I have a Vault cluster (3 nodes) behind a HAProxy (with a “VIP” domain).
How metrics work with a cluster ? Do I need to collect all datas from all nodes and add all datas ; or just collect metrics from the active node (from my VIP domain) ?
It is up to you - both approaches can be viable. Metrics for the active node only will be substantially more useful than no metrics at all, but metrics from each node individually may allow you monitor some things more clearly.