Add keepalive option to upstreams configuration

defaults/main.yml

@@ -59,6 +59,7 @@ nginx_vhosts: []
 nginx_upstreams: []
 # - name: myapp1
 #   strategy: "ip_hash" # "least_conn", etc.
+#   keepalive: 16 # optional
 #   servers: {
 #     "srv1.example.com",
 #     "srv2.example.com weight=3",

templates/nginx.conf.j2

@@ -53,6 +53,9 @@ http {
 {% for server in upstream.servers %}
         server {{ server }};
 {% endfor %}
+{% if upstream.keepalive is defined %}
+        keepalive {{ upstream.keepalive }};
+{% endif %}
     }
 {% endfor %}