Apache Avro 与 Thrift 比较

╰半夏微凉° 2022-06-18 06:08 235阅读 0赞

Avro和Thrift都是跨语言，基于二进制的高性能的通讯中间件. 它们都提供了数据序列化的功能和RPC服务. 总体功能上类似，但是哲学不一样. Thrift出自Facebook用于后台各个服务间的通讯,Thrift的设计强调统一的编程接口的多语言通讯框架. Avro出自Hadoop之父Doug Cutting, 在Thrift已经相当流行的情况下Avro的推出，其目标不仅是提供一套类似Thrift的通讯中间件更是要建立一个新的，标准性的云计算的数据交换和存储的Protocol。 这个和Thrift的理念不同，Thrift认为没有一个完美的方案可以解决所有问题，因此尽量保持一个Neutral框架，插入不同的实现并互相交互。而Avro偏向实用，排斥多种方案带来的 可能的混乱，主张建立一个统一的标准，并不介意采用特定的优化。Avro的创新之处在于融合了显式,declarative的Schema和高效二进制的数据表达，强调数据的自我描述，克服了以往单纯XML或二进制系统的缺陷。Avro对Schema动态加载功能，是Thrift编程接口所不具备的，符合了Hadoop上的Hive/Pig及NOSQL 等既属于ad hoc，又追求性能的应用需求.

## 语言绑定 ##

目前阶段Thrift比Avro支持的语言更丰富.

Thrift:  C++, C\#, Cocoa, Erlang, Haskell, Java, Ocami, Perl, PHP, Python, Ruby, Smalltalk.

Avro:   C, C++, Java, Python, Ruby, PHP.

## 数据类型 ##

从常见的数据类型的角度来说， Avro和Thrift非常接近，功能上并没有什么区别。

<table style=""> 
 <tbody style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> <strong></strong></td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> <strong>Avro</strong></td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> <strong>Thrift</strong></td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> <strong></strong></td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 基本类型</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal">  <p style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> </p> <p style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> true&nbsp;or&nbsp;false</p> </td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> N/A</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 8-bit signed integer</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> N/A</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> I16</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 16-bit signed integer</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> int</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> I32</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 32-bit signed integer</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> long</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> I64</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 64-bit signed integer</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> float</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> N/A</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 32-bit floating point</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> double</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> double</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 64-bit floating point</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> bytes</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> binary</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> Byte sequence</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> string</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> string</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> Character sequence</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 复杂类型</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> record</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> struct</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 用户自定义类型</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> enum</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> enum</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> array&lt;T&gt;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> list&lt;T&gt;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> N/A</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> set&lt;T&gt;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> map&lt;string,T&gt;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> map&lt;T1,T2&gt;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> Avro map的key <p style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> </p> <p style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 必须是string</p> </td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> union</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> union</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> fixed</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> N/A</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 固定大小的byte array <p style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> </p> <pre style="margin-top:0px; margin-right:0px; margin-bottom:1em; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent; white-space:pre-line; word-wrap:break-word; font-family:monospace,sans-serif">e.g. md5(16);</pre> </td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> RPC服务</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> protocol</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> service</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> RPC服务类型</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> error</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> exception</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> RPC异常类型</td> 
  </tr> 
  <tr style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0px; padding-right:0px; padding-bottom:0px; padding-left:0px; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:baseline; background-color:transparent"> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> &nbsp;</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> namespace</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> namespace</td> 
   <td style="margin-top:0px; margin-right:0px; margin-bottom:0px; margin-left:0px; padding-top:0.5em; padding-right:0.5em; padding-bottom:0.5em; padding-left:0.5em; border-top-width:0px; border-right-width:0px; border-bottom-width:0px; border-left-width:0px; border-style:initial; border-color:initial; outline-width:0px; outline-style:initial; outline-color:initial; font-size:14px; vertical-align:top; background-color:transparent; font-weight:normal"> 域名</td> 
  </tr> 
 </tbody> 
</table>

## 开发流程 ##

从开发者角度来说，Avro和Thrift也相当类似，

1)       同一个服务分别用Avro和Thrift来描述

Avro.idl:

protocol SimpleService \{

record Message \{

string topic;

bytes content;

long    createdTime;

string id;

string ipAddress;

map<string> props;

int publish(string context,array<Message> messages);

Thrift.idl:

struct Message \{

1: string topic

2: binary content

3: i64    createdTime

4: string id

5: string ipAddress

6: map<string,string> props

service SimpleService \{

i32 publish(1:string context,2:list<Message> messages);

2)       Avro和Thrift都支持IDL代码生成功能

java idl avro.idl idl.avro

java org.apache.avro.specific.SpecificCompiler idl.avro avro-gen

目标目录生成Message.java和SimpleService.java

thrift -gen java thrift.idl

同样的,目标目录生成Message.java和SimpleService.java

3)       客户端代码

Avro client :

