go 1.8 插件使用自定义界面 [英] go 1.8 plugin use custom interface

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问题描述

我想使用基于 go 插件的自定义界面，但我发现它不支持.

I want to use custom interface based on go plugin, but I found it's not support. 

package filter

import (
    "net/http"

    "github.com/valyala/fasthttp"
)

// Context filter context
type Context interface {
    SetStartAt(startAt int64)
    SetEndAt(endAt int64)
    GetStartAt() int64
    GetEndAt() int64

    GetProxyServerAddr() string
    GetProxyOuterRequest() *fasthttp.Request
    GetProxyResponse() *fasthttp.Response
    NeedMerge() bool

    GetOriginRequestCtx() *fasthttp.RequestCtx

    GetMaxQPS() int

    ValidateProxyOuterRequest() bool

    InBlacklist(ip string) bool
    InWhitelist(ip string) bool

    IsCircuitOpen() bool
    IsCircuitHalf() bool

    GetOpenToCloseFailureRate() int
    GetHalfTrafficRate() int
    GetHalfToOpenSucceedRate() int
    GetOpenToCloseCollectSeconds() int

    ChangeCircuitStatusToClose()
    ChangeCircuitStatusToOpen()

    RecordMetricsForRequest()
    RecordMetricsForResponse()
    RecordMetricsForFailure()
    RecordMetricsForReject()

    GetRecentlyRequestSuccessedCount(sec int) int
    GetRecentlyRequestCount(sec int) int
    GetRecentlyRequestFailureCount(sec int) int
}

// Filter filter interface
type Filter interface {
    Name() string

    Pre(c Context) (statusCode int, err error)
    Post(c Context) (statusCode int, err error)
    PostErr(c Context)
}

// BaseFilter base filter support default implemention
type BaseFilter struct{}

// Pre execute before proxy
func (f BaseFilter) Pre(c Context) (statusCode int, err error) {
    return http.StatusOK, nil
}

// Post execute after proxy
func (f BaseFilter) Post(c Context) (statusCode int, err error) {
    return http.StatusOK, nil
}

// PostErr execute proxy has errors
func (f BaseFilter) PostErr(c Context) {

}

这个包在我的 go 应用项目中.

This pkg is in my go app project.

package proxy

import (
    "errors"
    "plugin"
    "strings"

    "github.com/fagongzi/gateway/pkg/conf"
    "github.com/fagongzi/gateway/pkg/filter"
)

var (
    // ErrKnownFilter known filter error
    ErrKnownFilter = errors.New("unknow filter")
)

const (
    // FilterHTTPAccess access log filter
    FilterHTTPAccess = "HTTP-ACCESS"
    // FilterHeader header filter
    FilterHeader = "HEAD" // process header fiter
    // FilterXForward xforward fiter
    FilterXForward = "XFORWARD"
    // FilterBlackList blacklist filter
    FilterBlackList = "BLACKLIST"
    // FilterWhiteList whitelist filter
    FilterWhiteList = "WHITELIST"
    // FilterAnalysis analysis filter
    FilterAnalysis = "ANALYSIS"
    // FilterRateLimiting limit filter
    FilterRateLimiting = "RATE-LIMITING"
    // FilterCircuitBreake circuit breake filter
    FilterCircuitBreake = "CIRCUIT-BREAKE"
    // FilterValidation validation request filter
    FilterValidation = "VALIDATION"
)

func newFilter(filterSpec *conf.FilterSpec) (filter.Filter, error) {
    if filterSpec.External {
        return newExternalFilter(filterSpec)
    }

    input := strings.ToUpper(filterSpec.Name)

    switch input {
    case FilterHTTPAccess:
        return newAccessFilter(), nil
    case FilterHeader:
        return newHeadersFilter(), nil
    case FilterXForward:
        return newXForwardForFilter(), nil
    case FilterAnalysis:
        return newAnalysisFilter(), nil
    case FilterBlackList:
        return newBlackListFilter(), nil
    case FilterWhiteList:
        return newWhiteListFilter(), nil
    case FilterRateLimiting:
        return newRateLimitingFilter(), nil
    case FilterCircuitBreake:
        return newCircuitBreakeFilter(), nil
    case FilterValidation:
        return newValidationFilter(), nil
    default:
        return nil, ErrKnownFilter
    }
}

func newExternalFilter(filterSpec *conf.FilterSpec) (filter.Filter, error) {
    p, err := plugin.Open(filterSpec.ExternalPluginFile)
    if err != nil {
        return nil, err
    }

    s, err := p.Lookup("NewExternalFilter")
    if err != nil {
        return nil, err
    }

    sf := s.(func() (filter.Filter, error))
    return sf()
}

这是我的go app项目中加载插件的代码

This is the code of load plugin in my go app project

package main

import (
    "C"
    "strings"
    "time"

    "github.com/CodisLabs/codis/pkg/utils/log"
    "github.com/fagongzi/gateway/pkg/filter"
    "github.com/valyala/fasthttp"
)

// AccessFilter record the http access log
// log format: $remoteip "$method $path" $code "$agent" $svr $cost
type AccessFilter struct {
}

// NewExternalFilter create a External filter
func NewExternalFilter() (filter.Filter, error) {
    return &AccessFilter{}, nil
}

// Name return name of this filter
func (f *AccessFilter) Name() string {
    return "HTTP-ACCESS"
}

// Pre pre process
func (f *AccessFilter) Pre(c filter.Context) (statusCode int, err error) {
    return 200, nil
}

