rfq: add client-side keepalive to price oracle connections

In this commit, we add comprehensive client-side gRPC keepalive
parameters to the price oracle client connections. This addresses the
root cause of issue #1814 where connections to price oracle servers
were being silently closed after idle periods, resulting in "connection
reset by peer" errors during RFQ operations.

The key change is adding PermitWithoutStream set to true, which allows
the client to send keepalive pings even when there are no active RPC
calls. This is essential for long-lived connections that may experience
extended idle periods between price queries. Without this setting, idle
connections would be closed by intermediaries or the server itself,
leaving the client unaware of the broken connection until the next RPC
attempt.

We configure the client to ping the server every 30 seconds of
inactivity and wait 20 seconds for a response. These values are
conservative enough to detect connection issues quickly while avoiding
excessive network traffic. The same keepalive parameters are applied to
both TLS and insecure (testing-only) connection modes to ensure
consistent behavior.

Fixes #1814

Author: Roasbeef

rfq/oracle.go

@@ -18,6 +18,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/keepalive"
 )
 
 // PriceQueryIntent is an enum that represents the intent of a price rate
@@ -186,16 +187,38 @@ type RpcPriceOracle struct {
 	rawConn *grpc.ClientConn
 }
 
+// clientKeepaliveDialOption configures bidirectional health probing to prevent
+// idle RFQ connections from being silently terminated by network intermediaries
+// (NATs, load balancers) or aggressive server timeouts. Without active
+// keepalive, the first price query after an idle period would fail with
+// "connection reset by peer" and require a retry.
+var clientKeepaliveDialOption = grpc.WithKeepaliveParams(
+	keepalive.ClientParameters{
+		// Ping server after 30 seconds of inactivity.
+		Time: 30 * time.Second,
+
+		// Wait 20 seconds for ping response.
+		Timeout: 20 * time.Second,
+
+		// Permit keepalive pings even when there are no active
+		// streams. This is critical for long-lived connections with
+		// infrequent RFQ requests.
+		PermitWithoutStream: true,
+	},
+)
+
 // serverDialOpts returns the set of server options needed to connect to the
 // price oracle RPC server using a TLS connection.
 func serverDialOpts() ([]grpc.DialOption, error) {
 	var opts []grpc.DialOption
 
-	// Skip TLS certificate verification.
 	tlsConfig := tls.Config{InsecureSkipVerify: true}
 	transportCredentials := credentials.NewTLS(&tlsConfig)
+
 	opts = append(opts, grpc.WithTransportCredentials(transportCredentials))
 
+	opts = append(opts, clientKeepaliveDialOption)
+
 	return opts, nil
 }
 
@@ -209,6 +232,8 @@ func insecureServerDialOpts() ([]grpc.DialOption, error) {
 		insecure.NewCredentials(),
 	))
 
+	opts = append(opts, clientKeepaliveDialOption)
+
 	return opts, nil
 }