Add failover to mod proxy. If the service is unavailable,

check another worker in case this is balancer request.
In case the error in unrecoverable, fail with returned
status code.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@160848 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/modules/proxy/mod_proxy.c b/modules/proxy/mod_proxy.c
index dce3bf33941e6df540b2d0018a86d35ef7269d23..f3ad42be2fbbb803a144270bb02621b92cd265fa 100644 (file)
--- a/modules/proxy/mod_proxy.c
+++ b/modules/proxy/mod_proxy.c
@@ -515,7 +515,7 @@ static int proxy_needsdomain(request_rec *r, const char *url, const char *domain
 
 static int proxy_handler(request_rec *r)
 {
-    char *url, *scheme, *p;
+    char *uri, *scheme, *p;
     const char *p2;
     void *sconf = r->server->module_config;
     proxy_server_conf *conf = (proxy_server_conf *)
@@ -573,8 +573,8 @@ static int proxy_handler(request_rec *r)
     apr_table_set(r->headers_in, "Max-Forwards", 
                   apr_psprintf(r->pool, "%ld", (maxfwd > 0) ? maxfwd : 0));
 
-    url = r->filename + 6;
-    p = strchr(url, ':');
+    uri = r->filename + 6;
+    p = strchr(uri, ':');
     if (p == NULL) {
         ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                       "proxy_handler no URL in %s", r->filename);
@@ -583,12 +583,12 @@ static int proxy_handler(request_rec *r)
 
     /* If the host doesn't have a domain name, add one and redirect. */
     if (conf->domain != NULL) {
-        rc = proxy_needsdomain(r, url, conf->domain);
+        rc = proxy_needsdomain(r, uri, conf->domain);
         if (ap_is_HTTP_REDIRECT(rc))
             return HTTP_MOVED_PERMANENTLY;
     }
 
-    scheme = apr_pstrndup(r->pool, url, p - url);
+    scheme = apr_pstrndup(r->pool, uri, p - uri);
     /* Check URI's destination host against NoProxy hosts */
     /* Bypass ProxyRemote server lookup if configured as NoProxy */
     for (direct_connect = i = 0; i < conf->dirconn->nelts &&
@@ -602,7 +602,7 @@ static int proxy_handler(request_rec *r)
 #endif
 
     do {
-
+        char *url = uri;
         /* Try to obtain the most suitable worker */
         access_status = ap_proxy_pre_request(&worker, &balancer, r, conf, &url);
         if (access_status != OK)
@@ -648,10 +648,37 @@ static int proxy_handler(request_rec *r)
         ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                      "Running scheme %s handler (attempt %d)",
                      scheme, attempts);
-        if ((access_status = proxy_run_scheme_handler(r, worker, conf,
-                                                      url, NULL, 0)) == OK)
+        access_status = proxy_run_scheme_handler(r, worker, conf,
+                                                 url, NULL, 0);
+        if (access_status == OK)
+            break;
+        else if (access_status == HTTP_INTERNAL_SERVER_ERROR) {
+            /* Unrecoverable server error.
+             * We can not failover to another worker.
+             * Mark the worker as unusable if member of load balancer
+             */
+            if (balancer)
+                worker->s->status |= PROXY_WORKER_IN_ERROR;
             break;
-        
+        }
+        else if (access_status == HTTP_SERVICE_UNAVAILABLE) {
+            /* Recoverable server error.
+             * We can failover to another worker 
+             * Mark the worker as unusable if member of load balancer
+             */
+            if (balancer) {
+                worker->s->status |= PROXY_WORKER_IN_ERROR;
+            }
+        }
+        else {
+            /* Unrecoverable error.
+             * Return the origin status code to the client.
+             */
+            break;
+        }
+        /* Try again if the worker is unusable and the service is
+         * unavailable.
+         */
     } while (!PROXY_WORKER_IS_USABLE(worker) && 
              max_attempts > attempts++);