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abin — Wed, 03 Jan 2018 16:01:00 GMT

摘要: 前阵子从支付宝�{�?万块钱到余额宝，�q�是日常生活的一件普通小事，但作��Z��联网研发人员的职业病�Q�我��思考支付宝扣除1万之后，如果�pȝ��挂掉怎么办，�q�时余额宝�̎户�ƈ没有增加1万，数据��׃��出现不一致状况了。上�q�场景在各个�c�d��的系�l�中都能扑ֈ��怼�影子�Q�比如在电商�pȝ��中，当有用户下单后，除了在订单表插入一条记录外�Q�对应商品表的这个商品数量必��d��1吧，怎么保证�Q�！在搜索广告系�l�中�Q�当用户点击某广告后�Q�除了在点击... 阅读全文

abin 2018-01-04 00:01 发表评论

abin — Sun, 31 Dec 2017 08:41:00 GMT

微服务架构采用Scale Cube�Ҏ��设计应用架构�Q�将应用服务按功能拆分成一�l�相互协作的服务。每个服务负责一�l�特定、相关的功能。每个服务可以有自己独立的数据库�Q�从而保证与其他服务解耦�?/span>

微服务优�?/span>

1�?span style="font-family: SimHei, STHeiti; color: #666666; background-color: #ffffff;">通过分解巨大单体式应用�ؓ多个服务�Ҏ��解决了复杂性问题，每个微服务相对较��?/span>

2、每个单体应用不局限于固定的技术栈�Q?span style="font-family: SimHei, STHeiti; color: #666666; background-color: #ffffff;">开发者可以自由选择开发技术，提供API服务�?/span>

3�?span style="font-family: SimHei, STHeiti; color: #666666; background-color: #ffffff;">每个微服务独立的开发，部��v

4、单一职责功能�Q?span style="font-family: Arial; background-color: #ffffff;">每个服务都很���单，只关注于一个业务功�?/span>

5�?span style="font-size: 16px; color: #454545; background-color: #ffffff;">易于规模化开发，多个开发团队可以�ƈ行开发，每个团队负责一��Ҏ���?/span>

6、改善故障隔���R��一个服务宕��Z��会媄响其他的服务

微服务缺点：

1.开发者需要应对创建分布式�pȝ��所产生的额外的复杂因素

l  目前的IDE主要面对的是单体工程�E�序�Q�无法显�C�支持分布式应用的开�?/span>

l  ���试工作更加困难

l  需要采用服务间的通讯机制

l  很难在不采用分布式事务的情况下跨服务实现功能

l  跨服务实现要求功能要求团队之间的紧密协作

2.部��v复杂

3.内存占用量更�?/span>

abin 2017-12-31 16:41 发表评论

JDK 源码�?HashMap �?hash �Ҏ��原理是什么？

abin — Sun, 24 Dec 2017 14:38:00 GMT

JDK �?HashMap 中��用了一�?hash �Ҏ��来做 bit shifting�Q�在注释中说明是��Z��防止一些实现比较差的hashCode() �Ҏ��Q�请问原理是什么？JDK 的源码参见：GrepCode: java.util.HashMap (.java)

/**

* Applies a supplemental hash function to a given hashCode, which

* defends against poor quality hash functions. This is critical

* because HashMap uses power-of-two length hash tables, that

* otherwise encounter collisions for hashCodes that do not differ

* in lower bits. Note: Null keys always map to hash 0, thus index 0.

static int hash(int h) {

// This function ensures that hashCodes that differ only by

// constant multiples at each bit position have a bounded

// number of collisions (approximately 8 at default load factor).

h ^= (h >>> 20) ^ (h >>> 12);

return h ^ (h >>> 7) ^ (h >>> 4);

}

PS�Q�网上看见有��作者本��原理需要参见圣�l�《计��机�E�序设计艺术》的 Vol.3 里头的介�l�，不过木有看过��书�Q�求达�h介绍

�q�段代码�?#8220;扰动函数”�?br />题主贴的是Java 7的HashMap的源码，Java 8中这步已�l�简化了�Q�只做一��?6位右位移异或混合�Q�而不是四�ơ，但原理是不变的。下面以Java 8的源码�ؓ例解释，

//Java 8中的散列��g��化函数staticfinalinthash(Objectkey){inth;return(key==null)?0:(h=key.hashCode())^(h>>>16);//key.hashCode()为哈希算法，�q�回初始哈希值}
大家都知道上面代码里的key.hashCode()函数调用的是key键值类型自带的哈希函数�Q�返回int型散列倹{��理��Z��散列值是一个int型，如果直接拿散列��g��Z��标访问HashMap��L��l�的话，考虑�?�q�制32位带�W�号的int表��D��围从-2147483648�?147483648。前后加��h��大概40亿的映射�I�间。只要哈希函数映��得比较均匀松散�Q�一般应用是很难出现��撞的。但问题是一�?0争K��度的数组�Q�内存是放不下的。你惻I��HashMap扩容之前的数�l�初始大��才16。所以这个散列值是不能直接拿来用的。用之前�q�要先做�Ҏ��l�的长度取模�q�算�Q�得到的余数才能用来讉K��数组下标。源码中模运��是在这个indexFor( )函数里完成的�?br />
bucketIndex = indexFor(hash, table.length);indexFor的代码也很简单，��是把散列值和数组长度做一�?�?操作�Q?br />
static int indexFor(int h, int length) { return h & (length-1);}��Z��说一下，�q�也正好解释了�ؓ什么HashMap的数�l�长度要�?的整�ơ幂。因��P��数组长度-1�Q�正好相当于一�?#8220;低位掩码”�?#8220;�?#8221;操作的结果就是散列值的高位全部归零�Q�只保留低位��|��用来做数�l�下标访问。以初始长度16��Z��Q?6-1=15�?�q�制表示�?0000000 00000000 00001111。和某散列值做“�?#8221;操作如下�Q�结果就是截取了最低的四位倹{�?br />10100101 11000100 00100101& 00000000 00000000 00001111---------------------------------- 00000000 00000000 00000101 //高位全部归零�Q�只保留末四�?br />但这时候问题就来了�Q�这样就��我的散列值分布再松散�Q�要是只取最后几位的话，��撞也会很严重。更要命的是如果散列本��n做得不好�Q�分布上成等差数列的漏洞�Q�恰好��最后几个低位呈现规律性重复，��无比蛋疹{��这时�?#8220;扰动函数”的�h值就体现出来了，说到�q�里大家应该猜出来了。看下面�q�个图，

右位�U?6位，正好�?2bit的一半，自己的高半区和低半区做异或，��是��Z��混合原始哈希码的高位和低位，以此来加大低位的随机性。而且混合后的低位掺杂了高位的部分特征�Q�这样高位的信息也被变相保留下来。最后我们来看一下PeterLawley的一��专栏文章《An introduction to optimising a hashing strategy》里的的一个实验：他随机选取�?52个字�W�串�Q�在他们散列值完全没有冲�H�的前提下，对它们做低位掩码�Q�取数组下标�?br />

�l�果昄��Q�当HashMap数组长度�?12的时候，也就是用掩码取低9位的时候，在没有扰动函数的情况下，发生�?03�ơ碰撞，接近30%。而在使用了扰动函��C��后只�?2�ơ碰撞。碰撞减��了��近10%。看来扰动函数确实还是有功效的。但明显Java 8觉得扰动做一�ơ就够了�Q�做4�ơ的话，多了可能辚w��效用也不大，所谓�ؓ了效率考虑��改成一�ơ了�?br />------------------------------------------------------

https://www.zhihu.com/question/20733617

abin 2017-12-24 22:38 发表评论

GoLang之方法与接口

abin — Thu, 03 Aug 2017 03:34:00 GMT

Go语言没有沿袭传统面向对象�~�程中的诸多概念�Q�比如��ѝ��虚函数、构造函数和析构函数、隐藏的this指针�{��?/p>

�Ҏ��

Go 语言中同时有函数和方法�?span style="color: #ff0000;">�Ҏ��是一个包含了接受者（receiver�Q�的函数�Q�receiver可以是内�|�类型或者结构体�c�d��的一个值或者是一个指针。所有给定类型的�Ҏ��属于该类型的�Ҏ��集�?br />

