Healthcheck Loop

Bash · Example / how-to

📋 Overview

Poll an HTTP health endpoint until it succeeds or a timeout expires — useful for deploy wait scripts.

🔧 Core concepts

Piece	Role
Loop + sleep	Retry with backoff gap
`curl -fsS`	Fail on HTTP errors
Deadline	Absolute timeout
Exit codes	`0` healthy, `1` timed out

💡 Examples

healthcheck_loop.sh:

#!/usr/bin/env bash
set -euo pipefail

URL="${1:-http://127.0.0.1:8000/health}"
TIMEOUT_SEC="${TIMEOUT_SEC:-60}"
INTERVAL_SEC="${INTERVAL_SEC:-2}"
START="$(date +%s)"

echo "waiting for $URL (timeout ${TIMEOUT_SEC}s)"

while true; do
  if curl -fsS --max-time 5 "$URL" >/dev/null; then
    echo "healthy"
    exit 0
  fi

  NOW="$(date +%s)"
  ELAPSED="$((NOW - START))"
  if ((ELAPSED >= TIMEOUT_SEC)); then
    echo "error: timed out after ${TIMEOUT_SEC}s" >&2
    exit 1
  fi

  echo "not ready (${ELAPSED}s)…"
  sleep "$INTERVAL_SEC"
done

Usage:

chmod +x healthcheck_loop.sh
./healthcheck_loop.sh http://127.0.0.1:9000/healthz
TIMEOUT_SEC=120 INTERVAL_SEC=3 ./healthcheck_loop.sh https://example.com/health

⚠️ Pitfalls

curl without -f treats 500 as success — always use -f or check status.
Infinite loops without a deadline hang CI jobs.
DNS/TLS failures need clear stderr; avoid swallowing curl errors silently.

Healthcheck Loop

Healthcheck Loop

📋 Overview

🔧 Core concepts

💡 Examples

⚠️ Pitfalls

🔗 Related

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