increase default pool capacity

Ignore lower values, lntop won't start with pool_capacity <= 3 due to
router rpc handle.

README.md

@@ -39,7 +39,7 @@ macaroon = "/root/.lnd/data/chain/bitcoin/mainnet/admin.macaroon"
 macaroon_timeout = 60
 max_msg_recv_size = 52428800
 conn_timeout = 1000000
-pool_capacity = 3
+pool_capacity = 4
 
 [views]
 # views.channels is the view displaying channel list.

config/default.go

@@ -105,7 +105,7 @@ func NewDefault() *Config {
 			MacaroonTimeOut: 60,
 			MaxMsgRecvSize:  52428800,
 			ConnTimeout:     1000000,
-			PoolCapacity:    3,
+			PoolCapacity:    4,
 		},
 	}
 }

network/backend/lnd/lnd.go

@@ -21,6 +21,7 @@ import (
 
 const (
 	lndDefaultInvoiceExpiry = 3600
+	lndMinPoolCapacity      = 4
 )
 
 type Client struct {
@@ -479,6 +480,10 @@ func New(c *config.Network, logger logging.Logger) (*Backend, error) {
 		logger: logger.With(logging.String("name", c.Name)),
 	}
 
+	if c.PoolCapacity < lndMinPoolCapacity {
+		c.PoolCapacity = lndMinPoolCapacity
+		logger.Info("pool_capacity too small, ignoring")
+	}
 	backend.pool, err = pool.New(backend.NewClientConn, c.PoolCapacity, time.Duration(c.ConnTimeout))
 	if err != nil {
 		return nil, err