From 4d53631022f4c01878310298a9508cc7ee073012 Mon Sep 17 00:00:00 2001
From: Ruslan Ermilov <ru@nginx.com>
Date: Fri, 10 Apr 2015 14:48:36 +0300
Subject: [PATCH] Upstream: store peers as a linked list.

This is an API change.
---
 .../modules/ngx_http_upstream_hash_module.c   |  73 ++++++------
 .../ngx_http_upstream_ip_hash_module.c        |  16 ++-
 .../ngx_http_upstream_least_conn_module.c     |  21 ++--
 src/http/ngx_http_upstream_round_robin.c      | 105 ++++++++++++------
 src/http/ngx_http_upstream_round_robin.h      |  12 +-
 5 files changed, 140 insertions(+), 87 deletions(-)

diff --git a/src/http/modules/ngx_http_upstream_hash_module.c b/src/http/modules/ngx_http_upstream_hash_module.c
index daea0432c..249733f72 100644
--- a/src/http/modules/ngx_http_upstream_hash_module.c
+++ b/src/http/modules/ngx_http_upstream_hash_module.c
@@ -211,11 +211,19 @@ ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc, void *data)
         if (!hp->rrp.peers->weighted) {
             p = hp->hash % hp->rrp.peers->number;
 
+            peer = hp->rrp.peers->peer;
+            for (i = 0; i < p; i++) {
+                peer = peer->next;
+            }
+
         } else {
             w = hp->hash % hp->rrp.peers->total_weight;
 
-            for (i = 0; i < hp->rrp.peers->number; i++) {
-                w -= hp->rrp.peers->peer[i].weight;
+            for (peer = hp->rrp.peers->peer, i = 0;
+                 peer;
+                 peer = peer->next, i++)
+            {
+                w -= peer->weight;
                 if (w < 0) {
                     break;
                 }
@@ -234,8 +242,6 @@ ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc, void *data)
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "get hash peer, value:%uD, peer:%ui", hp->hash, p);
 
-        peer = &hp->rrp.peers->peer[p];
-
         if (peer->down) {
             goto next;
         }
@@ -256,7 +262,7 @@ ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc, void *data)
         }
     }
 
-    hp->rrp.current = p;
+    hp->rrp.current = peer;
 
     pc->sockaddr = peer->sockaddr;
     pc->socklen = peer->socklen;
@@ -306,8 +312,7 @@ ngx_http_upstream_init_chash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
 
     points->number = 0;
 
-    for (i = 0; i < peers->number; i++) {
-        peer = &peers->peer[i];
+    for (peer = peers->peer; peer; peer = peer->next) {
         server = &peer->server;
 
         /*
@@ -475,7 +480,7 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
     intptr_t                            m;
     ngx_str_t                          *server;
     ngx_int_t                           total;
-    ngx_uint_t                          i, n;
+    ngx_uint_t                          i, n, best_i;
     ngx_http_upstream_rr_peer_t        *peer, *best;
     ngx_http_upstream_chash_point_t    *point;
     ngx_http_upstream_chash_points_t   *points;
@@ -501,9 +506,13 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
                        hp->hash, server);
 
         best = NULL;
+        best_i = 0;
         total = 0;
 
-        for (i = 0; i < hp->rrp.peers->number; i++) {
+        for (peer = hp->rrp.peers->peer, i = 0;
+             peer;
+             peer = peer->next, i++)
+        {
 
             n = i / (8 * sizeof(uintptr_t));
             m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
@@ -512,8 +521,6 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
                 continue;
             }
 
-            peer = &hp->rrp.peers->peer[i];
-
             if (peer->down) {
                 continue;
             }
@@ -541,32 +548,13 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
 
             if (best == NULL || peer->current_weight > best->current_weight) {
                 best = peer;
+                best_i = i;
             }
         }
 
         if (best) {
             best->current_weight -= total;
-
-            i = best - &hp->rrp.peers->peer[0];
-
-            hp->rrp.current = i;
-
-            n = i / (8 * sizeof(uintptr_t));
-            m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
-
-            hp->rrp.tried[n] |= m;
-
-            if (now - best->checked > best->fail_timeout) {
-                best->checked = now;
-            }
-
-            pc->sockaddr = best->sockaddr;
-            pc->socklen = best->socklen;
-            pc->name = &best->name;
-
-            best->conns++;
-
-            return NGX_OK;
+            goto found;
         }
 
