The "reuseport" option of the "listen" directive.

When configured, an individual listen socket on a given address is
created for each worker process.  This allows to reduce in-kernel lock
contention on configurations with high accept rates, resulting in better
performance.  As of now it works on Linux and DragonFly BSD.

Note that on Linux incoming connection requests are currently tied up
to a specific listen socket, and if some sockets are closed, connection
requests will be reset, see https://lwn.net/Articles/542629/.  With
nginx, this may happen if the number of worker processes is reduced.
There is no such problem on DragonFly BSD.

Based on previous work by Sepherosa Ziehau and Yingqi Lu.

3 files changed, 19 insertions, 0 deletions

diff --git a/src/stream/ngx_stream.c b/src/stream/ngx_stream.c
index 18aea28af..1c5e7a87c 100644
--- a/src/stream/ngx_stream.c
+++ b/src/stream/ngx_stream.c
@@ -410,6 +410,10 @@ ngx_stream_optimize_servers(ngx_conf_t *cf, ngx_array_t *ports)
                 break;
             }
 
+            if (ngx_clone_listening(cf, ls) != NGX_OK) {
+                return NGX_CONF_ERROR;
+            }
+
             addr++;
             last--;
         }
diff --git a/src/stream/ngx_stream.h b/src/stream/ngx_stream.h
index 83a43a41f..a10f68fff 100644
--- a/src/stream/ngx_stream.h
+++ b/src/stream/ngx_stream.h
@@ -45,6 +45,9 @@ typedef struct {
 #if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
     unsigned                ipv6only:1;
 #endif
+#if (NGX_HAVE_REUSEPORT)
+    unsigned                reuseport:1;
+#endif
     unsigned                so_keepalive:2;
 #if (NGX_HAVE_KEEPALIVE_TUNABLE)
     int                     tcp_keepidle;
diff --git a/src/stream/ngx_stream_core_module.c b/src/stream/ngx_stream_core_module.c
index c0df412a5..c8d8e66bc 100644
--- a/src/stream/ngx_stream_core_module.c
+++ b/src/stream/ngx_stream_core_module.c
@@ -384,6 +384,18 @@ ngx_stream_core_listen(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 #endif
         }
 
+        if (ngx_strcmp(value[i].data, "reuseport") == 0) {
+#if (NGX_HAVE_REUSEPORT)
+            ls->reuseport = 1;
+            ls->bind = 1;
+#else
+            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                               "reuseport is not supported "
+                               "on this platform, ignored");
+#endif
+            continue;
+        }
+
         if (ngx_strcmp(value[i].data, "ssl") == 0) {
 #if (NGX_STREAM_SSL)
             ls->ssl = 1;