// Post execute after proxy
func (f *AccessFilter) Post(c filter.Context) (statusCode int, err error) {
    cost := (c.GetStartAt() - c.GetEndAt())

    log.Infof("%s %s "%s" %d "%s" %s %s",
        GetRealClientIP(c.GetOriginRequestCtx()),
        c.GetOriginRequestCtx().Method(),
        c.GetProxyOuterRequest().RequestURI(),
        c.GetProxyResponse().StatusCode(),
        c.GetOriginRequestCtx().UserAgent(),
        c.GetProxyServerAddr(),
        time.Duration(cost))

    return 200, nil
}

// PostErr post error process
func (f *AccessFilter) PostErr(c filter.Context) {

}

// GetRealClientIP get read client ip
func GetRealClientIP(ctx *fasthttp.RequestCtx) string {
    xforward := ctx.Request.Header.Peek("X-Forwarded-For")
    if nil == xforward {
        return strings.SplitN(ctx.RemoteAddr().String(), ":", 2)[0]
    }

    return strings.SplitN(string(xforward), ",", 2)[0]
}

这是插件的定义，它在我的插件项目中.plugin项目和go app项目是不同的项目.

This is the definition of plugin, it's in my plugin project. The plugin project and go app project are different projects.

panic: interface conversion: plugin.Symbol is func() (filter.Filter, error), not func() (filter.Filter, error)

你可以在这个项目中找到代码 https://github.com/fagongzi/gateway/tree/go18-plugin-support.

You can find code in this project https://github.com/fagongzi/gateway/tree/go18-plugin-support.

  1. filter.Filter 在 pkg/filter 包中.
  2. 在 proxy/factory.go 中加载插件文件
  3. plugin go file 在另一个项目中.
  1. filter.Filter is in pkg/filter package.
  2. load plugin file in proxy/factory.go
  3. plugin go file is in another project.

推荐答案

自定义界面工作正常.

但有一件重要的事情:你只能type assert 类型从插件中查找的值在插件外部定义(你不能引用插件中定义的类型).这也适用于复合类型"的每个组件，例如您只能键入 assert 一个函数类型，其参数和结果类型也在插件之外定义.

But one important thing: you can only type assert types from values looked up from plugins that are defined outside of the plugin (you can't refer types defined in plugins). This also applies to each component of "composite types", for example you can only type assert a function type whose parameter and result types are also defined outside of the plugin.

一种解决方案是在插件外部的包中定义接口，插件和您的应用程序都可以导入并引用它.

One solution is to define the interface in a package outside of the plugin, and both the plugin and your app can import it and refer to it.

在包filter中定义:

package filter

type Filter interface {
    Name() string
    Age() int
}

插件在包 pq 中并导入包 filter:

The plugin is in package pq and imports package filter:

package main

import (
    "fmt"
    "filter"
)

type plgFilter struct{}

func (plgFilter) Name() string { return "Bob" }
func (plgFilter) Age() int     { return 23 }

func GetFilter() (f filter.Filter, err error) {
    f = plgFilter{}
    fmt.Printf("[plugin GetFilter] Returning filter: %T %v
", f, f)
    return
}

主应用程序也导入(相同)包filter，加载插件，查找GetFilter()，调用它并使用返回的过滤器:

And the main app that also imports (the same) package filter, loads the plugin, looks up GetFilter(), calls it and also uses the returned Filter:

package main

import (
    "fmt"
    "filter"
    "plugin"
)

func main() {
    p, err := plugin.Open("pg/pg.so")
    if err != nil {
        panic(err)
    }

    GetFilter, err := p.Lookup("GetFilter")
    if err != nil {
        panic(err)
    }
    filter, err := GetFilter.(func() (filter.Filter, error))()
    fmt.Printf("GetFilter result: %T %v %v
", filter, filter, err)
    fmt.Println("	Name:", filter.Name())
    fmt.Println("	Age:", filter.Age())
}

输出:

[plugin GetFilter] Returning filter: main.plgFilter {}
GetFilter result: main.plgFilter {} <nil>
        Name: Bob
        Age: 23

2.使用插件返回interface{}，以及在主应用程序中定义的接口

另一种解决方案是让插件函数返回 interface{} 类型的值.您的主应用可以定义它期望的接口，并且可以对插件返回的 interface{} 值使用类型断言.

2. With plugin returning interface{}, and interface defined in main app

Another solution is to have the plugin function return a value of type interface{}. Your main app can define the interface it expects, and it can use type assertion on the interface{} value returned by the plugin.

这次没有filter包.

插件在 pq 包中:

package main

import (
    "fmt"
)

type plgFilter struct{}

func (plgFilter) Name() string { return "Bob" }
func (plgFilter) Age() int     { return 23 }

func GetFilterIface() (f interface{}, err error) {
    f = plgFilter{}
    fmt.Printf("[plugin GetFilterIface] Returning filter: %T %v
", f, f)
    return
}

和主应用程序:

package main

import (
    "fmt"
    "plugin"
)

func main() {
    p, err := plugin.Open("pg/pg.so")
    if err != nil {
        panic(err)
    }

    GetFilterIface, err := p.Lookup("GetFilterIface")
    if err != nil {
        panic(err)
    }
    filterIface, err := GetFilterIface.(func() (interface{}, error))()
    fmt.Printf("GetFilterIface result: %T %v %v
", filterIface, filterIface, err)
    myfilter := filterIface.(MyFilter)
    fmt.Println("	Name:", myfilter.Name())
    fmt.Println("	Age:", myfilter.Age())
}

type MyFilter interface {
    Name() string
    Age() int
}

输出:

[plugin GetFilterIface] Returning filter: main.plgFilter {}
GetFilterIface result: main.plgFilter {} <nil>
        Name: Bob
        Age: 23

另请参阅相关问题:Go 插件依赖项如何工作?

这篇关于go 1.8 插件使用自定义界面的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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