1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "mod_proxy.h"
18#include "scoreboard.h"
19#include "ap_mpm.h"
20#include "apr_version.h"
21#include "ap_hooks.h"
22
23module AP_MODULE_DECLARE_DATA lbmethod_bybusyness_module;
24
25static int (*ap_proxy_retry_worker_fn)(const char *proxy_function,
26        proxy_worker *worker, server_rec *s) = NULL;
27
28static proxy_worker *find_best_bybusyness(proxy_balancer *balancer,
29                                request_rec *r)
30{
31
32    int i;
33    proxy_worker **worker;
34    proxy_worker *mycandidate = NULL;
35    int cur_lbset = 0;
36    int max_lbset = 0;
37    int checking_standby;
38    int checked_standby;
39
40    int total_factor = 0;
41
42    if (!ap_proxy_retry_worker_fn) {
43        ap_proxy_retry_worker_fn =
44                APR_RETRIEVE_OPTIONAL_FN(ap_proxy_retry_worker);
45        if (!ap_proxy_retry_worker_fn) {
46            /* can only happen if mod_proxy isn't loaded */
47            return NULL;
48        }
49    }
50
51    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server, APLOGNO(01211)
52                 "proxy: Entering bybusyness for BALANCER (%s)",
53                 balancer->s->name);
54
55    /* First try to see if we have available candidate */
56    do {
57
58        checking_standby = checked_standby = 0;
59        while (!mycandidate && !checked_standby) {
60
61            worker = (proxy_worker **)balancer->workers->elts;
62            for (i = 0; i < balancer->workers->nelts; i++, worker++) {
63                if  (!checking_standby) {    /* first time through */
64                    if ((*worker)->s->lbset > max_lbset)
65                        max_lbset = (*worker)->s->lbset;
66                }
67                if (
68                    ((*worker)->s->lbset != cur_lbset) ||
69                    (checking_standby ? !PROXY_WORKER_IS_STANDBY(*worker) : PROXY_WORKER_IS_STANDBY(*worker)) ||
70                    (PROXY_WORKER_IS_DRAINING(*worker))
71                    ) {
72                    continue;
73                }
74
75                /* If the worker is in error state run
76                 * retry on that worker. It will be marked as
77                 * operational if the retry timeout is elapsed.
78                 * The worker might still be unusable, but we try
79                 * anyway.
80                 */
81                if (!PROXY_WORKER_IS_USABLE(*worker)) {
82                    ap_proxy_retry_worker_fn("BALANCER", *worker, r->server);
83                }
84
85                /* Take into calculation only the workers that are
86                 * not in error state or not disabled.
87                 */
88                if (PROXY_WORKER_IS_USABLE(*worker)) {
89
90                    (*worker)->s->lbstatus += (*worker)->s->lbfactor;
91                    total_factor += (*worker)->s->lbfactor;
92
93                    if (!mycandidate
94                        || (*worker)->s->busy < mycandidate->s->busy
95                        || ((*worker)->s->busy == mycandidate->s->busy && (*worker)->s->lbstatus > mycandidate->s->lbstatus))
96                        mycandidate = *worker;
97
98                }
99
100            }
101
102            checked_standby = checking_standby++;
103
104        }
105
106        cur_lbset++;
107
108    } while (cur_lbset <= max_lbset && !mycandidate);
109
110    if (mycandidate) {
111        mycandidate->s->lbstatus -= total_factor;
112        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server, APLOGNO(01212)
113                     "proxy: bybusyness selected worker \"%s\" : busy %" APR_SIZE_T_FMT " : lbstatus %d",
114                     mycandidate->s->name, mycandidate->s->busy, mycandidate->s->lbstatus);
115
116    }
117
118    return mycandidate;
119
120}
121
122/* assumed to be mutex protected by caller */
123static apr_status_t reset(proxy_balancer *balancer, server_rec *s) {
124    int i;
125    proxy_worker **worker;
126    worker = (proxy_worker **)balancer->workers->elts;
127    for (i = 0; i < balancer->workers->nelts; i++, worker++) {
128        (*worker)->s->lbstatus = 0;
129        (*worker)->s->busy = 0;
130    }
131    return APR_SUCCESS;
132}
133
134static apr_status_t age(proxy_balancer *balancer, server_rec *s) {
135        return APR_SUCCESS;
136}
137
138static const proxy_balancer_method bybusyness =
139{
140    "bybusyness",
141    &find_best_bybusyness,
142    NULL,
143    &reset,
144    &age
145};
146
147
148static void register_hook(apr_pool_t *p)
149{
150    ap_register_provider(p, PROXY_LBMETHOD, "bybusyness", "0", &bybusyness);
151}
152
153AP_DECLARE_MODULE(lbmethod_bybusyness) = {
154    STANDARD20_MODULE_STUFF,
155    NULL,       /* create per-directory config structure */
156    NULL,       /* merge per-directory config structures */
157    NULL,       /* create per-server config structure */
158    NULL,       /* merge per-server config structures */
159    NULL,       /* command apr_table_t */
160    register_hook /* register hooks */
161};
162