AWS Certified CloudOps Engineer - Associate
Troubleshooting ELB and Target Health
How to read a target health reason code, the ordered list of causes behind an unhealthy target, the fail-open behavior that hides an outage, and the difference between an ELB error code and a target error code.
Intermediate 28 minutes 6 Learning Objectives
- Interpret target health states and reason codes from describe-target-health
- Diagnose an unhealthy target by working through security groups, network ACLs, ping path, timeout, and matcher in order
- Explain fail-open behavior and predict when a load balancer routes to unhealthy targets
- Configure target group health thresholds for DNS failover and routing failover
- Distinguish HTTP 502, 503, 504, and 460 by the failure each one describes
- Select the CloudWatch metric and statistic that proves a given failure mode