From 1532b0ef6d48ce5346dea644ca477cb26c087928 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Fri, 3 Aug 2018 18:04:56 +0100
Subject: [PATCH 1/2] Level: Remove chunks from chunk send queue on unload When
 a chunk request task crashes, these can get stuck and never get removed. This
 allows using /gc to collect the bad chunk in order to fix the bug.

---
 src/pocketmine/level/Level.php | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index f7f9c2a0e..6dd1d9763 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -2754,6 +2754,8 @@ class Level implements ChunkManager, Metadatable{
 		unset($this->chunkCache[$chunkHash]);
 		unset($this->blockCache[$chunkHash]);
 		unset($this->changedBlocks[$chunkHash]);
+		unset($this->chunkSendQueue[$chunkHash]);
+		unset($this->chunkSendTasks[$chunkHash]);
 
 		$this->timings->doChunkUnload->stopTiming();
 

From 9ff5c65fb613276bb59a710606b898ac1bff73b0 Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <odigiman@gmail.com>
Date: Fri, 3 Aug 2018 18:23:32 +0100
Subject: [PATCH 2/2] Level: Make async chunk sending aware of faults
 Previously any random error could occur during an AsyncTask preparing a
 chunk, and the Level would never know about it and thus never send the chunk.

I don't know how many invisible-chunk bug cases this fixes, but I expect it's quite a lot.
---
 src/pocketmine/level/Level.php | 42 +++++++++++++++-------------------
 1 file changed, 19 insertions(+), 23 deletions(-)

diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index 6dd1d9763..b63cb72d7 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -191,7 +191,7 @@ class Level implements ChunkManager, Metadatable{
 
 	/** @var Player[][] */
 	private $chunkSendQueue = [];
-	/** @var bool[] */
+	/** @var ChunkRequestTask[] */
 	private $chunkSendTasks = [];
 
 	/** @var bool[] */
@@ -2456,7 +2456,7 @@ class Level implements ChunkManager, Metadatable{
 	}
 
 	private function sendChunkFromCache(int $x, int $z){
-		if(isset($this->chunkSendTasks[$index = Level::chunkHash($x, $z)])){
+		if(isset($this->chunkSendQueue[$index = Level::chunkHash($x, $z)])){
 			foreach($this->chunkSendQueue[$index] as $player){
 				/** @var Player $player */
 				if($player->isConnected() and isset($player->usedChunks[$index])){
@@ -2464,7 +2464,6 @@ class Level implements ChunkManager, Metadatable{
 				}
 			}
 			unset($this->chunkSendQueue[$index]);
-			unset($this->chunkSendTasks[$index]);
 		}
 	}
 
@@ -2473,11 +2472,17 @@ class Level implements ChunkManager, Metadatable{
 			$this->timings->syncChunkSendTimer->startTiming();
 
 			foreach($this->chunkSendQueue as $index => $players){
-				if(isset($this->chunkSendTasks[$index])){
-					continue;
-				}
 				Level::getXZ($index, $x, $z);
-				$this->chunkSendTasks[$index] = true;
+
+				if(isset($this->chunkSendTasks[$index])){
+					if($this->chunkSendTasks[$index]->isCrashed()){
+						unset($this->chunkSendTasks[$index]);
+						$this->server->getLogger()->error("Failed to prepare chunk $x $z for sending, retrying");
+					}else{
+						//Not ready for sending yet
+						continue;
+					}
+				}
 				if(isset($this->chunkCache[$index])){
 					$this->sendChunkFromCache($x, $z);
 					continue;
@@ -2490,7 +2495,8 @@ class Level implements ChunkManager, Metadatable{
 				}
 				assert($chunk->getX() === $x and $chunk->getZ() === $z, "Chunk coordinate mismatch: expected $x $z, but chunk has coordinates " . $chunk->getX() . " " . $chunk->getZ() . ", did you forget to clone a chunk before setting?");
 
-				$this->server->getAsyncPool()->submitTask(new ChunkRequestTask($this, $x, $z, $chunk));
+				$this->server->getAsyncPool()->submitTask($task = new ChunkRequestTask($this, $x, $z, $chunk));
+				$this->chunkSendTasks[$index] = $task;
 
 				$this->timings->syncChunkSendPrepareTimer->stopTiming();
 			}
@@ -2503,24 +2509,14 @@ class Level implements ChunkManager, Metadatable{
 		$this->timings->syncChunkSendTimer->startTiming();
 
 		$index = Level::chunkHash($x, $z);
+		unset($this->chunkSendTasks[$index]);
 
-		if(!isset($this->chunkCache[$index]) and $this->server->getMemoryManager()->canUseChunkCache()){
-			$this->chunkCache[$index] = $payload;
-			$this->sendChunkFromCache($x, $z);
-			$this->timings->syncChunkSendTimer->stopTiming();
-			return;
+		$this->chunkCache[$index] = $payload;
+		$this->sendChunkFromCache($x, $z);
+		if(!$this->server->getMemoryManager()->canUseChunkCache()){
+			unset($this->chunkCache[$index]);
 		}
 
-		if(isset($this->chunkSendTasks[$index])){
-			foreach($this->chunkSendQueue[$index] as $player){
-				/** @var Player $player */
-				if($player->isConnected() and isset($player->usedChunks[$index])){
-					$player->sendChunk($x, $z, $payload);
-				}
-			}
-			unset($this->chunkSendQueue[$index]);
-			unset($this->chunkSendTasks[$index]);
-		}
 		$this->timings->syncChunkSendTimer->stopTiming();
 	}