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author | Arno Töll <debian@toell.net> | 2012-01-08 22:53:17 +0100 |
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committer | Arno Töll <debian@toell.net> | 2012-01-08 22:53:17 +0100 |
commit | e072a2dd866b7cb9f14319b80326a4e7fd16fcdf (patch) | |
tree | a49dfc56d94a26011fe157835ff6cbe14edbd8a9 /modules/proxy/balancers/mod_lbmethod_byrequests.c | |
parent | 0890390c00801651d08d3794e13b31a5dabbf5ef (diff) | |
download | apache2-e072a2dd866b7cb9f14319b80326a4e7fd16fcdf.tar.gz |
Imported Upstream version 2.3.16-beta
Diffstat (limited to 'modules/proxy/balancers/mod_lbmethod_byrequests.c')
-rw-r--r-- | modules/proxy/balancers/mod_lbmethod_byrequests.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/modules/proxy/balancers/mod_lbmethod_byrequests.c b/modules/proxy/balancers/mod_lbmethod_byrequests.c new file mode 100644 index 00000000..015de12a --- /dev/null +++ b/modules/proxy/balancers/mod_lbmethod_byrequests.c @@ -0,0 +1,198 @@ +/* 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 */ +}; |