Add support for MaxOpenConnections

CHANGELOG.md

@@ -38,6 +38,9 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## Unreleased
 
+### Improvments
+* (rpc) [#1229](https://github.com/evmos/ethermint/pull/1229) Add support for configuring RPC `MaxOpenConnections`
+
 ### State Machine Breaking
 
 * (deps) [\#1159](https://github.com/evmos/ethermint/pull/1159) Bump Geth version to `v1.10.19`.

rpc/websockets.go

@@ -74,7 +74,7 @@ type websocketsServer struct {
 	logger   log.Logger
 }
 
-func NewWebsocketsServer(clientCtx client.Context, logger log.Logger, tmWSClient *rpcclient.WSClient, cfg config.Config) WebsocketsServer {
+func NewWebsocketsServer(clientCtx client.Context, logger log.Logger, tmWSClient *rpcclient.WSClient, cfg *config.Config) WebsocketsServer {
 	logger = logger.With("api", "websocket-server")
 	_, port, _ := net.SplitHostPort(cfg.JSONRPC.Address)
 

server/config/config.go

@@ -49,6 +49,8 @@ const (
 	DefaultHTTPIdleTimeout = 120 * time.Second
 	// DefaultAllowUnprotectedTxs value is false
 	DefaultAllowUnprotectedTxs = false
+	// 0 Max open connections represents unlimited amount of connections
+	DefaultMaxOpenConnections = 0
 )
 
 var evmTracers = []string{"json", "markdown", "struct", "access_list"}
@@ -103,6 +105,9 @@ type JSONRPCConfig struct {
 	// AllowUnprotectedTxs restricts unprotected (non EIP155 signed) transactions to be submitted via
 	// the node's RPC when global parameter is disabled.
 	AllowUnprotectedTxs bool `mapstructure:"allow-unprotected-txs"`
+	// MaxOpenConnections sets the maximum number of simultaneous connections
+	// for the server listener.
+	MaxOpenConnections int `mapstructure:"max-open-connections"`
 }
 
 // TLSConfig defines the certificate and matching private key for the server.
@@ -202,6 +207,7 @@ func DefaultJSONRPCConfig() *JSONRPCConfig {
 		HTTPTimeout:         DefaultHTTPTimeout,
 		HTTPIdleTimeout:     DefaultHTTPIdleTimeout,
 		AllowUnprotectedTxs: DefaultAllowUnprotectedTxs,
+		MaxOpenConnections:  DefaultMaxOpenConnections,
 	}
 }
 
@@ -292,19 +298,20 @@ func GetConfig(v *viper.Viper) Config {
 			MaxTxGasWanted: v.GetUint64("evm.max-tx-gas-wanted"),
 		},
 		JSONRPC: JSONRPCConfig{
-			Enable:          v.GetBool("json-rpc.enable"),
-			API:             v.GetStringSlice("json-rpc.api"),
-			Address:         v.GetString("json-rpc.address"),
-			WsAddress:       v.GetString("json-rpc.ws-address"),
-			GasCap:          v.GetUint64("json-rpc.gas-cap"),
-			FilterCap:       v.GetInt32("json-rpc.filter-cap"),
-			FeeHistoryCap:   v.GetInt32("json-rpc.feehistory-cap"),
-			TxFeeCap:        v.GetFloat64("json-rpc.txfee-cap"),
-			EVMTimeout:      v.GetDuration("json-rpc.evm-timeout"),
-			LogsCap:         v.GetInt32("json-rpc.logs-cap"),
-			BlockRangeCap:   v.GetInt32("json-rpc.block-range-cap"),
-			HTTPTimeout:     v.GetDuration("json-rpc.http-timeout"),
-			HTTPIdleTimeout: v.GetDuration("json-rpc.http-idle-timeout"),
+			Enable:             v.GetBool("json-rpc.enable"),
+			API:                v.GetStringSlice("json-rpc.api"),
+			Address:            v.GetString("json-rpc.address"),
+			WsAddress:          v.GetString("json-rpc.ws-address"),
+			GasCap:             v.GetUint64("json-rpc.gas-cap"),
+			FilterCap:          v.GetInt32("json-rpc.filter-cap"),
+			FeeHistoryCap:      v.GetInt32("json-rpc.feehistory-cap"),
+			TxFeeCap:           v.GetFloat64("json-rpc.txfee-cap"),
+			EVMTimeout:         v.GetDuration("json-rpc.evm-timeout"),
+			LogsCap:            v.GetInt32("json-rpc.logs-cap"),
+			BlockRangeCap:      v.GetInt32("json-rpc.block-range-cap"),
+			HTTPTimeout:        v.GetDuration("json-rpc.http-timeout"),
+			HTTPIdleTimeout:    v.GetDuration("json-rpc.http-idle-timeout"),
+			MaxOpenConnections: v.GetInt("json-rpc.max-open-connections"),
 		},
 		TLS: TLSConfig{
 			CertificatePath: v.GetString("tls.certificate-path"),

server/config/toml.go

@@ -66,6 +66,10 @@ http-idle-timeout = "{{ .JSONRPC.HTTPIdleTimeout }}"
 # the node's RPC when the global parameter is disabled.
 allow-unprotected-txs = {{ .JSONRPC.AllowUnprotectedTxs }}
 
