_proxy |
| */ |
| ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests); |
| } |
| |
| 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 */ |
| }; |
