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定义了Handlers属性，是一个Middleware数组；Pipeline定义了Apply方法，它会从后往前挨个执行Middleware函数；Middleware函数接收fasthttp.RequestHandler，返回fasthttp.RequestHandler

实例

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定义了pipeline属性，其useComponents方法接收fasthttp.RequestHandler)，对其执行pipeline.Apply

小结

dapr的Pipeline定义了Handlers属性，是一个Middleware数组；Pipeline定义了Apply方法，它会从后往前挨个执行Middleware函数；Middleware函数接收fasthttp.RequestHandler，返回fasthttp.RequestHandler。

doc

• dapr