Add in independent bytraffic lbmethod

/* 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 "apr_hooks.h"

module AP_MODULE_DECLARE_DATA lbmethod_bytraffic_module;

/*

 * The idea behind the find_best_bytraffic scheduler is the following:

 *

 * We know the amount of traffic (bytes in and out) handled by each

 * worker. We normalize that traffic by each workers' weight. So assuming

 * a setup as below:

 *

 * worker     a    b    c

 * lbfactor   1    1    3

 *

 * the scheduler will allow worker c to handle 3 times the

 * traffic of a and b. If each request/response results in the

 * same amount of traffic, then c would be accessed 3 times as

 * often as a or b. If, for example, a handled a request that

 * resulted in a large i/o bytecount, then b and c would be

 * chosen more often, to even things out.

 */

static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,

                                         request_rec *r)

{

    int i;

    apr_off_t mytraffic = 0;

    apr_off_t curmin = 0;

    proxy_worker *worker;

    proxy_worker *mycandidate = NULL;

    int cur_lbset = 0;

    int max_lbset = 0;

    int checking_standby;

    int checked_standby;

    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,

                 "proxy: Entering bytraffic for BALANCER (%s)",

                 balancer->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)

                    continue;

                if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(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("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)) {

                    mytraffic = (worker->s->transferred/worker->s->lbfactor) +

                                (worker->s->read/worker->s->lbfactor);

                    if (!mycandidate || mytraffic < curmin) {

                        mycandidate = worker;

                        curmin = mytraffic;

                    }

                }

            }

            checked_standby = checking_standby++;

        }

        cur_lbset++;

    } while (cur_lbset <= max_lbset && !mycandidate);

    if (mycandidate) {

        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,

                     "proxy: bytraffic selected worker \"%s\" : busy %" APR_SIZE_T_FMT,

                     mycandidate->name, mycandidate->s->busy);

    }

    return mycandidate;

}

static const proxy_balancer_method bytraffic =

{

    "bytraffic",

    &find_best_bytraffic,

    NULL

};

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, "bytraffic", "0", &bytraffic);

}

module AP_MODULE_DECLARE_DATA lbmethod_bytraffic_module = {

    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 */

};