# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1296822810 -10800
# Node ID a4beaef2fb086c34dc6fbbeb37b8415c37318d67
# Parent f02ddde4a240628b002b3fc85aa19bb38e7c5d85
Reuse keepalive connections if worker connections aren't enough.

This allows to set keepalive_timeout high enough, and don't care if you
have enough worker_connections to handle load spikes (either natural, or
caused by CARP failover or something like). LRU queue will effectively
lower keepalive timeout if there are not enough worker connections.

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
@@ -12,6 +12,9 @@
ngx_os_io_t ngx_io;


+static void ngx_drain_connections(void);
+
+
ngx_listening_t *
ngx_create_listening(ngx_conf_t *cf, void *sockaddr, socklen_t socklen)
{
@@ -719,6 +722,11 @@ ngx_get_connection(ngx_socket_t s, ngx_l
c = ngx_cycle->free_connections;

if (c == NULL) {
+ ngx_drain_connections();
+ c = ngx_cycle->free_connections;
+ }
+
+ if (c == NULL) {
ngx_log_error(NGX_LOG_ALERT, log, 0,
"%ui worker_connections are not enough",
ngx_cycle->connection_n);
@@ -861,6 +869,8 @@ ngx_close_connection(ngx_connection_t *c

#endif

+ ngx_reusable_connection(c, 0);
+
log_error = c->log_error;

ngx_free_connection(c);
@@ -900,6 +910,51 @@ ngx_close_connection(ngx_connection_t *c
}


+void
+ngx_reusable_connection(ngx_connection_t *c, ngx_uint_t reusable)
+{
+ ngx_log_debug1(NGX_LOG_DEBUG_CORE, c->log, 0,
+ "reusable connection: %ui", reusable);
+
+ if (c->reusable) {
+ ngx_queue_remove(&c->queue);
+ }
+
+ c->reusable = reusable;
+
+ if (reusable) {
+ /* need cast as ngx_cycle is volatile */
+
+ ngx_queue_insert_head(
+ (ngx_queue_t *) &ngx_cycle->reusable_connections_queue, &c->queue);
+ }
+}
+
+
+static void
+ngx_drain_connections(void)
+{
+ ngx_int_t i;
+ ngx_queue_t *q;
+ ngx_connection_t *c;
+
+ for (i = 0; i < 32; i++) {
+ if (ngx_queue_empty(&ngx_cycle->reusable_connections_queue)) {
+ break;
+ }
+
+ q = ngx_queue_last(&ngx_cycle->reusable_connections_queue);
+ c = ngx_queue_data(q, ngx_connection_t, queue);
+
+ ngx_log_debug0(NGX_LOG_DEBUG_CORE, c->log, 0,
+ "reusing connection");
+
+ c->close = 1;
+ c->read->handler(c->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
--- a/src/core/ngx_connection.h
+++ b/src/core/ngx_connection.h
@@ -135,6 +135,8 @@ struct ngx_connection_s {

ngx_buf_t *buffer;

+ ngx_queue_t queue;
+
ngx_atomic_uint_t number;

ngx_uint_t requests;
@@ -150,6 +152,7 @@ struct ngx_connection_s {
unsigned destroyed:1;

unsigned idle:1;
+ unsigned reusable:1;
unsigned close:1;

unsigned sendfile:1;
@@ -186,5 +189,6 @@ ngx_int_t ngx_connection_error(ngx_conne
ngx_connection_t *ngx_get_connection(ngx_socket_t s, ngx_log_t *log);
void ngx_free_connection(ngx_connection_t *c);

+void ngx_reusable_connection(ngx_connection_t *c, ngx_uint_t reusable);

#endif /* _NGX_CONNECTION_H_INCLUDED_ */
diff --git a/src/core/ngx_cycle.c b/src/core/ngx_cycle.c
--- a/src/core/ngx_cycle.c
+++ b/src/core/ngx_cycle.c
@@ -181,6 +181,9 @@ ngx_init_cycle(ngx_cycle_t *old_cycle)
cycle->listening.pool = pool;


+ ngx_queue_init(&cycle->reusable_connections_queue);
+
+
cycle->conf_ctx = ngx_pcalloc(pool, ngx_max_module * sizeof(void *));
if (cycle->conf_ctx == NULL) {
ngx_destroy_pool(pool);
diff --git a/src/core/ngx_cycle.h b/src/core/ngx_cycle.h
--- a/src/core/ngx_cycle.h
+++ b/src/core/ngx_cycle.h
@@ -44,6 +44,8 @@ struct ngx_cycle_s {
ngx_connection_t *free_connections;
ngx_uint_t free_connection_n;

+ ngx_queue_t reusable_connections_queue;
+
ngx_array_t listening;
ngx_array_t pathes;
ngx_list_t open_files;
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -2589,6 +2589,7 @@ ngx_http_set_keepalive(ngx_http_request_
#endif

c->idle = 1;
+ ngx_reusable_connection(c, 1);

if (rev->ready) {
ngx_post_event(rev, &ngx_posted_events);
@@ -2698,6 +2699,7 @@ ngx_http_keepalive_handler(ngx_event_t *
c->log->action = "reading client request line";

c->idle = 0;
+ ngx_reusable_connection(c, 0);

ngx_http_init_request(rev);
}

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