+# MaxOpenConnections sets the maximum number of simultaneous connections
+# for the server listener.
+max-open-connections = {{ .JSONRPC.MaxOpenConnections }}
+
 ###############################################################################
 ###                             TLS Configuration                           ###
 ###############################################################################

server/flags/flags.go

@@ -47,6 +47,7 @@ const (
 	JSONRPCHTTPTimeout         = "json-rpc.http-timeout"
 	JSONRPCHTTPIdleTimeout     = "json-rpc.http-idle-timeout"
 	JSONRPCAllowUnprotectedTxs = "json-rpc.allow-unprotected-txs"
+	JSONRPCMaxOpenConnections  = "json-rpc.max-open-connections"
 )
 
 // EVM flags

server/json_rpc.go

@@ -18,7 +18,7 @@ import (
 )
 
 // StartJSONRPC starts the JSON-RPC server
-func StartJSONRPC(ctx *server.Context, clientCtx client.Context, tmRPCAddr, tmEndpoint string, config config.Config) (*http.Server, chan struct{}, error) {
+func StartJSONRPC(ctx *server.Context, clientCtx client.Context, tmRPCAddr, tmEndpoint string, config *config.Config) (*http.Server, chan struct{}, error) {
 	tmWsClient := ConnectTmWS(tmRPCAddr, tmEndpoint, ctx.Logger)
 
 	logger := ctx.Logger.With("module", "geth")
@@ -70,10 +70,15 @@ func StartJSONRPC(ctx *server.Context, clientCtx client.Context, tmRPCAddr, tmEn
 	}
 	httpSrvDone := make(chan struct{}, 1)
 
+	ln, err := Listen(httpSrv.Addr, config)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	errCh := make(chan error)
 	go func() {
 		ctx.Logger.Info("Starting JSON-RPC server", "address", config.JSONRPC.Address)
-		if err := httpSrv.ListenAndServe(); err != nil {
+		if err := httpSrv.Serve(ln); err != nil {
 			if err == http.ErrServerClosed {
 				close(httpSrvDone)
 				return

server/start.go

@@ -164,6 +164,7 @@ which accepts a path for the resulting pprof file.
 	cmd.Flags().Bool(srvflags.JSONRPCAllowUnprotectedTxs, config.DefaultAllowUnprotectedTxs, "Allow for unprotected (non EIP155 signed) transactions to be submitted via the node's RPC when the global parameter is disabled")
 	cmd.Flags().Int32(srvflags.JSONRPCLogsCap, config.DefaultLogsCap, "Sets the max number of results can be returned from single `eth_getLogs` query")
 	cmd.Flags().Int32(srvflags.JSONRPCBlockRangeCap, config.DefaultBlockRangeCap, "Sets the max block range allowed for `eth_getLogs` query")
+	cmd.Flags().Int(srvflags.JSONRPCMaxOpenConnections, config.DefaultMaxOpenConnections, "Sets the maximum number of simultaneous connections for the server listener")
 
 	cmd.Flags().String(srvflags.EVMTracer, config.DefaultEVMTracer, "the EVM tracer type to collect execution traces from the EVM transaction execution (json|struct|access_list|markdown)")
 	cmd.Flags().Uint64(srvflags.EVMMaxTxGasWanted, config.DefaultMaxTxGasWanted, "the gas wanted for each eth tx returned in ante handler in check tx mode")
@@ -426,7 +427,7 @@ func startInProcess(ctx *server.Context, clientCtx client.Context, appCreator ty
 
 		tmEndpoint := "/websocket"
 		tmRPCAddr := cfg.RPC.ListenAddress
-		httpSrv, httpSrvDone, err = StartJSONRPC(ctx, clientCtx, tmRPCAddr, tmEndpoint, config)
+		httpSrv, httpSrvDone, err = StartJSONRPC(ctx, clientCtx, tmRPCAddr, tmEndpoint, &config)
 		if err != nil {
 			return err
 		}

server/util.go

@@ -1,12 +1,15 @@
 package server
 
 import (
+	"net"
 	"net/http"
 	"time"
 
+	"github.com/evmos/ethermint/server/config"
 	"github.com/gorilla/mux"
 	"github.com/improbable-eng/grpc-web/go/grpcweb"
 	"github.com/spf13/cobra"
+	"golang.org/x/net/netutil"
 
 	sdkserver "github.com/cosmos/cosmos-sdk/server"
 	"github.com/cosmos/cosmos-sdk/server/types"
@@ -97,3 +100,17 @@ func MountGRPCWebServices(
 		})
 	}
 }
+
+func Listen(addr string, config *config.Config) (net.Listener, error) {
+	if addr == "" {
+		addr = ":http"
+	}
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	if config.JSONRPC.MaxOpenConnections > 0 {
+		ln = netutil.LimitListener(ln, config.JSONRPC.MaxOpenConnections)
+	}
+	return ln, err
+}

testutil/network/util.go

@@ -131,7 +131,7 @@ func startInProcess(cfg Config, val *Validator) error {
 		tmEndpoint := "/websocket"
 		tmRPCAddr := val.RPCAddress
 
-		val.jsonrpc, val.jsonrpcDone, err = server.StartJSONRPC(val.Ctx, val.ClientCtx, tmRPCAddr, tmEndpoint, *val.AppConfig)
+		val.jsonrpc, val.jsonrpcDone, err = server.StartJSONRPC(val.Ctx, val.ClientCtx, tmRPCAddr, tmEndpoint, val.AppConfig)
 		if err != nil {
 			return err
 		}