         hp->hash++;
@@ -576,6 +564,27 @@ ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
             return NGX_BUSY;
         }
     }
+
+found:
+
+    hp->rrp.current = best;
+
+    pc->sockaddr = best->sockaddr;
+    pc->socklen = best->socklen;
+    pc->name = &best->name;
+
+    best->conns++;
+
+    if (now - best->checked > best->fail_timeout) {
+        best->checked = now;
+    }
+
+    n = best_i / (8 * sizeof(uintptr_t));
+    m = (uintptr_t) 1 << best_i % (8 * sizeof(uintptr_t));
+
+    hp->rrp.tried[n] |= m;
+
+    return NGX_OK;
 }
 
 
diff --git a/src/http/modules/ngx_http_upstream_ip_hash_module.c b/src/http/modules/ngx_http_upstream_ip_hash_module.c
index 638e0778b..2c6506d6f 100644
--- a/src/http/modules/ngx_http_upstream_ip_hash_module.c
+++ b/src/http/modules/ngx_http_upstream_ip_hash_module.c
@@ -181,11 +181,19 @@ ngx_http_upstream_get_ip_hash_peer(ngx_peer_connection_t *pc, void *data)
         if (!iphp->rrp.peers->weighted) {
             p = hash % iphp->rrp.peers->number;
 
+            peer = iphp->rrp.peers->peer;
+            for (i = 0; i < p; i++) {
+                peer = peer->next;
+            }
+
         } else {
             w = hash % iphp->rrp.peers->total_weight;
 
-            for (i = 0; i < iphp->rrp.peers->number; i++) {
-                w -= iphp->rrp.peers->peer[i].weight;
+            for (peer = iphp->rrp.peers->peer, i = 0;
+                 peer;
+                 peer = peer->next, i++)
+            {
+                w -= peer->weight;
                 if (w < 0) {
                     break;
                 }
@@ -204,8 +212,6 @@ ngx_http_upstream_get_ip_hash_peer(ngx_peer_connection_t *pc, void *data)
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "get ip hash peer, hash: %ui %04XA", p, m);
 
-        peer = &iphp->rrp.peers->peer[p];
-
         /* ngx_lock_mutex(iphp->rrp.peers->mutex); */
 
         if (peer->down) {
@@ -236,7 +242,7 @@ ngx_http_upstream_get_ip_hash_peer(ngx_peer_connection_t *pc, void *data)
         }
     }
 
-    iphp->rrp.current = p;
+    iphp->rrp.current = peer;
 
     pc->sockaddr = peer->sockaddr;
     pc->socklen = peer->socklen;
diff --git a/src/http/modules/ngx_http_upstream_least_conn_module.c b/src/http/modules/ngx_http_upstream_least_conn_module.c
index f2a4ec9eb..61b538631 100644
--- a/src/http/modules/ngx_http_upstream_least_conn_module.c
+++ b/src/http/modules/ngx_http_upstream_least_conn_module.c
@@ -130,7 +130,10 @@ ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
     p = 0;
 #endif
 
-    for (i = 0; i < peers->number; i++) {
+    for (peer = peers->peer, i = 0;
+         peer;
+         peer = peer->next, i++)
+    {
 
         n = i / (8 * sizeof(uintptr_t));
         m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
@@ -139,8 +142,6 @@ ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
             continue;
         }
 
-        peer = &peers->peer[i];
-
         if (peer->down) {
             continue;
         }
@@ -181,8 +182,10 @@ ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "get least conn peer, many");
 
-        for (i = p; i < peers->number; i++) {
-
+        for (peer = best, i = p;
+             peer;
+             peer = peer->next, i++)
+        {
             n = i / (8 * sizeof(uintptr_t));
             m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
 
@@ -190,8 +193,6 @@ ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
                 continue;
             }
 
-            peer = &peers->peer[i];
-
             if (peer->down) {
                 continue;
             }
@@ -233,7 +234,7 @@ ngx_http_upstream_get_least_conn_peer(ngx_peer_connection_t *pc, void *data)
 
     best->conns++;
 
