mod_proxy: Make ap_proxy_retry_worker() into an optional function. Allows

mod_lbmethod_bybusyness, mod_lbmethod_byrequests, mod_lbmethod_bytraffic
and mod_lbmethod_heartbeat to be loaded without mod_proxy yet being present,
which happens when modules are loaded in alphabetical order.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1209754 13f79535-47bb-0310-9956-ffa450edef68

modules/proxy/balancers/mod_lbmethod_bybusyness.c

@@ -22,6 +22,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_bybusyness_module;
 
+static int (*ap_proxy_retry_worker_fn)(const char *proxy_function,
+        proxy_worker *worker, server_rec *s) = NULL;
+
 static proxy_worker *find_best_bybusyness(proxy_balancer *balancer,
                                 request_rec *r)
 {
@@ -36,6 +39,15 @@ static proxy_worker *find_best_bybusyness(proxy_balancer *balancer,
 
     int total_factor = 0;
 
+    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,
                  "proxy: Entering bybusyness for BALANCER (%s)",
                  balancer->s->name);
@@ -66,8 +78,9 @@ static proxy_worker *find_best_bybusyness(proxy_balancer *balancer,
                  * The worker might still be unusable, but we try
                  * anyway.
                  */
-                if (!PROXY_WORKER_IS_USABLE(*worker))
+                if (!PROXY_WORKER_IS_USABLE(*worker)) {
-                    ap_proxy_retry_worker("BALANCER", *worker, r->server);
+                    ap_proxy_retry_worker_fn("BALANCER", *worker, r->server);
+                }
 
                 /* Take into calculation only the workers that are
                  * not in error state or not disabled.

modules/proxy/balancers/mod_lbmethod_byrequests.c

@@ -22,6 +22,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_byrequests_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_byrequests scheduler is the following:
  *
@@ -80,6 +83,15 @@ static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
     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,
                  "proxy: Entering byrequests for BALANCER (%s)",
                  balancer->s->name);
@@ -109,7 +121,7 @@ static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
                  * anyway.
                  */
                 if (!PROXY_WORKER_IS_USABLE(*worker))
-                    ap_proxy_retry_worker("BALANCER", *worker, r->server);
+                    ap_proxy_retry_worker_fn("BALANCER", *worker, r->server);
                 /* Take into calculation only the workers that are
                  * not in error state or not disabled.
                  */

modules/proxy/balancers/mod_lbmethod_bytraffic.c

@@ -22,6 +22,9 @@
 
 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:
  *
@@ -52,6 +55,15 @@ static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
     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,
                  "proxy: Entering bytraffic for BALANCER (%s)",
                  balancer->s->name);
@@ -81,7 +93,7 @@ static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
                  * anyway.
                  */
                 if (!PROXY_WORKER_IS_USABLE(*worker))
-                    ap_proxy_retry_worker("BALANCER", *worker, r->server);
+                    ap_proxy_retry_worker_fn("BALANCER", *worker, r->server);
                 /* Take into calculation only the workers that are
                  * not in error state or not disabled.
                  */

modules/proxy/balancers/mod_lbmethod_heartbeat.c

@@ -31,6 +31,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_heartbeat_module;
 
+static int (*ap_proxy_retry_worker_fn)(const char *proxy_function,
+        proxy_worker *worker, server_rec *s) = NULL;
+
 static const ap_slotmem_provider_t *storage = NULL;
 static ap_slotmem_instance_t *hm_serversmem = NULL;
 
@@ -270,6 +273,15 @@ static proxy_worker *find_best_hb(proxy_balancer *balancer,
         ap_get_module_config(r->server->module_config,
                              &lbmethod_heartbeat_module);
 
+    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;
+        }
+    }
+
     apr_pool_create(&tpool, r->pool);
 
     servers = apr_hash_make(tpool);
@@ -297,7 +309,7 @@ static proxy_worker *find_best_hb(proxy_balancer *balancer,
         }
 
         if (!PROXY_WORKER_IS_USABLE(*worker)) {
-            ap_proxy_retry_worker("BALANCER", *worker, r->server);
+            ap_proxy_retry_worker_fn("BALANCER", *worker, r->server);
         }
 
         if (PROXY_WORKER_IS_USABLE(*worker)) {

modules/proxy/mod_proxy.c

@@ -19,6 +19,7 @@
 #include "apr_optional.h"
 #include "scoreboard.h"
 #include "mod_status.h"
+#include "proxy_util.h"
 
 #if (MODULE_MAGIC_NUMBER_MAJOR > 20020903)
 #include "mod_ssl.h"
@@ -2512,6 +2513,8 @@ static void register_hooks(apr_pool_t *p)
     /* child init handling */
     ap_hook_child_init(child_init, aszPred, NULL, APR_HOOK_MIDDLE);
 
+    /* register optional functions within proxy_util.c */
+    proxy_util_register_hooks(p);
 }
 
