[nginx] svn commit: r4872 - trunk/src/core

[mdounin at mdounin.ru]

Author: mdounin
Date: 2012-09-28 18:28:38 +0000 (Fri, 28 Sep 2012)
New Revision: 4872
URL: http://trac.nginx.org/nginx/changeset/4872/nginx

Log:
Resolver: cached addresses are returned with random rotation now.

This ensures balancing when working with dynamically resolved upstream
servers with multiple addresses.

Based on patch by Anton Jouline.


Modified:
   trunk/src/core/ngx_resolver.c

Modified: trunk/src/core/ngx_resolver.c
===================================================================
--- trunk/src/core/ngx_resolver.c	2012-09-28 13:49:26 UTC (rev 4871)
+++ trunk/src/core/ngx_resolver.c	2012-09-28 18:28:38 UTC (rev 4872)
@@ -88,6 +88,8 @@
 static void ngx_resolver_free(ngx_resolver_t *r, void *p);
 static void ngx_resolver_free_locked(ngx_resolver_t *r, void *p);
 static void *ngx_resolver_dup(ngx_resolver_t *r, void *src, size_t size);
+static in_addr_t *ngx_resolver_rotate(ngx_resolver_t *r, in_addr_t *src,
+    ngx_uint_t n);
 static u_char *ngx_resolver_log_error(ngx_log_t *log, u_char *buf, size_t len);
 
 
@@ -445,8 +447,7 @@
 
                 if (naddrs != 1) {
                     addr = 0;
-                    addrs = ngx_resolver_dup(r, rn->u.addrs,
-                                             naddrs * sizeof(in_addr_t));
+                    addrs = ngx_resolver_rotate(r, rn->u.addrs, naddrs);
                     if (addrs == NULL) {
                         return NGX_ERROR;
                     }
@@ -2135,6 +2136,28 @@
 }
 
 
+static in_addr_t *
+ngx_resolver_rotate(ngx_resolver_t *r, in_addr_t *src, ngx_uint_t n)
+{
+    void        *dst, *p;
+    ngx_uint_t   j;
+
+    dst = ngx_resolver_alloc(r, n * sizeof(in_addr_t));
+
+    j = ngx_random() % n;
+
+    if (j == 0) {
+        ngx_memcpy(dst, src, n * sizeof(in_addr_t));
+        return dst;
+    }
+
+    p = ngx_cpymem(dst, &src[j], (n - j) * sizeof(in_addr_t));
+    ngx_memcpy(p, src, j * sizeof(in_addr_t));
+
+    return dst;
+}
+
+
 char *
 ngx_resolver_strerror(ngx_int_t err)
 {