Core: idle connections now closed only once on exiting.

Iterating through all connections takes a lot of CPU time, especially
with large number of worker connections configured.  As a result
nginx processes used to consume CPU time during graceful shutdown.
To mitigate this we now only do a full scan for idle connections when
shutdown signal is received.

Transitions of connections to idle ones are now expected to be
avoided if the ngx_exiting flag is set.  The upstream keepalive module
was modified to follow this.

1 files changed, 2 insertions, 17 deletions

diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index c69932ecd..5da09116f 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -728,9 +728,6 @@ ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
 {
     ngx_int_t worker = (intptr_t) data;
 
-    ngx_uint_t         i;
-    ngx_connection_t  *c;
-
     ngx_process = NGX_PROCESS_WORKER;
     ngx_worker = worker;
 
@@ -741,19 +738,6 @@ ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
     for ( ;; ) {
 
         if (ngx_exiting) {
-
-            c = cycle->connections;
-
-            for (i = 0; i < cycle->connection_n; i++) {
-
-                /* THREAD: lock */
-
-                if (c[i].fd != -1 && c[i].idle) {
-                    c[i].close = 1;
-                    c[i].read->handler(c[i].read);
-                }
-            }
-
             ngx_event_cancel_timers();
 
             if (ngx_event_timer_rbtree.root == ngx_event_timer_rbtree.sentinel)
@@ -781,8 +765,9 @@ ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
             ngx_setproctitle("worker process is shutting down");
 
             if (!ngx_exiting) {
-                ngx_close_listening_sockets(cycle);
                 ngx_exiting = 1;
+                ngx_close_listening_sockets(cycle);
+                ngx_close_idle_connections(cycle);
             }
         }