From 8ee9cf07c510a72ea8e005a9d38df4724ea36b95 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 f09d358e29..f2c172ff18 100644 --- a/src/main/java/net/minecraft/server/MinecraftServer.java +++ b/src/main/java/net/minecraft/server/MinecraftServer.java @@ -85,6 +85,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati public final Map worldServer = Maps.newIdentityHashMap(); private PlayerList playerList; private boolean isRunning = true; + private boolean isRestarting = false; // Paper - flag to signify we're attempting to restart private boolean isStopped; private int ticks; protected final Proxy c; @@ -654,7 +655,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati if (this.playerList != null) { MinecraftServer.LOGGER.info("Saving players"); this.playerList.savePlayers(); - this.playerList.u(); + this.playerList.u(isRestarting); // Paper try { Thread.sleep(100); } catch (InterruptedException ex) {} // CraftBukkit - SPIGOT-625 - give server at least a chance to send packets } @@ -704,9 +705,16 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati return this.isRunning; } + // Paper start - allow passing of the intent to restart public void safeShutdown() { + safeShutdown(false); + } + + public void safeShutdown(boolean isRestarting) { this.isRunning = false; + this.isRestarting = isRestarting; } + // Paper end private boolean canSleepForTick() { return System.nanoTime() - lastTick + catchupTime < TICK_TIME; // Paper - improved "are we lagging" check to match our own diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java index 9570a8800b..9d44dcb3b2 100644 --- a/src/main/java/net/minecraft/server/PlayerList.java +++ b/src/main/java/net/minecraft/server/PlayerList.java @@ -1336,10 +1336,15 @@ public abstract class PlayerList { entityplayer.playerInteractManager.b(generatoraccess.getWorldData().getGameType()); } + // Paper start - Extract method to allow for restarting flag public void u() { + u(false); + } + + public void u(boolean isRestarting) { // CraftBukkit start - disconnect safely for (EntityPlayer player : this.players) { - player.playerConnection.disconnect(this.server.server.getShutdownMessage()); // CraftBukkit - add custom shutdown message + player.playerConnection.disconnect(!isRestarting ? this.server.server.getShutdownMessage() : org.spigotmc.SpigotConfig.restartMessage); // CraftBukkit - add custom shutdown message // Paper - add isRestarting flag } // CraftBukkit end // Paper start - Remove collideRule team if it exists @@ -1350,6 +1355,7 @@ public abstract class PlayerList { } // Paper end } + // Paper end // CraftBukkit start public void sendMessage(IChatBaseComponent[] iChatBaseComponents) { diff --git a/src/main/java/org/spigotmc/RestartCommand.java b/src/main/java/org/spigotmc/RestartCommand.java index 944151d140..061cbe7fcf 100644 --- a/src/main/java/org/spigotmc/RestartCommand.java +++ b/src/main/java/org/spigotmc/RestartCommand.java @@ -46,86 +46,123 @@ public class RestartCommand extends Command org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper try { - String[] split = restartScript.split( " " ); - if ( split.length > 0 && new File( split[0] ).isFile() ) + // Paper - extract method and cleanup + boolean isRestarting = addShutdownHook(restartScript); + if (isRestarting) { + 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(); + + shutdownServer(isRestarting); + } catch ( Exception ex ) + { + ex.printStackTrace(); + } + } + + // 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 ) ) { - System.out.println( "Attempting to restart with " + restartScript ); + p.playerConnection.disconnect(SpigotConfig.restartMessage); + } + // Give the socket a chance to send the packets + try + { + Thread.sleep( 100 ); + } catch ( InterruptedException ex ) + { + } - // Disable Watchdog - WatchdogThread.doStop(); + closeSocket(); - // 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(); + // Actually shutdown + try + { + MinecraftServer.getServer().stop(); + } catch ( Throwable t ) + { + } - // Give time for it to kick in - try - { - Thread.sleep( 100 ); - } catch ( InterruptedException ex ) - { - } + // Actually stop the JVM + System.exit(0); - // Actually shutdown - try - { - MinecraftServer.getServer().stop(); - } catch ( Throwable t ) - { - } + } else + { + // Mark the server to shutdown at the end of the tick + MinecraftServer.getServer().safeShutdown(isRestarting); - // This will be done AFTER the server has completely halted - Thread shutdownHook = new Thread() - { - @Override - public void run() - { - try - { - 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 ) - { - 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().stop(); - } catch ( Throwable t ) - { - } + // 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 ); - } catch ( Exception ex ) + } + } + + // 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 { - ex.printStackTrace(); + Thread.sleep( 100 ); + } catch ( InterruptedException ex ) + { + } + } + // Paper end + + // Paper - copied from above and modified to return if the hook registered + private static boolean addShutdownHook(final String restartScript) { + + String[] split = restartScript.split( " " ); + if ( split.length > 0 && new File( split[0] ).isFile() ) + { + Thread shutdownHook = new Thread() { + @Override + public void run() { + try { + 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) { + e.printStackTrace(); + } + } + }; + + shutdownHook.setDaemon(true); + Runtime.getRuntime().addShutdownHook(shutdownHook); + return true; + } else { + return false; } } } -- 2.20.1