ren readme

Author: altairbow

README_CN.md

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+# django-db-connection-pool
+
+驱动 Django MySQL、Oracle、PostgreSQL连接池的轮子, 基于 SQLAlchemy 队列池
+* [English version](https://github.com/altairbow/django-db-connection-pool/blob/master/README.md)
+
+#### 快速开始
+1. 使用 `pip` 安装所有所支持的数据库组件:
+    ```bash
+    $ pip install django-db-connection-pool[all]
+    ```
+    或者是选择性安装数据库组件:
+    ```bash
+    $ pip install django-db-connection-pool[mysql,oracle,postgresql]
+    ```
+
+2. 更新 DATABASES 的 配置
+    * ##### MySQL  
+        将 ENGINE `django.db.backends.mysql` 更改为 `dj_db_conn_pool.backends.mysql`:
+        ```
+        DATABASES = {
+            'default': {
+                ...
+                'ENGINE': 'dj_db_conn_pool.backends.mysql'
+                ...
+            }
+        }
+        ```
+    
+    * ##### Oracle  
+        将 ENGINE `django.db.backends.oracle` 更改为 `dj_db_conn_pool.backends.oracle`:
+        ```
+        DATABASES = {
+            'default': {
+                ...
+                'ENGINE': 'dj_db_conn_pool.backends.oracle'
+                ...
+            }
+        }
+        ```
+    * ##### PostgreSQL  
+        将 ENGINE `django.db.backends.postgresql` 更改为 `dj_db_conn_pool.backends.postgresql`:
+        ```
+        DATABASES = {
+            'default': {
+                ...
+                'ENGINE': 'dj_db_conn_pool.backends.postgresql'
+                ...
+            }
+        }
+        ```
+    * ##### 连接池配置（可选）
+        目前连接池限制用户传入的连接池配置为：POOL_SIZE（连接池容量）、MAX_OVERFLOW（连接池容量上下浮动最大值）
+        这两个参数包含在 `POOL_OPTIONS` 内，例如下面的配置，default 的连接池常规容量为10个连接，最大浮动10个，
+        即为：在 default 连接池创建后，随着程序对连接池的请求，连接池内连接将逐步增加到10个，如果在连接池内连接
+        全部用光后，程序又请求了第11个连接，此时的连接池容量将短暂超过 POOL_SIZE，但最大不超过 POOL_SIZE + MAX_OVERFLOW，
+        如果程序请求 default 数据库的连接数量超过 POOL_SIZE + MAX_OVERFLOW，那连接池将一直等待直到程序释放连接。
+        ```
+        DATABASES = {
+            'default': {
+                ...
+                'POOL_OPTIONS' : {
+                    'POOL_SIZE': 10,
+                    'MAX_OVERFLOW': 10
+                }
+                ...
+             }
+         }
+        ```
+        
+        附这两个参数的解释：(摘录于 SQLAlchemy 的文档):
+        
+        * **pool_size**: The size of the pool to be maintained,
+                  defaults to 5. This is the largest number of connections that
+                  will be kept persistently in the pool. Note that the pool
+                  begins with no connections; once this number of connections
+                  is requested, that number of connections will remain.
+                  `pool_size` can be set to 0 to indicate no size limit; to
+                  disable pooling, use a :class:`~sqlalchemy.pool.NullPool`
+                  instead.
+        
+        * **max_overflow**: The maximum overflow size of the
+                  pool. When the number of checked-out connections reaches the
+                  size set in pool_size, additional connections will be
+                  returned up to this limit. When those additional connections
+                  are returned to the pool, they are disconnected and
+                  discarded. It follows then that the total number of
+                  simultaneous connections the pool will allow is pool_size +
+                  `max_overflow`, and the total number of "sleeping"
+                  connections the pool will allow is pool_size. `max_overflow`
+                  can be set to -1 to indicate no overflow limit; no limit
+                  will be placed on the total number of concurrent
+                  connections. Defaults to 10.