From 2a44572fb2dc7a74307a1b90c48958978245b4c7 Mon Sep 17 00:00:00 2001
From: Luck <git@lucko.me>
Date: Sat, 16 Jan 2021 18:24:10 +0000
Subject: [PATCH] Fix non-daemon command manager thread sometimes preventing
 shutdown

---
 .../luckperms/common/command/CommandManager.java  | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/common/src/main/java/me/lucko/luckperms/common/command/CommandManager.java b/common/src/main/java/me/lucko/luckperms/common/command/CommandManager.java
index f2f82913d..f0cec28b8 100644
--- a/common/src/main/java/me/lucko/luckperms/common/command/CommandManager.java
+++ b/common/src/main/java/me/lucko/luckperms/common/command/CommandManager.java
@@ -72,8 +72,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
@@ -83,16 +82,13 @@ import java.util.stream.Collectors;
 public class CommandManager {
 
     private final LuckPermsPlugin plugin;
-
-    // the default executor to run commands on
-    private final ExecutorService executor = Executors.newSingleThreadExecutor();
-
+    private final ReentrantLock lock;
     private final TabCompletions tabCompletions;
-
     private final Map<String, Command<?>> mainCommands;
 
     public CommandManager(LuckPermsPlugin plugin) {
         this.plugin = plugin;
+        this.lock = new ReentrantLock(true); // enable fairness
         this.tabCompletions = new TabCompletions(plugin);
         this.mainCommands = ImmutableList.<Command<?>>builder()
                 .add(new UserParentCommand())
@@ -134,13 +130,16 @@ public class CommandManager {
 
     public CompletableFuture<CommandResult> executeCommand(Sender sender, String label, List<String> args) {
         return CompletableFuture.supplyAsync(() -> {
+            this.lock.lock();
             try {
                 return execute(sender, label, args);
             } catch (Throwable e) {
                 this.plugin.getLogger().severe("Exception whilst executing command: " + args, e);
                 return null;
+            } finally {
+                this.lock.unlock();
             }
-        }, this.executor);
+        }, this.plugin.getBootstrap().getScheduler().async());
     }
 
     public boolean hasPermissionForAny(Sender sender) {