如下面的�q�个例子�Q�定义了一个新�c�d��Integer�Q�它和int一��P��只是为它内置的int�c�d��增加了个新方法Less()

type Integer int   func (a Integer) Less(b Integer) bool {     return a < b  }  func main() {     var a Integer = 1       if a.Less(2) {         fmt.Println("less then 2")     }    }

可以看出�Q�Go语言在自定义�c�d��的对象中没有C++/Java那种隐藏的this指针�Q�而是在定义成员方法时昑ּ�声明了其所属的对象�?/p>

method的语法如下：

func (r ReceiverType) funcName(parameters) (results)

当调用method�Ӟ��会将receiver作�ؓ函数的第一个参敎ͼ�

funcName(r, parameters);

所以，receiver是值类型还是指针类型要看method的作用。如果要修改对象的��|��需要传递对象的指针�?/p>

指针作�ؓReceiver会对实例对象的内容发生操�?而普通类型作为Receiver仅仅是以副本作�ؓ操作对象,�q�不对原实例对象发生操作�?/p>

func (a *Ingeger) Add(b Integer) {     *a += b }  func main() {     var a Integer = 1      a.Add(3)     fmt.Println("a =", a)     //  a = 4 }

如果Add�Ҏ��不��用指针，则a�q�回的结果不变，�q�是因�ؓGo语言函数的参��C��是基于��g��递�?/p>

注意�Q?span style="color: #ff0000;">当方法的接受者是指针�Ӟ��即��用值类型调用那么方法内部也是对指针的操作�?/span>

之前说过�Q�Go语言没有构造函数的概念�Q�通常使用一个全局函数来完成。例如：

func NewRect(x, y, width, height float64) *Rect {     return &Rect{x, y, width, height} }     func main() {     rect1 := NewRect(1,2,10,20)     fmt.Println(rect1.width) }

匿名�l�合

Go语言提供了��承，但是采用了组合的语法�Q�我们将其称为匿名组合，例如�Q?/span>

type Base struct {     name string }  func (base *Base) Set(myname string) {     base.name = myname }  func (base *Base) Get() string {     return base.name }  type Derived struct {     Base     age int  }  func (derived *Derived) Get() (nm string, ag int) {     return derived.name, derived.age }   func main() {     b := &Derived{}      b.Set("sina")     fmt.Println(b.Get()) }

例子中，在Base�c�d��定义了get()和set()两个�Ҏ��Q�而Derived�c�d��l�承了Base�c�，�q�改写了Get()�Ҏ��Q�在Derived对象调用Set()�Ҏ��Q�会加蝲基类对应的方法；而调用Get()�Ҏ��Ӟ��加蝲�z��c�L��写的�Ҏ��?/p>

�l�合的类型和被组合的�c�d��包含同名成员�Ӟ�� 会不会有问题呢？可以参考下面的例子�Q?/p>

type Base struct {     name string     age int }  func (base *Base) Set(myname string, myage int) {     base.name = myname     base.age = myage }  type Derived struct {     Base     name string }  func main() {     b := &Derived{}      b.Set("sina", 30)     fmt.Println("b.name =",b.name, "\tb.Base.name =", b.Base.name)     fmt.Println("b.age =",b.age, "\tb.Base.age =", b.Base.age) }

��D��义和引用语义

��D��义和引用语义的差别在于赋��|��比如

b = a b.Modify()

如果b的修改不会媄响a的��|��那么此类型属于值类型；如果会媄响a的��|��那么此类型是引用�c�d��?/span>

Go语言中的大多数类型都��Z��D��义，包括�Q?/p>

基本�c�d��Q�如byte、int、bool、float32、string�{�；
复合�c�d��Q�如arry、struct、pointer�{�；

C语言中的数组比较特别�Q�通过函数传递一个数�l�的时候基于引用语义，但是在结构体定义数组变量的时候基于��D��义。而在Go语言中，数组和基本类型没有区别，是很�U��a的值类型，例如�Q?/p>

var a = [3] int{1,2,3} var b = a b[1]++ fmt.Println(a, b)   // [1 2 3] [1 3 3]

从结果看�Q�b=a赋��D��句是数组内容的完整复�Ӟ��要想表达引用�Q�需要用指针�Q?/p>

var a = [3] int{1,2,3} var b = &a　　　　// 引用语义 b[1]++ fmt.Println(a, b)   // [1 3 3] [1 3 3]

接口

Interface 是一�l�抽象方法（未具体实现的�Ҏ��/仅包含方法名参数�q�回值的�Ҏ��Q�的集合�Q�如果实��C�� interface 中的所有方法，卌��c?对象��实��C��该接口�?/p>

Interface 的声明格式：

type interfaceName interface {       //�Ҏ��列表   }

Interface 可以被�Q意对象实玎ͼ�一个类�?对象也可以实现多�?interface�Q?br />interface的变量可以持有�Q意实现该interface�c�d��的对象�?/span>

如下面的例子�Q?/p>

package main      import "fmt"      type Human struct {         name string         age int         phone string     }      type Student struct {         Human //匿名字段         school string         loan float32     }      type Employee struct {         Human //匿名字段         company string         money float32     }      //Human实现SayHi�Ҏ��     func (h Human) SayHi() {         fmt.Printf("Hi, I am %s you can call me on %s\n", h.name, h.phone)     }      //Human实现Sing�Ҏ��     func (h Human) Sing(lyrics string) {         fmt.Println("La la la la...", lyrics)     }      //Employee重蝲Human的SayHi�Ҏ��     func (e Employee) SayHi() {         fmt.Printf("Hi, I am %s, I work at %s. Call me on %s\n", e.name,             e.company, e.phone)         }      // Interface Men被Human,Student和Employee实现     // 因�ؓ�q�三个类型都实现了这两个�Ҏ��     type Men interface {         SayHi()         Sing(lyrics string)     }      func main() {         mike := Student{Human{"Mike", 25, "222-222-XXX"}, "MIT", 0.00}         paul := Student{Human{"Paul", 26, "111-222-XXX"}, "Harvard", 100}         sam := Employee{Human{"Sam", 36, "444-222-XXX"}, "Golang Inc.", 1000}         tom := Employee{Human{"Tom", 37, "222-444-XXX"}, "Things Ltd.", 5000}          //定义Men�c�d��的变量i         var i Men          //i能存储Student         i = mike　　　　         fmt.Println("This is Mike, a Student:")         i.SayHi()         i.Sing("November rain")          //i也能存储Employee         i = tom         fmt.Println("This is tom, an Employee:")         i.SayHi()         i.Sing("Born to be wild")          //定义了slice Men         fmt.Println("Let's use a slice of Men and see what happens")         x := make([]Men, 3)         //�q�三个都是不同类型的元素�Q�但是他们实��C��interface同一个接�?/span>         x[0], x[1], x[2] = paul, sam, mike          for _, value := range x{             value.SayHi()         }     }

�I�接�?/h3>

�I�interface(interface{})不包含�Q何的method�Q�正因�ؓ如此�Q?span style="background-color: #ffff00;">所有的�c�d��都实��C��I�interface。空interface对于描述起不��C�Q何的作用(因�ؓ它不包含��M��的method�Q�，但是�I�interface在我们需要存储�Q意类型的数值的时候相当有用，因�ؓ它可以存储�Q意类型的数倹{��它有点�c�M��于C语言的void*�c�d��?/span>

// 定义a为空接口     var a interface{}     var i int = 5     s := "Hello world"     // a可以存储��L���c�d��的数�?/span>     a = i     a = s

interface的变量里面可以存储�Q意类型的数��|��该类型实��C��interface�Q�，那么我们怎么反向知道�q�个interface变量里面实际保存了的是哪个类型的对象呢？目前常用的有两种�Ҏ��Q�switch��试、Comma-ok断言�?/p>

switch��试如下�Q?/p>

type Element interface{} type List [] Element  type Person struct {     name string     age int  }  //打印 func (p Person) String() string {     return "(name: " + p.name + " - age: "+strconv.Itoa(p.age)+ " years)" }  func main() {     list := make(List, 3)     list[0] = 1 //an int      list[1] = "Hello" //a string     list[2] = Person{"Dennis", 70}       for index, element := range list{         switch value := element.(type) {             case int:                 fmt.Printf("list[%d] is an int and its value is %d\n", index, value)             case string:                 fmt.Printf("list[%d] is a string and its value is %s\n", index, value)             case Person:                 fmt.Printf("list[%d] is a Person and its value is %s\n", index, value)             default:                 fmt.Println("list[%d] is of a different type", index)         }        }    }

