Status code (expected value): 301 (change according to your environment; I initially set it to 200)<\/li>\n<\/ul>\nIf left as is, when your nginx configuration redirects all HTTP traffic to HTTPS with a 301 status, it will conflict with the health check’s expected value.<\/p>\n
The Stumbling Block: Backend Health is Critical and Traffic Won’t Forward<\/h2>\n
Even if you create an NLB, traffic naturally won’t forward if the backend health is Critical. In my case, the return value of the health check was the culprit.<\/p>\n
My nginx configuration was set up to 301 redirect all HTTP (80) traffic to HTTPS.<\/p>\n
server {\n listen 80;\n listen [::]:80;\n server_name donguri3.net www.donguri3.net;\n\n return 301 https:\/\/$host$request_uri;\n}<\/pre>\n <\/p>\n
If you run `curl -I` against the private IP in this state, it will naturally return `HTTP\/1.1 301`. In other words, nginx is returning a 301 “correctly.”
\nHowever, if the NLB is configured to “expect an HTTP 200,” it treats the 301 response as unhealthy, resulting in a Critical status.<\/p>\n
Once resolved, the overall health status turns to OK, and the Network Load Balancer starts functioning properly.<\/p>\n
Conclusion: Make Your Entry Point Resilient for $0, Even Without Knowing the Root Cause<\/h2>\n
When OCI1 became “unreachable despite being running,” checking the console yielded no clues. There was no OCI outage notice. OCI2 was operating normally. Furthermore, metrics were missing only on OCI1\u2014under these conditions, fighting the issue by purely investigating the cause would mean prolonged downtime at the entry point.<\/p>\n
Therefore, I prepared an entry point (WireGuard + nginx) on OCI2 as well, created a Network Load Balancer (NLB) within the Always Free tier limits, and made the entry point redundant.<\/p>\n
By matching the health check’s expected status code to 301 to accommodate nginx’s behavior, I achieved an “uninterrupted entry point” with zero additional cost. While root cause analysis can be done later, the stress of a dead entry point can be eliminated first.<\/p>\n
If you run into the same issue, definitely give this a try.<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
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![\"Outage](\"https:\/\/donguri3.net\/wp-content\/uploads\/2025\/12\/b4e7adf0be4d5680087a742270dbc5df.png\")
<\/a><\/p>\n