From a274d4e56506b4b6100ed14ea1d2b51bf25eb70f Mon Sep 17 00:00:00 2001
From: Sunil Narasimhamurthy <sunnrs@amazon.com>
Date: Wed, 29 Nov 2023 00:04:43 +0000
Subject: [PATCH] disable hot restart capability in Envoy

---
 agent/agent.go               | 4 ++++
 agent/agent_test.go          | 7 ++++++-
 agent/config/agent_config.go | 3 +++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/agent/agent.go b/agent/agent.go
index 0cf608de..016f0414 100644
--- a/agent/agent.go
+++ b/agent/agent.go
@@ -73,6 +73,10 @@ func buildCommandArgs(agentConfig config.AgentConfig) []string {
 		args = append(args, strconv.Itoa(listenerDrainWaitTime))
 	}
 
+	if agentConfig.DisableHotRestart {
+		args = append(args, "--disable-hot-restart")
+	}
+
 	if len(agentConfig.CommandArgs) > 0 {
 		args = append(args, agentConfig.CommandArgs...)
 	}
diff --git a/agent/agent_test.go b/agent/agent_test.go
index 44c41efd..744d03c8 100644
--- a/agent/agent_test.go
+++ b/agent/agent_test.go
@@ -49,7 +49,7 @@ func TestBuildCommandArgs(t *testing.T) {
 
 	arguments := buildCommandArgs(agentConfig)
 
-	assert.Equal(t, len(arguments), 7)
+	assert.Equal(t, len(arguments), 8)
 	assert.ElementsMatch(t, []string{
 		agentConfig.CommandPath,
 		"-c",
@@ -58,6 +58,7 @@ func TestBuildCommandArgs(t *testing.T) {
 		agentConfig.EnvoyLogLevel,
 		"--drain-time-s",
 		strconv.Itoa(int(agentConfig.ListenerDrainWaitTime / time.Second)),
+		"--disable-hot-restart",
 	}, arguments)
 }
 
@@ -68,6 +69,7 @@ func TestBuildCommandArgsNoEnvoyParameters(t *testing.T) {
 	agentConfig.EnvoyConfigPath = ""
 	agentConfig.EnvoyLogLevel = ""
 	agentConfig.ListenerDrainWaitTime = 0
+	agentConfig.DisableHotRestart = false
 
 	arguments := buildCommandArgs(agentConfig)
 
@@ -128,6 +130,7 @@ func TestKeepCommandAlive(t *testing.T) {
 	agentConfig.EnvoyConfigPath = ""
 	agentConfig.EnvoyLogLevel = ""
 	agentConfig.ListenerDrainWaitTime = 0
+	agentConfig.DisableHotRestart = false
 	agentConfig.CommandPath, _ = exec.LookPath("sleep")
 	agentConfig.CommandArgs = []string{sleepTime.String()}
 
@@ -167,6 +170,7 @@ func TestKeepCommandAliveWithRestart(t *testing.T) {
 	agentConfig.EnvoyConfigPath = ""
 	agentConfig.EnvoyLogLevel = ""
 	agentConfig.ListenerDrainWaitTime = 0
+	agentConfig.DisableHotRestart = false
 	agentConfig.EnvoyRestartCount = 2
 	agentConfig.CommandPath, _ = exec.LookPath("sleep")
 	agentConfig.CommandArgs = []string{"3"}
@@ -365,6 +369,7 @@ func TestLoggingToFileWithCommandExecution(t *testing.T) {
 	agentConfig.EnvoyConfigPath = ""
 	agentConfig.EnvoyLogLevel = ""
 	agentConfig.ListenerDrainWaitTime = 0
+	agentConfig.DisableHotRestart = false
 	agentConfig.CommandPath, _ = exec.LookPath("echo")
 	agentConfig.CommandArgs = []string{
 		"this", "is", "my", "test.",
diff --git a/agent/config/agent_config.go b/agent/config/agent_config.go
index 01f47c22..b2148141 100644
--- a/agent/config/agent_config.go
+++ b/agent/config/agent_config.go
@@ -65,6 +65,7 @@ const (
 	ENVOY_LISTENER_DRAINING_ENDPOINT_URL = "/drain_listeners"
 	ENVOY_CONCURRENCY_DEFAULT            = -1  // we will not set concurrency [envoy --concurrency] by default.
 	ENVOY_CONCURRENCY_FOR_RELAY_DEFAULT  = "1" // For relay we are defaulting it to 1
+	DISABLE_HOT_RESTART_DEFAULT          = true
 
 	// agent relay mode
 	ENABLE_RELAY_MODE_FOR_XDS_DEFAULT      = false
@@ -157,6 +158,7 @@ type AgentConfig struct {
 	ListenerPortMapping             string
 	MaxLogFileSizeMB                float64
 	MaxLogCount                     int
+	DisableHotRestart               bool
 
 	XdsEndpointUdsPath string
 
@@ -499,6 +501,7 @@ func (config *AgentConfig) SetDefaults() {
 	}
 
 	config.EnvoyConcurrency = getEnvValueAsInt("ENVOY_CONCURRENCY", ENVOY_CONCURRENCY_DEFAULT)
+	config.DisableHotRestart = getEnvValueAsBool("DISABLE_HOT_RESTART", DISABLE_HOT_RESTART_DEFAULT)
 
 	validateEnvoyLogLevel(&config.EnvoyLogLevel)