Which configuration best ensures accurate health status without false failures?
hard📝 Best Practice Q15 of 15
AWS - Elastic Load Balancing
You want to configure a health check for a web service behind an AWS Application Load Balancer. The service sometimes takes up to 8 seconds to respond under load. Which configuration best ensures accurate health status without false failures?
ASet TimeoutSeconds to 10, IntervalSeconds to 30, HealthyThresholdCount to 3, UnhealthyThresholdCount to 2
BSet TimeoutSeconds to 5, IntervalSeconds to 10, HealthyThresholdCount to 2, UnhealthyThresholdCount to 2
CSet TimeoutSeconds to 3, IntervalSeconds to 5, HealthyThresholdCount to 5, UnhealthyThresholdCount to 5
DSet TimeoutSeconds to 1, IntervalSeconds to 15, HealthyThresholdCount to 1, UnhealthyThresholdCount to 1
Step-by-Step Solution
Solution:
Step 1: Match TimeoutSeconds to max response time
The service can take up to 8 seconds, so TimeoutSeconds should be at least 8 to avoid false failures. Set TimeoutSeconds to 10, IntervalSeconds to 30, HealthyThresholdCount to 3, UnhealthyThresholdCount to 2 sets 10 seconds, which is suitable.
Step 2: Choose thresholds and intervals for stability
Longer IntervalSeconds (30) and thresholds (3 healthy, 2 unhealthy) help avoid flapping due to temporary slow responses.
Step 3: Evaluate other options
Options A, C, and D have TimeoutSeconds too low or thresholds too sensitive, risking false unhealthy marks.
Final Answer:
Set TimeoutSeconds to 10, IntervalSeconds to 30, HealthyThresholdCount to 3, UnhealthyThresholdCount to 2 -> Option A
Quick Check:
Timeout ≥ max response + stable thresholds = Set TimeoutSeconds to 10, IntervalSeconds to 30, HealthyThresholdCount to 3, UnhealthyThresholdCount to 2 [OK]
Quick Trick:Timeout must exceed max response time to avoid false failures [OK]
Common Mistakes:
Setting TimeoutSeconds less than max response time
Using too low thresholds causing flapping
Ignoring service response variability
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