如果使用Comma-ok断言的话�Q?/p>

func main() {     list := make(List, 3)     list[0] = 1 // an int     list[1] = "Hello" // a string     list[2] = Person{"Dennis", 70}      for index, element := range list {         if value, ok := element.(int); ok {             fmt.Printf("list[%d] is an int and its value is %d\n", index, value)         } else if value, ok := element.(string); ok {             fmt.Printf("list[%d] is a string and its value is %s\n", index, value)         } else if value, ok := element.(Person); ok {             fmt.Printf("list[%d] is a Person and its value is %s\n", index, value)         } else {             fmt.Printf("list[%d] is of a different type\n", index)         }     } }

嵌入接口

正如struct�c�d��可以包含一个匿名字�D�，interface也可以嵌套另外一个接口�?/p>

如果一个interface1作�ؓinterface2的一个嵌入字�D�，那么interface2隐式的包含了interface1里面的method�?/p>

反射

所谓反��（reflect�Q�就是能��查程序在�q�行时的状态�?/p>

使用reflect一般分成三步，下面��要的讲解一下：要去反射是一个类型的�?�q�些值都实现了空interface)�Q�首先需要把它�{化成reflect对象(reflect.Type或者reflect.Value�Q�根据不同的情况调用不同的函�?。这两种获取方式如下�Q?/p>

 t := reflect.TypeOf(i)    //得到�c�d��的元数据,通过t我们能获取类型定义里面的所有元�?/span>  v := reflect.ValueOf(i)   //得到实际的��|��通过v我们获取存储在里面的��|���q�可以去改变�?/span>

转化为reflect对象之后我们��可以进行一些操作了�Q�也��是��reflect对象转化成相应的��|��例如

tag := t.Elem().Field(0).Tag  //获取定义在struct里面的标�{?/span> name := v.Elem().Field(0).String()  //获取存储在第一个字�D�里面的�?/span>

获取反射��D��q�回相应的类型和数�?/p>

var x float64 = 3.4 v := reflect.ValueOf(x) fmt.Println("type:", v.Type()) fmt.Println("kind is float64:", v.Kind() == reflect.Float64) fmt.Println("value:", v.Float())

最后，反射的话�Q�那么反��的字段必须是可修改的，我们前面学习�q�传值和传引用，�q�个里面也是一��L��道理。反��的字段必须是可��d��的意思是�Q�如果下面这样写�Q�那么会发生错误

var x float64 = 3.4 v := reflect.ValueOf(x) v.SetFloat(7.1)

如果要修改相应的��|��必须�q�样�?/p>

var x float64 = 3.4 p := reflect.ValueOf(&x) v := p.Elem() v.SetFloat(7.1)

上面只是对反��的��单介�l�，更深入的理解�q�需要自己在�~�程中不断的实践�?/p>

参考文档：

http://se77en.cc/2014/05/05/methods-interfaces-and-embedded-types-in-golang/

http://se77en.cc/2014/05/04/choose-whether-to-use-a-value-or-pointer-receiver-on-methods/

http://www.cnblogs.com/chenny7/p/4497969.html

abin 2017-08-03 11:34 发表评论

老虞要学GoLang-函数(�?

abin — Wed, 02 Aug 2017 08:39:00 GMT

不可或缺的函敎ͼ�在Go中定义函数的方式如下�Q?/p>

func (p myType ) funcName ( a, b int , c string ) ( r , s int ) {     return }

通过函数定义�Q�我们可以看到Go中函数和其他语言中的共性和�Ҏ�?/p>

共�?/h3>
关键�?#8212;—func
�Ҏ��?#8212;—funcName
入参——— a,b int,b string
�q�回�?#8212;— r,s int
函数�?#8212;— {}

�Ҏ�?/h3>
Go中函数的�Ҏ��是非常��L��Q�给我们带来不一��L��~�程体验�?/p>

为特定类型定义函敎ͼ�即�ؓ�c�d��对象定义�Ҏ��

在Go中通过�l�函数标明所属类型，来给该类型定义方法，上面�?nbsp;p myType 卌��C�给myType声明了一个方法， p myType 不是必须的。如果没有，则纯�_Ҏ��一个函敎ͼ�通过包名�U�访问。packageName.funcationName

如：

//定义新的�c�d��double�Q�主要目的是�l�float64�c�d��扩充�Ҏ�� type double float64  //判断a是否�{�于b func (a double) IsEqual(b double) bool {     var r = a - b     if r == 0.0 {         return true     } else if r < 0.0 {         return r > -0.0001     }     return r < 0.0001 }  //判断a是否�{�于b func IsEqual(a, b float64) bool {     var r = a - b     if r == 0.0 {         return true     } else if r < 0.0 {         return r > -0.0001     }     return r < 0.0001 }  func main() {     var a double = 1.999999     var b double = 1.9999998     fmt.Println(a.IsEqual(b))     fmt.Println(a.IsEqual(3))     fmt.Println( IsEqual( (float64)(a), (float64)(b) ) )  }

上述�C�Z��?float64 基本�c�d��扩充了方法IsEqual�Q�该�Ҏ��主要是解决精度问题�?其方法调用方式�ؓ�Q?nbsp;a.IsEqual(double) �Q�如果不扩充�Ҏ��Q�我们只能��用函�?code style="margin: 0px 2px; padding: 0px 5px; border: 1px solid #eaeaea; background-color: #f8f8f8; border-radius: 3px; white-space: nowrap; font-family: monospace, Monaco;">IsEqual(a, b float64)

入参中，如果�q�箋的参数类型一��_��则可以省略连�l�多个参数的�c�d��Q�只保留最后一个类型声明�?/h4>
�?nbsp;`func IsEqual(a, b float64) bool` �q�个�Ҏ��只保留了一个类型声�?此时入参a和b均是float64数据�c�d��?�q�样也是可以的： `func IsEqual(a, b float64, accuracy int) bool`

变参�Q�入参支持变�?卛_��接受不确定数量的同一�c�d��的参�?/h4>
�?nbsp;`func Sum(args ...int)` 参数args是的slice�Q�其元素�c�d��为int 。经�怋�用的fmt.Printf��是一个接受�Q意个数参数的函数 `fmt.Printf(format string, args ...interface{})`

支持多返回�?/h4>

前面我们定义函数时返回值有两个r,s 。这是非常有用的�Q�我在写C#代码�Ӟ��常常��Z��从已有函��C��获得更多的信息，需要修改函数签名，使用out ,ref �{�方式去获得更多�q�回�l�果。而现在��用Go时则很简单，直接在返回值后面添加返回参数即可�?/p>

�?在C#中一个字�W�串转换为int�c�d��旉��辑代码

int v=0;  if ( int.TryPase("123456",out v) ) {     //code }

而在Go中，则可以这样实�?逻辑�_��而明��?/p>

if v,isOk :=int.TryPase("123456") ; isOk {     //code }

同时在Go中很多函数充分利用了多返回�?/p>

func (file *File) Write(b []byte) (n int, err error)
func Sincos(x float64) (sin, cos float64)

那么如果我只需要某一个返回��|��而不兛_��其他�q�回值的话，我该如何办呢�Q?�q�时可以��单的使用�W�号下划�U?#8221;_“ 来忽略不兛_��的返回倹{��如�Q?/p>

_, cos = math.Sincos(3.1415) //只需要cos计算的�?

