From 8c54cd10ab0e362854f0350f3e4c2cb24ec9ee90 Mon Sep 17 00:00:00 2001
From: Jim Jagielski <jim@apache.org>
Date: Tue, 13 Nov 2007 21:55:05 +0000
Subject: [PATCH] Add extremely butt-ugly sub-mod that exists simply to show
 how to use providers in sub-mods to extend lbmethods in mod_proxy...

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@594659 13f79535-47bb-0310-9956-ffa450edef68
---
 modules/proxy/mod_lbmethod_rr.c | 122 ++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 modules/proxy/mod_lbmethod_rr.c

diff --git a/modules/proxy/mod_lbmethod_rr.c b/modules/proxy/mod_lbmethod_rr.c
new file mode 100644
index 0000000000..7fca58190f
--- /dev/null
+++ b/modules/proxy/mod_lbmethod_rr.c
@@ -0,0 +1,122 @@
+/* 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.
+ */
+
+/* Round Robin lbmethod module for Apache proxy */
+
+/* NOTE: This is designed simply to provide some info on how to create
+         extra lbmethods via sub-modules... This code is ugly
+         and needs work to actually do round-robin "right"
+         but that is left as an exercise for the reader */
+
+#define CORE_PRIVATE
+
+#include "mod_proxy.h"
+#include "scoreboard.h"
+#include "ap_mpm.h"
+#include "apr_version.h"
+#include "apr_hooks.h"
+
+#if APR_HAVE_UNISTD_H
+#include <unistd.h> /* for getpid() */
+#endif
+
+module AP_MODULE_DECLARE_DATA proxy_balancer_rr_module;
+
+typedef struct {
+    int index;
+} rr_data ;
+
+/*
+ */
+static proxy_worker *find_best_roundrobin(proxy_balancer *balancer,
+                                         request_rec *r)
+{
+    int i;
+    proxy_worker *worker;
+    proxy_worker *mycandidate = NULL;
+    int checking_standby;
+    int checked_standby;
+    rr_data *ctx;
+
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
+                 "proxy: Entering roundrobin for BALANCER %s (%d)",
+                 balancer->name, (int)getpid());
+    
+    /* The index of the candidate last chosen is stored in ctx->index */
+    if (!balancer->context) {
+        /* UGLY */
+        ctx = apr_pcalloc(r->server->process->pconf, sizeof(rr_data));
+        balancer->context = (void *)ctx;
+        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
+                 "proxy: Creating roundrobin ctx for BALANCER %s (%d)",
+                 balancer->name, (int)getpid());
+    } else {
+        ctx = (rr_data *)balancer->context;
+    }
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
+                 "proxy: roundrobin index: %d (%d)",
+                 ctx->index, (int)getpid());
+
+    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 (i < ctx->index)
+                    continue;
+                if ( (checking_standby ? !PROXY_WORKER_IS_STANDBY(worker) : PROXY_WORKER_IS_STANDBY(worker)) )
+                    continue;
+                if (!PROXY_WORKER_IS_USABLE(worker))
+                    ap_proxy_retry_worker("BALANCER", worker, r->server);
+                if (PROXY_WORKER_IS_USABLE(worker)) {
+                    mycandidate = worker;
+                    break;
+                }
+            }
+            checked_standby = checking_standby++;
+        }
+    } while (!mycandidate);
+
+    ctx->index += 1;
+    if (ctx->index >= balancer->workers->nelts) {
+        ctx->index = 0;
+    }
+    return mycandidate;
+}
+
+static const proxy_balancer_method roundrobin =
+{
+    "roundrobin",
+    &find_best_roundrobin,
+    NULL
+};
+
+
+static void ap_proxy_rr_register_hook(apr_pool_t *p)
+{
+    ap_register_provider(p, PROXY_LBMETHOD, "roundrobin", "0", &roundrobin);
+}
+
+module AP_MODULE_DECLARE_DATA proxy_balancer_rr_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 */
+    ap_proxy_rr_register_hook /* register hooks */
+};
-- 
2.40.0