# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1597074787 -10800
# Node ID 5440ff4ac6fc4a177d1f6365fccde27e08dfe4dc
# Parent  b9071b8751942e6b07674b6905eb64d148172834
Core: reusing connections in advance.

Reworked connections reuse, so closing connections is attempted in
advance, as long as number of free connections is less than 1/16 of
worker connections configured.  This ensures that new connections can
be handled even if closing a reusable connection requires some time,
for example, for a lingering close (ticket #2017).

The 1/16 ratio is selected to be smaller than 1/8 used for disabling
accept when working with accept mutex, so nginx will try to balance
new connections to different workers first, and will start reusing
connections only if this won't help.

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -1107,12 +1107,9 @@ ngx_get_connection(ngx_socket_t s, ngx_l
         return NULL;
     }
 
-    c = ngx_cycle->free_connections;
+    ngx_drain_connections((ngx_cycle_t *) ngx_cycle);
 
-    if (c == NULL) {
-        ngx_drain_connections((ngx_cycle_t *) ngx_cycle);
-        c = ngx_cycle->free_connections;
-    }
+    c = ngx_cycle->free_connections;
 
     if (c == NULL) {
         ngx_log_error(NGX_LOG_ALERT, log, 0,
@@ -1298,7 +1295,9 @@ ngx_drain_connections(ngx_cycle_t *cycle
     ngx_queue_t       *q;
     ngx_connection_t  *c;
 
-    if (cycle->reusable_connections_n == 0) {
+    if (cycle->free_connection_n > cycle->connection_n / 16
+        || cycle->reusable_connections_n == 0)
+    {
         return;
     }