Add --max-sessions, --session-timeout args. Enforce max sessions.

server/args.go

@@ -30,6 +30,8 @@ type Args struct {
 	NotifierPort                string
 	JSONRPCPort                 int
 	JSONRPCHTTPPort             int
+	MaxSessions                 int
+	SessionTimeout              int
 	EsIndex                     string
 	RefreshDelta                int
 	CacheTTL                    int
@@ -61,6 +63,8 @@ const (
 	DefaultPrometheusPort              = "2112"
 	DefaultNotifierPort                = "18080"
 	DefaultJSONRPCPort                 = 50001
+	DefaultMaxSessions                 = 10000
+	DefaultSessionTimeout              = 300
 	DefaultRefreshDelta                = 5
 	DefaultCacheTTL                    = 5
 	DefaultPeerFile                    = "peers.txt"
@@ -129,6 +133,8 @@ func ParseArgs(searchRequest *pb.SearchRequest) *Args {
 	notifierPort := parser.String("", "notifier-port", &argparse.Options{Required: false, Help: "notifier port", Default: DefaultNotifierPort})
 	jsonRPCPort := parser.Int("", "json-rpc-port", &argparse.Options{Required: false, Help: "JSON RPC port", Validate: validatePort})
 	jsonRPCHTTPPort := parser.Int("", "json-rpc-http-port", &argparse.Options{Required: false, Help: "JSON RPC over HTTP port", Validate: validatePort})
+	maxSessions := parser.Int("", "max-sessions", &argparse.Options{Required: false, Help: "Maximum number of electrum clients that can be connected", Default: DefaultMaxSessions})
+	sessionTimeout := parser.Int("", "session-timeout", &argparse.Options{Required: false, Help: "Session inactivity timeout (seconds)", Default: DefaultSessionTimeout})
 	esIndex := parser.String("", "esindex", &argparse.Options{Required: false, Help: "elasticsearch index name", Default: DefaultEsIndex})
 	refreshDelta := parser.Int("", "refresh-delta", &argparse.Options{Required: false, Help: "elasticsearch index refresh delta in seconds", Default: DefaultRefreshDelta})
 	cacheTTL := parser.Int("", "cachettl", &argparse.Options{Required: false, Help: "Cache TTL in minutes", Default: DefaultCacheTTL})
@@ -183,6 +189,8 @@ func ParseArgs(searchRequest *pb.SearchRequest) *Args {
 		NotifierPort:                *notifierPort,
 		JSONRPCPort:                 *jsonRPCPort,
 		JSONRPCHTTPPort:             *jsonRPCHTTPPort,
+		MaxSessions:                 *maxSessions,
+		SessionTimeout:              *sessionTimeout,
 		EsIndex:                     *esIndex,
 		RefreshDelta:                *refreshDelta,
 		CacheTTL:                    *cacheTTL,

server/jsonrpc_service.go

@@ -11,6 +11,7 @@ import (
 	gorilla_rpc "github.com/gorilla/rpc"
 	gorilla_json "github.com/gorilla/rpc/json"
 	log "github.com/sirupsen/logrus"
+	"golang.org/x/net/netutil"
 )
 
 type gorillaRpcCodec struct {
@@ -79,7 +80,7 @@ func (s *Server) StartJsonRPC() error {
 				s.sessionManager.addSession(conn)
 			}
 		}
-		go acceptConnections(listener)
+		go acceptConnections(netutil.LimitListener(listener, s.sessionManager.sessionsMax))
 	}
 
 fail1:

server/server.go

@@ -333,7 +333,7 @@ func MakeHubServer(ctx context.Context, args *Args) *Server {
 		HeightSubs:       make(map[net.Addr]net.Conn),
 		HeightSubsMut:    sync.RWMutex{},
 		NotifierChan:     make(chan interface{}),
-		sessionManager:   newSessionManager(myDB, &chain),
+		sessionManager:   newSessionManager(myDB, &chain, args.MaxSessions, args.SessionTimeout),
 	}
 
 	// Start up our background services

server/session.go

@@ -18,8 +18,6 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-var SESSION_INACTIVE_TIMEOUT = 2 * time.Minute
-
 type headerNotification struct {
 	internal.HeightHash
 	blockHeader         [HEADER_SIZE]byte
@@ -118,6 +116,9 @@ type sessionManager struct {
 	// sessionsMut protects sessions, headerSubs, hashXSubs state
 	sessionsMut    sync.RWMutex
 	sessions       sessionMap
+	sessionsWait   sync.WaitGroup
+	sessionsMax    int
+	sessionTimeout time.Duration
 	db             *db.ReadOnlyDBColumnFamily
 	chain          *chaincfg.Params
 	// headerSubs are sessions subscribed via 'blockchain.headers.subscribe'
@@ -126,9 +127,11 @@ type sessionManager struct {
 	hashXSubs map[[HASHX_LEN]byte]sessionMap
 }
 
-func newSessionManager(db *db.ReadOnlyDBColumnFamily, chain *chaincfg.Params) *sessionManager {
+func newSessionManager(db *db.ReadOnlyDBColumnFamily, chain *chaincfg.Params, sessionsMax, sessionTimeout int) *sessionManager {
 	return &sessionManager{
 		sessions:       make(sessionMap),
+		sessionsMax:    sessionsMax,
+		sessionTimeout: time.Duration(sessionTimeout) * time.Second,
 		db:             db,
 		chain:          chain,
 		headerSubs:     make(sessionMap),
@@ -153,12 +156,14 @@ func (sm *sessionManager) stop() {
 }
 
 func (sm *sessionManager) manage() {
+	sm.sessionsMut.Lock()
 	for _, sess := range sm.sessions {
-		if time.Since(sess.lastRecv) > SESSION_INACTIVE_TIMEOUT {
+		if time.Since(sess.lastRecv) > sm.sessionTimeout {
-			sm.removeSession(sess)
+			sm.removeSessionLocked(sess)
 			log.Infof("session %v timed out", sess.addr.String())
 		}
 	}
+	sm.sessionsMut.Unlock()
 
 	// TEMPORARY TESTING: Send fake notification for specific address.
 	address, _ := lbcutil.DecodeAddress("bNe63fYgYNA85ZQ56p7MwBtuCL7MXPRfrm", sm.chain)
@@ -220,7 +225,12 @@ func (sm *sessionManager) addSession(conn net.Conn) {
 		goto fail
 	}
 
-	go s1.ServeCodec(&SessionServerCodec{jsonrpc.NewServerCodec(conn), sess})
+	sm.sessionsWait.Add(1)
+	go func() {
+		s1.ServeCodec(&SessionServerCodec{jsonrpc.NewServerCodec(conn), sess})
+		log.Infof("session %v goroutine exit", sess.addr.String())
+		sm.sessionsWait.Done()
+	}()
 	return
 
 fail:
@@ -230,6 +240,10 @@ fail:
 func (sm *sessionManager) removeSession(sess *session) {
 	sm.sessionsMut.Lock()
 	defer sm.sessionsMut.Unlock()
+	sm.removeSessionLocked(sess)
+}
+
+func (sm *sessionManager) removeSessionLocked(sess *session) {
 	if sess.headersSub {
 		delete(sm.headerSubs, sess.addr)
 	}