* mod_proxy: Remove load order and link dependency between mod_lbmethod_*

  modules and mod_proxy by providing mod_proxy's ap_proxy_balancer_get_best_worker
  as an optional function.

PR: 62557


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1836381 13f79535-47bb-0310-9956-ffa450edef68

5 files changed, 90 insertions, 3 deletions

diff --git a/modules/proxy/balancers/mod_lbmethod_bybusyness.c b/modules/proxy/balancers/mod_lbmethod_bybusyness.c
index 709512bb5e..99f8b14b04 100644
--- a/modules/proxy/balancers/mod_lbmethod_bybusyness.c
+++ b/modules/proxy/balancers/mod_lbmethod_bybusyness.c
@@ -22,6 +22,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_bybusyness_module;
 
+static APR_OPTIONAL_FN_TYPE(ap_proxy_balancer_get_best_worker)
+                            *ap_proxy_balancer_get_best_worker_fn = NULL;
+
 static int is_best_bybusyness(proxy_worker *current, proxy_worker *prev_best, void *baton)
 {
     int *total_factor = (int *)baton;
@@ -44,7 +47,7 @@ static proxy_worker *find_best_bybusyness(proxy_balancer *balancer,
 {
     int total_factor = 0;
     proxy_worker *worker =
-        ap_proxy_balancer_get_best_worker(balancer, r, is_best_bybusyness,
+        ap_proxy_balancer_get_best_worker_fn(balancer, r, is_best_bybusyness,
                                           &total_factor);
 
     if (worker) {
@@ -82,9 +85,32 @@ static const proxy_balancer_method bybusyness =
     NULL
 };
 
+/* post_config hook: */
+static int lbmethod_bybusyness_post_config(apr_pool_t *pconf, apr_pool_t *plog,
+        apr_pool_t *ptemp, server_rec *s)
+{
+
+    /* lbmethod_bybusyness_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) {
+        return OK;
+    }
+
+    ap_proxy_balancer_get_best_worker_fn =
+                 APR_RETRIEVE_OPTIONAL_FN(ap_proxy_balancer_get_best_worker);
+    if (!ap_proxy_balancer_get_best_worker_fn) {
+        ap_log_error(APLOG_MARK, APLOG_EMERG, 0, s, APLOGNO()
+                     "mod_proxy must be loaded for mod_lbmethod_bybusyness");
+        return !OK;
+    }
+
+    return OK;
+}
+
 static void register_hook(apr_pool_t *p)
 {
     ap_register_provider(p, PROXY_LBMETHOD, "bybusyness", "0", &bybusyness);
+    ap_hook_post_config(lbmethod_bybusyness_post_config, NULL, NULL, APR_HOOK_MIDDLE);
 }
 
 AP_DECLARE_MODULE(lbmethod_bybusyness) = {
diff --git a/modules/proxy/balancers/mod_lbmethod_byrequests.c b/modules/proxy/balancers/mod_lbmethod_byrequests.c
index 0483a70fec..07822e702b 100644
--- a/modules/proxy/balancers/mod_lbmethod_byrequests.c
+++ b/modules/proxy/balancers/mod_lbmethod_byrequests.c
@@ -22,6 +22,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_byrequests_module;
 
+static APR_OPTIONAL_FN_TYPE(ap_proxy_balancer_get_best_worker)
+                            *ap_proxy_balancer_get_best_worker_fn = NULL;
+
 static int is_best_byrequests(proxy_worker *current, proxy_worker *prev_best, void *baton)
 {
     int *total_factor = (int *)baton;
@@ -81,7 +84,7 @@ static proxy_worker *find_best_byrequests(proxy_balancer *balancer,
                                 request_rec *r)
 {
     int total_factor = 0;
-    proxy_worker *worker = ap_proxy_balancer_get_best_worker(balancer, r, is_best_byrequests, &total_factor);
+    proxy_worker *worker = ap_proxy_balancer_get_best_worker_fn(balancer, r, is_best_byrequests, &total_factor);
 
     if (worker) {
         worker->s->lbstatus -= total_factor;
@@ -123,6 +126,28 @@ static const proxy_balancer_method byrequests =
     NULL
 };
 
+/* post_config hook: */
+static int lbmethod_byrequests_post_config(apr_pool_t *pconf, apr_pool_t *plog,
+        apr_pool_t *ptemp, server_rec *s)
+{
+
+    /* lbmethod_byrequests_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) {
+        return OK;
+    }
+
+    ap_proxy_balancer_get_best_worker_fn =
+                 APR_RETRIEVE_OPTIONAL_FN(ap_proxy_balancer_get_best_worker);
+    if (!ap_proxy_balancer_get_best_worker_fn) {
+        ap_log_error(APLOG_MARK, APLOG_EMERG, 0, s, APLOGNO()
+                     "mod_proxy must be loaded for mod_lbmethod_byrequests");
+        return !OK;
+    }
+
+    return OK;
+}
+
 static void register_hook(apr_pool_t *p)
 {
     /* Only the mpm_winnt has child init hook handler.
@@ -130,6 +155,7 @@ static void register_hook(apr_pool_t *p)
      * initializes and after the mod_proxy
      */
     ap_register_provider(p, PROXY_LBMETHOD, "byrequests", "0", &byrequests);
+    ap_hook_post_config(lbmethod_byrequests_post_config, NULL, NULL, APR_HOOK_MIDDLE);
 }
 
