go/p2p: Close connection to seed node after every request

Bootstrap client, which is responsible for peer discovery and advertisement,
now terminates connection to the seed node after every request. This action
should free up recourses (e.g. inbound/outbound connections) on both sides
without affecting performance since discovered peers are cached (see retention
period) and advertisement is done infrequently (see TTL).

.changelog/5456.bugfix.md

@@ -0,0 +1,7 @@
+go/p2p: Close connection to seed node after every request
+
+Bootstrap client, which is responsible for peer discovery and advertisement,
+now terminates connection to the seed node after every request. This action
+should free up recourses (e.g. inbound/outbound connections) on both sides
+without affecting performance since discovered peers are cached (see retention
+period) and advertisement is done infrequently (see TTL).

go/p2p/discovery/bootstrap/client.go

@@ -133,6 +133,13 @@ func (c *client) Advertise(ctx context.Context, ns string, _ ...discovery.Option
 
 	pf.RecordSuccess()
 
+	// Close connections after every call because requests to the seed node are infrequent.
+	if err = c.rc.Close(c.seed.ID); err != nil {
+		c.logger.Warn("failed to close connections to seed node",
+			"err", err,
+		)
+	}
+
 	return res.TTL, nil
 }
 
@@ -239,6 +246,13 @@ func (c *client) fetchPeers(ctx context.Context, ns string, limit int) []peer.Ad
 		pf.RecordFailure()
 	}
 
+	// Close connections after every call because requests to the seed node are infrequent.
+	if err := c.rc.Close(c.seed.ID); err != nil {
+		c.logger.Warn("failed to close connections to seed node",
+			"err", err,
+		)
+	}
+
 	return cache.peers
 }
 

go/p2p/rpc/client.go

@@ -2,6 +2,7 @@ package rpc
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"reflect"
 	"sync"
@@ -13,7 +14,7 @@ import (
 	"github.com/libp2p/go-libp2p/core/protocol"
 
 	"github.com/oasisprotocol/oasis-core/go/common/cbor"
-	"github.com/oasisprotocol/oasis-core/go/common/errors"
+	commonErrors "github.com/oasisprotocol/oasis-core/go/common/errors"
 	"github.com/oasisprotocol/oasis-core/go/common/logging"
 	"github.com/oasisprotocol/oasis-core/go/common/workerpool"
 )
@@ -252,6 +253,9 @@ type Client interface {
 		opts ...CallMultiOption,
 	) ([]interface{}, []PeerFeedback, error)
 
+	// Close closes all connections to the given peer.
+	Close(peerID core.PeerID) error
+
 	// RegisterListener subscribes the listener to the client notification events.
 	// If the listener is already registered this is a noop operation.
 	RegisterListener(l ClientListener)
@@ -273,6 +277,7 @@ type client struct {
 	logger *logging.Logger
 }
 
+// Implements Client.
 func (c *client) Call(
 	ctx context.Context,
 	peer core.PeerID,
@@ -283,6 +288,7 @@ func (c *client) Call(
 	return c.CallOne(ctx, []core.PeerID{peer}, method, body, rsp, opts...)
 }
 
+// Implements Client.
 func (c *client) CallOne(
 	ctx context.Context,
 	peers []core.PeerID,
@@ -345,6 +351,7 @@ func (c *client) CallOne(
 	return pf, err
 }
 
+// Implements Client.
 func (c *client) CallMulti(
 	ctx context.Context,
 	peers []core.PeerID,
@@ -449,7 +456,7 @@ func (c *client) timeCall(
 
 	if err != nil {
 		// If the caller canceled the context we should not degrade the peer.
-		if !errors.Is(err, context.Canceled) {
+		if !commonErrors.Is(err, context.Canceled) {
 			c.recordFailure(peerID, latency)
 		}
 
@@ -519,7 +526,7 @@ func (c *client) call(
 
 	// Decode response.
 	if rawRsp.Error != nil {
-		return errors.FromCode(rawRsp.Error.Module, rawRsp.Error.Code, rawRsp.Error.Message)
+		return commonErrors.FromCode(rawRsp.Error.Module, rawRsp.Error.Code, rawRsp.Error.Message)
 	}
 
 	if rsp != nil {
@@ -528,13 +535,25 @@ func (c *client) call(
 	return nil
 }
 
+// Implements Client.
+func (c *client) Close(peerID core.PeerID) error {
+	var errs error
+	for _, conn := range c.host.Network().ConnsToPeer(peerID) {
+		err := conn.Close()
+		errs = errors.Join(errs, err)
+	}
+	return errs
+}
+
+// Implements Client.
 func (c *client) RegisterListener(l ClientListener) {
 	c.listeners.Lock()
 	defer c.listeners.Unlock()
 
 	c.listeners.m[l] = struct{}{}
 }
 
+// Implements Client.
 func (c *client) UnregisterListener(l ClientListener) {
 	c.listeners.Lock()
 	defer c.listeners.Unlock()

go/p2p/rpc/nop.go

@@ -82,6 +82,13 @@ func (c *nopClient) CallMulti(
 	return nil, nil, errUnsupported
 }
 
+// Implements Client.
+func (c *nopClient) Close(
+	peer.ID,
+) error {
+	return nil
+}
+
 // Implements Client.
 func (c *nopClient) RegisterListener(ClientListener) {}