-    rrp->current = p;
+    rrp->current = best;
 
     n = p / (8 * sizeof(uintptr_t));
     m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));
@@ -266,8 +267,8 @@ failed:
 
     /* all peers failed, mark them as live for quick recovery */
 
-    for (i = 0; i < peers->number; i++) {
-        peers->peer[i].fails = 0;
+    for (peer = peers->peer; peer; peer = peer->next) {
+        peer->fails = 0;
     }
 
     pc->name = peers->name;
diff --git a/src/http/ngx_http_upstream_round_robin.c b/src/http/ngx_http_upstream_round_robin.c
index 61c042f70..8d7046ade 100644
--- a/src/http/ngx_http_upstream_round_robin.c
+++ b/src/http/ngx_http_upstream_round_robin.c
@@ -34,7 +34,7 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
     ngx_url_t                      u;
     ngx_uint_t                     i, j, n, w;
     ngx_http_upstream_server_t    *server;
-    ngx_http_upstream_rr_peer_t   *peer;
+    ngx_http_upstream_rr_peer_t   *peer, **peerp;
     ngx_http_upstream_rr_peers_t  *peers, *backup;
 
     us->peer.init = ngx_http_upstream_init_round_robin_peer;
@@ -61,12 +61,16 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
             return NGX_ERROR;
         }
 
-        peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
-                              + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
+        peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
         if (peers == NULL) {
             return NGX_ERROR;
         }
 
+        peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
+        if (peer == NULL) {
+            return NGX_ERROR;
+        }
+
         peers->single = (n == 1);
         peers->number = n;
         peers->weighted = (w != n);
@@ -74,7 +78,7 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
         peers->name = &us->host;
 
         n = 0;
-        peer = peers->peer;
+        peerp = &peers->peer;
 
         for (i = 0; i < us->servers->nelts; i++) {
             if (server[i].backup) {
@@ -92,6 +96,9 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
                 peer[n].fail_timeout = server[i].fail_timeout;
                 peer[n].down = server[i].down;
                 peer[n].server = server[i].name;
+
+                *peerp = &peer[n];
+                peerp = &peer[n].next;
                 n++;
             }
         }
@@ -116,12 +123,16 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
             return NGX_OK;
         }
 
-        backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
-                              + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
+        backup = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
         if (backup == NULL) {
             return NGX_ERROR;
         }
 
+        peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
+        if (peer == NULL) {
+            return NGX_ERROR;
+        }
+
         peers->single = 0;
         backup->single = 0;
         backup->number = n;
@@ -130,7 +141,7 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
         backup->name = &us->host;
 
         n = 0;
-        peer = backup->peer;
+        peerp = &backup->peer;
 
         for (i = 0; i < us->servers->nelts; i++) {
             if (!server[i].backup) {
@@ -148,6 +159,9 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
                 peer[n].fail_timeout = server[i].fail_timeout;
                 peer[n].down = server[i].down;
                 peer[n].server = server[i].name;
+
+                *peerp = &peer[n];
+                peerp = &peer[n].next;
                 n++;
             }
         }
@@ -184,19 +198,23 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
 
     n = u.naddrs;
 
-    peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t)
-                              + sizeof(ngx_http_upstream_rr_peer_t) * (n - 1));
+    peers = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peers_t));
     if (peers == NULL) {
         return NGX_ERROR;
     }
 
+    peer = ngx_pcalloc(cf->pool, sizeof(ngx_http_upstream_rr_peer_t) * n);
+    if (peer == NULL) {
+        return NGX_ERROR;
+    }
+
     peers->single = (n == 1);
     peers->number = n;
     peers->weighted = 0;
     peers->total_weight = n;
     peers->name = &us->host;
 
-    peer = peers->peer;
+    peerp = &peers->peer;
 
     for (i = 0; i < u.naddrs; i++) {
         peer[i].sockaddr = u.addrs[i].sockaddr;
@@ -207,6 +225,8 @@ ngx_http_upstream_init_round_robin(ngx_conf_t *cf,
         peer[i].current_weight = 0;
         peer[i].max_fails = 1;
         peer[i].fail_timeout = 10;
+        *peerp = &peer[i];
+        peerp = &peer[i].next;
     }
 
     us->peer.data = peers;
@@ -236,7 +256,7 @@ ngx_http_upstream_init_round_robin_peer(ngx_http_request_t *r,
     }
 
     rrp->peers = us->peer.data;
-    rrp->current = 0;
+    rrp->current = NULL;
 
     n = rrp->peers->number;
 
