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HAProxy backend max active session
warning

Description HAproxy backend {{ $labels.fqdn }}/{{ $labels.backend }} is reaching session limit (> 80%).
Query for 2m 
>>>
	
				
					((sum by (backend) (
				
			
				
					
					
						avg_over_time
					
				
			
				
					(
				
			
				
					
				
			
				
					[2m]) * 100) / sum by (backend) (
				
			
				
					
					
						avg_over_time
					
				
			
				
					(
				
			
				
					
				
			
				
					[2m])))) > 80
Query Explanation

The rule calculates the average number of active sessions per backend over the last 2 minutes, divides it by the configured session limit for that backend, multiplies by 100, and fires when this percentage exceeds 80 %. Thus, if a backend’s current sessions are consistently above 80 % of its max limit, the alert triggers.

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