Create check_nethermind_rpc.sh add rpc healthcheck helper script

nethermind/check_nethermind_rpc.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Simple healthcheck for a Nethermind JSON-RPC endpoint.
+# Can be used from Docker HEALTHCHECK or external monitoring.
+#
+# Environment (optional):
+#   BASE_NETHERMIND_RPC_URL    - RPC URL to probe (default: http://localhost:8545)
+#   BASE_NETHERMIND_RPC_TIMEOUT - curl timeout in seconds (default: 3)
+
+RPC_URL="${BASE_NETHERMIND_RPC_URL:-http://localhost:8545}"
+TIMEOUT="${BASE_NETHERMIND_RPC_TIMEOUT:-3}"
+
+log_err() {
+  echo "[nethermind-health] $*" >&2
+}
+
+if ! command -v curl >/dev/null 2>&1; then
+  log_err "curl not found in PATH"
+  exit 1
+fi
+
+payload='{"jsonrpc":"2.0","id":1,"method":"eth_syncing","params":[]}'
+
+response="$(curl -sS \
+  --max-time "${TIMEOUT}" \
+  -H "Content-Type: application/json" \
+  -d "${payload}" \
+  "${RPC_URL}" 2>/dev/null || true)"
+
+if [ -z "${response}" ]; then
+  log_err "empty response from ${RPC_URL}"
+  exit 1
+fi
+
+# Consider node healthy if:
+#   - it reports "result": false (fully synced), or
+#   - eth_syncing structure contains "currentBlock" (sync in progress).
+if echo "${response}" | grep -q '"result":false'; then
+  echo "ok: nethermind is synced"
+  exit 0
+fi
+
+if echo "${response}" | grep -q '"currentBlock"'; then
+  echo "ok: nethermind is syncing"
+  exit 0
+fi
+
+log_err "unexpected eth_syncing response: ${response}"
+exit 1