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Add in independent byrequests lbmethod
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@722949 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Jim Jagielski
165
modules/proxy/balancers/mod_lbmethod_byrequests.c
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165
modules/proxy/balancers/mod_lbmethod_byrequests.c
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/* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "mod_proxy.h"
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#include "scoreboard.h"
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#include "ap_mpm.h"
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#include "apr_version.h"
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#include "apr_hooks.h"
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module AP_MODULE_DECLARE_DATA lbmethod_byrequests_module;
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/*
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* The idea behind the find_best_byrequests scheduler is the following:
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*
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* lbfactor is "how much we expect this worker to work", or "the worker's
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* normalized work quota".
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*
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* lbstatus is "how urgent this worker has to work to fulfill its quota
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* of work".
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*
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* We distribute each worker's work quota to the worker, and then look
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* which of them needs to work most urgently (biggest lbstatus). This
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* worker is then selected for work, and its lbstatus reduced by the
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* total work quota we distributed to all workers. Thus the sum of all
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* lbstatus does not change.(*)
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*
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* If some workers are disabled, the others will
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* still be scheduled correctly.
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*
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* If a balancer is configured as follows:
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*
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* worker a b c d
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* lbfactor 25 25 25 25
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*
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* And b gets disabled, the following schedule is produced:
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*
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* a c d a c d a c d ...
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*
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* Note that the above lbfactor setting is the *exact* same as:
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*
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* worker a b c d
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* lbfactor 1 1 1 1
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*
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* Asymmetric configurations work as one would expect. For
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* example:
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*
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* worker a b c d
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* lbfactor 1 1 1 2
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*
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* would have a, b and c all handling about the same
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* amount of load with d handling twice what a or b
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* or c handles individually. So we could see:
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*
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* b a d c d a c d b d ...
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*
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*/
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static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
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request_rec *r)
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{
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int i;
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int total_factor = 0;
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proxy_worker *worker;
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proxy_worker *mycandidate = NULL;
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int cur_lbset = 0;
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int max_lbset = 0;
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int checking_standby;
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int checked_standby;
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: Entering byrequests for BALANCER (%s)",
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balancer->name);
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/* First try to see if we have available candidate */
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do {
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checking_standby = checked_standby = 0;
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while (!mycandidate && !checked_standby) {
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worker = (proxy_worker *)balancer->workers->elts;
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for (i = 0; i < balancer->workers->nelts; i++, worker++) {
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if (!checking_standby) { /* first time through */
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if (worker->s->lbset > max_lbset)
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max_lbset = worker->s->lbset;
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}
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if (worker->s->lbset > cur_lbset)
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continue;
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if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
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continue;
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/* If the worker is in error state run
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* retry on that worker. It will be marked as
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* operational if the retry timeout is elapsed.
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* The worker might still be unusable, but we try
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* anyway.
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*/
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if (!PROXY_WORKER_IS_USABLE(worker))
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ap_proxy_retry_worker("BALANCER", worker, r->server);
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/* Take into calculation only the workers that are
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* not in error state or not disabled.
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*/
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if (PROXY_WORKER_IS_USABLE(worker)) {
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worker->s->lbstatus += worker->s->lbfactor;
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total_factor += worker->s->lbfactor;
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if (!mycandidate || worker->s->lbstatus > mycandidate->s->lbstatus)
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mycandidate = worker;
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}
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}
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checked_standby = checking_standby++;
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}
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cur_lbset++;
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} while (cur_lbset <= max_lbset && !mycandidate);
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if (mycandidate) {
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mycandidate->s->lbstatus -= total_factor;
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ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
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"proxy: byrequests selected worker \"%s\" : busy %" APR_SIZE_T_FMT " : lbstatus %d",
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mycandidate->name, mycandidate->s->busy, mycandidate->s->lbstatus);
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}
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return mycandidate;
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}
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/*
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* How to add additional lbmethods:
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* 1. Create func which determines "best" candidate worker
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* (eg: find_best_bytraffic, above)
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* 2. Register it as a provider.
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*/
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static const proxy_balancer_method byrequests =
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{
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"byrequests",
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&find_best_byrequests,
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NULL
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};
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static void register_hook(apr_pool_t *p)
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{
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/* Only the mpm_winnt has child init hook handler.
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* make sure that we are called after the mpm
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* initializes and after the mod_proxy
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*/
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ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
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}
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module AP_MODULE_DECLARE_DATA lbmethod_byrequests_module = {
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STANDARD20_MODULE_STUFF,
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NULL, /* create per-directory config structure */
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NULL, /* merge per-directory config structures */
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NULL, /* create per-server config structure */
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NULL, /* merge per-server config structures */
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NULL, /* command apr_table_t */
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register_hook /* register hooks */
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};
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