@@ -280,7 +300,7 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
     socklen_t                          socklen;
     ngx_uint_t                         i, n;
     struct sockaddr                   *sockaddr;
-    ngx_http_upstream_rr_peer_t       *peer;
+    ngx_http_upstream_rr_peer_t       *peer, **peerp;
     ngx_http_upstream_rr_peers_t      *peers;
     ngx_http_upstream_rr_peer_data_t  *rrp;
 
@@ -295,18 +315,21 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
         r->upstream->peer.data = rrp;
     }
 
-    peers = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peers_t)
-                     + sizeof(ngx_http_upstream_rr_peer_t) * (ur->naddrs - 1));
+    peers = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peers_t));
     if (peers == NULL) {
         return NGX_ERROR;
     }
 
+    peer = ngx_pcalloc(r->pool, sizeof(ngx_http_upstream_rr_peer_t)
+                                * ur->naddrs);
+    if (peer == NULL) {
+        return NGX_ERROR;
+    }
+
     peers->single = (ur->naddrs == 1);
     peers->number = ur->naddrs;
     peers->name = &ur->host;
 
-    peer = peers->peer;
-
     if (ur->sockaddr) {
         peer[0].sockaddr = ur->sockaddr;
         peer[0].socklen = ur->socklen;
@@ -316,8 +339,10 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
         peer[0].current_weight = 0;
         peer[0].max_fails = 1;
         peer[0].fail_timeout = 10;
+        peers->peer = peer;
 
     } else {
+        peerp = &peers->peer;
 
         for (i = 0; i < ur->naddrs; i++) {
 
@@ -356,11 +381,13 @@ ngx_http_upstream_create_round_robin_peer(ngx_http_request_t *r,
             peer[i].current_weight = 0;
             peer[i].max_fails = 1;
             peer[i].fail_timeout = 10;
+            *peerp = &peer[i];
+            peerp = &peer[i].next;
         }
     }
 
     rrp->peers = peers;
-    rrp->current = 0;
+    rrp->current = NULL;
 
     if (rrp->peers->number <= 8 * sizeof(uintptr_t)) {
         rrp->tried = &rrp->data;
@@ -409,12 +436,14 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
     /* ngx_lock_mutex(peers->mutex); */
 
     if (peers->single) {
-        peer = &peers->peer[0];
+        peer = peers->peer;
 
         if (peer->down) {
             goto failed;
         }
 
+        rrp->current = peer;
+
     } else {
 
         /* there are several peers */
@@ -426,8 +455,8 @@ ngx_http_upstream_get_round_robin_peer(ngx_peer_connection_t *pc, void *data)
         }
 
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
-                       "get rr peer, current: %ui %i",
-                       rrp->current, peer->current_weight);
+                       "get rr peer, current: %p %i",
+                       peer, peer->current_weight);
     }
 
     pc->sockaddr = peer->sockaddr;
@@ -468,8 +497,8 @@ failed:
 
     /* all peers failed, mark them as live for quick recovery */
 
-    for (i = 0; i < peers->number; i++) {
-        peers->peer[i].fails = 0;
+    for (peer = peers->peer; peer; peer = peer->next) {
+        peer->fails = 0;
     }
 
     /* ngx_unlock_mutex(peers->mutex); */
@@ -486,7 +515,7 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
     time_t                        now;
     uintptr_t                     m;
     ngx_int_t                     total;
-    ngx_uint_t                    i, n;
+    ngx_uint_t                    i, n, p;
     ngx_http_upstream_rr_peer_t  *peer, *best;
 
     now = ngx_time();
@@ -494,7 +523,14 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
     best = NULL;
     total = 0;
 