命名�q�回�?/h4>

前面我们说了函数可以有多个返回��|��q�里我还要说的是�Q�在函数定义时可以给所有的�q�回值分别命名，�q�样��p��在函��C��L��位置�l�不同返回值复�Ӟ��而不需要在return语句中才指定�q�回倹{��同时也能增强可��L��，也提高godoc所生成文档的可��L�?/p>

如果不支持命名返回��|��我可能会是这样做�?/p>

func ReadFull(r Reader, buf []byte) (int, error) {     var n int     var err error      for len(buf) > 0  {         var nr int         nr, err = r.Read(buf)          n += nr         if err !=nil {             return n,err         }         buf = buf[nr:]     }     return n,err }

但支持给�q�回值命名后�Q�实际上��是省略了变量的声明�Q�return时无需写成return n,err 而是��直接将��D��?/p>

func ReadFull(r Reader, buf []byte) (n int, err error) {     for len(buf) > 0 && err == nil {         var nr int         nr, err = r.Read(buf)         n += nr         buf = buf[nr:]     }     return }

函数也是“�?#8221;

和Go中其他东西一��P��函数也是��|��q�样��可以声明一个函数类型的变量�Q�将函数作�ؓ参数传递�?/p>

声明函数为值的变量(匿名函数:可赋��g��变量�Q�也可直接执�?

//赋�?fc := func(msg string) {     fmt.Println("you say :", msg) } fmt.Printf("%T \n", fc) fc("hello,my love") //直接执行 func(msg string) {     fmt.Println("say :", msg) }("I love to code")

输出�l�果如下�Q�这里表明fc 的类型�ؓ�Q�func(string)

func(string)  you say : hello,my love say : I love to code

��函��C��为入参（回调函数�Q�，能带来便利。如日志处理�Q��ؓ了统一处理�Q�将信息均通过指定函数去记录日志，且是否记录日志还有开�?/p>

func Log(title string, getMsg func() string) {     //如果开启日志记�?则记录日�?    if true {         fmt.Println(title, ":", getMsg())     } } //---------调用-------------- count := 0 msg := func() string {     count++     return "您没有即使提醒我,已触犯法�? } Log("error", msg) Log("warring", msg) Log("info", msg) fmt.Println(count)

�q�里输出�l�果如下�Q�count 也发生了变化

error : 您没有即使提醒我,已触犯法�?warring : 您没有即使提醒我,已触犯法�?info : 您没有即使提醒我,已触犯法�?3

函数也是“�c�d��”

你有没有注意��C��面示例中�?nbsp;fc := func(msg string)... �Q�既然匿名函数可以赋值给一个变量，同时我们�l�常�q�样�l�int赋�?nbsp;value := 2 ,是否我们可以声明func(string) �c�d�� 呢，当然是可以的�?/p>

//一个记录日志的�c�d���Q�func(string) type saveLog func(msg string)  //���字�W�串转换为int64,如果转换��p�|调用saveLog func stringToInt(s string, log saveLog) int64 {      if value, err := strconv.ParseInt(s, 0, 0); err != nil {         log(err.Error())         return 0     } else {         return value     } }  //记录日志消息的具体实�?func myLog(msg string) {     fmt.Println("Find Error:", msg) }  func main() {     stringToInt("123", myLog) //转换时将调用mylog记录日志     stringToInt("s", myLog) }

�q�里我们定义了一个类型，专门用作记录日志的标准接口。在stringToInt函数中如果�{换失败则调用我自己定义的接口函数�q�行日志处理�Q�至于最�l�执行的哪个函数�Q�则无需兛_��?/p>

defer 延迟函数

defer 又是一个创斎ͼ�它的作用是：延迟执行�Q�在声明时不会立��x��行，而是在函数return后时按照后进先出的原则依�ơ执行每一个defer。这样带来的好处是，能确保我们定义的函数能百分之百能够被执行刎ͼ��q�样��p��做很多我们想做的事，如释放资源，清理数据�Q�记录日志等

�q�里我们重点来说明下defer的执行顺�?/p>

func deferFunc() int {     index := 0      fc := func() {          fmt.Println(index, "匿名函数1")         index++          defer func() {             fmt.Println(index, "匿名函数1-1")             index++         }()     }      defer func() {         fmt.Println(index, "匿名函数2")         index++     }()      defer fc()      return func() int {         fmt.Println(index, "匿名函数3")         index++         return index     }() }  func main() {     deferFunc() }

�q�里输出�l�果如下�Q?/p>

0 匿名函数3 1 匿名函数1 2 匿名函数1-1 3 匿名函数2

有如下结论：

defer 是在执行完return 后执�?/li>
defer 后进先执�?/li>

另外�Q�我们常使用defer��d��闭IO,在正常打开文�g后，��q��d��明一个defer�Q�这样就不会忘记关闭文�g�Q�也能保证在出现异常�{�不可预料的情况下也能关闭文件。而不像其他语�a��Q?code style="margin: 0px 2px; padding: 0px 5px; border: 1px solid #eaeaea; background-color: #f8f8f8; border-radius: 3px; white-space: nowrap; font-family: monospace, Monaco;">try-catch 或�?nbsp;using() 方式�q�行处理�?/p>

file , err :=os.Open(file) if err != nil {     return err } defer file.Close()  //dosomething with file

后箋�Q�我��讨论：作用域、传值和传指�?以及保留函数init(),main()

本笔��C��所写代码存储位�|�：

defer.go
defineFunctionType.go
function.go

http://www.cnblogs.com/howDo/archive/2013/06/04/GoLang-function.html

abin 2017-08-02 16:39 发表评论

MySQL触发器Trigger实例��?

abin — Thu, 18 Aug 2016 09:25:00 GMT

MySQL触发器Trigger实例��?/div>

发表�?68 天前 ⁄ IT技�?/a> ⁄ 暂无评论

以前��x��的数据存储过�E�不太懂其中奥妙�Q�最�q�遇到跨数据�?/a>�Q�同时对多个表进行CURD�Q�Create增、Update攏V��Read诅R��Delete删）�Q�怎么才能让繁琐的数据CURD同步变得更容易呢�Q�相信很多�h会首先想��C��MySQL存储�q�程、触发器�Q�这�U�想法确实不错。于是饶有兴��地亲自写了CUD�Q�增、改、删�Q�触发器的实例，用触发器实现多表数据同步更新�?/p>

定义�Q?何�ؓMySQL触发器？

在MySQL Server里面也就是对某一个表的一定的操作�Q�触发某�U�条�Ӟ��Insert,Update,Delete �{�）�Q�从而自动执行的一�D늨�序。从�q�种意义上讲触发器是一个特�D�的存储�q�程。下面通过MySQL触发器实例，来了解一下触发器的工作过�E�吧�Q?/p>

一、创建MySQL实例数据表：

在mysql的默认的��试test数据库下�Q�创��Z��个表t_a与t_b�Q?/p>

    /*Table structure for table `t_a` */
    DROP TABLE IF EXISTS `t_a`;
    CREATE TABLE `t_a` (
      `id` smallint(1) unsigned NOT NULL AUTO_INCREMENT,
      `username` varchar(20) DEFAULT NULL,
      `groupid` mediumint(8) unsigned NOT NULL DEFAULT '0',
      PRIMARY KEY (`id`)
    ) ENGINE=MyISAM AUTO_INCREMENT=16 DEFAULT CHARSET=latin1;

    /*Data for the table `t_a` */
    LOCK TABLES `t_a` WRITE;
    UNLOCK TABLES;

    /*Table structure for table `t_b` */
    DROP TABLE IF EXISTS `t_b`;
    CREATE TABLE `t_b` (
      `id` smallint(1) unsigned NOT NULL AUTO_INCREMENT,
      `username` varchar(20) DEFAULT NULL,
      `groupid` mediumint(8) unsigned NOT NULL DEFAULT '0',
      PRIMARY KEY (`id`)
    ) ENGINE=MyISAM AUTO_INCREMENT=57 DEFAULT CHARSET=latin1;

    /*Data for the table `t_b` */
    LOCK TABLES `t_b` WRITE;
    UNLOCK TABLES;

