Based on a fresh audit against the Arcadia V2 modpack (444 mods, including
Curios + Accessories + SophisticatedBackpacks/Storage + RS2 + Cosmetic
Armor Reworked). Three perf wins + two opportunistic fixes.
Perf
- Heartbeat period 10s -> 30s. Paired with the 60s staleness threshold
this keeps failure-detection latency unchanged while cutting 3x the
server_info UPDATE traffic per server.
- Per-player hash-skip for unchanged snapshots (SaveToFile + staggered
auto-save). computeSnapshotHash() rolls over inventory/equipment/
enderchest/effects/xp/health/food/mod-data; when an auto-save produces
the same hash as the last successful write, the BG task returns early
and no UPDATE hits MySQL. Idle-server reduction is >95%. Logout /
shutdown / death never use the skip and refresh the hash on success
so post-logout rejoin doesn't wrongly skip.
- Batched backpack + SS saves. saveBackpackSnapshots / saveSSSnapshots
now build one transaction via executeBatchTransaction instead of
N sequential REPLACE INTO calls. A player with 3 backpacks + 2
shulkers drops from 5 network round-trips to 1 per logout save.
Per-entry fallback preserved on transaction failure.
- Periodic-save tick short-circuits when the player list is empty —
no main-thread hop, no log line, no DB heartbeat on empty servers.
Compat notes (no code change needed)
- CosmeticArmours (modid=cosmeticarmoursmod) items are worn in vanilla
armor slots (Helmet / Chestplate / Leggings / Boots inner classes) —
already captured by the core armor[] serialization. No handler needed.
- CosmeticWeapons uses the same pattern via main hand / offhand — also
already covered by core inventory serialization.
Cleanup
- removePlayerLock now also clears the hash cache so a player who
fully logged out doesn't leave a stale hash behind.
Adds three utilities to harden PlayerSync against ungraceful server exits:
CrashRecovery.java
- installShutdownHook: registers a non-daemon JVM shutdown hook that calls
VanillaSync.emergencyFlushAll() synchronously when the process is killed
(SIGTERM, kill, OOM, host reboot). Covers the case where the normal
ServerStoppingEvent path never runs.
- clearOrphanedOnlineFlags: on startup, clears any online=1 player_data
rows pointing to this server_id (left by a previous crash). Reports the
count via SyncLogger so admins can see recovery activity.
- reportZombiePeers: logs peer server_ids whose heartbeat is missing or
stale (>60s), exposing the root of doPlayerJoin poll timeouts.
HeartbeatService.java
- Single-thread daemon scheduler pinging server_info.last_update every 10s.
- Lets peer servers distinguish live from dead via isPeerServerStale().
- Stopped explicitly in VanillaSync.onServerShutdown before pool close.
VanillaSync.emergencyFlushAll()
- Synchronous best-effort flush for every online player. No executor, no
locks — the server is dying, we just want data on disk. Writes player_data,
backpacks, SS, RS2 directly; logs SAVE/SKIPPED/FAILED per player via
SyncLogger so post-mortem analysis is possible.
PlayerSync.onServerStarting wires the four new calls after table init.
Fixes the production issue where players remained online=1 forever after
kill -9 and the 30s poll timeouts waiting for zombie server_ids.
