Interview › Scripting (Bash, Groovy)

How would you write a health-check script that polls a URL until it returns 200? [Advanced]

Answer

I would poll the URL with curl, require HTTP 200, sleep between attempts, and enforce a timeout or maximum attempts. The script should print diagnostics and exit nonzero if the service never becomes healthy.

Technical explanation

Use curl -fsS to fail on HTTP errors, show errors, and stay quiet on success.

Use --max-time to prevent one request from hanging forever.

For Kubernetes rollouts, prefer native readiness and kubectl rollout status, but URL polling is useful for external checks.

Hands-on example

#!/usr/bin/env bash
set -euo pipefail
url=${1:?url required}
for attempt in {1..30}; do
if code=$(curl -sS -o /dev/null -w '%{http_code}' --max-time 3 "$url") && [[ "$code" == "200" ]]; then
echo "healthy"
exit 0
fi
echo "waiting for 200, got ${code:-curl-error}" >&2
sleep 2
done
echo "service did not become healthy: $url" >&2
exit 1

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