refactor: cleanup server logic (backport cosmos#15041)

cleanup for easier review

CHANGELOG.md

@@ -45,6 +45,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (gov) [#15979](https://github.com/cosmos/cosmos-sdk/pull/15979) Improve gov error message when failing to convert v1 proposal to v1beta1.
 * (server) [#16061](https://github.com/cosmos/cosmos-sdk/pull/16061) add comet bootstrap command
 * (store) [#16067](https://github.com/cosmos/cosmos-sdk/pull/16067) Add local snapshots management commands.
+* (server) [#15041](https://github.com/cosmos/cosmos-sdk/pull/15041) Remove unnecessary sleeps from gRPC and API server initiation. The servers will start and accept requests as soon as they're ready.
 
 ### Bug Fixes
 

go.mod

@@ -53,6 +53,7 @@ require (
 	github.com/tidwall/btree v1.5.0
 	golang.org/x/crypto v0.7.0
 	golang.org/x/exp v0.0.0-20230310171629-522b1b587ee0
+	golang.org/x/sync v0.1.0
 	google.golang.org/genproto v0.0.0-20230306155012-7f2fa6fef1f4
 	google.golang.org/grpc v1.54.0
 	google.golang.org/protobuf v1.30.0

go.sum

@@ -1146,6 +1146,8 @@ golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180823144017-11551d06cbcc/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=

server/api/server.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"context"
 	"fmt"
 	"net"
 	"net/http"
@@ -50,6 +51,7 @@ func CustomGRPCHeaderMatcher(key string) (string, bool) {
 	switch strings.ToLower(key) {
 	case grpctypes.GRPCBlockHeightHeader:
 		return grpctypes.GRPCBlockHeightHeader, true
+
 	default:
 		return runtime.DefaultHeaderMatcher(key)
 	}
@@ -86,9 +88,12 @@ func New(clientCtx client.Context, logger log.Logger) *Server {
 
 // Start starts the API server. Internally, the API server leverages Tendermint's
 // JSON RPC server. Configuration options are provided via config.APIConfig
-// and are delegated to the Tendermint JSON RPC server. The process is
-// non-blocking, so an external signal handler must be used.
-func (s *Server) Start(cfg config.Config) error {
+// and are delegated to the Tendermint JSON RPC server.
+//
+// Note, this creates a blocking process if the server is started successfully.
+// Otherwise, an error is returned. The caller is expected to provide a Context
+// that is properly canceled or closed to indicate the server should be stopped.
+func (s *Server) Start(ctx context.Context, cfg config.Config) error {
 	s.mtx.Lock()
 
 	tmCfg := tmrpcserver.DefaultConfig()
@@ -105,17 +110,38 @@ func (s *Server) Start(cfg config.Config) error {
 
 	s.registerGRPCGatewayRoutes()
 	s.listener = listener
-	var h http.Handler = s.Router
 
 	s.mtx.Unlock()
 
-	if cfg.API.EnableUnsafeCORS {
-		allowAllCORS := handlers.CORS(handlers.AllowedHeaders([]string{"Content-Type"}))
-		return tmrpcserver.Serve(s.listener, allowAllCORS(h), s.logger, tmCfg)
-	}
+	errCh := make(chan error)
+
+	// Start the API in an external goroutine as Serve is blocking and will return
+	// an error upon failure, which we'll send on the error channel that will be
+	// consumed by the for block below.
+	go func(enableUnsafeCORS bool) {
+		s.logger.Info("starting API server...", "address", cfg.API.Address)
 
-	s.logger.Info("starting API server...")
-	return tmrpcserver.Serve(s.listener, s.Router, s.logger, tmCfg)
+		if enableUnsafeCORS {
+			allowAllCORS := handlers.CORS(handlers.AllowedHeaders([]string{"Content-Type"}))
+			errCh <- tmrpcserver.Serve(s.listener, allowAllCORS(s.Router), s.logger, tmCfg)
+		} else {
+			errCh <- tmrpcserver.Serve(s.listener, s.Router, s.logger, tmCfg)
+		}
+	}(cfg.API.EnableUnsafeCORS)
+
+	// Start a blocking select to wait for an indication to stop the server or that
+	// the server failed to start properly.
+	select {
+	case <-ctx.Done():
+		// The calling process cancelled or closed the provided context, so we must
+		// gracefully stop the API server.
+		s.logger.Info("stopping API server...", "address", cfg.API.Address)
+		return s.Close()
+
+	case err := <-errCh:
+		s.logger.Error("failed to start API server", "err", err)
+		return err
+	}
 }
 
 // Close closes the API server.

server/grpc/grpc_web.go

@@ -1,19 +1,20 @@
 package grpc
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/improbable-eng/grpc-web/go/grpcweb"
+	"github.com/tendermint/tendermint/libs/log"
 	"google.golang.org/grpc"
 
 	"github.com/cosmos/cosmos-sdk/server/config"
-	"github.com/cosmos/cosmos-sdk/server/types"
 )
 
