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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Discuss] Use gRPC gateway to generate REST endpoints","articleBody":"## Introduction\r\n\r\nRight now, feast-java uses `RestController` ([example code](https://github.com/feast-dev/feast-java/blob/8541f36ecf28569db7ece35e936b5e9d83db3cde/serving/src/main/java/feast/serving/controller/ServingServiceRestController.java)) to implement REST endpoints for both feast-core and feast-serving. However, this approach will increase maintenance cost. Therefore, generating REST endpoint from proto definitions is a cleaner way.\r\n\r\n## Proposed Change\r\n\r\nUse [grpc-gateway](https://github.com/grpc-ecosystem/grpc-gateway) to generate the REST endpoint. \r\n\r\n### Steps\r\n#### 1. Add gateway server to translate REST call into gRPC call to another process inside the container\r\nThe example gateway server will look like:\r\n\r\n```\r\npackage main\r\n\r\nimport (\r\n\t\"context\"\r\n\t\"flag\"\r\n\t\"fmt\"\r\n\t\"net/http\"\r\n\r\n\t\"github.com/golang/glog\"\r\n\t\"github.com/grpc-ecosystem/grpc-gateway/v2/runtime\"\r\n\t\"google.golang.org/grpc\"\r\n\r\n\tcoreGateWay \"pkg/gateway/generated/feast/core\"\r\n\tservingGateWay \"pkg/gateway/generated/feast/serving\"\r\n)\r\n\r\n// gRPC serving endpoint\r\nvar servingServerEndpoint = flag.String(\"serving-server-endpoint\", \"localhost:6566\", \"gRPC server endpoint\")\r\n\r\nfunc run() error {\r\n\tctx := context.Background()\r\n\tctx, cancel := context.WithCancel(ctx)\r\n\tdefer cancel()\r\n\r\n\tmux := runtime.NewServeMux()\r\n\topts := []grpc.DialOption{grpc.WithInsecure()}\r\n\r\n\t// Register ServingServing endpoint\r\n\terr = servingGateWay.RegisterServingServiceHandlerFromEndpoint(ctx, mux, *servingServerEndpoint, opts)\r\n\tif err != nil {\r\n\t\treturn err\r\n\t}\r\n\r\n\t// Start HTTP server (and proxy calls to gRPC server endpoint)\r\n\treturn http.ListenAndServe(\":8000\", mux)\r\n}\r\n\r\nfunc main() {\r\n\tflag.Parse()\r\n\tdefer glog.Flush()\r\n\r\n\tif err := run(); err != nil {\r\n\t\tfmt.Println(err)\r\n\t\tglog.Fatal(err)\r\n\t}\r\n}\r\n```\r\n\r\n#### 2. Use [supervisord](http://supervisord.org/) to start two processes inside a container\r\n\r\nWe can provide instructions to use different entry points. Here's an example config:\r\n\r\n```\r\n[supervisord]\r\nnodaemon=true\r\n\r\n[program:serving]\r\ndirectory=/\r\nuser=root\r\ncommand=java -jar /opt/feast/feast-serving.jar --spring.config.location=classpath:/application.yml,file:/etc/feast/%(ENV_FEAST_SERVING_YML_NAME)s \r\n\r\n[program:gateway]\r\ndirectory=/\r\nuser=root\r\ncommand=/opt/feast/gateway_server \r\n            --serving-server-endpoint=%(ENV_FEAST_SERVING_URL)s\r\nnumprocs=1\r\n```\r\n\r\n#### 3. Remove existing REST controllers' code\r\n\r\nAs titled.","author":{"url":"https://github.com/randxie","@type":"Person","name":"randxie"},"datePublished":"2021-04-04T17:51:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":8},"url":"https://github.com/20/feast-java-old/issues/20"}