Reduce spawn cycle skips on stack size updates with improved timeout by Copilot · Pull Request #94 · NighterDevelopment/SmartSpawner

Copilot · 2025-11-01T09:04:15Z

Loot generation cycles were being skipped when spawner stack size updates held the dataLock, causing missed spawns.

Changes

SpawnerLootGenerator.java

Increase tryLock(50ms) timeout to tryLock(500ms) for dataLock acquisition (line 111)
Increase tryLock() timeout to tryLock(500ms) for lootGenerationLock re-acquisition (line 181)

Before/After

Before:

// Skip cycle if stack update in progress (50ms timeout)
boolean dataLockAcquired = spawner.getDataLock().tryLock(50, TimeUnit.MILLISECONDS);
if (!dataLockAcquired) {
    return;  // Skip this spawn cycle
}

After:

// Wait longer for stack update to complete (500ms timeout)
boolean dataLockAcquired = spawner.getDataLock().tryLock(500, TimeUnit.MILLISECONDS);
if (!dataLockAcquired) {
    return;  // Skip this spawn cycle
}

Thread Safety & Timer Synchronization

No deadlock risk: locks acquired on different threads in async flow
500ms timeout is long enough for most stack updates to complete
Prevents indefinite blocking that could interfere with timer display in SpawnerGuiViewManager
Maintains accurate timer countdown in GUI by avoiding long lock holds
Compatible with GUI timer's 100ms timeout for lock acquisition

Original prompt

When spawner stack get updated spawnloot cycle skip the current cycle what if I want to remove that? it should because of the lock in SpawnerLootGenerator
                if (!updateLockAcquired) {
                    // Lock is held, stack size is changing, skip this update
                    return;
                }

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Changed tryLock() to lock() in two locations: 1. When acquiring dataLock to read spawn timing (line 109) 2. When re-acquiring lootGenerationLock for update phase (line 168) This ensures spawn/loot cycles continue even when spawner stack is being updated, instead of skipping the cycle. Co-authored-by: ptthanh02 <73684260+ptthanh02@users.noreply.github.com>

ptthanh02 · 2025-11-01T09:19:28Z

@copilot But will it sync with the timer countdown in Spawner GUI? you can view in SpawnerGuiViewManager

Copilot · 2025-11-01T09:21:17Z

@copilot But will it sync with the timer countdown in Spawner GUI? you can view in SpawnerGuiViewManager

Good catch! There is a potential timer sync issue with the current changes.

The problem: When spawnLootToSpawner() blocks waiting for dataLock (during stack updates), the GUI timer calculation in SpawnerGuiViewManager.calculateTimeUntilNextSpawn() tries to acquire the same lock with a 100ms timeout. If it fails, it shows "1 second" as a fallback, which could make the timer inaccurate.

Additionally, there's a conflict where both SpawnerGuiViewManager (line 1362) and SpawnerLootGenerator (line 218) can update lastSpawnTime, which could cause the timer to reset unexpectedly.

I should revert to using tryLock() with a longer timeout instead of blocking lock() to allow the timer to stay synchronized. Would you like me to adjust the timeout values to find a better balance between not skipping cycles and maintaining timer accuracy?

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If you need me to access, download, or install something from one of these locations, you can either:

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Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Changed from blocking lock() to tryLock(500ms) to maintain better timer synchronization with SpawnerGuiViewManager while still waiting for stack updates to complete. This prevents indefinite blocking that could cause timer display issues. Co-authored-by: ptthanh02 <73684260+ptthanh02@users.noreply.github.com>

ptthanh02 · 2025-11-01T09:34:09Z

@copilot is there any performance issue or exploitable potential? also when stack the spawner setLastSpawnTime get reset so do really need the lock?

Copilot · 2025-11-01T09:36:05Z

@copilot is there any performance issue or exploitable potential? also when stack the spawner setLastSpawnTime get reset so do really need the lock?

Excellent questions! Here's my analysis:

Performance issue: Line 181 waits up to 500ms on the main thread (via runLocationTask), which could cause lag spikes if multiple concurrent loot generations occur. Line 111 is less problematic as it runs on a scheduler thread.

Exploit potential: You're absolutely right about the race condition! If loot generation starts before a stack update, it could overwrite the reset lastSpawnTime (line 245 in SpawnerData), potentially allowing immediate spawns after stacking - exactly the exploit setStackSize tries to prevent.

Lock at 237-244: The current tryLock() with no timeout is actually correct - it immediately fails if a stack update is in progress, preventing the exploit. If we can't acquire the lock, we skip updating lastSpawnTime, preserving the reset from setStackSize.

Recommendation: Revert line 181 back to immediate tryLock() (no timeout) to avoid main thread lag and prevent the exploit. Keep line 111 at 500ms since it's not on the main thread. This maintains the original exploit protection while still reducing skip frequency during the read phase.

Should I make this change?

Copilot AI self-assigned this Nov 1, 2025

Initial plan

aad12c2

Copilot AI assigned ptthanh02 Nov 1, 2025

Copilot started work on behalf of ptthanh02 November 1, 2025 09:04 View session

Copilot AI changed the title ~~[WIP] Remove cycle skip when spawner stack updates~~ Remove spawn cycle skip on stack size updates Nov 1, 2025

Copilot AI requested a review from ptthanh02 November 1, 2025 09:13

Copilot finished work on behalf of ptthanh02 November 1, 2025 09:13

Copilot started work on behalf of ptthanh02 November 1, 2025 09:19 View session

Copilot AI changed the title ~~Remove spawn cycle skip on stack size updates~~ Reduce spawn cycle skips on stack size updates with improved timeout Nov 1, 2025

Copilot finished work on behalf of ptthanh02 November 1, 2025 09:26

Copilot started work on behalf of ptthanh02 November 1, 2025 09:34 View session

Copilot finished work on behalf of ptthanh02 November 1, 2025 09:36

ptthanh02 marked this pull request as ready for review November 1, 2025 13:38

ptthanh02 closed this Nov 1, 2025

ptthanh02 deleted the copilot/remove-cycle-skip-on-update branch November 1, 2025 13:43

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Reduce spawn cycle skips on stack size updates with improved timeout#94

Reduce spawn cycle skips on stack size updates with improved timeout#94
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Before/After

Thread Safety & Timer Synchronization

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