Add in independent bytraffic lbmethod

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@722950 13f79535-47bb-0310-9956-ffa450edef68

modules/proxy/balancers/mod_lbmethod_bytraffic.c

@@ -0,0 +1,132 @@
+/* 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 */
+};