URL url = new URL ( “http”, HOST, PORT, “/”);

Transceiver trans = new HttpTransceiver(url);

SimpleService proxy=

= (SimpleService)SpecificRequestor.getClient(SimpleService.class, transceiver);

…

Thrift client :

TTransport transport = new TFramedTransport(new TSocket(HOST,PORT));

TProtocol protocol = new TCompactProtocol(transport);

transport.open();

SimpleService.Client client = new SimpleService.Client(protocol);

…

4)       服务器端 Avro和Thrift都生成接口需要实现：

Avro server:

public static class ServiceImpl implements SimpleService \{

Responder responder = new SpecificResponder(SimpleService.class, new ServiceImpl());

Server server = new HttpServer(responder, PORT);

Thrift server:

public static class ServerImpl implements SimpleService.Iface \{

TServerTransport serverTransport=new TServerSocket(PORT);

TServer server=new TSimpleServer(processor,serverTransport,new TFramedTransport.Factory(), new TCompactProtocol.Factory());

server.serve();

## Schema处理 ##

Avro和Thrift处理Schema方法截然不同。

Thrift是一个面向编程的系统, 完全依赖于IDL->Binding Language的代码生成。 Schema也“隐藏”在生成的代码中了，完全静态。为了让系统识别处理一个新的数据源，必须走编辑IDL，代码生成，编译载入的流程。

[![a1.jpg][]][a1.jpg]

与此对照，虽然Avro也支持基于IDL的Schema描述,但Avro内部Schema还是显式的,存在于JSON格式的文件当中，Avro可以把IDL格式的Schema转化成JSON格式的。

Avro支持2种方式。Avro-specific方式和Thrift的方式相似，依赖代码生成产生特定的类，并内嵌JSON Schema.　Avro-generic方式支持Schema的动态加载，用通用的结构(map)代表数据对象，不需要编译加载直接就可以处理新的数据源。

[![a2.jpg][]][a2.jpg]

## Serialization ##

对于序列化Avro制定了一个协议，而Thrift的设计目标是一个框架，它没有强制规定序列化的格式。

Avro规定一个标准的序列化的格式，即无论是文件存储还是网络传输，数据的Schema(in JASON)都出现在数据的前面。数据本身并不包含任何Metadata(Tag). 在文件储存的时候，schema出现在文件头中。在网络传输的时候Schema出现在初始的握手阶段.这样的好处一是使数据self describe,提高了数据的透明度和可操作性，二是减少了数据本身的信息量提高存储效率，可谓一举二得了

[![a3.jpg][]][a3.jpg]

Avro的这种协议提供了很多优化的机会:

*  对数据作Projection，通过扫描schema只对感兴趣的部分作反序列化。

*  支持schema的versioning和mapping ,不同的版本的Reader和Writer可以通过查询schema相互交换数据(schema的aliases支持mapping),这比thrift采用的给每个域编号的方法优越多了

Avro的Schema允许定义数据的排序Order并在序列化的时候遵循这个顺序。这样话不需要反序列化就可以直接对数据进行排序,在Hadoop里很管用.

另外一个Avro的特性是采用block链表结构，突破了用单一整型表示大小的限制。比如Array或Map由一系列Block组成，每个Block包含计数器和对应的元素，计数器为0标识结束。

[![a4.jpg][]][a4.jpg]

Thrift提供了多种序列化的实现：

TCompactProtocol: 最高效的二进制序列化协议，但并不是所有的绑定语言都支持。

TBinaryProtocol: 缺省简单二进制序列化协议.

与Avro不同，Thrift的数据存储的时候是每个Field前面都是带Tag的，这个Tag用于标识这个域的类型和顺序ID（IDL中定义，用于Versioning）。在同一批数据里面，这些Tag的信息是完全相同的，当数据条数大的时候这显然就浪费了。

[![a51.jpg][]][a51.jpg]

## RPC服务 ##

Avro提供了

HttpServer : 缺省,基于Jetty内核的服务.

NettyServer: 新的基于Netty的服务.