 // StartGRPCWeb starts a gRPC-Web server on the given address.
-func StartGRPCWeb(grpcSrv *grpc.Server, config config.Config) (*http.Server, error) {
+func StartGRPCWeb(ctx context.Context, logger log.Logger, grpcSrv *grpc.Server, config config.Config) error {
 	var options []grpcweb.Option
 	if config.GRPCWeb.EnableUnsafeCORS {
 		options = append(options,
@@ -32,15 +33,24 @@ func StartGRPCWeb(grpcSrv *grpc.Server, config config.Config) (*http.Server, err
 
 	errCh := make(chan error)
 	go func() {
+		logger.Info("starting gRPC web server...", "address", config.GRPCWeb.Address)
 		if err := grpcWebSrv.ListenAndServe(); err != nil {
 			errCh <- fmt.Errorf("[grpc] failed to serve: %w", err)
 		}
 	}()
 
+	// Start a blocking select to wait for an indication to stop the server or that
+	// the server failed to start properly.
 	select {
+	case <-ctx.Done():
+		// The calling process cancelled or closed the provided context, so we must
+		// gracefully stop the gRPC-web server.
+		logger.Info("stopping gRPC web server...", "address", config.GRPCWeb.Address)
+		grpcWebSrv.Close()
+		return nil
+
 	case err := <-errCh:
-		return nil, err
-	case <-time.After(types.ServerStartTime): // assume server started successfully
-		return grpcWebSrv, nil
+		logger.Error("failed to start gRPC Web server", "err", err)
+		return err
 	}
 }

server/grpc/server.go

@@ -1,10 +1,11 @@
 package grpc
 
 import (
+	"context"
 	"fmt"
 	"net"
-	"time"
 
+	"github.com/tendermint/tendermint/libs/log"
 	"google.golang.org/grpc"
 
 	"github.com/cosmos/cosmos-sdk/client"
@@ -16,8 +17,9 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
-// StartGRPCServer starts a gRPC server on the given address.
-func StartGRPCServer(clientCtx client.Context, app types.Application, cfg config.GRPCConfig) (*grpc.Server, error) {
+// NewGRPCServer returns a correctly configured and initialized gRPC server.
+// Note, the caller is responsible for starting the server. See StartGRPCServer.
+func NewGRPCServer(clientCtx client.Context, app types.Application, cfg config.GRPCConfig) (*grpc.Server, error) {
 	maxSendMsgSize := cfg.MaxSendMsgSize
 	if maxSendMsgSize == 0 {
 		maxSendMsgSize = config.DefaultGRPCMaxSendMsgSize
@@ -45,39 +47,58 @@ func StartGRPCServer(clientCtx client.Context, app types.Application, cfg config
 			for _, m := range clientCtx.TxConfig.SignModeHandler().Modes() {
 				modes[m.String()] = (int32)(m)
 			}
+
 			return modes
 		}(),
 		ChainID:           clientCtx.ChainID,
 		SdkConfig:         sdk.GetConfig(),
 		InterfaceRegistry: clientCtx.InterfaceRegistry,
 	})
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to register reflection service: %w", err)
 	}
 
 	// Reflection allows external clients to see what services and methods
 	// the gRPC server exposes.
 	gogoreflection.Register(grpcSrv)
 
+	return grpcSrv, nil
+}
+
+// StartGRPCServer starts the provided gRPC server on the address specified in cfg.
+//
+// Note, this creates a blocking process if the server is started successfully.
+// Otherwise, an error is returned. The caller is expected to provide a Context
+// that is properly canceled or closed to indicate the server should be stopped.
+func StartGRPCServer(ctx context.Context, logger log.Logger, cfg config.GRPCConfig, grpcSrv *grpc.Server) error {
 	listener, err := net.Listen("tcp", cfg.Address)
 	if err != nil {
-		return nil, err
+		return fmt.Errorf("failed to listen on address %s: %w", cfg.Address, err)
 	}
 
 	errCh := make(chan error)
+
+	// Start the gRPC in an external goroutine as Serve is blocking and will return
+	// an error upon failure, which we'll send on the error channel that will be
+	// consumed by the for block below.
 	go func() {
-		err = grpcSrv.Serve(listener)
-		if err != nil {
-			errCh <- fmt.Errorf("failed to serve: %w", err)
-		}
+		logger.Info("starting gRPC server...", "address", cfg.Address)
+		errCh <- grpcSrv.Serve(listener)
 	}()
 
+	// Start a blocking select to wait for an indication to stop the server or that
+	// the server failed to start properly.
 	select {
-	case err := <-errCh:
-		return nil, err
+	case <-ctx.Done():
+		// The calling process cancelled or closed the provided context, so we must
+		// gracefully stop the gRPC server.
+		logger.Info("stopping gRPC server...", "address", cfg.Address)
+		grpcSrv.GracefulStop()
+
+		return nil
 
-	case <-time.After(types.ServerStartTime):
-		// assume server started successfully
-		return grpcSrv, nil
+	case err := <-errCh:
+		logger.Error("failed to start gRPC server", "err", err)
+		return err
 	}
 }