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/* 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_bytraffic_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_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;
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(01209)
"proxy: Entering bytraffic 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)) {
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, APLOGNO(01210)
"proxy: bytraffic selected worker \"%s\" : busy %" APR_SIZE_T_FMT,
mycandidate->s->name, mycandidate->s->busy);
}
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;
(*worker)->s->busy = 0;
(*worker)->s->transferred = 0;
(*worker)->s->read = 0;
}
return APR_SUCCESS;
}
static apr_status_t age(proxy_balancer *balancer, server_rec *s)
{
return APR_SUCCESS;
}
static const proxy_balancer_method bytraffic =
{
"bytraffic",
&find_best_bytraffic,
NULL,
&reset,
&age,
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);
}
AP_DECLARE_MODULE(lbmethod_bytraffic) = {
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 */
};
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