feature: implemented keepalive pooling in 'balancer_by_lua*'. (#38)

.travis.yml

@@ -81,7 +81,7 @@ install:
   - git clone https://github.com/openresty/rds-json-nginx-module.git ../rds-json-nginx-module
   - git clone https://github.com/openresty/srcache-nginx-module.git ../srcache-nginx-module
   - git clone https://github.com/openresty/redis2-nginx-module.git ../redis2-nginx-module
-  - git clone https://github.com/openresty/lua-resty-core.git ../lua-resty-core
+  - git clone -b keepalive https://github.com/openresty/lua-resty-core.git ../lua-resty-core
   - git clone https://github.com/openresty/lua-resty-lrucache.git ../lua-resty-lrucache
   - git clone https://github.com/openresty/lua-resty-mysql.git ../lua-resty-mysql
   - git clone https://github.com/openresty/lua-resty-string.git ../lua-resty-string

README.markdown

@@ -1132,6 +1132,7 @@ Directives
 * [log_by_lua_file](#log_by_lua_file)
 * [balancer_by_lua_block](#balancer_by_lua_block)
 * [balancer_by_lua_file](#balancer_by_lua_file)
+* [balancer_keepalive](#balancer_keepalive)
 * [lua_need_request_body](#lua_need_request_body)
 * [ssl_certificate_by_lua_block](#ssl_certificate_by_lua_block)
 * [ssl_certificate_by_lua_file](#ssl_certificate_by_lua_file)
@@ -2597,6 +2598,29 @@ This directive was first introduced in the `v0.10.0` release.
 
 [Back to TOC](#directives)
 
+balancer_keepalive
+------------------
+
+**syntax:** *balancer_keepalive <total-connections>*
+
+**context:** *upstream*
+
+**phase:** *loading-config*
+
+The `total-connections` parameter sets the maximum number of idle
+keepalive connections to upstream servers that are preserved in the cache of
+each worker process. When this number is exceeded, the least recently used
+connections are closed.
+
+It should be particularly noted that the keepalive directive does not limit the
+total number of connections to upstream servers that an nginx worker process
+can open. The connections parameter should be set to a number small enough to
+let upstream servers process new incoming connections as well.
+
+This directive was first introduced in the `v0.10.21` release.
+
+[Back to TOC](#directives)
+
 lua_need_request_body
 ---------------------
 

doc/HttpLuaModule.wiki

@@ -2186,6 +2186,26 @@ When a relative path like <code>foo/bar.lua</code> is given, they will be turned
 
 This directive was first introduced in the <code>v0.10.0</code> release.
 
+== balancer_keepalive ==
+
+'''syntax:''' ''balancer_keepalive <total-connections>''
+
+'''context:''' ''upstream''
+
+'''phase:''' ''loading-config''
+
+The <code>total-connections</code> parameter sets the maximum number of idle
+keepalive connections to upstream servers that are preserved in the cache of
+each worker process. When this number is exceeded, the least recently used
+connections are closed.
+
+It should be particularly noted that the keepalive directive does not limit the
+total number of connections to upstream servers that an nginx worker process
+can open. The connections parameter should be set to a number small enough to
+let upstream servers process new incoming connections as well.
+
+This directive was first introduced in the <code>v0.10.21</code> release.
+
 == lua_need_request_body ==
 
 '''syntax:''' ''lua_need_request_body <on|off>''