-    for (i = 0; i < rrp->peers->number; i++) {
+#if (NGX_SUPPRESS_WARN)
+    p = 0;
+#endif
+
+    for (peer = rrp->peers->peer, i = 0;
+         peer;
+         peer = peer->next, i++)
+    {
 
         n = i / (8 * sizeof(uintptr_t));
         m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
@@ -503,8 +539,6 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
             continue;
         }
 
-        peer = &rrp->peers->peer[i];
-
         if (peer->down) {
             continue;
         }
@@ -525,6 +559,7 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
 
         if (best == NULL || peer->current_weight > best->current_weight) {
             best = peer;
+            p = i;
         }
     }
 
@@ -532,12 +567,10 @@ ngx_http_upstream_get_peer(ngx_http_upstream_rr_peer_data_t *rrp)
         return NULL;
     }
 
-    i = best - &rrp->peers->peer[0];
+    rrp->current = best;
 
-    rrp->current = i;
-
-    n = i / (8 * sizeof(uintptr_t));
-    m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));
+    n = p / (8 * sizeof(uintptr_t));
+    m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));
 
     rrp->tried[n] |= m;
 
@@ -565,7 +598,7 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
 
     /* TODO: NGX_PEER_KEEPALIVE */
 
-    peer = &rrp->peers->peer[rrp->current];
+    peer = rrp->current;
 
     if (rrp->peers->single) {
 
@@ -589,8 +622,8 @@ ngx_http_upstream_free_round_robin_peer(ngx_peer_connection_t *pc, void *data,
         }
 
         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
-                       "free rr peer failed: %ui %i",
-                       rrp->current, peer->effective_weight);
+                       "free rr peer failed: %p %i",
+                       peer, peer->effective_weight);
 
         if (peer->effective_weight < 0) {
             peer->effective_weight = 0;
@@ -629,7 +662,7 @@ ngx_http_upstream_set_round_robin_peer_session(ngx_peer_connection_t *pc,
     ngx_ssl_session_t            *ssl_session;
     ngx_http_upstream_rr_peer_t  *peer;
 
-    peer = &rrp->peers->peer[rrp->current];
+    peer = rrp->current;
 
     /* TODO: threads only mutex */
     /* ngx_lock_mutex(rrp->peers->mutex); */
@@ -665,7 +698,7 @@ ngx_http_upstream_save_round_robin_peer_session(ngx_peer_connection_t *pc,
     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "save session: %p", ssl_session);
 
-    peer = &rrp->peers->peer[rrp->current];
+    peer = rrp->current;
 
     /* TODO: threads only mutex */
     /* ngx_lock_mutex(rrp->peers->mutex); */
diff --git a/src/http/ngx_http_upstream_round_robin.h b/src/http/ngx_http_upstream_round_robin.h
index 8927d98c6..53beac8e3 100644
--- a/src/http/ngx_http_upstream_round_robin.h
+++ b/src/http/ngx_http_upstream_round_robin.h
@@ -14,7 +14,9 @@
 #include <ngx_http.h>
 
 
-typedef struct {
+typedef struct ngx_http_upstream_rr_peer_s   ngx_http_upstream_rr_peer_t;
+
+struct ngx_http_upstream_rr_peer_s {
     struct sockaddr                *sockaddr;
     socklen_t                       socklen;
     ngx_str_t                       name;
@@ -38,7 +40,9 @@ typedef struct {
 #if (NGX_HTTP_SSL)
     ngx_ssl_session_t              *ssl_session;   /* local to a process */
 #endif
-} ngx_http_upstream_rr_peer_t;
+
+    ngx_http_upstream_rr_peer_t    *next;
+};
 
 
 typedef struct ngx_http_upstream_rr_peers_s  ngx_http_upstream_rr_peers_t;
@@ -55,13 +59,13 @@ struct ngx_http_upstream_rr_peers_s {
 
     ngx_http_upstream_rr_peers_t   *next;
 
-    ngx_http_upstream_rr_peer_t     peer[1];
+    ngx_http_upstream_rr_peer_t    *peer;
 };
 
 
 typedef struct {
     ngx_http_upstream_rr_peers_t   *peers;
-    ngx_uint_t                      current;
+    ngx_http_upstream_rr_peer_t    *current;
     uintptr_t                      *tried;
     uintptr_t                       data;
 } ngx_http_upstream_rr_peer_data_t;