← Problem Library
Network L4 NETWORK-1484 · 10 min

An NGINX upstream DNS update is correct and one pool still serves dead backends because keepalive sockets outlive the resolver refresh

New IPs are published, but old keepalive connections keep sending traffic to the retired backend set.

NetworkFoundation OpsLevel 4Free10 min
Scenario

Traffic continues hitting dead backend IPs after a DNS cutover behind NGINX.

What to check first
  • Identify the primary failure signal in the The Resolver Learned the New Address and the Keepalive Pool Kept Calling the Old Number From Memory scenario.
  • Separate visible symptoms from the underlying technical dependency.
  • Describe the safest recovery path and the follow-up prevention work.
Checking checklist
  1. Summarize the current impact and the last known change.
  2. Collect direct evidence from logs, runtime state, and configuration before changing anything.
  3. Separate immediate recovery from permanent prevention work.
Recovery and prevention

Compare keepalive lifetime and resolver refresh before reducing DNS TTL further.

Questions worth viewing together
Should I translate commands, logs, or product names?

No. Keep commands, logs, file names, APIs, and product names unchanged, then explain the reasoning in the selected UI language.

What should the answer focus on?

State the root cause, the evidence that supports it, and the safest recovery direction.

Why can the scenario remain in the original language?

The source scenario is treated as an incident artifact. Guidance, checklist, hints, and explanations can be localized around it.