 AP_DECLARE_MODULE(lbmethod_byrequests) = {
diff --git a/modules/proxy/balancers/mod_lbmethod_bytraffic.c b/modules/proxy/balancers/mod_lbmethod_bytraffic.c
index 343c59ac32..b87db5adc6 100644
--- a/modules/proxy/balancers/mod_lbmethod_bytraffic.c
+++ b/modules/proxy/balancers/mod_lbmethod_bytraffic.c
@@ -22,6 +22,9 @@
 
 module AP_MODULE_DECLARE_DATA lbmethod_bytraffic_module;
 
+static APR_OPTIONAL_FN_TYPE(ap_proxy_balancer_get_best_worker)
+                            *ap_proxy_balancer_get_best_worker_fn = NULL;
+
 static int is_best_bytraffic(proxy_worker *current, proxy_worker *prev_best, void *baton)
 {
     apr_off_t *min_traffic = (apr_off_t *)baton;
@@ -59,7 +62,7 @@ static proxy_worker *find_best_bytraffic(proxy_balancer *balancer,
 {
     apr_off_t min_traffic = 0;
 
-    return ap_proxy_balancer_get_best_worker(balancer, r, is_best_bytraffic,
+    return ap_proxy_balancer_get_best_worker_fn(balancer, r, is_best_bytraffic,
                                              &min_traffic);
 }
 
@@ -93,6 +96,28 @@ static const proxy_balancer_method bytraffic =
     NULL
 };
 
+/* post_config hook: */
+static int lbmethod_bytraffic_post_config(apr_pool_t *pconf, apr_pool_t *plog,
+        apr_pool_t *ptemp, server_rec *s)
+{
+
+    /* lbmethod_bytraffic_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) {
+        return OK;
+    }
+
+    ap_proxy_balancer_get_best_worker_fn =
+                 APR_RETRIEVE_OPTIONAL_FN(ap_proxy_balancer_get_best_worker);
+    if (!ap_proxy_balancer_get_best_worker_fn) {
+        ap_log_error(APLOG_MARK, APLOG_EMERG, 0, s, APLOGNO()
+                     "mod_proxy must be loaded for mod_lbmethod_bytraffic");
+        return !OK;
+    }
+
+    return OK;
+}
+
 static void register_hook(apr_pool_t *p)
 {
     /* Only the mpm_winnt has child init hook handler.
@@ -100,6 +125,7 @@ static void register_hook(apr_pool_t *p)
      * initializes and after the mod_proxy
      */
     ap_register_provider(p, PROXY_LBMETHOD, "bytraffic", "0", &bytraffic);
+    ap_hook_post_config(lbmethod_bytraffic_post_config, NULL, NULL, APR_HOOK_MIDDLE);
 }
 
 AP_DECLARE_MODULE(lbmethod_bytraffic) = {
diff --git a/modules/proxy/mod_proxy.h b/modules/proxy/mod_proxy.h
index ae8be929bc..cec243840b 100644
--- a/modules/proxy/mod_proxy.h
+++ b/modules/proxy/mod_proxy.h
@@ -880,6 +880,14 @@ PROXY_DECLARE(proxy_worker *) ap_proxy_balancer_get_best_worker(proxy_balancer *
                                                                 request_rec *r,
                                                                 proxy_is_best_callback_fn_t *is_best,
                                                                 void *baton);
+/*
+ * Needed by the lb modules.
+ */
+APR_DECLARE_OPTIONAL_FN(proxy_worker *, ap_proxy_balancer_get_best_worker,
+                                        (proxy_balancer *balancer,
+                                         request_rec *r,
+                                         proxy_is_best_callback_fn_t *is_best,
+                                         void *baton));
 
 /**
  * Find the shm of the worker as needed
diff --git a/modules/proxy/proxy_util.c b/modules/proxy/proxy_util.c
index e8eecb2070..bb24ca0802 100644
--- a/modules/proxy/proxy_util.c
+++ b/modules/proxy/proxy_util.c
@@ -4079,4 +4079,5 @@ void proxy_util_register_hooks(apr_pool_t *p)
 {
     APR_REGISTER_OPTIONAL_FN(ap_proxy_retry_worker);
     APR_REGISTER_OPTIONAL_FN(ap_proxy_clear_connection);
+    APR_REGISTER_OPTIONAL_FN(ap_proxy_balancer_get_best_worker);
 }