聊聊dapr的Pipeline

序

本文主要研究一下dapr的Pipeline

Pipeline

dapr/pkg/middleware/http/http_pipeline.go

import (
    "github.com/dapr/dapr/pkg/config"
    "github.com/valyala/fasthttp"
)

type Middleware func(h fasthttp.RequestHandler) fasthttp.RequestHandler

// HTTPPipeline defines the middleware pipeline to be plugged into Dapr sidecar
type Pipeline struct {
    Handlers []Middleware
}

func BuildHTTPPipeline(spec config.PipelineSpec) (Pipeline, error) {
    return Pipeline{}, nil
}

func (p Pipeline) Apply(handler fasthttp.RequestHandler) fasthttp.RequestHandler {
    for i := len(p.Handlers) - 1; i >= 0; i-- {
        handler = p.Handlers[i](handler)
    }
    return handler
}

Pipeline定義了Handlers屬性，是一個Middleware數組；Pipeline定義了Apply方法，它會從後往前挨個執行Middleware函數；Middleware函數接收fasthttp.RequestHandler，返回fasthttp.RequestHandler

實例

dapr/pkg/http/server.go

type server struct {
    config      ServerConfig
    tracingSpec config.TracingSpec
    metricSpec  config.MetricSpec
    pipeline    http_middleware.Pipeline
    api         API
}

func (s *server) useComponents(next fasthttp.RequestHandler) fasthttp.RequestHandler {
    return s.pipeline.Apply(next)
}

server定義了pipeline屬性，其useComponents方法接收fasthttp.RequestHandler)，對其執行pipeline.Apply

小結

dapr的Pipeline定義了Handlers屬性，是一個Middleware數組；Pipeline定義了Apply方法，它會從後往前挨個執行Middleware函數；Middleware函數接收fasthttp.RequestHandler，返回fasthttp.RequestHandler。

doc

• dapr