some tracer class fixes / unhardcode jaeger IP

classes/config.php

@@ -192,6 +192,9 @@ class Config {
 	/** delay updates for this feed if received HTTP 429 (Too Many Requests) for this amount of seconds (base value, actual delay is base...base*2) */
 	const HTTP_429_THROTTLE_INTERVAL = "HTTP_429_THROTTLE_INTERVAL";
 
+	/** host running Jaeger collector to receive traces (disabled if empty) */
+	const JAEGER_REPORTING_HOST = "JAEGER_REPORTING_HOST";
+
 	/** default values for all global configuration options */
 	private const _DEFAULTS = [
 		Config::DB_TYPE => [ "pgsql", 									Config::T_STRING ],
@@ -249,6 +252,7 @@ class Config {
 		Config::HTTP_USER_AGENT => [ 'Tiny Tiny RSS/%s (https://tt-rss.org/)',
 																					Config::T_STRING ],
 		Config::HTTP_429_THROTTLE_INTERVAL => [ 3600,				Config::T_INT ],
+		Config::JAEGER_REPORTING_HOST => [ "",							Config::T_STRING ],
 	];
 
 	/** @var Config|null */