在t_a表上分创��Z��个CUD�Q�增、改、删�Q?个触发器�Q�将t_a的表数据与t_b同步实现CUD�Q�注意创��发器每个表同�c�M��件有且仅有一个对应触发器�Q��ؓ什么只能对一个触发器�Q�不解释啦，看MYSQL的说明帮助文档吧�?/p>

二、创建MySQL实例触发器：

在实例数据表t_a上依�ơ按照下面步骤创建tr_a_insert、tr_a_update、tr_a_delete三个触发�?/p>

1、创建INSERT触发器trigger_a_insert�Q?/strong>

    DELIMITER $$

    USE `test`$$

    --判断数据库中是否存在tr_a_insert触发�?br />    DROP TRIGGER /*!50032 IF EXISTS */ `tr_a_insert`$$
    --不存在tr_a_insert触发器，开始创��发器
    --Trigger触发条�g为insert成功后进行触�?br />    CREATE
        /*!50017 DEFINER = 'root'@'localhost' */
        TRIGGER `tr_a_insert` AFTER INSERT ON `t_a`
        FOR EACH ROW BEGIN
            --Trigger触发后，同时对t_b新增同步一条数�?br />            INSERT INTO `t_b` SET username = NEW.username, groupid=NEW.groupid;
        END;
    $$

    DELIMITER;

2、创建UPDATE触发器trigger_a_update�Q?/strong>

    DELIMITER $$

    USE `test`$$
    --判断数据库中是否存在tr_a_update触发�?br />    DROP TRIGGER /*!50032 IF EXISTS */ `tr_a_update`$$
    --不存在tr_a_update触发器，开始创��发器
    --Trigger触发条�g为update成功后进行触�?br />    CREATE
        /*!50017 DEFINER = 'root'@'localhost' */
        TRIGGER `tr_a_update` AFTER UPDATE ON `t_a`
        FOR EACH ROW BEGIN
        --Trigger触发后，当t_a表groupid,username数据有更�Ҏ��Q�对t_b表同步一条更新后的数�?br />          IF new.groupid != old.groupid OR old.username != new.username THEN
            UPDATE `t_b` SET groupid=NEW.groupid,username=NEW.username WHEREusername=OLD.username AND groupid=OLD.groupid;
          END IF;

        END;
    $$

    DELIMITER ;

3、创建DELETE触发器trigger_a_delete�Q?/strong>

    DELIMITER $$

    USE `test`$$
    --判断数据库中是否存在tr_a_delete触发�?br />    DROP TRIGGER /*!50032 IF EXISTS */ `tr_a_delete`$$
    --不存在tr_a_delete触发器，开始创��发器
    --Trigger触发条�g为delete成功后进行触�?br />    CREATE
        /*!50017 DEFINER = 'root'@'localhost' */
        TRIGGER `tr_a_delete` AFTER DELETE ON `t_a`
        FOR EACH ROW BEGIN
            --t_a表数据删除后�Q�t_b表关联条件相同的数据也同步删�?br />            DELETE FROM `t_b` WHERE username=Old.username AND groupid=OLD.groupid;
        END;
    $$

    DELIMITER ;

三、测试MySQL实例触发器：

分别��试实现t_a与t_b实现数据同步CUD(增、改、删)3个Triggers

1、测试MySQL的实例tr_a_insert触发器：

在t_a表中新增一条数据，然后分别查询t_a/t_b表的数据是否数据同步�Q�测试触发器成功标志�Q�t_a表无论在何种情况下，新增了一条或多条记录集时�Q�没有t_b表做��M��数据insert操作�Q�它同时新增了一��L��多条记录集�?/p>
下面来进行MySQL触发器实例测试：

    --t_a表新增一条记录集
        INSERT INTO `t_a` (username,groupid) VALUES ('sky54.net',123)

        --查询t_a�?br />        SELECT id,username,groupid FROM `t_a`

        --查询t_b�?br />        SELECT id,username,groupid FROM `t_b`

2、测试MySQL的实例tr_a_update、tr_a_delete触发器：

�q�两个MySQL触发器测试原理、步骤与tr_a_insert触发器一��L��Q�先修改/删除一条数据，然后分别查看t_a、t_b表的数据变化情况�Q�数据变化同步说明Trigger实例成功�Q�否则需要逐步排查错误原因�?/p>
世界上�Q何一�U�事物都其其优点和缺点，优点与缺�Ҏ��自��n一个相对立的面。当然这里不是强�?#8220;世界非黑即白”式的“二元�?#8221;�Q?#8220;存在卛_��?#8221;嘛。当�?MySQL触发器的优点不说了，说一下不��之处，MySQL Trigger没有很好的调试、管理环境，难于在各�U�系�l�环境下��试�Q�测试比MySQL存储�q�程要难�Q�所以徏议在生成环境下，��量用存储过�E�来代替 MySQL触发器�?/p>
本篇�l�束前再��一下，支持触发器的MySQL版本需�?.0以上�Q?.0以前版本的MySQL升��?.0以后版本方可使用触发器哦�Q?/p>

http://blog.csdn.net/hireboy/article/details/18079183

abin 2016-08-18 17:25 发表评论

聊聊高�ƈ发系�l�之限流�Ҏ��-1

abin — Tue, 14 Jun 2016 05:38:00 GMT
     摘要: 在开发高�q�发�pȝ��时有三把利器用来保护�pȝ��Q�缓存、降�U�和限流。缓存的目的是提升系�l�访问速度和增大系�l�能处理的容量，可谓是抗高�ƈ发流量的银弹�Q�而降�U�是当服务出问题或者媄响到核心��程的性能则需要暂时屏蔽掉�Q�待高峰或者问题解军_��再打开�Q�而有些场景�ƈ不能用缓存和降��来解冻I��比如�E��~��源（�U�杀、抢购）、写服务�Q�如评论、下单）、频�J�的复杂查询�Q�评论的最后几��）�Q�因此需有一�U�手�D�|��限制�q�些场景的�ƈ�?��h��量，即限...  阅读全文

abin 2016-06-14 13:38 发表评论

shadowsocks 安装

abin — Fri, 13 May 2016 14:56:00 GMT

Install the Command Line Client
If you prefer command line client, then you can install it on your Linux with the following command.
Debian
sudo apt-get install python-pip sudo pip install shadowsocks
Ubuntu
Yes, you can use the above commands to install shadowsocks client on ubuntu. But it will install it under ~/.local/bin/ directory and it causes loads of trouble. So I suggest using su to become root first and then issue the following two commands.
apt-get install python-pip pip install shadowsocks
Fedora/Centos
sudo yum install python-setuptools or sudo dnf install python-setuptools sudo easy_install pip sudo pip install shadowsocks
OpenSUSE
sudo zypper install python-pip sudo pip install shadowsocks
Archlinux
sudo pacman -S python-pip sudo pip install shadowsocks
As you can see the command of installing shadowsocks client is the same to the command of installing shadowsocks server, because the above command will install both the client and the server. You can verify this by looking at the installation script output
Downloading/unpacking shadowsocks Downloading shadowsocks-2.8.2.tar.gz Running setup.py (path:/tmp/pip-build-PQIgUg/shadowsocks/setup.py) egg_info for package shadowsocks Installing collected packages: shadowsocks Running setup.py install for shadowsocks Installing sslocal script to /usr/local/bin Installing ssserver script to /usr/local/bin Successfully installed shadowsocks Cleaning up...
sslocal is the client software and ssserver is the server software. On some Linux distros such as ubuntu, the shadowsocks client sslocal is installed under /usr/local/bin. On Others such as Archsslocal is installed under /usr/bin/. Your can use whereis command to find the exact location.
user@debian:~$ whereis sslocal sslocal: /usr/local/bin/sslocal
Create a Configuration File
we will create a configuration file under /etc/
sudo vi /etc/shadowsocks.json
Put the following text in the file. Replace server-ip with your actual IP and set a password.
{
"server":"server-ip",
"server_port":8000,
"local_address": "127.0.0.1",
"local_port":1080,
"password":"your-password",
"timeout":600,
"method":"aes-256-cfb"
}
Save and close the file. Next start the client using command line
sslocal -c /etc/shadowsocks.json
To run in the background
sudo sslocal -c /etc/shadowsocks.json -d start
Auto Start the Client on System Boot
Edit /etc/rc.local file
sudo vi /etc/rc.local
Put the following line above the exit 0 line:
sudo sslocal -c /etc/shadowsocks.json -d start
Save and close the file. Next time you start your computer, shadowsocks client will automatically start and connect to your shadowsocks server.
Check if It Works
After you rebooted your computer, enter the following command in terminal:
sudo systemctl status rc-local.service
If your sslocal command works then you will get this ouput:

