When using the HAProxy in multi process mode, each process has its own memory area and therefore has its own statistics.
This implies that each process needs to have a dedicated socket or endpoint for giving access to its statistics.
Accordingly, in the Datadog configuration file for HAProxy, each socket or endpoint has to be declared as an instance.
Otherwise they share the same
/haproxy_stats endpoint, and getting the HAProxy statistics from it shows the stats only for the process assigned to the current request.
Refreshing the page in your browser shows the stats from a different process than previously:
If your HAproxy integration is not well configured, you may notice: