From cf3fc85196e13e52db055dbc594d437dcc9765ac Mon Sep 17 00:00:00 2001
From: Juan Font Alonso <juanfontalonso@gmail.com>
Date: Tue, 12 Jul 2022 12:27:28 +0200
Subject: [PATCH] Make tailnet updates check configurable

---
 config-example.yaml |  6 ++++++
 config.go           | 16 ++++++++++++++++
 poll.go             |  5 ++---
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/config-example.yaml b/config-example.yaml
index 9740f3ad..c32f9416 100644
--- a/config-example.yaml
+++ b/config-example.yaml
@@ -103,6 +103,12 @@ disable_check_updates: false
 # Time before an inactive ephemeral node is deleted?
 ephemeral_node_inactivity_timeout: 30m
 
+# Period to check for changes in the tailnet. A value too low will severily affect
+# CPU consumption of Headscale. A value too high (over 60s) will cause problems
+# to the nodes, as they won't get updates or keep alive messages on time.
+# In case of doubts, do not touch the default 10s.
+changes_check_interval: 10s
+
 # SQLite config
 db_type: sqlite3
 db_path: /var/lib/headscale/db.sqlite
diff --git a/config.go b/config.go
index 9e71a750..0ef09110 100644
--- a/config.go
+++ b/config.go
@@ -26,6 +26,7 @@ type Config struct {
 	GRPCAddr                       string
 	GRPCAllowInsecure              bool
 	EphemeralNodeInactivityTimeout time.Duration
+	ChangesCheckInterval           time.Duration
 	IPPrefixes                     []netaddr.IPPrefix
 	PrivateKeyPath                 string
 	BaseDomain                     string
@@ -162,6 +163,8 @@ func LoadConfig(path string, isFile bool) error {
 
 	viper.SetDefault("ephemeral_node_inactivity_timeout", "120s")
 
+	viper.SetDefault("changes_check_interval", "10s")
+
 	if err := viper.ReadInConfig(); err != nil {
 		log.Warn().Err(err).Msg("Failed to read configuration from disk")
 
@@ -217,6 +220,15 @@ func LoadConfig(path string, isFile bool) error {
 		)
 	}
 
+	maxChangesCheckInterval, _ := time.ParseDuration("60s")
+	if viper.GetDuration("changes_check_interval") > maxChangesCheckInterval {
+		errorText += fmt.Sprintf(
+			"Fatal config error: changes_check_interval (%s) is set too high, must be less than %s",
+			viper.GetString("changes_check_interval"),
+			maxChangesCheckInterval,
+		)
+	}
+
 	if errorText != "" {
 		//nolint
 		return errors.New(strings.TrimSuffix(errorText, "\n"))
@@ -478,6 +490,10 @@ func GetHeadscaleConfig() (*Config, error) {
 			"ephemeral_node_inactivity_timeout",
 		),
 
+		ChangesCheckInterval: viper.GetDuration(
+			"changes_check_interval",
+		),
+
 		DBtype: viper.GetString("db_type"),
 		DBpath: AbsolutePathFromConfigPath(viper.GetString("db_path")),
 		DBhost: viper.GetString("db_host"),
diff --git a/poll.go b/poll.go
index 9218495d..95fb542c 100644
--- a/poll.go
+++ b/poll.go
@@ -16,8 +16,7 @@ import (
 )
 
 const (
-	keepAliveInterval   = 60 * time.Second
-	updateCheckInterval = 10 * time.Second
+	keepAliveInterval = 60 * time.Second
 )
 
 type contextKey string
@@ -640,7 +639,7 @@ func (h *Headscale) scheduledPollWorker(
 	machine *Machine,
 ) {
 	keepAliveTicker := time.NewTicker(keepAliveInterval)
-	updateCheckerTicker := time.NewTicker(updateCheckInterval)
+	updateCheckerTicker := time.NewTicker(h.cfg.ChangesCheckInterval)
 
 	defer closeChanWithLog(
 		updateChan,