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lightwalletd/monitor_lwd.sh

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#!/usr/bin/env bash
# Copyright 2024-2026 The DragonX Developers
# Released under GPLv3
#
# Monitors lightwalletd and restarts it automatically if it crashes.
# Usage: ./monitor_lwd.sh &
# or: nohup ./monitor_lwd.sh >> /tmp/lwd-monitor.log 2>&1 &
set -euo pipefail
SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
LWD_BIN="$SCRIPT_DIR/lightwalletd"
LWD_ARGS="-bind-addr lite.dragonx.is:9069 -conf-file $HOME/.hush/DRAGONX/DRAGONX.conf -no-tls"
LOGFILE="$SCRIPT_DIR/lwd-monitor.log"
PIDFILE="/tmp/lwd-monitor.pid"
RESTART_DELAY=5 # seconds to wait before restarting after a crash
MAX_RAPID_RESTARTS=5 # max restarts within the rapid window before backing off
RAPID_WINDOW=120 # seconds — if this many restarts happen within this window, back off
BACKOFF_DELAY=60 # seconds to wait when backing off
# Colors
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'
log() {
echo -e "[$(date '+%Y-%m-%d %H:%M:%S')] $1" | tee -a "$LOGFILE"
}
cleanup() {
log "${YELLOW}Monitor shutting down...${NC}"
if [[ -n "${LWD_PID:-}" ]] && kill -0 "$LWD_PID" 2>/dev/null; then
log "Stopping lightwalletd (PID $LWD_PID)..."
kill "$LWD_PID" 2>/dev/null || true
wait "$LWD_PID" 2>/dev/null || true
fi
rm -f "$PIDFILE"
log "Monitor stopped."
exit 0
}
trap cleanup SIGINT SIGTERM
# Prevent duplicate monitors
if [[ -f "$PIDFILE" ]]; then
OLD_PID=$(cat "$PIDFILE")
if kill -0 "$OLD_PID" 2>/dev/null; then
echo "Monitor already running (PID $OLD_PID). Exiting."
exit 1
fi
rm -f "$PIDFILE"
fi
echo $$ > "$PIDFILE"
# Check binary exists
if [[ ! -x "$LWD_BIN" ]]; then
log "${RED}ERROR: lightwalletd binary not found at $LWD_BIN${NC}"
log "Build it first with: make build"
rm -f "$PIDFILE"
exit 1
fi
# Check conf file exists
CONF_FILE="$HOME/.hush/DRAGONX/DRAGONX.conf"
if [[ ! -f "$CONF_FILE" ]]; then
log "${RED}ERROR: DRAGONX.conf not found at $CONF_FILE${NC}"
rm -f "$PIDFILE"
exit 1
fi
log "${GREEN}DragonX lightwalletd monitor started (PID $$)${NC}"
log "Binary: $LWD_BIN"
log "Args: $LWD_ARGS"
restart_times=()
LWD_PID=""
while true; do
# Start lightwalletd
log "${GREEN}Starting lightwalletd...${NC}"
$LWD_BIN $LWD_ARGS >> "$LOGFILE" 2>&1 &
LWD_PID=$!
log "lightwalletd started with PID $LWD_PID"
# Wait for it to exit
wait "$LWD_PID" || true
EXIT_CODE=$?
LWD_PID=""
if [[ $EXIT_CODE -eq 0 ]]; then
log "${YELLOW}lightwalletd exited cleanly (code 0). Not restarting.${NC}"
break
fi
log "${RED}lightwalletd crashed with exit code $EXIT_CODE${NC}"
# Track restart frequency for backoff
NOW=$(date +%s)
restart_times+=("$NOW")
# Trim old entries outside the rapid window
CUTOFF=$((NOW - RAPID_WINDOW))
filtered=()
for t in "${restart_times[@]}"; do
if (( t >= CUTOFF )); then
filtered+=("$t")
fi
done
restart_times=("${filtered[@]}")
if (( ${#restart_times[@]} >= MAX_RAPID_RESTARTS )); then
log "${YELLOW}Too many restarts (${#restart_times[@]} in ${RAPID_WINDOW}s). Backing off for ${BACKOFF_DELAY}s...${NC}"
sleep "$BACKOFF_DELAY"
restart_times=()
else
log "Restarting in ${RESTART_DELAY}s..."
sleep "$RESTART_DELAY"
fi
done
rm -f "$PIDFILE"
log "Monitor exiting."