● rc-local.service - /etc/rc.local

Compatibility Loaded: loaded (/etc/systemd/system/rc-local.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2015-11-27 03:19:25 CST; 2min 39s ago
Process: 881 ExecStart=/etc/rc.local start (code=exited, status=0/SUCCESS)
CGroup: /system.slice/rc-local.service
├─ 887 watch -n 60 su matrix -c ibam
└─1112 /usr/bin/python /usr/local/bin/sslocal -c /etc/shadowsocks....
As you can see from the last line, the sslocal command created a process whose pid is 1112 on my machine. It means shadowsocks client is running smoothly. And of course you can tell your browser to connect through your shadowsocks client to see if everything goes well.
If for some reason your /etc/rc.local script won’t run, then check the following post to find the solution.
How to enable /etc/rc.local with SystemdInstall the Command Line Client
If you prefer command line client, then you can install it on your Linux with the following command.
Debian
sudo apt-get install python-pip sudo pip install shadowsocks
Ubuntu
Yes, you can use the above commands to install shadowsocks client on ubuntu. But it will install it under ~/.local/bin/ directory and it causes loads of trouble. So I suggest using su to become root first and then issue the following two commands.
apt-get install python-pip pip install shadowsocks
Fedora/Centos
sudo yum install python-setuptools or sudo dnf install python-setuptools sudo easy_install pip sudo pip install shadowsocks
OpenSUSE
sudo zypper install python-pip sudo pip install shadowsocks
Archlinux
sudo pacman -S python-pip sudo pip install shadowsocks
As you can see the command of installing shadowsocks client is the same to the command of installing shadowsocks server, because the above command will install both the client and the server. You can verify this by looking at the installation script output
Downloading/unpacking shadowsocks Downloading shadowsocks-2.8.2.tar.gz Running setup.py (path:/tmp/pip-build-PQIgUg/shadowsocks/setup.py) egg_info for package shadowsocks Installing collected packages: shadowsocks Running setup.py install for shadowsocks Installing sslocal script to /usr/local/bin Installing ssserver script to /usr/local/bin Successfully installed shadowsocks Cleaning up...
sslocal is the client software and ssserver is the server software. On some Linux distros such as ubuntu, the shadowsocks client sslocal is installed under /usr/local/bin. On Others such as Archsslocal is installed under /usr/bin/. Your can use whereis command to find the exact location.
user@debian:~$ whereis sslocal sslocal: /usr/local/bin/sslocal
Create a Configuration File
we will create a configuration file under /etc/
sudo vi /etc/shadowsocks.json
Put the following text in the file. Replace server-ip with your actual IP and set a password.
{ "server":"server-ip", "server_port":8000, "local_address": "127.0.0.1", "local_port":1080, "password":"your-password", "timeout":600, "method":"aes-256-cfb" }
Save and close the file. Next start the client using command line
sslocal -c /etc/shadowsocks.json
To run in the background
sudo sslocal -c /etc/shadowsocks.json -d start
Auto Start the Client on System Boot
Edit /etc/rc.local file
sudo vi /etc/rc.local
Put the following line above the exit 0 line:
sudo sslocal -c /etc/shadowsocks.json -d start
Save and close the file. Next time you start your computer, shadowsocks client will automatically start and connect to your shadowsocks server.
Check if It Works
After you rebooted your computer, enter the following command in terminal:
sudo systemctl status rc-local.service
If your sslocal command works then you will get this ouput:
● rc-local.service - /etc/rc.local Compatibility Loaded: loaded (/etc/systemd/system/rc-local.service; enabled; vendor preset: enabled) Active: active (running) since Fri 2015-11-27 03:19:25 CST; 2min 39s ago Process: 881 ExecStart=/etc/rc.local start (code=exited, status=0/SUCCESS) CGroup: /system.slice/rc-local.service ├─ 887 watch -n 60 su matrix -c ibam └─1112 /usr/bin/python /usr/local/bin/sslocal -c /etc/shadowsocks....
As you can see from the last line, the sslocal command created a process whose pid is 1112 on my machine. It means shadowsocks client is running smoothly. And of course you can tell your browser to connect through your shadowsocks client to see if everything goes well.
If for some reason your /etc/rc.local script won’t run, then check the following post to find the solution.
How to enable /etc/rc.local with Systemd

abin 2016-05-13 22:56 发表评论

httpClient Https 单向不验�?httpClient�q�接�?

abin — Wed, 27 Apr 2016 11:04:00 GMT

废话��说�Q�直接上代码�Q�以前都是调用别人写好的�Q�现在有旉��自己弄下�Q�具体功能如下：
1、httpClient+http+�U�程池：
2、httpClient+https(单向不验证证�?+�U�程池：

https�?TOMCAT_HOME%/conf/server.xml里面的配�|�文�?br />
maxThreads="150" scheme="https" secure="true"
clientAuth="false" keystoreFile="D:/tomcat.keystore"
keystorePass="heikaim" sslProtocol="TLS" executor="tomcatThreadPool"/>
其中 clientAuth="false"表示不开启证书验证，只是单存的走https

package com.abin.lee.util;

import org.apache.commons.collections4.MapUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.http.*;
import org.apache.http.client.HttpRequestRetryHandler;
import org.apache.http.client.config.CookieSpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.ConnectTimeoutException;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.NoopHostnameVerifier;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;

import javax.net.ssl.*;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.UnknownHostException;
import java.nio.charset.Charset;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.*;

/**
* Created with IntelliJ IDEA.
* User: abin
* Date: 16-4-18
* Time: 上午10:24
* To change this template use File | Settings | File Templates.
*/
public class HttpClientUtil {
private static CloseableHttpClient httpsClient = null;
private static CloseableHttpClient httpClient = null;

static {
httpClient = getHttpClient();
httpsClient = getHttpsClient();
}

public static CloseableHttpClient getHttpClient() {
try {
httpClient = HttpClients.custom()
.setConnectionManager(PoolManager.getHttpPoolInstance())
.setConnectionManagerShared(true)
.setDefaultRequestConfig(requestConfig())
.setRetryHandler(retryHandler())
.build();
} catch (Exception e) {
e.printStackTrace();
}
return httpClient;
}

public static CloseableHttpClient getHttpsClient() {
try {
//Secure Protocol implementation.
SSLContext ctx = SSLContext.getInstance("SSL");
//Implementation of a trust manager for X509 certificates
TrustManager x509TrustManager = new X509TrustManager() {
public void checkClientTrusted(X509Certificate[] xcs,
String string) throws CertificateException {
}
public void checkServerTrusted(X509Certificate[] xcs,
String string) throws CertificateException {
}
public X509Certificate[] getAcceptedIssuers() {
return null;
}
};
ctx.init(null, new TrustManager[]{x509TrustManager}, null);
//首先讄��全局的标准cookie�{�略
// RequestConfig requestConfig = RequestConfig.custom().setCookieSpec(CookieSpecs.STANDARD_STRICT).build();
ConnectionSocketFactory connectionSocketFactory = new SSLConnectionSocketFactory(ctx, hostnameVerifier);
Registry socketFactoryRegistry = RegistryBuilder.create()
.register("http", PlainConnectionSocketFactory.INSTANCE)
.register("https", connectionSocketFactory).build();
// 讄��q�接�?br /> httpsClient = HttpClients.custom()
.setConnectionManager(PoolsManager.getHttpsPoolInstance(socketFactoryRegistry))
.setConnectionManagerShared(true)
.setDefaultRequestConfig(requestConfig())
.setRetryHandler(retryHandler())
.build();
} catch (Exception e) {
e.printStackTrace();
}
return httpsClient;
}

