From: William A. Rowe Jr <wrowe@apache.org>
Date: Wed, 11 Aug 2004 22:58:03 +0000 (+0000)
Subject: Add finding of a most suitable worker.
X-Git-Tag: post_ajp_proxy~18
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=392b0fc5fc803f19d87d057c437536b935affc11;p=apache

Add finding of a most suitable worker.

Submitted by: mturk


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104612 13f79535-47bb-0310-9956-ffa450edef68
---

diff --git a/modules/proxy/proxy_balancer.c b/modules/proxy/proxy_balancer.c
index 9d6d367f3e..b83da582c5 100644
--- a/modules/proxy/proxy_balancer.c
+++ b/modules/proxy/proxy_balancer.c
@@ -23,7 +23,7 @@
 
 module AP_MODULE_DECLARE_DATA proxy_balancer_module;
 
-#if APR_HAS_THREADS1
+#if APR_HAS_THREADS
 #define PROXY_BALANCER_LOCK(b)      apr_thread_mutex_lock((b)->mutex)
 #define PROXY_BALANCER_UNLOCK(b)    apr_thread_mutex_unlock((b)->mutex)
 #else
@@ -130,6 +130,90 @@ static proxy_runtime_worker *find_session_route(proxy_balancer *balancer,
         return NULL;
 }
 
+static proxy_runtime_worker *find_best_worker(proxy_balancer *balancer,
+                                              request_rec *r)
+{
+    int i;
+    double total_status = 0.0;
+    proxy_runtime_worker *worker = (proxy_runtime_worker *)balancer->workers->elts;
+    proxy_runtime_worker *candidate = NULL;
+
+    /* First try to see if we have available candidate */
+    for (i = 0; i < balancer->workers->nelts; i++) {
+        /* If the worker is not error state
+         * or not in disabled mode
+         */
+
+        /* TODO: read the scoreboard status */
+        if (worker->w->status < 2) {
+            if (!candidate)
+                candidate = worker;
+            else {
+                /* See if the worker has a larger number of free channels */
+                if (worker->w->cp->nfree > candidate->w->cp->nfree)
+                    candidate = worker;
+            }
+            total_status += worker->lbstatus;
+        }
+        worker++;
+    }
+    if (!candidate) {
+        /* All the workers are in error state or disabled.
+         * If the balancer has a timeout wait.
+         */
+#if APR_HAS_THREADS
+        if (balancer->timeout) {
+            /* XXX: This can perhaps be build using some 
+             * smarter mechanism, like tread_cond.
+             * But since the statuses can came from 
+             * different childs, use the provided algo. 
+             */
+            apr_interval_time_t timeout = balancer->timeout;
+            apr_interval_time_t step, tval = 0;
+            balancer->timeout = 0;
+            step = timeout / 100;
+            while (tval < timeout) {
+                apr_sleep(step);
+                /* Try again */
+                if ((candidate = find_best_worker(balancer, r)))
+                    break;
+                tval += step;
+            }
+            /* restore the timeout */
+            balancer->timeout = timeout;
+        }
+#endif
+    }
+    else {
+        /* We have at least one candidate that is not in
+         * error state or disabled.
+         * Now calculate the appropriate one 
+         */
+        for (i = 0; i < balancer->workers->nelts; i++) {
+            /* If the worker is not error state
+             * or not in disabled mode
+             */
+            if (worker->w->status > 2) {
+                /* 1. Find the worker with higher lbstatus.
+                 * Lbstatus is of higher importance then
+                 * the number of empty slots.
+                 */
+                if (worker->lbstatus > candidate->lbstatus) {
+                    candidate = worker;
+                }
+            }
+            worker++;
+        }
+        /* XXX: The lbfactor can be update using bytes transfered
+         * Right now, use the round-robin scheme
+         */
+        candidate->lbstatus += candidate->lbfactor;
+        if (candidate->lbstatus >= total_status)
+            candidate->lbstatus = candidate->lbfactor;
+    }
+    return candidate;
+}
+
 static int proxy_balancer_pre_request(proxy_worker **worker,
                                       proxy_balancer **balancer,
                                       request_rec *r,
@@ -140,6 +224,7 @@ static int proxy_balancer_pre_request(proxy_worker **worker,
     char *route;
     apr_status_t rv;
 
+    *worker = NULL;
     /* Spet 1: check if the url is for us */
     if (!(*balancer = ap_proxy_get_balancer(r->pool, conf, *url)))
         return DECLINED;
@@ -155,6 +240,10 @@ static int proxy_balancer_pre_request(proxy_worker **worker,
             return HTTP_SERVICE_UNAVAILABLE;
         }
     }
+    else {
+        /* We have a sticky load balancer */
+        *worker = runtime->w;
+    }
     /* Lock the LoadBalancer
      * XXX: perhaps we need the process lock here
      */
@@ -163,6 +252,23 @@ static int proxy_balancer_pre_request(proxy_worker **worker,
                      "proxy_balancer_pre_request: lock");
         return DECLINED;
     }
+    if (!*worker) {
+        runtime = find_best_worker(*balancer, r);
+        if (!runtime) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, 0, r->server,
+                         "balancer: (%s). All workers in error state.",
+                         (*balancer)->name);
+        
+            PROXY_BALANCER_UNLOCK(*balancer);
+            return HTTP_SERVICE_UNAVAILABLE;
+        }
+        /* TODO: rewrite the url to coresponds to worker scheme */
+
+        *worker = runtime->w;
+    }
+    /* Decrease the free channels number */
+    if ((*worker)->cp->nfree)
+        --(*worker)->cp->nfree;
 
     PROXY_BALANCER_UNLOCK(*balancer);
 
@@ -178,8 +284,20 @@ static int proxy_balancer_post_request(proxy_worker *worker,
     if (!balancer)
         access_status = DECLINED;
     else { 
-        
+        apr_status_t rv;
+        if ((rv = PROXY_BALANCER_LOCK(balancer)) != APR_SUCCESS) {
+            ap_log_error(APLOG_MARK, APLOG_ERR, rv, r->server,
+                     "proxy_balancer_post_request: lock");
+            return DECLINED;
+        }
+        /* increase the free channels number */
+        if (worker->cp->nfree)
+            worker->cp->nfree++;
+        /* TODO: calculate the bytes transfered */
+
+        /* TODO: update the scoreboard status */
 
+        PROXY_BALANCER_UNLOCK(balancer);        
         access_status = OK;
     }