gRPC 转 Rest 的几种实现

[jxlwqq]

• 业务代码中使用 gRPC Gateway
• 使用 Istio Envoy Filter: gRPC-JSON Transcoder
• 使用 Kong 等网关的 gRPC-gateway 插件
• 业务代码中使用 Gin 等 Web 框架自行实现一个 HTTP Server，内部的业务逻辑与 gRPC 复用

[jxlwqq]

Envoy Filter gRPC-JSON Transcoder Demo:

apiVersion: networking.istio.io/v1alpha3
kind: EnvoyFilter
metadata:
  name: myapp-grpc-transcoder
spec:
  workloadSelector:
    labels:
      app: myapp # match your deployment
  configPatches:
  - applyTo: HTTP_FILTER
    match:
      context: SIDECAR_INBOUND
      listener:
        filterChain:
          filter:
            name: envoy.filters.network.http_connection_manager
            subFilter:
              name: envoy.filters.http.router
        portNumber: 50051 # application port
    patch:
      operation: INSERT_BEFORE
      value:
        name: envoy.filters.http.grpc_json_transcoder
        typed_config:
          "@type": type.googleapis.com/envoy.extensions.filters.http.grpc_json_transcoder.v3.GrpcJsonTranscoder
          services:
          - mycompany.myapi.v1.MyService # your gRPC service
          print_options:
            add_whitespace: true
            always_print_enums_as_ints: false
            always_print_primitive_fields: true
            preserve_proto_field_names: false
          convert_grpc_status: true
          proto_descriptor_bin: # base64 encoded proto descriptor

参考：

istio/istio#7652

https://www.tetrate.io/blog/grpc-transcoding-with-istio/

需要设置 proto_descriptor_bin，跟业务逻辑有一定的耦合，如果 proto 文件发生变更，EnvoyFilter 也要跟着更新。

性能方面存疑，没有具体测试过。

[jxlwqq]

本 demo 使用 gRPC Gateway，部分代码如下：

blog-microservices/cmd/blog/main.go

Lines 72 to 87 in 541be82

	// Start HTTP server
	logger.Infof("HTTP Listening on port %s", conf.Blog.Server.HTTP.Port)
	httpMux := runtime.NewServeMux()
	opts := []grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())}
	if err = v1.RegisterBlogServiceHandlerFromEndpoint(context.Background(), httpMux, conf.Blog.Server.GRPC.Port, opts); err != nil {
	logger.Fatal(err)
	}
	httpServer := &http.Server{
	Addr: conf.Blog.Server.HTTP.Port,
	Handler: httpMux,
	}
	go func() {
	if err = httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
	logger.Fatal(err)
	}
	}()

[jxlwqq]

Kong 插件在 Kubernetes 集群的使用如下：

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
metadata:
  name: <grpc-gateway-example>
config: 
  proto: path/to/hello.proto
plugin: grpc-gateway
---
apiVersion: networking/v1beta1
kind: Ingress
metadata:
  name: {ROUTE}
  annotations:
    kubernetes.io/ingress.class: kong
    konghq.com/plugins: <grpc-gateway-example>
spec:
  rules:
  - host: examplehostname.com
    http:
      paths:
      - path: /bar
        backend:
          serviceName: echo
          servicePort: 80