Health Check

How the health of Backend Services is measured, check types and how the health status is interpreted.

• What does a Health Check do; what happens if I don't assign one?LB-07-001
• What is the default health check behavior (Period, Timeout, Required Successes, Required Failures)?LB-07-002
• Which health check types are supported?LB-07-003
• What is the difference between a TCP port check and an HTTP check; which should I choose?LB-07-004
• How many seconds does it take for a server to be considered "down", and how do I calculate it?LB-07-005
• How do I expect a specific status code (e.g. 200, 302) in an HTTP health check?LB-07-006
• How do I verify a specific text (e.g. "OK") in the response content?LB-07-007
• What is "Expect Negative Result" used for?LB-07-008
• Can certificate verification be done in an HTTPS health check?LB-07-009
• Can I check a different IP/port of the server for the health check (Use Different IP for Health Check)?LB-07-010
• Which source IP are health check packets sent from; can I change it?LB-07-011
• Which IPs should I allow on the server firewall for health checks?LB-07-012
• How should I set the Period, Timeout, Required Successes and Required Failures values?LB-07-013
• What are the recommended values for slow-responding services (databases, reporting)?LB-07-014
• How do I health check DNS servers?LB-07-015
• How do I see the health check history (when a server went down/up)?LB-07-016
• What does Enable HC Logs do; should I turn it off?LB-07-017
• If I change a health check profile, which Backend Services are affected?LB-07-018
• What do users see if all servers are down; can I show a custom page instead?LB-07-019
• What kind of /health endpoint should I design in my application for health checks?LB-07-020
• How do I health check UDP services other than DNS (UDP scenario, Hex/Base64/text)?LB-07-021
• Can authenticated / STARTTLS checks be done for LDAP, SMTP and FTP?LB-07-022
• The server is running, but TR7 shows it as down; why?LB-07-023
• The server has failed, but TR7 still sends traffic to it; why?LB-07-024
• The health check keeps going back and forth between up/down (flapping); what should I do?LB-07-025
• Health check requests are filling up my backend logs; what can I do?LB-07-026
• Can I assign more than one health check to a Backend Service?LB-07-027
• How many seconds does it take for a health check result to affect traffic?LB-07-028
• Can I validate a JSON response field by field in a health check (Content Check Mode: JSONata Expression)?LB-07-029
• Can I specify a Host / SNI in a health check (Virtual domain)?LB-07-030
• Can I see only status changes in the health check logs (Only Change Logs / All Logs)?LB-07-031