From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Zach Brown Date: Fri, 12 May 2017 23:34:11 -0500 Subject: [PATCH] Properly handle async calls to restart the server The watchdog thread calls the server restart function asynchronously. Prior to this change, it attempted to do several non-safe operations from the watchdog thread, rather than the main. Specifically, because of a separate upstream change, it causes player entities to be ticked asynchronously, among other things. This is dangerous. This patch moves the old handling into a synchronous variant, for calls from the restart command, and adds separate handling for async calls, such as those from the watchdog thread. When calling from the watchdog thread, we cannot assume the main thread is in a tickable state; it may be completely deadlocked. In order to handle this, we mark the server as stopping, in order to account for situations where the server should complete a tick reasonbly soon, i.e. 99% of cases. Should the server not enter a state where it is stopping within 10 seconds, We will assume that the server has in fact deadlocked and will proceed to force kill the server. This modification does not force restart the server should we actually enter a deadlocked state where the server is stopping, whereas this will in most cases exit within a reasonable amount of time, to put a fixed limit on a process that will have plugins and worlds saving to the disk has a high potential to result in corruption/dataloss. diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java index 629304c403c596bf81dd8de919f0fcb5c77bd403..80d8b0b0eac47b8d8e62db60da9daf0da8671fb3 100644 --- a/src/main/java/net/minecraft/server/MinecraftServer.java +++ b/src/main/java/net/minecraft/server/MinecraftServer.java @@ -88,6 +88,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant worldServer = Maps.newLinkedHashMap(); // CraftBukkit - keep order, k+v already use identity methods private PlayerList playerList; private volatile boolean isRunning = true; + private volatile boolean isRestarting = false; // Paper - flag to signify we're attempting to restart private boolean isStopped; private int ticks; protected final Proxy proxy; @@ -723,7 +724,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant 0 && new File( split[0] ).isFile() ) + // Paper - extract method and cleanup + boolean isRestarting = addShutdownHook( restartScript ); + if ( isRestarting ) { - System.out.println( "Attempting to restart with " + restartScript ); + System.out.println( "Attempting to restart with " + SpigotConfig.restartScript ); + } else + { + System.out.println( "Startup script '" + SpigotConfig.restartScript + "' does not exist! Stopping server." ); + } + // Stop the watchdog + WatchdogThread.doStop(); - // Disable Watchdog - WatchdogThread.doStop(); + shutdownServer( isRestarting ); + // Paper end + } catch ( Exception ex ) + { + ex.printStackTrace(); + } + } - // Kick all players - for ( EntityPlayer p : (List< EntityPlayer>) MinecraftServer.getServer().getPlayerList().players ) - { - p.playerConnection.disconnect(SpigotConfig.restartMessage); - } - // Give the socket a chance to send the packets - try - { - Thread.sleep( 100 ); - } catch ( InterruptedException ex ) - { - } - // Close the socket so we can rebind with the new process - MinecraftServer.getServer().getServerConnection().b(); + // Paper start - sync copied from above with minor changes, async added + private static void shutdownServer(boolean isRestarting) + { + if ( MinecraftServer.getServer().isMainThread() ) + { + // Kick all players + for ( EntityPlayer p : com.google.common.collect.ImmutableList.copyOf( MinecraftServer.getServer().getPlayerList().players ) ) + { + p.playerConnection.disconnect(SpigotConfig.restartMessage); + } + // Give the socket a chance to send the packets + try + { + Thread.sleep( 100 ); + } catch ( InterruptedException ex ) + { + } - // Give time for it to kick in - try - { - Thread.sleep( 100 ); - } catch ( InterruptedException ex ) - { - } + closeSocket(); - // Actually shutdown - try - { - MinecraftServer.getServer().close(); - } catch ( Throwable t ) - { - } + // Actually shutdown + try + { + MinecraftServer.getServer().close(); // calls stop() + } catch ( Throwable t ) + { + } + + // Actually stop the JVM + System.exit( 0 ); - // This will be done AFTER the server has completely halted - Thread shutdownHook = new Thread() + } else + { + // Mark the server to shutdown at the end of the tick + MinecraftServer.getServer().safeShutdown( false, isRestarting ); + + // wait 10 seconds to see if we're actually going to try shutdown + try + { + Thread.sleep( 10000 ); + } + catch (InterruptedException ignored) + { + } + + // Check if we've actually hit a state where the server is going to safely shutdown + // if we have, let the server stop as usual + if (MinecraftServer.getServer().isStopped()) return; + + // If the server hasn't stopped by now, assume worse case and kill + closeSocket(); + System.exit( 0 ); + } + } + // Paper end + + // Paper - Split from moved code + private static void closeSocket() + { + // Close the socket so we can rebind with the new process + MinecraftServer.getServer().getServerConnection().b(); + + // Give time for it to kick in + try + { + Thread.sleep( 100 ); + } catch ( InterruptedException ex ) + { + } + } + // Paper end + + // Paper start - copied from above and modified to return if the hook registered + private static boolean addShutdownHook(String restartScript) + { + String[] split = restartScript.split( " " ); + if ( split.length > 0 && new File( split[0] ).isFile() ) + { + Thread shutdownHook = new Thread() + { + @Override + public void run() { - @Override - public void run() + try { - try + String os = System.getProperty( "os.name" ).toLowerCase(java.util.Locale.ENGLISH); + if ( os.contains( "win" ) ) { - String os = System.getProperty( "os.name" ).toLowerCase(java.util.Locale.ENGLISH); - if ( os.contains( "win" ) ) - { - Runtime.getRuntime().exec( "cmd /c start " + restartScript ); - } else - { - Runtime.getRuntime().exec( "sh " + restartScript ); - } - } catch ( Exception e ) + Runtime.getRuntime().exec( "cmd /c start " + restartScript ); + } else { - e.printStackTrace(); + Runtime.getRuntime().exec( "sh " + restartScript ); } + } catch ( Exception e ) + { + e.printStackTrace(); } - }; - - shutdownHook.setDaemon( true ); - Runtime.getRuntime().addShutdownHook( shutdownHook ); - } else - { - System.out.println( "Startup script '" + SpigotConfig.restartScript + "' does not exist! Stopping server." ); - - // Actually shutdown - try - { - MinecraftServer.getServer().close(); - } catch ( Throwable t ) - { } - } - System.exit( 0 ); - } catch ( Exception ex ) + }; + + shutdownHook.setDaemon( true ); + Runtime.getRuntime().addShutdownHook( shutdownHook ); + return true; + } else { - ex.printStackTrace(); + return false; } } + // Paper end + }