Status: introduced the "ngx_stat_waiting" counter.

And corresponding variable $connections_waiting was added.

Previously, waiting connections were counted as the difference between
active connections and the sum of reading and writing connections.
That made it impossible to count more than one request in one connection
as reading or writing (as is the case for SPDY).

Also, we no longer count connections in handshake state as waiting.

src/core/ngx_connection.c

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 09ad15f..60f4d51 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -970,6 +970,10 @@
 
     if (c->reusable) {
         ngx_queue_remove(&c->queue);
+
+#if (NGX_STAT_STUB)
+        (void) ngx_atomic_fetch_add(ngx_stat_waiting, -1);
+#endif
     }
 
     c->reusable = reusable;
@@ -979,6 +983,10 @@
 
         ngx_queue_insert_head(
             (ngx_queue_t *) &ngx_cycle->reusable_connections_queue, &c->queue);
+
+#if (NGX_STAT_STUB)
+        (void) ngx_atomic_fetch_add(ngx_stat_waiting, 1);
+#endif
     }
 }
 

src/event/ngx_event.c

diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c
index cbae0ee..b7205f4 100644
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -73,6 +73,8 @@
 ngx_atomic_t  *ngx_stat_reading = &ngx_stat_reading0;
 ngx_atomic_t   ngx_stat_writing0;
 ngx_atomic_t  *ngx_stat_writing = &ngx_stat_writing0;
+ngx_atomic_t   ngx_stat_waiting0;
+ngx_atomic_t  *ngx_stat_waiting = &ngx_stat_waiting0;
 
 #endif
 
@@ -511,7 +513,8 @@
            + cl          /* ngx_stat_requests */
            + cl          /* ngx_stat_active */
            + cl          /* ngx_stat_reading */
-           + cl;         /* ngx_stat_writing */
+           + cl          /* ngx_stat_writing */
+           + cl;         /* ngx_stat_waiting */
 
 #endif
 
@@ -558,6 +561,7 @@
     ngx_stat_active = (ngx_atomic_t *) (shared + 6 * cl);
     ngx_stat_reading = (ngx_atomic_t *) (shared + 7 * cl);
     ngx_stat_writing = (ngx_atomic_t *) (shared + 8 * cl);
+    ngx_stat_waiting = (ngx_atomic_t *) (shared + 9 * cl);
 
 #endif
 

src/event/ngx_event.h

diff --git a/src/event/ngx_event.h b/src/event/ngx_event.h
index 2096da2..93c457c 100644
--- a/src/event/ngx_event.h
+++ b/src/event/ngx_event.h
@@ -511,6 +511,7 @@
 extern ngx_atomic_t  *ngx_stat_active;
 extern ngx_atomic_t  *ngx_stat_reading;
 extern ngx_atomic_t  *ngx_stat_writing;
+extern ngx_atomic_t  *ngx_stat_waiting;
 
 #endif
 

src/http/modules/ngx_http_stub_status_module.c

diff --git a/src/http/modules/ngx_http_stub_status_module.c b/src/http/modules/ngx_http_stub_status_module.c
index e2ac949..83a35cd 100644
--- a/src/http/modules/ngx_http_stub_status_module.c
+++ b/src/http/modules/ngx_http_stub_status_module.c
@@ -73,6 +73,9 @@
     { ngx_string("connections_writing"), NULL, ngx_http_stub_status_variable,
       2, NGX_HTTP_VAR_NOCACHEABLE, 0 },
 
+    { ngx_string("connections_waiting"), NULL, ngx_http_stub_status_variable,
+      3, NGX_HTTP_VAR_NOCACHEABLE, 0 },
+
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
 };
 
@@ -83,7 +86,7 @@
     ngx_int_t          rc;
     ngx_buf_t         *b;
     ngx_chain_t        out;
-    ngx_atomic_int_t   ap, hn, ac, rq, rd, wr;
+    ngx_atomic_int_t   ap, hn, ac, rq, rd, wr, wa;
 
     if (r->method != NGX_HTTP_GET && r->method != NGX_HTTP_HEAD) {
         return NGX_HTTP_NOT_ALLOWED;
@@ -126,6 +129,7 @@
     rq = *ngx_stat_requests;
     rd = *ngx_stat_reading;
     wr = *ngx_stat_writing;
+    wa = *ngx_stat_waiting;
 
     b->last = ngx_sprintf(b->last, "Active connections: %uA \n", ac);
 
@@ -135,7 +139,7 @@
     b->last = ngx_sprintf(b->last, " %uA %uA %uA \n", ap, hn, rq);
 
     b->last = ngx_sprintf(b->last, "Reading: %uA Writing: %uA Waiting: %uA \n",
-                          rd, wr, ac - (rd + wr));
+                          rd, wr, wa);
 
     r->headers_out.status = NGX_HTTP_OK;
     r->headers_out.content_length_n = b->last - b->pos;
@@ -177,6 +181,10 @@
         value = *ngx_stat_writing;
         break;
 
+    case 3:
+        value = *ngx_stat_waiting;
+        break;
+
     /* suppress warning */
     default:
         value = 0;