From cd214fca89443e5aca5d27cf51ea32adea9feec2 Mon Sep 17 00:00:00 2001
From: Andy Xie <andy.xning@gmail.com>
Date: Fri, 5 Jul 2019 15:49:27 +0800
Subject: [PATCH] allow limit to traced message

---
 server/client.go    |  9 +++++++--
 server/opts.go      |  5 +++++
 server/opts_test.go |  1 +
 server/reload.go    | 17 ++++++++++++++++-
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/server/client.go b/server/client.go
index 1452cdeedf..d3580a10bd 100644
--- a/server/client.go
+++ b/server/client.go
@@ -1010,8 +1010,13 @@ func (c *client) traceMsg(msg []byte) {
 	if !c.trace {
 		return
 	}
-	// FIXME(dlc), allow limits to printable payload.
-	c.Tracef("<<- MSG_PAYLOAD: [%q]", msg[:len(msg)-LEN_CR_LF])
+
+	maxTrace := c.srv.getOpts().MaxTracedMsgLen
+	if maxTrace != 0 && (len(msg)-LEN_CR_LF) > maxTrace {
+		c.Tracef("<<- MSG_PAYLOAD: [\"%s...\"]", msg[:maxTrace])
+	} else {
+		c.Tracef("<<- MSG_PAYLOAD: [%q]", msg[:len(msg)-LEN_CR_LF])
+	}
 }
 
 func (c *client) traceInOp(op string, arg []byte) {
diff --git a/server/opts.go b/server/opts.go
index f2e04aa034..5c5bfa3155 100644
--- a/server/opts.go
+++ b/server/opts.go
@@ -190,6 +190,8 @@ type Options struct {
 	WriteDeadline    time.Duration `json:"-"`
 	MaxClosedClients int           `json:"-"`
 	LameDuckDuration time.Duration `json:"-"`
+	// MaxTracedMsgLen is the maximum printable length for traced messages.
+	MaxTracedMsgLen int `json:"-"`
 
 	// Operating a trusted NATS server
 	TrustedKeys      []string              `json:"-"`
@@ -539,6 +541,8 @@ func (o *Options) ProcessConfigFile(configFile string) error {
 			o.MaxPending = v.(int64)
 		case "max_connections", "max_conn":
 			o.MaxConn = int(v.(int64))
+		case "max_traced_msg_len":
+			o.MaxTracedMsgLen = int(v.(int64))
 		case "max_subscriptions", "max_subs":
 			o.MaxSubs = int(v.(int64))
 		case "ping_interval":
@@ -2551,6 +2555,7 @@ func ConfigureOptions(fs *flag.FlagSet, args []string, printVersion, printHelp,
 	fs.StringVar(&opts.TLSCert, "tlscert", "", "Server certificate file.")
 	fs.StringVar(&opts.TLSKey, "tlskey", "", "Private key for server certificate.")
 	fs.StringVar(&opts.TLSCaCert, "tlscacert", "", "Client certificate CA for verification.")
+	fs.IntVar(&opts.MaxTracedMsgLen, "max_traced_msg_len", 0, "Maximum printable length for traced messages. 0 for unlimited")
 
 	// The flags definition above set "default" values to some of the options.
 	// Calling Parse() here will override the default options with any value
diff --git a/server/opts_test.go b/server/opts_test.go
index b645591449..83c12a6cf4 100644
--- a/server/opts_test.go
+++ b/server/opts_test.go
@@ -61,6 +61,7 @@ func TestDefaultOptions(t *testing.T) {
 		},
 		ConnectErrorReports:   DEFAULT_CONNECT_ERROR_REPORTS,
 		ReconnectErrorReports: DEFAULT_RECONNECT_ERROR_REPORTS,
+		MaxTracedMsgLen:       0,
 	}
 
 	opts := &Options{}
diff --git a/server/reload.go b/server/reload.go
index 1511fcfdad..a8ff586077 100644
--- a/server/reload.go
+++ b/server/reload.go
@@ -523,6 +523,20 @@ func (r *reconnectErrorReports) Apply(s *Server) {
 	s.Noticef("Reloaded: reconnect_error_reports = %v", r.newValue)
 }
 
+// maxTracedMsgLenOption implements the option interface for the `max_traced_msg_len` setting.
+type maxTracedMsgLenOption struct {
+	noopOption
+	newValue int
+}
+
+// Apply the setting by updating the maximum traced message length.
+func (m *maxTracedMsgLenOption) Apply(server *Server) {
+	server.mu.Lock()
+	defer server.mu.Unlock()
+	server.opts.MaxTracedMsgLen = m.newValue
+	server.Noticef("Reloaded: max_traced_msg_len = %d", m.newValue)
+}
+
 // Reload reads the current configuration file and applies any supported
 // changes. This returns an error if the server was not started with a config
 // file or an option which doesn't support hot-swapping was changed.
@@ -771,6 +785,8 @@ func (s *Server) diffOptions(newOpts *Options) ([]option, error) {
 			// Ignore NoLog and NoSigs options since they are not parsed and only used in
 			// testing.
 			continue
+		case "maxtracedmsglen":
+			diffOpts = append(diffOpts, &maxTracedMsgLenOption{newValue: newValue.(int)})
 		case "port":
 			// check to see if newValue == 0 and continue if so.
 			if newValue == 0 {
@@ -778,7 +794,6 @@ func (s *Server) diffOptions(newOpts *Options) ([]option, error) {
 				continue
 			}
 			fallthrough
-
 		default:
 			// TODO(ik): Implement String() on those options to have a nice print.
 			// %v is difficult to figure what's what, %+v print private fields and