Merge pull request envoyproxy#108 from helight/zh_intro-arch_overview…

…-http-http_filters

Zh intro arch overview http http filters

docs/root/intro/arch_overview/http/http_filters.rst

@@ -1,50 +1,39 @@
 .. _arch_overview_http_filters:
 
-HTTP filters
+HTTP 过滤器
 ============
 
-Much like the :ref:`network level filter <arch_overview_network_filters>` stack, Envoy supports an
-HTTP level filter stack within the connection manager. Filters can be written that operate on HTTP
-level messages without knowledge of the underlying physical protocol (HTTP/1.1, HTTP/2, etc.) or
-multiplexing capabilities. There are three types of HTTP level filters:
-
-* **Decoder**: Decoder filters are invoked when the connection manager is decoding parts of the
-  request stream (headers, body, and trailers).
-* **Encoder**: Encoder filters are invoked when the connection manager is about to encode parts of
-  the response stream (headers, body, and trailers).
-* **Decoder/Encoder**: Decoder/Encoder filters are invoked both when the connection manager is
-  decoding parts of the request stream and when the connection manager is about to encode parts of
-  the response stream.
-
-The API for HTTP level filters allows the filters to operate without knowledge of the underlying
-protocol. Like network level filters, HTTP filters can stop and continue iteration to subsequent
-filters. This allows for more complex scenarios such as health check handling, calling a rate
-limiting service, buffering, routing, generating statistics for application traffic such as
-DynamoDB, etc. HTTP level filters can also share state (static and dynamic) among
-themselves within the context of a single request stream. Refer to :ref:`data sharing
-between filters <arch_overview_data_sharing_between_filters>` for more details. Envoy already
-includes several HTTP level filters that are documented in this architecture overview as well as
-the :ref:`configuration reference <config_http_filters>`.
+和 :ref:`网络层的过滤器 <arch_overview_network_filters>` 很像，Envoy 支持了链接管理中的 HTTP 层过滤器。
+可以开发过滤器处理 HTTP 层的消息，而不用知道底层的物理协议（比如，HTTP/1.1、HTTP/2）或者多路复用功能。HTTP 层
+的过滤器有 3 种类型：
+
+* **解码器**: 解码过滤器用于链接管理器解码部分请求流（分请头，正文和 trailer 信息）。
+* **编码器**: 编码过滤器用于链接管理器编码部响应求流（响应头，正文和 trailer 信息）。
+* **解码器/编码器**: 解码/编码过滤器同时用于链接管理器解码部分请求流和编码部分相应流。
+
+HTTP 层过滤器的 API 可以让过滤器处理消息而不用知道底层协议。像网络层过滤器一样，HTTP 过滤器能停止和继续
+处理后续的过滤器。这样可以处理更复杂的场景，比如处理健康检查，调用一个限流服务，缓存，路由，给像 DynamoDB 这样的应用
+收集流量统计信息等。HTTP 层的过滤器也能在单个请求流的上下文中共享状态（静态和动态）。参考这里可以了解更多：
+:ref:`过滤器间的数据共享 <arch_overview_data_sharing_between_filters>`。Envoy 已经有了几个 HTTP 层的过滤器，
+这些过滤器也记录在了架构概述中 :ref:`配置参考 <config_http_filters>` 。
+
 
 .. _arch_overview_http_filters_ordering:
 
-Filter ordering
+过滤器顺序
 ---------------
 
-Filter ordering in the :ref:`http_filters field <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.http_filters>`
-matters. If filters are configured in the following order (and assuming all three filters are
-decoder/encoder filters):
+过滤器顺序在 :ref:`http_filters 字段 <envoy_v3_api_field_extensions.filters.network.http_connection_manager.v3.HttpConnectionManager.http_filters>`
+中很重要。如果按照如下顺序配置过滤器（假设这 3 个过滤器都是 解码/编码过滤器）：
 
 .. code-block:: yaml
 
   http_filters:
     - A
     - B
-    # The last configured filter has to be a terminal filter, as determined by the
-    # NamedHttpFilterConfigFactory::isTerminalFilter() function. This is most likely the router
-    # filter.
+    # 配置在最后的过滤器必须是一个终结过滤器，由 NamedHttpFilterConfigFactory::isTerminalFilter() 函数决定。
+    # 这个过滤器很可能是路由过滤器。
     - C
 
-The connection manager will invoke decoder filters in the order: ``A``, ``B``, ``C``.
-On the other hand, the connection manager will invoke encoder filters in the **reverse**
-order: ``C``, ``B``, ``A``.
+链接管理器将会按照这样的顺序来调用 decoder filter：``A``、``B``、``C``。
+另一方面，链接管理器将会以**相反**的顺序调用 encoder filter：``C``，``B``，``A``。