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CompletableFuture join() causing main thread hang

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1

1

I have two blocks of code that seem to be causing the main server thread to hang, but Im really not sure why it's hanging...

public static synchronized CompletableFuture<Void> saveAllToDatabase() 
 return CompletableFuture.runAsync(() -> 
 for (UUID u : timeMap.keySet()) 
 saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217
 
 );


public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) 
 return CompletableFuture.runAsync(() -> 
 if (timeMap.get(uuid) == null) return;
 long l = getTime(uuid);
 long p = getPoints(uuid).join(); //This is PlaytimeManager:199
 Playtime.getData().save(uuid, l, p);
 );


public static CompletableFuture<Long> getPoints(UUID u) 
 Database d = Playtime.getData();
 return CompletableFuture.supplyAsync(() -> 
 if (d.isSaved(u)) return getCachedPoints(u) == 0 ? d.getPlayer(u).getPoints() : getCachedPoints(u);
 return getCachedPoints(u);
 );

The #join() methods are causing the hanging, but they're wrapped in an async CompletableFuture so I'm unsure how exactly it's hanging...

The stack trace:
https://pastebin.com/5QhJPPhn

java asynchronous hang completable-future

share|improve this question

edited Mar 7 at 7:38

James Andrew

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What is the returning type for getPoints(uuid) method?
  
  – Bukharov Sergey
  Mar 7 at 7:31
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It returns a CompletableFuture<Long>. Code updated in original post with the getPoints method
  
  – James Andrew
  Mar 7 at 7:37
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  tried with minimum code and removed dependent modules, works fine for me public static synchronized CompletableFuture<Void> saveAllToDatabase() return CompletableFuture.runAsync(() -> for (UUID u : timeMap.keySet()) saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217 );
  
  – dkb
  Mar 7 at 8:48
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) return CompletableFuture.runAsync(() -> long p = getPoints(uuid).join(); //This is PlaytimeManager:199 System.out.println(uuid.toString() + ":" + p); );
  
  – dkb
  Mar 7 at 8:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  public static CompletableFuture<Long> getPoints(UUID u) return CompletableFuture.supplyAsync(() -> 10L);
  
  – dkb
  Mar 7 at 8:49
  

  
  
  
  

 | 
show 2 more comments

1

1

I have two blocks of code that seem to be causing the main server thread to hang, but Im really not sure why it's hanging...

public static synchronized CompletableFuture<Void> saveAllToDatabase() 
 return CompletableFuture.runAsync(() -> 
 for (UUID u : timeMap.keySet()) 
 saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217
 
 );


public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) 
 return CompletableFuture.runAsync(() -> 
 if (timeMap.get(uuid) == null) return;
 long l = getTime(uuid);
 long p = getPoints(uuid).join(); //This is PlaytimeManager:199
 Playtime.getData().save(uuid, l, p);
 );


public static CompletableFuture<Long> getPoints(UUID u) 
 Database d = Playtime.getData();
 return CompletableFuture.supplyAsync(() -> 
 if (d.isSaved(u)) return getCachedPoints(u) == 0 ? d.getPlayer(u).getPoints() : getCachedPoints(u);
 return getCachedPoints(u);
 );

The #join() methods are causing the hanging, but they're wrapped in an async CompletableFuture so I'm unsure how exactly it's hanging...

The stack trace:
https://pastebin.com/5QhJPPhn

java asynchronous hang completable-future

share|improve this question

edited Mar 7 at 7:38

James Andrew

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  What is the returning type for getPoints(uuid) method?
  
  – Bukharov Sergey
  Mar 7 at 7:31
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It returns a CompletableFuture<Long>. Code updated in original post with the getPoints method
  
  – James Andrew
  Mar 7 at 7:37
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  tried with minimum code and removed dependent modules, works fine for me public static synchronized CompletableFuture<Void> saveAllToDatabase() return CompletableFuture.runAsync(() -> for (UUID u : timeMap.keySet()) saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217 );
  
  – dkb
  Mar 7 at 8:48
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) return CompletableFuture.runAsync(() -> long p = getPoints(uuid).join(); //This is PlaytimeManager:199 System.out.println(uuid.toString() + ":" + p); );
  
  – dkb
  Mar 7 at 8:49
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  public static CompletableFuture<Long> getPoints(UUID u) return CompletableFuture.supplyAsync(() -> 10L);
  
  – dkb
  Mar 7 at 8:49
  

  
  
  
  

 | 
show 2 more comments

I have two blocks of code that seem to be causing the main server thread to hang, but Im really not sure why it's hanging...

public static synchronized CompletableFuture<Void> saveAllToDatabase() 
 return CompletableFuture.runAsync(() -> 
 for (UUID u : timeMap.keySet()) 
 saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217
 
 );


public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) 
 return CompletableFuture.runAsync(() -> 
 if (timeMap.get(uuid) == null) return;
 long l = getTime(uuid);
 long p = getPoints(uuid).join(); //This is PlaytimeManager:199
 Playtime.getData().save(uuid, l, p);
 );


public static CompletableFuture<Long> getPoints(UUID u) 
 Database d = Playtime.getData();
 return CompletableFuture.supplyAsync(() -> 
 if (d.isSaved(u)) return getCachedPoints(u) == 0 ? d.getPlayer(u).getPoints() : getCachedPoints(u);
 return getCachedPoints(u);
 );

The #join() methods are causing the hanging, but they're wrapped in an async CompletableFuture so I'm unsure how exactly it's hanging...

The stack trace:
https://pastebin.com/5QhJPPhn

java asynchronous hang completable-future

share|improve this question

edited Mar 7 at 7:38

James Andrew

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

public static synchronized CompletableFuture<Void> saveAllToDatabase() 
 return CompletableFuture.runAsync(() -> 
 for (UUID u : timeMap.keySet()) 
 saveUUIDToDatabase(u).join(); //This is PlaytimeManager:217
 
 );


public static synchronized CompletableFuture<Void> saveUUIDToDatabase(UUID uuid) 
 return CompletableFuture.runAsync(() -> 
 if (timeMap.get(uuid) == null) return;
 long l = getTime(uuid);
 long p = getPoints(uuid).join(); //This is PlaytimeManager:199
 Playtime.getData().save(uuid, l, p);
 );


public static CompletableFuture<Long> getPoints(UUID u) 
 Database d = Playtime.getData();
 return CompletableFuture.supplyAsync(() -> 
 if (d.isSaved(u)) return getCachedPoints(u) == 0 ? d.getPlayer(u).getPoints() : getCachedPoints(u);
 return getCachedPoints(u);
 );

share|improve this question

edited Mar 7 at 7:38

James Andrew

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

share|improve this question

edited Mar 7 at 7:38

James Andrew

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

asked Mar 7 at 6:07

James AndrewJames Andrew

7219

asked Mar 7 at 6:07

James AndrewJames Andrew

7219