// 配置��h��的超时设�|?br /> //首先讄��全局的标准cookie�{�略
public static RequestConfig requestConfig(){
RequestConfig requestConfig = RequestConfig.custom()
.setCookieSpec(CookieSpecs.STANDARD_STRICT)
.setConnectionRequestTimeout(20000)
.setConnectTimeout(20000)
.setSocketTimeout(20000)
.build();
return requestConfig;
}

public static HttpRequestRetryHandler retryHandler(){
//��h��重试处理
HttpRequestRetryHandler httpRequestRetryHandler = new HttpRequestRetryHandler() {
public boolean retryRequest(IOException exception,int executionCount, HttpContext context) {
if (executionCount >= 5) {// 如果已经重试�?�ơ，��放�?br /> return false;
}
if (exception instanceof NoHttpResponseException) {// 如果服务器丢掉了�q�接�Q�那么就重试
return true;
}
if (exception instanceof SSLHandshakeException) {// 不要重试SSL握手异常
return false;
}
if (exception instanceof InterruptedIOException) {// ��时
return false;
}
if (exception instanceof UnknownHostException) {// 目标服务器不可达
return false;
}
if (exception instanceof ConnectTimeoutException) {// �q�接被拒�l?br /> return false;
}
if (exception instanceof SSLException) {// ssl握手异常
return false;
}

HttpClientContext clientContext = HttpClientContext.adapt(context);
HttpRequest request = clientContext.getRequest();
// 如果��h��是幂�{�的�Q�就再次��试
if (!(request instanceof HttpEntityEnclosingRequest)) {
return true;
}
return false;
}
};
return httpRequestRetryHandler;
}

//创徏HostnameVerifier
//用于解决javax.net.ssl.SSLException: hostname in certificate didn't match: <123.125.97.66> != <123.125.97.241>
static HostnameVerifier hostnameVerifier = new NoopHostnameVerifier(){
@Override
public boolean verify(String s, SSLSession sslSession) {
return super.verify(s, sslSession);
}
};

public static class PoolManager {
public static PoolingHttpClientConnectionManager clientConnectionManager = null;
private static int maxTotal = 200;
private static int defaultMaxPerRoute = 100;

private PoolManager(){
clientConnectionManager.setMaxTotal(maxTotal);
clientConnectionManager.setDefaultMaxPerRoute(defaultMaxPerRoute);
}

private static class PoolManagerHolder{
public static PoolManager instance = new PoolManager();
}

public static PoolManager getInstance() {
if(null == clientConnectionManager)
clientConnectionManager = new PoolingHttpClientConnectionManager();
return PoolManagerHolder.instance;
}

public static PoolingHttpClientConnectionManager getHttpPoolInstance() {
PoolManager.getInstance();
// System.out.println("getAvailable=" + clientConnectionManager.getTotalStats().getAvailable());
// System.out.println("getLeased=" + clientConnectionManager.getTotalStats().getLeased());
// System.out.println("getMax=" + clientConnectionManager.getTotalStats().getMax());
// System.out.println("getPending="+clientConnectionManager.getTotalStats().getPending());
return PoolManager.clientConnectionManager;
}

}

public static class PoolsManager {
public static PoolingHttpClientConnectionManager clientConnectionManager = null;
private static int maxTotal = 200;
private static int defaultMaxPerRoute = 100;

private PoolsManager(){
clientConnectionManager.setMaxTotal(maxTotal);
clientConnectionManager.setDefaultMaxPerRoute(defaultMaxPerRoute);
}

private static class PoolsManagerHolder{
public static PoolsManager instance = new PoolsManager();
}

public static PoolsManager getInstance(Registry socketFactoryRegistry) {
if(null == clientConnectionManager)
clientConnectionManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
return PoolsManagerHolder.instance;
}

public static PoolingHttpClientConnectionManager getHttpsPoolInstance(Registry socketFactoryRegistry) {
PoolsManager.getInstance(socketFactoryRegistry);
// System.out.println("getAvailable=" + clientConnectionManager.getTotalStats().getAvailable());
// System.out.println("getLeased=" + clientConnectionManager.getTotalStats().getLeased());
// System.out.println("getMax=" + clientConnectionManager.getTotalStats().getMax());
// System.out.println("getPending="+clientConnectionManager.getTotalStats().getPending());
return PoolsManager.clientConnectionManager;
}

}

public static String httpPost(Map request, String httpUrl){
String result = "";
CloseableHttpClient httpClient = getHttpClient();
try {
if(MapUtils.isEmpty(request))
throw new Exception("��h��参数不能为空");
HttpPost httpPost = new HttpPost(httpUrl);
List nvps = new ArrayList();
for(Iterator> iterator=request.entrySet().iterator(); iterator.hasNext();){
Map.Entry entry = iterator.next();
nvps.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
}
httpPost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));
System.out.println("Executing request: " + httpPost.getRequestLine());
CloseableHttpResponse response = httpClient.execute(httpPost);
result = EntityUtils.toString(response.getEntity());
System.out.println("Executing response: "+ result);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
try {
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}

public static String httpPost(String json, String httpUrl, Map headers){
String result = "";
CloseableHttpClient httpClient = getHttpClient();
try {
if(StringUtils.isBlank(json))
throw new Exception("��h��参数不能为空");
HttpPost httpPost = new HttpPost(httpUrl);
for(Iterator> iterator=headers.entrySet().iterator();iterator.hasNext();){
Map.Entry entry = iterator.next();
Header header = new BasicHeader(entry.getKey(), entry.getValue());
httpPost.setHeader(header);
}
httpPost.setEntity(new StringEntity(json, Charset.forName("UTF-8")));
System.out.println("Executing request: " + httpPost.getRequestLine());
CloseableHttpResponse response = httpClient.execute(httpPost);
result = EntityUtils.toString(response.getEntity());
System.out.println("Executing response: "+ result);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
try {
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}

public static String httpGet(String httpUrl, Map headers) {
String result = "";
CloseableHttpClient httpClient = getHttpClient();
try {
HttpGet httpGet = new HttpGet(httpUrl);
System.out.println("Executing request: " + httpGet.getRequestLine());
for(Iterator> iterator=headers.entrySet().iterator();iterator.hasNext();){
Map.Entry entry = iterator.next();
Header header = new BasicHeader(entry.getKey(), entry.getValue());
httpGet.setHeader(header);
}
CloseableHttpResponse response = httpClient.execute(httpGet);
result = EntityUtils.toString(response.getEntity());
System.out.println("Executing response: "+ result);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
try {
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}

public static String httpGet(String httpUrl) {
String result = "";
CloseableHttpClient httpClient = getHttpClient();
try {
HttpGet httpGet = new HttpGet(httpUrl);
System.out.println("Executing request: " + httpGet.getRequestLine());
CloseableHttpResponse response = httpClient.execute(httpGet);
result = EntityUtils.toString(response.getEntity());
System.out.println("Executing response: "+ result);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
try {
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}

maven依赖�Q?br />

org.apache.httpcomponents
httpclient
4.5.2

org.apache.httpcomponents
httpcore
4.4.4

org.apache.httpcomponents
httpmime
4.5.2

<dependency>
<groupId>org.apache.commonsgroupId>
<artifactId>commons-collections4artifactId>
<version>4.1version>
dependency>

abin 2016-04-27 19:04 发表评论

Redis 代理服务Twemproxy

abin — Tue, 03 Nov 2015 11:30:00 GMT

1、twemproxy explore

  当我们有大量 Redis �?Memcached 的时候，通常只能通过客户端的一些数据分配算法（比如一致性哈希）�Q?/span>来实现集��存储的�Ҏ��?/span>虽然Redis 2.6版本已经发布Redis Cluster�Q�但�q�不是很成熟适用正式生��环境�?span style="color:#333333; font-family:Helvetica,Tahoma,Arial,sans-serif; font-size:14px; line-height:25.200000762939453px"> Redis �?Cluster �Ҏ��q�没有正式推��Z��前，我们通过 Proxy 的方式来实现集群存储�?/span>

Twitter�Q�世界最大的Redis集群之一部��v在Twitter用于为用��h��供时间��u数据。Twitter Open Source部门提供了Twemproxy�?/span>

Twemproxy,也叫nutcraker。是一个twtter开源的一个redis和memcache代理服务器�?redis作�ؓ一个高效的�~�存服务器，非常��h��应用价倹{��但是当使用比较多的时候，��希望可以通过某种方式 �l�一�q?/span>行管理。避免每个应用每个客��L��理�q�接的松散性。同时在一定程度上变得可以控制�?/p>
Twemproxy是一个快速的单线�E�代理程序，支持Memcached ASCII协议和更新的Redis协议�Q?/span>

它全部用C写成�Q��用Apache 2.0 License授权。项目在Linux上可以工作，而在OSX上无法编译，因�ؓ它依赖了epoll API.

