Reduced maximum Server Timing headers size for nginx

See #52

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Changed
+- reduced maximum Server Timing headers size to 2K (half of possible nginx defaults) 
+
 ## 3.3.4 - 2020-11-16
 
 ### Fixed

src/Manager/Server_Timing_Manager.php

@@ -63,7 +63,7 @@ class Server_Timing_Manager {
 
 			$header .= sprintf( '%s;dur=%.2f;desc="%s", ', $record->get_category(), $duration, $record->get_name() );
 
-			if ( strlen( $header ) > 4000 ) { // 8+KB headers break proxies, so we cut off at 1/2 that limit.
+			if ( strlen( $header ) > 2000 ) { // 8+KB headers break proxies, 4+KB nginx, so we cut off at 1/2 that limit.
 				break;
 			}
 		}