refactor: cleanup server logic (#15041)

CHANGELOG.md

@@ -80,6 +80,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (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.
 * (x/staking) [#14864](https://github.com/cosmos/cosmos-sdk/pull/14864) `create-validator` CLI command now takes a json file as an arg instead of having a bunch of required flags to it.
 * (cli) [#14659](https://github.com/cosmos/cosmos-sdk/pull/14659)  Added ability to query blocks by either height/hash `simd q block --type=height|hash <height|hash>`.
 * (store) [#14410](https://github.com/cosmos/cosmos-sdk/pull/14410) `rootmulti.Store.loadVersion` has validation to check if all the module stores' height is correct, it will error if any module store has incorrect height.
@@ -179,6 +180,11 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### API Breaking Changes
 
+* (server) [#15041](https://github.com/cosmos/cosmos-sdk/pull/15041) Refactor how gRPC and API servers are started to remove unnecessary sleeps:
+    * Remove `ServerStartTime` constant.
+    * Rename `WaitForQuitSignals` to `ListenForQuitSignals`. Note, this function is no longer blocking. Thus the caller is expected to provide a `context.CancelFunc` which indicates that when a signal is caught, that any spawned processes can gracefully exit.
+    * `api.Server#Start` now accepts a `context.Context`. The caller is responsible for ensuring that the context is canceled such that the API server can gracefully exit. The caller does not need to stop the server.
+    * To start the gRPC server you must first create the server via `NewGRPCServer`, after which you can start the gRPC server via `StartGRPCServer` which accepts a `context.Context`. The caller is responsible for ensuring that the context is canceled such that the gRPC server can gracefully exit. The caller does not need to stop the server.
 * (types) [#15067](https://github.com/cosmos/cosmos-sdk/pull/15067) Remove deprecated alias from `types/errors`. Use `cosmossdk.io/errors` instead.
 * (testutil) [#14991](https://github.com/cosmos/cosmos-sdk/pull/14991) The `testutil/testdata_pulsar` package has moved to `testutil/testdata/testpb`.
 * (simapp) [#14977](https://github.com/cosmos/cosmos-sdk/pull/14977) Move simulation helpers functions (`AppStateFn` and `AppStateRandomizedFn`) to `testutil/sims`. These takes an extra genesisState argument which is the default state of the app.

go.mod

@@ -54,6 +54,7 @@ require (
 	github.com/tendermint/go-amino v0.16.0
 	golang.org/x/crypto v0.6.0
 	golang.org/x/exp v0.0.0-20230213192124-5e25df0256eb
+	golang.org/x/sync v0.1.0
 	google.golang.org/genproto v0.0.0-20230202175211-008b39050e57
 	google.golang.org/grpc v1.53.0
 	google.golang.org/protobuf v1.28.2-0.20230208135220-49eaa78c6c9c

go.sum

@@ -991,6 +991,7 @@ 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 v0.1.0 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"
@@ -29,11 +30,10 @@ type Server struct {
 	Router            *mux.Router
 	GRPCGatewayRouter *runtime.ServeMux
 	ClientCtx         client.Context
+	GRPCSrv           *grpc.Server
+	logger            log.Logger
+	metrics           *telemetry.Metrics
 
-	GRPCSrv *grpc.Server
-
-	logger  log.Logger
-	metrics *telemetry.Metrics
 	// Start() is blocking and generally called from a separate goroutine.
 	// Close() can be called asynchronously and access shared memory
 	// via the listener. Therefore, we sync access to Start and Close with
@@ -51,6 +51,7 @@ func CustomGRPCHeaderMatcher(key string) (string, bool) {
 	switch strings.ToLower(key) {
 	case grpctypes.GRPCBlockHeightHeader:
 		return grpctypes.GRPCBlockHeightHeader, true
+
 	default:
 		return runtime.DefaultHeaderMatcher(key)
 	}
@@ -88,9 +89,12 @@ func New(clientCtx client.Context, logger log.Logger, grpcSrv *grpc.Server) *Ser
 
 // Start starts the API server. Internally, the API server leverages CometBFT's
 // JSON RPC server. Configuration options are provided via config.APIConfig
-// and are delegated to the CometBFT 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 CometBFT 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()
 
 	cmtCfg := tmrpcserver.DefaultConfig()
@@ -134,13 +138,35 @@ func (s *Server) Start(cfg config.Config) error {
 	// register grpc-gateway routes (after grpc-web server as the first match is used)
 	s.Router.PathPrefix("/").Handler(s.GRPCGatewayRouter)
 
-	s.logger.Info("starting API server...")
-	if cfg.API.EnableUnsafeCORS {
-		allowAllCORS := handlers.CORS(handlers.AllowedHeaders([]string{"Content-Type"}))
-		return tmrpcserver.Serve(s.listener, allowAllCORS(s.Router), s.logger, cmtCfg)
-	}
+	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)
 
-	return tmrpcserver.Serve(s.listener, s.Router, s.logger, cmtCfg)
+		if enableUnsafeCORS {
+			allowAllCORS := handlers.CORS(handlers.AllowedHeaders([]string{"Content-Type"}))
+			errCh <- tmrpcserver.Serve(s.listener, allowAllCORS(s.Router), s.logger, cmtCfg)
+		} else {
+			errCh <- tmrpcserver.Serve(s.listener, s.Router, s.logger, cmtCfg)
+		}
+	}(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/server.go

@@ -1,10 +1,11 @@
 package grpc
 
 import (
+	"context"
 	"fmt"
 	"net"
-	"time"
 
+	"cosmossdk.io/log"
 	"google.golang.org/grpc"
 
 	"github.com/cosmos/cosmos-sdk/client"
@@ -17,8 +18,9 @@ import (
 	_ "github.com/cosmos/cosmos-sdk/types/tx/amino" // Import amino.proto file for reflection
 )
 
-// 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
@@ -46,39 +48,58 @@ 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
 	}
 }