Retry access in case the settings database is locked

Create `settings::_safer_query` class proc to allow 5 tries with 1s delay; use it for `_nval_setting` and `_tval_setting` methods

webif/lib/settings.class

@@ -54,6 +54,21 @@ class settings {
 	rtschedule	0
 }
 
+proc {settings _safer_query} { queryText args } {
+	global settingsdb
+	# allow 5 (too many?) tries with 1s (too long?) delay to get access
+	for {set lockCnt 5} {} {sleep 1} {
+		try {
+			$settingsdb query $queryText {*}$args
+		} on error {msg opts} {
+			if {[string first "database is locked" $msg] >= 0 && [incr lockCnt -1] > 0} {
+				continue
+			}
+			return {*}$opts $msg
+		}
+	}
+}
+
 settings method hostname {{name ""}} {
 	if {$name == ""} {
 		# Get
@@ -104,11 +119,10 @@ settings method smtp_server {{server ""}} {
 }
 
 settings method _nval_setting {name {val -1}} {
-	global settingsdb
 
 	if {$val == -1} {
 		# Get
-		set res [$settingsdb query "
+		set res [settings::_safer_query "
 			select nval from settings
 			where name = '$name'
 		"]
@@ -118,7 +132,7 @@ settings method _nval_setting {name {val -1}} {
 		return 0
 	} else {
 		# Set
-		$settingsdb query "
+		settings::_safer_query "
 			replace into settings(name,nval)
 			values('$name', $val)
 		"
@@ -127,11 +141,10 @@ settings method _nval_setting {name {val -1}} {
 }
 
 settings method _tval_setting {name {val -1} {def 0}} {
-	global settingsdb
 
 	if {$val eq "-1"} {
 		# Get
-		set res [$settingsdb query "
+		set res [settings::_safer_query "
 			select tval from settings
 			where name = '$name'
 		"]
@@ -141,7 +154,7 @@ settings method _tval_setting {name {val -1} {def 0}} {
 		return $def
 	} else {
 		# Set
-		$settingsdb query "
+		settings::_safer_query "
 			replace into settings(name,tval)
 			values('$name', '%s')
 		" $val