Make it optional

dendrite-sample.monolith.yaml

@@ -212,6 +212,13 @@ federation_api:
   # enable this option in production as it presents a security risk!
   disable_tls_validation: false
 
+  # Disable HTTP keepalives, which also prevents connection reuse. Dendrite will typically
+  # keep HTTP connections open to remote hosts for 5 minutes as they can be reused much
+  # more quickly than opening new connections each time. Disabling keepalives will close
+  # HTTP connections immediately after a successful request but may result in more CPU and
+  # memory being used on TLS handshakes for each new connection instead.
+  disable_http_keepalives: false
+
   # Perspective keyservers to use as a backup when direct key fetches fail. This may
   # be required to satisfy key requests for servers that are no longer online when
   # joining some rooms.

dendrite-sample.polylith.yaml

@@ -219,6 +219,13 @@ federation_api:
   # enable this option in production as it presents a security risk!
   disable_tls_validation: false
 
+  # Disable HTTP keepalives, which also prevents connection reuse. Dendrite will typically
+  # keep HTTP connections open to remote hosts for 5 minutes as they can be reused much
+  # more quickly than opening new connections each time. Disabling keepalives will close
+  # HTTP connections immediately after a successful request but may result in more CPU and
+  # memory being used on TLS handshakes for each new connection instead.
+  disable_http_keepalives: false
+
   # Perspective keyservers to use as a backup when direct key fetches fail. This may
   # be required to satisfy key requests for servers that are no longer online when
   # joining some rooms.

setup/base/base.go

@@ -373,7 +373,7 @@ func (b *BaseDendrite) CreateFederationClient() *gomatrixserverlib.FederationCli
 	opts := []gomatrixserverlib.ClientOption{
 		gomatrixserverlib.WithTimeout(time.Minute * 5),
 		gomatrixserverlib.WithSkipVerify(b.Cfg.FederationAPI.DisableTLSValidation),
-		gomatrixserverlib.WithKeepAlives(true),
+		gomatrixserverlib.WithKeepAlives(!b.Cfg.FederationAPI.DisableHTTPKeepalives),
 	}
 	if b.Cfg.Global.DNSCache.Enabled {
 		opts = append(opts, gomatrixserverlib.WithDNSCache(b.DNSCache))

setup/config/config_federationapi.go

@@ -22,6 +22,11 @@ type FederationAPI struct {
 	// on remote federation endpoints. This is not recommended in production!
 	DisableTLSValidation bool `yaml:"disable_tls_validation"`
 
+	// DisableHTTPKeepalives prevents Dendrite from keeping HTTP connections
+	// open for reuse for future requests. Connections will be closed quicker
+	// but we may spend more time on TLS handshakes instead.
+	DisableHTTPKeepalives bool `yaml:"disable_http_keepalives"`
+
 	// Perspective keyservers, to use as a backup when direct key fetch
 	// requests don't succeed
 	KeyPerspectives KeyPerspectives `yaml:"key_perspectives"`
@@ -39,6 +44,7 @@ func (c *FederationAPI) Defaults(opts DefaultOpts) {
 	}
 	c.FederationMaxRetries = 16
 	c.DisableTLSValidation = false
+	c.DisableHTTPKeepalives = false
 	if opts.Generate {
 		c.KeyPerspectives = KeyPerspectives{
 			{