Apache Thrift使用总结

使用感受

之前对Thrift的理解有点不准确,使用之后发现Thrift比想象中的要简单得多。

Thrift做的事情就是跨语言的分布式RPC,通过编写.thrift文件声明接口类和方法,client调用定义的方法,Server端实现定义的接口。尽管的确RPC是须要网络请求,但不像Netty这样的NIO网络编程库(还要关注许多传输数据中的细节,比方数据怎样序列化、怎样在字节数组里建立结构、怎样在两端解析字节数组、怎样处理Handler里的事件状态、怎样把多个Handler按顺序串起来),Thrift掩盖了传输数据这件事情,开发人员使用的时候就是纯纯的RPC的使用感受。


基本使用

Thrift使用起来差点儿没有不论什么门槛,能够看这篇HelloWorld的文章,尽管有点老,可是看完之后基本使用起来没有不论什么障碍了。

官方给出的这个样例更加全面些,全面在.thrift文件中能够声明的东西列的更全些。

以下看看两个.thrift的定义:

shared.thrift

/**
 * This Thrift file can be included by other Thrift files that want to share
 * these definitions.
 */

namespace java com.baidu.mordor.sink.service

struct SharedStruct {
  1: i32 key
  2: string value
}

service SharedService {
  SharedStruct getStruct(1: i32 key)
}

tutorial.thrift

/**
 * The first thing to know about are types. The available types in Thrift are:
 *
 *  bool        Boolean, one byte
 *  byte        Signed byte
 *  i16         Signed 16-bit integer
 *  i32         Signed 32-bit integer
 *  i64         Signed 64-bit integer
 *  double      64-bit floating point value
 *  string      String
 *  binary      Blob (byte array)
 *  map<t1,t2>  Map from one type to another
 *  list<t1>    Ordered list of one type
 *  set<t1>     Set of unique elements of one type
 *
 * Did you also notice that Thrift supports C style comments?
 */

// Just in case you were wondering... yes. We support simple C comments too.

/**
 * Thrift files can reference other Thrift files to include common struct
 * and service definitions. These are found using the current path, or by
 * searching relative to any paths specified with the -I compiler flag.
 *
 * Included objects are accessed using the name of the .thrift file as a
 * prefix. i.e. shared.SharedObject
 */
include "shared.thrift"

/**
 * Thrift files can namespace, package, or prefix their output in various
 * target languages.
 */
namespace java com.baidu.mordor.sink.service


/**
 * Thrift lets you do typedefs to get pretty names for your types. Standard
 * C style here.
 */
typedef i32 MyInteger

/**
 * Thrift also lets you define constants for use across languages. Complex
 * types and structs are specified using JSON notation.
 */
const i32 INT32CONSTANT = 9853
const map<string,string> MAPCONSTANT = {‘hello‘:‘world‘, ‘goodnight‘:‘moon‘}

/**
 * You can define enums, which are just 32 bit integers. Values are optional
 * and start at 1 if not supplied, C style again.
 */
enum Operation {
  ADD = 1,
  SUBTRACT = 2,
  MULTIPLY = 3,
  DIVIDE = 4
}

/**
 * Structs are the basic complex data structures. They are comprised of fields
 * which each have an integer identifier, a type, a symbolic name, and an
 * optional default value.
 *
 * Fields can be declared "optional", which ensures they will not be included
 * in the serialized output if they aren‘t set.  Note that this requires some
 * manual management in some languages.
 */
struct Work {
  1: i32 num1 = 0,
  2: i32 num2,
  3: Operation op,
  4: optional string comment,
}

/**
 * Structs can also be exceptions, if they are nasty.
 */
exception InvalidOperation {
  1: i32 what,
  2: string why
}

/**
 * Ahh, now onto the cool part, defining a service. Services just need a name
 * and can optionally inherit from another service using the extends keyword.
 */
service Calculator extends shared.SharedService {

   void ping(),

   i32 add(1:i32 num1, 2:i32 num2),

   i32 calculate(1:i32 logid, 2:Work w) throws (1:InvalidOperation ouch),

   /**
    * This method has a oneway modifier. That means the client only makes
    * a request and does not listen for any response at all. Oneway methods
    * must be void.
    */
   oneway void zip()

}


Thrift通过IDL(接口定义语言),在.thrift文件中声明接口类和方法,声明struct结构、const、Exception等,还能够include别的.thrift文件,这套语法与C很类似。通过编写IDL和generate代码,做到了不同语言之间的RPC,client实现接口类和使用结构类的时候很easy好用。
上面样例的代码能够从官方下载到,能够放到本地看一下他的使用,很easy。


Thrift重要组件

Thrift API里三个重要组成部分:Protocal,Transport,Server。


Protocal定义了消息怎样序列化。常见的是TBinaryProtocol,TJSONProtocol,TCompactProtocol。


Transport定义了消息在client和服务端怎样通信。常见的是TSocket,TFramedTransport,TNonblockingTransport等。


Server从transport端接收序列化后的消息,依据protocal反序列化回来,然后调用用户实现的消息handler(接口实现类),最后把返回的数据序列化后再传回给client。常见的TServer为TSimpleServer,THsHaServer,TThreadPoolServer,TNonBlockingServer,TThreadedSelectorServer。以下会详细介绍各个Server的特点,开发人员须要选择适合自己场景的一套 Server+相应的Transport+相应的Protocol。


TServer说明

Thrift实现的几种不同的TServer。对于Java而言,版本号按0.9.0为准:

TSimpleServer在sever端仅仅有一个I/O堵塞的单线程,每次仅仅接受并服务一个client,适合測试使用,不能用于线上服务。


TNonblockingServer改动了TSimpleServer里堵塞的缺点,借助NIO里的Selector实现非堵塞I/O,同意多个client连接而且client能够使用select()选择。可是处理消息和select()的是同一个线程,当有大量client连接的时候,性能是不理想的。


 THsHaServer(半同步半异步server)在以上基础上,使用一个单独线程来处理网络I/O,一个worker线程池来处理消息。优点是仅仅要有空暇worker线程,消息能够被及时、并行处理,吞吐量会大一些。


TThreadedSelectorServer,与THsHaServer的差别是处理网络I/O也是多线程了,它维护两个线程池,一个负责网络I/O,一个负责数据处理。优点是当网络I/O是瓶颈的情况下,性能比THsHaServer更好。


TThreadPoolServer有一个专用的线程来接收connections,连接被建立后,会从ThreadPoolExecutor里取一个工作线程来负责这次连接,直到连接断开后线程回到线程池里,且线程池大小可配。也就是说,并发性的大小可依据服务器设定,假设不介意开许多线程的话,TThreadPoolServer是个还不错的选择。


全文完 :)


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