personal_infra/ansible/roles/bitcoin_knots/templates/healthcheck.sh.j2

#!/bin/bash
# Bitcoin Knots health check — managed by Ansible (roles/bitcoin_knots)
#
# The exit code is the answer and systemd keeps it:
#     systemctl is-failed bitcoin-knots-healthcheck.service
# Reporting anywhere else is optional and generic.
#
#

RPC_HOST="{{ bitcoin_rpc_bind }}"
RPC_PORT={{ bitcoin_rpc_port }}
RPC_USER="{{ bitcoin_rpc_user }}"
RPC_PASSWORD="{{ bitcoin_rpc_password }}"
PUSH_URL="${HEALTHCHECK_PUSH_URL:-}"

# Check if bitcoind RPC is responding
check_bitcoind() {
    local response
    response=$(curl -s --max-time 30 \
        --user "${RPC_USER}:${RPC_PASSWORD}" \
        --data-binary '{"jsonrpc":"1.0","id":"healthcheck","method":"getblockchaininfo","params":[]}' \
        --header 'Content-Type: application/json' \
        "http://${RPC_HOST}:${RPC_PORT}" 2>&1)
    
    if [ $? -eq 0 ]; then
        # Check if response contains a non-null error
        # Successful responses have "error": null, failures have "error": {...}
        if echo "$response" | grep -q '"error":null\|"error": null'; then
            return 0
        else
            return 1
        fi
    else
        return 1
    fi
}

report() {
    local status=$1
    local msg=$2
    
    # No push URL is normal, not an error: the exit code below is still a
    # complete answer for anything reading unit state.
    [ -n "$PUSH_URL" ] || return 0
    
    # URL encode spaces in message
    local encoded_msg="${msg// /%20}"
    
    if ! curl -s --max-time 10 --retry 2 -o /dev/null \
        "${PUSH_URL}?status=${status}&msg=${encoded_msg}&ping="; then
        return 1
    fi
}

# Main health check
if check_bitcoind; then
    report "up" "OK"
    exit 0
else
    report "down" "bitcoind RPC not responding"
    exit 1
fi