 AP_DECLARE_MODULE(proxy) =

modules/proxy/mod_proxy.h

@@ -27,6 +27,7 @@
  */
 
 #include "apr_hooks.h"
+#include "apr_optional.h"
 #include "apr.h"
 #include "apr_lib.h"
 #include "apr_strings.h"
@@ -769,9 +770,8 @@ PROXY_DECLARE(int) ap_proxy_determine_connection(apr_pool_t *p, request_rec *r,
  * @note The error status of the worker will cleared if the retry interval has
  * elapsed since the last error.
  */
-PROXY_DECLARE(int) ap_proxy_retry_worker(const char *proxy_function,
+APR_DECLARE_OPTIONAL_FN(int, ap_proxy_retry_worker,
-                                         proxy_worker *worker,
+        (const char *proxy_function, proxy_worker *worker, server_rec *s));
-                                         server_rec *s);
 
 /**
  * Acquire a connection from worker connection pool

modules/proxy/mod_proxy_balancer.c

@@ -28,6 +28,9 @@ ap_slotmem_provider_t *storage = NULL;
 
 module AP_MODULE_DECLARE_DATA proxy_balancer_module;
 
+static int (*ap_proxy_retry_worker_fn)(const char *proxy_function,
+        proxy_worker *worker, server_rec *s) = NULL;
+
 /*
  * Register our mutex type before the config is read so we
  * can adjust the mutex settings using the Mutex directive.
@@ -224,7 +227,7 @@ static proxy_worker *find_route_worker(proxy_balancer *balancer,
                      * The worker might still be unusable, but we try
                      * anyway.
                      */
-                    ap_proxy_retry_worker("BALANCER", worker, r->server);
+                    ap_proxy_retry_worker_fn("BALANCER", worker, r->server);
                     if (PROXY_WORKER_IS_USABLE(worker)) {
                             return worker;
                     } else {
@@ -248,7 +251,7 @@ static proxy_worker *find_route_worker(proxy_balancer *balancer,
                                  * The worker might still be unusable, but we try
                                  * anyway.
                                  */
-                                ap_proxy_retry_worker("BALANCER", rworker, r->server);
+                                ap_proxy_retry_worker_fn("BALANCER", rworker, r->server);
                             }
                             if (rworker && PROXY_WORKER_IS_USABLE(rworker))
                                 return rworker;
@@ -413,7 +416,7 @@ static void force_recovery(proxy_balancer *balancer, server_rec *s)
         }
         else {
             /* Try if we can recover */
-            ap_proxy_retry_worker("BALANCER", *worker, s);
+            ap_proxy_retry_worker_fn("BALANCER", *worker, s);
             if (!((*worker)->s->status & PROXY_WORKER_IN_ERROR)) {
                 ok = 1;
                 break;
@@ -696,8 +699,19 @@ static int balancer_post_config(apr_pool_t *pconf, apr_pool_t *plog,
 
     /* balancer_post_config() will be called twice during startup.  So, don't
      * set up the static data the 1st time through. */
-    if (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_CREATE_PRE_CONFIG)
+    if (ap_state_query(AP_SQ_MAIN_STATE) == AP_SQ_MS_CREATE_PRE_CONFIG) {
         return OK;
+    }
+
+    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) {
+            ap_log_error(
+                    APLOG_MARK, APLOG_EMERG, 0, s, "mod_proxy must be loaded for mod_proxy_balancer");
+            return !OK;
+        }
+    }
 
     /*
      * Get slotmem setups

modules/proxy/proxy_util.c

@@ -20,6 +20,7 @@
 #include "scoreboard.h"
 #include "apr_version.h"
 #include "apr_hash.h"
+#include "proxy_util.h"
 
 #if APR_HAVE_UNISTD_H
 #include <unistd.h>         /* for getpid() */
@@ -1977,8 +1978,7 @@ PROXY_DECLARE(apr_status_t) ap_proxy_initialize_worker(proxy_worker *worker, ser
     return rv;
 }
 
-PROXY_DECLARE(int) ap_proxy_retry_worker(const char *proxy_function,
+static int ap_proxy_retry_worker(const char *proxy_function, proxy_worker *worker,
-                                         proxy_worker *worker,
         server_rec *s)
 {
     if (worker->s->status & PROXY_WORKER_IN_ERROR) {
@@ -3024,3 +3024,7 @@ PROXY_DECLARE(apr_status_t) ap_proxy_sync_balancer(proxy_balancer *b, server_rec
     return APR_SUCCESS;
 }
 
+void proxy_util_register_hooks(apr_pool_t *p)
+{
+    APR_REGISTER_OPTIONAL_FN(ap_proxy_retry_worker);
+}

modules/proxy/proxy_util.h

@@ -0,0 +1,36 @@
+/* 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.
+ */
+
+#ifndef PROXY_UTIL_H_
+#define PROXY_UTIL_H_
+
+/**
+ * @file  proxy_util.h
+ * @brief Internal interfaces private to mod_proxy.
+ *
+ * @defgroup MOD_PROXY_PRIVATE Private
+ * @ingroup MOD_PROXY
+ * @{
+ */
+
+/**
+ * Register optional functions declared within proxy_util.c.
+ */
+void proxy_util_register_hooks(apr_pool_t *p);
+
+/** @} */
+
+#endif /* PROXY_UTIL_H_ */