去1.8插件使用自定义界面

Question

我想使用基于go插件的自定义界面,但我发现它不支持.

filter.Filter的定义

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pkg是我的go app项目.

加载插件文件

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项目中的加载插件代码

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.插件项目和go app项目是不同的项目.

我发现了错误:

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

您可以在此项目中找到代码https://github.com/fagongzi/gateway/tree/go18-plugin-support.

1. filter.Filter 在pkg/filter包中.
2. load plugin file 在proxy/factory.go中
3. plugin go file 在另一个项目中.

Answer 1

自定义界面工作正常.

但有一点很重要:你只能从插件外部定义的值中键入断言类型(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,您只能键入断言一个函数类型,其参数和结果类型也在插件之外定义.

1.使用插件外部的通用包

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

在包中定义它filter:

package filter

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

该插件在包pq和导入包中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\n", 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\n", filter, filter, err)
    fmt.Println("\tName:", filter.Name())
    fmt.Println("\tAge:", 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{},并在主应用程序中定义界面

另一个解决方案是让插件函数返回一个类型的值interface{}.您的主应用程序可以定义它所期望的接口,并且可以interface{}对插件返回的值使用类型断言.

filter这次没有包裹.

该插件包装pq:

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\n", f, f)
    return
}

主要的应用程序:

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\n", filterIface, filterIface, err)
    myfilter := filterIface.(MyFilter)
    fmt.Println("\tName:", myfilter.Name())
    fmt.Println("\tAge:", 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？