Sticky: $upstream_sticky_status variable.

Possible values are:
    empty  - the request to the upstream with no sticky enabled
    "new"  - request without sticky information
    "hit"  - request with sticky information was routed to desired backend
    "miss" - request with sticky information was routed to backend selected
             by balancing algorithm

src/http/modules/ngx_http_upstream_sticky_module.c

@@ -126,15 +126,19 @@ ngx_http_upstream_sticky_select_peer(ngx_http_upstream_rr_peer_data_t *rrp,
     ngx_uint_t   i, n;
 
     ngx_http_request_t                   *r;
+    ngx_http_upstream_state_t            *us;
     ngx_http_upstream_rr_peer_t          *peer;
     ngx_http_upstream_rr_peers_t         *peers;
     ngx_http_upstream_sticky_srv_conf_t  *scf;
 
     r = pc->ctx;
 
     hint = &sp->hint;
+    us = r->upstream->state;
 
     if (hint->len == 0) {
+        us->sticky_status = NGX_HTTP_UPSTREAM_STICKY_STATUS_NEW;
+
         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "sticky: no hint provided");
         return NGX_OK;
@@ -200,6 +204,8 @@ ngx_http_upstream_sticky_select_peer(ngx_http_upstream_rr_peer_data_t *rrp,
             continue;
         }
 
+        us->sticky_status = NGX_HTTP_UPSTREAM_STICKY_STATUS_HIT;
+
         ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "sticky: found matching peer %ui", i);
 
@@ -236,6 +242,8 @@ ngx_http_upstream_sticky_select_peer(ngx_http_upstream_rr_peer_data_t *rrp,
         goto again;
     }
 
+    us->sticky_status = NGX_HTTP_UPSTREAM_STICKY_STATUS_MISS;
+
     ngx_log_debug0(NGX_LOG_DEBUG_HTTP, pc->log, 0, "sticky: no match");
 
     ngx_http_upstream_rr_peers_unlock(peers);

src/http/ngx_http_upstream.c

@@ -11,6 +11,12 @@
 #include <ngx_http.h>
 
 
+#if (NGX_HTTP_UPSTREAM_STICKY)
+static ngx_int_t ngx_http_upstream_sticky_status_variable(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
+#endif
+
+
 #if (NGX_HTTP_CACHE)
 static ngx_int_t ngx_http_upstream_cache(ngx_http_request_t *r,
     ngx_http_upstream_t *u);
@@ -445,6 +451,14 @@ static ngx_http_variable_t  ngx_http_upstream_vars[] = {
       ngx_http_upstream_cache_etag, 0,
       NGX_HTTP_VAR_NOCACHEABLE|NGX_HTTP_VAR_NOHASH, 0 },
 
+#endif
+
+#if (NGX_HTTP_UPSTREAM_STICKY)
+
+    { ngx_string("upstream_sticky_status"), NULL,
+      ngx_http_upstream_sticky_status_variable, 0,
+      NGX_HTTP_VAR_NOCACHEABLE, 0 },
+
 #endif
 
     { ngx_string("upstream_http_"), NULL, ngx_http_upstream_header_variable,
@@ -6103,6 +6117,84 @@ ngx_http_upstream_cache_etag(ngx_http_request_t *r,
 #endif
 
 
+#if (NGX_HTTP_UPSTREAM_STICKY)
+
+static ngx_str_t  ngx_http_upstream_sticky_status[4] = {
+    ngx_string(""),
+    ngx_string("new"),    /* NGX_HTTP_UPSTREAM_STICKY_STATUS_NEW */
+    ngx_string("hit"),    /* NGX_HTTP_UPSTREAM_STICKY_STATUS_HIT */
+    ngx_string("miss")    /* NGX_HTTP_UPSTREAM_STICKY_STATUS_MISS */
+};
+
+
+static ngx_int_t
+ngx_http_upstream_sticky_status_variable(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    u_char                     *p;
+    size_t                      len;
+    ngx_uint_t                  i;
+    ngx_http_upstream_state_t  *state;
+
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+
+    if (r->upstream_states == NULL || r->upstream_states->nelts == 0) {
+        v->not_found = 1;
+        return NGX_OK;
+    }
+
+    len = r->upstream_states->nelts * (sizeof("miss") - 1 + 2);
+
+    p = ngx_pnalloc(r->pool, len);
+    if (p == NULL) {
+        return NGX_ERROR;
+    }
+
+    v->data = p;
+
+    i = 0;
+    state = r->upstream_states->elts;
+
+    for ( ;; ) {
+        if (state[i].status) {
+            p = ngx_sprintf(p, "%V",
+                     &ngx_http_upstream_sticky_status[state[i].sticky_status]);
+
+        } else {
+            *p++ = '-';
+        }
+
+        if (++i == r->upstream_states->nelts) {
+            break;
+        }
+
+        if (state[i].peer) {
+            *p++ = ',';
+            *p++ = ' ';
+
+        } else {
+            *p++ = ' ';
+            *p++ = ':';
+            *p++ = ' ';
+
+            if (++i == r->upstream_states->nelts) {
+                break;
+            }
+
+            continue;
+        }
+    }
+
+    v->len = p - v->data;
+
+    return NGX_OK;
+}
+
+#endif
+
+
 static char *
 ngx_http_upstream(ngx_conf_t *cf, ngx_command_t *cmd, void *dummy)
 {

src/http/ngx_http_upstream.h

@@ -45,6 +45,11 @@
 
 #define NGX_HTTP_UPSTREAM_INVALID_HEADER     40
 
+/* zero indicates no sticky */
+#define NGX_HTTP_UPSTREAM_STICKY_STATUS_NEW  1
+#define NGX_HTTP_UPSTREAM_STICKY_STATUS_HIT  2
+#define NGX_HTTP_UPSTREAM_STICKY_STATUS_MISS 3
+
 
 #define NGX_HTTP_UPSTREAM_IGN_XA_REDIRECT    0x00000002
 #define NGX_HTTP_UPSTREAM_IGN_XA_EXPIRES     0x00000004
@@ -66,6 +71,9 @@ typedef struct {
     off_t                            response_length;
     off_t                            bytes_received;
     off_t                            bytes_sent;
+#if (NGX_HTTP_UPSTREAM_STICKY)
+    ngx_uint_t                       sticky_status;
+#endif
 
     ngx_str_t                       *peer;
 } ngx_http_upstream_state_t;