Amending Global Broker metrics behaviour

Amending Guide as per description in #163

guide/sections/part2/global-services.adoc

@@ -88,9 +88,10 @@ In the following sections and for each Global Service, a set of metrics is defin
 ** Additional features including anti-loop detection, notification message format compliance, validation of the published topic, and provision of metrics are required.
 
 * When receiving a message from a WIS centre or Global Service broker, The metric ``wmo_wis2_gb_messages_received_total`` will be increased by 1.
-* A Global Broker will check if the topic on which the message is received is valid (in particular, a discovery metadata record must exist with a corresponding topic so that data can be made available using this topic). If the topic is invalid, the Global Broker will discard non-compliant messages and will raise an alert. The metric ``wmo_wis2_gb_messages_no_metadata_total`` will be increased by 1. Global Broker should not request Global Discovery Catalogue for each notification message but should keep a cache of all valid topics for every ``centre-id``.
+* A Global Broker will check if a discovery metadata record exists corresponding to the topic on which a message has been published. If there is no corresponding discovery metadata record, the Global Broker will discard non-compliant messages and will raise an alert. The metric ``wmo_wis2_gb_messages_no_metadata_total`` will be increased by 1. Global Broker should not request information from the Global Discovery Catalogue for each notification message but should keep a cache of all valid topics for every ``centre-id``.
+* A Global Broker will check if the topic on which the message is received is valid. If the topic is invalid, the Global Broker will discard non-compliant messages and will raise an alert. The metric ``wmo_wis2_gb_invalid_topic_total`` will be increased by 1.
 * During the pre-operational phase (2024), Global Broker will not discard the message but will send a message on the `monitor` topic hierarchy to inform the originating centre and its GISC.
-* A Global Broker will validate notification messages against the standard format (see _Manual on WIS_, Volume II – Appendix E: WIS2 Notification Message), discarding non-compliant messages and raising an alert. The metric ``wmo_wis2_gb_messages_invalid_total`` will be increased by 1.
+* A Global Broker will validate notification messages against the standard format (see _Manual on WIS_, Volume II – Appendix E: WIS2 Notification Message), discarding non-compliant messages and raising an alert. The metric ``wmo_wis2_gb_invalid_format_total`` will be increased by 1.
 * A Global Broker instance will republish a message only once. Using the message id as defined in the WIS2 Notification Message, the Global Broker will record the id of messages already published and will discard subsequent identical (with the same message id) messages. This is the anti-loop feature of the Global Broker.
 * When publishing a message to the local broker, the metric ``wmo_wis2_gb_messages_published_total`` will be increased by 1.
 * All above defined metrics will be made available on HTTPS endpoints that the Global Monitor will ingest from regularly.