Thrift提供了：

TThreadPolServer: 多线程服务

TNonBlockingServer: 单线程 non blocking的服务

THsHaServer: 多线程 non blocking的服务

## Benchmarking ##

测试环境：2台4核 Intel  Xeon 2.66GHz， 8G memory, Linux, 分别做客户端，服务器。

Object definition:

record Message \{

string topic;

bytes payload;

long createdTime;

string id;

string ipAddress;

map<string,string > props;

Actual instance:

msg.createdTime : System.nanoTime();

msg.ipAddress : “127.0.0.1″;

msg.topic : “pv”;

msg.payload : byte\[100\]

msg.id : UUID.randomUUID().toString();

msg.props : **new** HashMap<String,String>();

msg.props.put(“author”, “tjerry”);

msg.props.put(“date”, **new** Date().toString());

msg.props.put(“status”, “new”);

Serialization size

[![a6.jpg][]][a6.jpg]

Avro的序列化产生的结果最小

Serialization speed

[![a7.jpg][]][a7.jpg]

Thrift-binary因为序列化方式简单反而看上去速度最快.

Deserialization speed

[![a8.jpg][]][a8.jpg]

这里 Thrift的速度很快， 因与它内部实现采用zero-copy的改进有关.不过在RPC综合测试里这一优势

似乎并未体现出来.

序列化测试数据采集利用了[http://code.google.com/p/thrift-protobuf-compare/][http_code.google.com_p_thrift-protobuf-compare]所提供的框架,

原始输出：

Starting

,   Object create,       Serialize,  /w Same Object,     Deserialize, and Check Media,   and Check All,      Total Time, Serialized Size

avro-generic        ,      8751.30500,     10938.00000,      1696.50000,     16825.00000,     16825.00000,     16825.00000,     27763.00000,        221

avro-specific       ,      8566.88000,     10534.50000,      1242.50000,     18157.00000,     18157.00000,     18157.00000,     28691.50000,        221

thrift-compact      ,      6784.61500,     11665.00000,      4214.00000,      1799.00000,      1799.00000,      1799.00000,     13464.00000,        227

thrift-binary       ,      6721.19500,     12386.50000,      4478.00000,      1692.00000,      1692.00000,      1692.00000,     14078.50000,        273

RPC测试用例：

客户端向服务器发送一组固定长度的message,为了能够同时测试序列和反序列，服务器收到后将原message返回给客户端．

array<Message> publish(string context,　array<Message> messages);

测试使用了Avro Netty Server和 Thrift HaHa Server因为他们都是基于异步IO的并且适用于高并发的环境。

结果

[![avro1.jpg][]][avro1.jpg]

[![avro21.jpg][]][avro21.jpg]

从这个测试来看，再未到达网络瓶颈前，Avro Netty比Thrift HsHa服务提供了更高的吞吐率和更快的响应，另外 avro占用的内存高些。

通过进一步实验,发现不存在绝对的Avro和Thrift服务哪一个更快,决定于给出的test case,或者说与程序的用法有关,比如当前测试用例是Batch模式，大量发送fine grained的对象(接近后台tt,hadoop的用法),这个情况下Avro有优势. 但是对于每次只传一个对象的chatty客户端,情况就出现逆转变成Thrift更高效了.还有当数据结构里blob比例变大的情况下,Avro和Thrift的差别也在减小.

## Conclusion ##

*  Thrift适用于程序对程序静态的数据交换，要求schema预知并相对固定。

*  Avro在Thrift基础上增加了对schema动态的支持且性能上不输于Thrift。

*  Avro显式schema设计使它更适用于搭建数据交换及存储的通用工具和平台,特别是在后台。

*  目前Thrift的优势在于更多的语言支持和相对成熟。

本文转自：

[http://www.tbdata.org/archives/1307][http_www.tbdata.org_archives_1307]

扩展阅读：

1、Apache Thrift架构入门介绍以及谁在使用Thrift：[http://www.renren.it/a/JAVAbiancheng/JAVAzonghe/20111010/Apache-Thrift-architecture-introduction-.html][http_www.renren.it_a_JAVAbiancheng_JAVAzonghe_20111010_Apache-Thrift-architecture-introduction-.html]

2、thrife apache官方站点：[http://thrift.apache.org/][http_thrift.apache.org]

[a1.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a1.jpg
[a2.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a2.jpg
[a3.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a3.jpg
[a4.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a4.jpg
[a51.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a51.jpg
[a6.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a6.jpg
[a7.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a7.jpg
[a8.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/a8.jpg
[http_code.google.com_p_thrift-protobuf-compare]: http://code.google.com/p/thrift-protobuf-compare/
[avro1.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/avro1.jpg
[avro21.jpg]: http://www.tbdata.org/wp-content/uploads/2010/12/avro21.jpg
[http_www.tbdata.org_archives_1307]: http://www.tbdata.org/archives/1307
[http_www.renren.it_a_JAVAbiancheng_JAVAzonghe_20111010_Apache-Thrift-architecture-introduction-.html]: http://www.renren.it/a/JAVAbiancheng/JAVAzonghe/20111010/Apache-Thrift-architecture-introduction-.html
[http_thrift.apache.org]: http://thrift.apache.org/