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.

2 files changed, 21 insertions, 0 deletions

diff --git a/src/core/ngx_connection.c b/src/core/ngx_connection.c
index 00c5a08e6..9f2675b88 100644
--- a/src/core/ngx_connection.c
+++ b/src/core/ngx_connection.c
@@ -1163,6 +1163,26 @@ ngx_drain_connections(void)
 }
 
 
+void
+ngx_close_idle_connections(ngx_cycle_t *cycle)
+{
+    ngx_uint_t         i;
+    ngx_connection_t  *c;
+
+    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_int_t
 ngx_connection_local_sockaddr(ngx_connection_t *c, ngx_str_t *s,
     ngx_uint_t port)
diff --git a/src/core/ngx_connection.h b/src/core/ngx_connection.h
index a49aa9579..c3aca7f47 100644
--- a/src/core/ngx_connection.h
+++ b/src/core/ngx_connection.h
@@ -215,6 +215,7 @@ ngx_int_t ngx_open_listening_sockets(ngx_cycle_t *cycle);
 void ngx_configure_listening_sockets(ngx_cycle_t *cycle);
 void ngx_close_listening_sockets(ngx_cycle_t *cycle);
 void ngx_close_connection(ngx_connection_t *c);
+void ngx_close_idle_connections(ngx_cycle_t *cycle);
 ngx_int_t ngx_connection_local_sockaddr(ngx_connection_t *c, ngx_str_t *s,
     ngx_uint_t port);
 ngx_int_t ngx_connection_error(ngx_connection_t *c, ngx_err_t err, char *text);