Twemproxy 通过引入一个代理层�Q�可以将其后端的多台 Redis �?Memcached 实例�q�行�l�一��理与分配，使应用程序只需要在 Twemproxy 上进行操作，而不用关心后面具体有多少个真实的 Redis �?Memcached 存储�?/span>

2�?/span>twemproxy�Ҏ��：

支持��p�|节点自动删除

可以讄��重新�q�接该节点的旉��
可以讄��q�接多少�ơ之后删除该节点
该方式适合作�ؓcache存储

支持讄��HashTag

通过HashTag可以自己讑֮��两个KEYhash到同一个实例上厅R�?/li>

减少与redis的直接连接数

保持与redis的长�q�接
可设�|�代理与后台每个redis�q�接的数�?/li>

自动分片到后端多个redis实例�?/p>
多种hash��法�Q?span style="font-family:Verdana,Arial,Helvetica,sans-serif; font-size:14px; line-height:25px">能够使用不同的策略和散列函数支持一致性hash�?/span>
可以讄��后端实例的权�?/li>

避免单点问题

可以�q��部��v多个代理�?client自动选择可用的一�?/li>

支持redis pipelining request

支持��h��的流式与批处理，降低来回的消�?/span>

支持状态监�?/p>
可设�|�状态监控ip和端口，讉K��ip和端口可以得��C��个json格式的状态信息串
可设�|�监控信息刷新间隔时�?/li>

高吞吐量

�q�接复用�Q�内存复用�?/li>
��多个连接请求，�l�成reids pipelining�l�一向redis��h��?/li>

另外可以修改redis的源代码�Q�抽取出redis中的前半部分�Q�作��Z��个中间代理层。最�l�都是通过linux下的epoll 事�g机制提高�q�发效率�Q�其中nutcraker本��n也是使用epoll的事件机制。�ƈ且在性能��试上的表现非常��?/p>

3、twemproxy问题与不��?/span>

Twemproxy �׃��其自�w�原理限�Ӟ��有一些不��之处，如：

不支持针对多个值的操作�Q�比如取sets的子交�ƈ补等�Q�MGET �?DEL 除外�Q?/span>
不支持Redis的事务操�?/span>
出错提示�q�不够完�?/span>
也不支持select操作

4、安装与配置

具体的安装步骤可用查看github�Q?a target="_blank">https://github.com/twitter/twemproxy
Twemproxy 的安装，主要命��o如下�Q?nbsp;

apt-get install automake
apt-get install libtool
git clone git://github.com/twitter/twemproxy.git
cd twemproxy
autoreconf -fvi
./configure --enable-debug=log
make
src/nutcracker -h

通过上面的命令就��安装好了，然后是具体的配置�Q�下面是一个典型的配置

    redis1:
      listen: 127.0.0.1:6379 #使用哪个端口启动Twemproxy
      redis: true #是否是Redis的proxy
      hash: fnv1a_64 #指定具体的hash函数
      distribution: ketama #具体的hash��法
      auto_eject_hosts: true #是否在结�Ҏ��法响应的时候��时摘除结�?
      timeout: 400 #��时旉��Q�毫�U�）
      server_retry_timeout: 2000 #重试的时��_��毫秒�Q?
      server_failure_limit: 1 #�l�点故障多少�ơ就��摘除掉
      servers: #下面表示所有的Redis节点�Q�IP:端口�?权重�Q?
       - 127.0.0.1:6380:1
       - 127.0.0.1:6381:1
       - 127.0.0.1:6382:1

    redis2:
      listen: 0.0.0.0:10000
      redis: true
      hash: fnv1a_64
      distribution: ketama
      auto_eject_hosts: false
      timeout: 400
      servers:
       - 127.0.0.1:6379:1
       - 127.0.0.1:6380:1
       - 127.0.0.1:6381:1
       - 127.0.0.1:6382:1

你可以同时开启多�?Twemproxy 实例�Q�它们都可以�q�行��d��Q�这样你的应用程序就可以完全避免所谓的单点故障�?

http://blog.csdn.net/hguisu/article/details/9174459/

abin 2015-11-03 19:30 发表评论

亚洲乱码中文字幕小综合,日韩亚洲人成在线,亚洲国产精品一区二区第四页

JDK 源码�?HashMap �?hash �Ҏ��原理是什么？

GoLang之方法与接口

�Ҏ��

匿名�l�合

��D��义和引用语义

接口

嵌入接口

反射

老虞要学GoLang-函数(�?

共�?/h3>关键�?#8212;—func�Ҏ���?#8212;—funcName入参——— a,b int,b string�q�回�?#8212;— r,s int函数�?#8212;— {}

�Ҏ�?/h3>Go中函数的�Ҏ��是非常��L���Q�给我们带来不一��L���~�程体验�?/p>

为特定类型定义函敎ͼ�即�ؓ�c�d��对象定义�Ҏ��

函数也是“�?#8221;

函数也是“�c�d��”

defer 延迟函数

MySQL触发器Trigger实例��?

聊聊高�ƈ发系�l�之限流�Ҏ��-1

shadowsocks 安装

Install the Command Line Client

Debian

Ubuntu

Fedora/Centos

OpenSUSE

Archlinux

Create a Configuration File

To run in the background

Auto Start the Client on System Boot

Check if It Works

How to enable /etc/rc.local with SystemdInstall the Command Line Client

If you prefer command line client, then you can install it on your Linux with the following command.

Debian

sudo apt-get install python-pip sudo pip install shadowsocks

Ubuntu

Yes, you can use the above commands to install shadowsocks client on ubuntu. But it will install it under ~/.local/bin/ directory and it causes loads of trouble. So I suggest using su to become root first and then issue the following two commands.apt-get install python-pip pip install shadowsocks

Fedora/Centos

sudo yum install python-setuptools or sudo dnf install python-setuptools sudo easy_install pip sudo pip install shadowsocks

OpenSUSE

sudo zypper install python-pip sudo pip install shadowsocks

Archlinux

Create a Configuration File

To run in the background

sudo sslocal -c /etc/shadowsocks.json -d start

Auto Start the Client on System Boot

Edit /etc/rc.local filesudo vi /etc/rc.localPut the following line above the exit 0 line:sudo sslocal -c /etc/shadowsocks.json -d startSave and close the file. Next time you start your computer, shadowsocks client will automatically start and connect to your shadowsocks server.

Check if It Works

httpClient Https 单向不验�?httpClient�q�接�?

Redis 代理服务Twemproxy

1、twemproxy explore

3、twemproxy问题与不��?/span>

4、安装与配置

共�?/h3>
关键�?#8212;—func
�Ҏ��?#8212;—funcName
入参——— a,b int,b string
�q�回�?#8212;— r,s int
函数�?#8212;— {}

�Ҏ�?/h3>
Go中函数的�Ҏ��是非常��L��Q�给我们带来不一��L��~�程体验�?/p>

Yes, you can use the above commands to install shadowsocks client on ubuntu. But it will install it under ~/.local/bin/ directory and it causes loads of trouble. So I suggest using su to become root first and then issue the following two commands.
apt-get install python-pip pip install shadowsocks

Edit /etc/rc.local file
sudo vi /etc/rc.local
Put the following line above the exit 0 line:
sudo sslocal -c /etc/shadowsocks.json -d start
Save and close the file. Next time you start your computer, shadowsocks client will automatically start and connect to your shadowsocks server.