add simple JSON-RPC healthcheck script

geth/check_geth_rpc.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Simple JSON-RPC healthcheck for Base op-geth.
+#
+# Usage:
+#   BASE_GETH_RPC_URL=http://localhost:8545 ./geth/check_geth_rpc.sh
+#
+# The script calls `eth_blockNumber` and considers the node healthy
+# if it returns a non-empty result.
+
+RPC_URL="${BASE_GETH_RPC_URL:-http://localhost:8545}"
+TIMEOUT="${BASE_GETH_RPC_TIMEOUT:-3}"
+
+log_err() {
+  echo "[geth-health] $*" >&2
+}
+
+if ! command -v curl >/dev/null 2>&1; then
+  log_err "curl not found in PATH"
+  exit 1
+fi
+
+payload='{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'
+
+response="$(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 ${RPC_URL}"
+  exit 1
+fi
+
+if ! echo "${response}" | grep -q '"result"'; then
+  log_err "eth_blockNumber did not return a result: ${response}"
+  exit 1
+fi
+
+echo "[geth-health] ok: JSON-RPC is responding at ${RPC_URL}"
+exit 0