Paper/patches/server/0128-Properly-handle-async-calls-to-restart-the-server.patch
Bjarne Koll c5a10665b8
Remove wall-time / unused skip tick protection (#11412)
Spigot still maintains some partial implementation of "tick skipping", a
practice in which the MinecraftServer.currentTick field is updated not
by an increment of one per actual tick, but instead set to
System.currentTimeMillis() / 50. This behaviour means that the tracked
tick may "skip" a tick value in case a previous tick took more than the
expected 50ms.

To compensate for this in important paths, spigot/craftbukkit
implements "wall-time". Instead of incrementing/decrementing ticks on
block entities/entities by one for each call to their tick() method,
they instead increment/decrement important values, like
an ItemEntity's age or pickupDelay, by the difference of
`currentTick - lastTick`, where `lastTick` is the value of
`currentTick` during the last tick() call.

These "fixes" however do not play nicely with minecraft's simulation
distance as entities/block entities implementing the above behaviour
would "catch up" their values when moving from a non-ticking chunk to a
ticking one as their `lastTick` value remains stuck on the last tick in
a ticking chunk and hence lead to a large "catch up" once ticked again.

Paper completely removes the "tick skipping" behaviour (See patch
"Further-improve-server-tick-loop"), making the above precautions
completely unnecessary, which also rids paper of the previous described
incompatibility with non-ticking chunks.
2024-09-19 16:36:07 +02:00

291 lines
12 KiB
Diff

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Zach Brown <zach.brown@destroystokyo.com>
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 10d69b48158460e5739d1e41a83fcaeec819fac6..5d03477919ce892f6dfb4b2304c03733e10e3721 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -242,6 +242,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
private Map<ResourceKey<Level>, ServerLevel> levels;
private PlayerList playerList;
private volatile boolean running;
+ private volatile boolean isRestarting = false; // Paper - flag to signify we're attempting to restart
private boolean stopped;
private int tickCount;
private int ticksUntilAutosave;
@@ -937,7 +938,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
if (this.playerList != null) {
MinecraftServer.LOGGER.info("Saving players");
this.playerList.saveAll();
- this.playerList.removeAll();
+ this.playerList.removeAll(this.isRestarting); // Paper
try { Thread.sleep(100); } catch (InterruptedException ex) {} // CraftBukkit - SPIGOT-625 - give server at least a chance to send packets
}
@@ -1017,6 +1018,12 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
}
public void halt(boolean waitForShutdown) {
+ // Paper start - allow passing of the intent to restart
+ this.safeShutdown(waitForShutdown, false);
+ }
+ public void safeShutdown(boolean waitForShutdown, boolean isRestarting) {
+ this.isRestarting = isRestarting;
+ // Paper end
this.running = false;
if (waitForShutdown) {
try {
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index e17f4f3882ae77a67e8bfad04646f02c2bbb6669..d5f17d7e3b56ca87ec9070b69265ce098de61f69 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -1143,8 +1143,15 @@ public abstract class PlayerList {
}
public void removeAll() {
+ // Paper start - Extract method to allow for restarting flag
+ this.removeAll(false);
+ }
+
+ public void removeAll(boolean isRestarting) {
+ // Paper end
// CraftBukkit start - disconnect safely
for (ServerPlayer player : this.players) {
+ if (isRestarting) player.connection.disconnect(net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer.legacySection().deserialize(org.spigotmc.SpigotConfig.restartMessage)); else // Paper
player.connection.disconnect(java.util.Objects.requireNonNullElseGet(this.server.server.shutdownMessage(), net.kyori.adventure.text.Component::empty)); // CraftBukkit - add custom shutdown message // Paper - Adventure
}
// CraftBukkit end
diff --git a/src/main/java/org/spigotmc/RestartCommand.java b/src/main/java/org/spigotmc/RestartCommand.java
index de8c703803bcd074f765a44cabc7c635176b716d..824c4ad135ea5177f416687c7042639ed126b70b 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -46,86 +46,134 @@ public class RestartCommand extends Command
AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
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 " + 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 ( ServerPlayer p : (List<ServerPlayer>) MinecraftServer.getServer().getPlayerList().players )
- {
- p.connection.disconnect( CraftChatMessage.fromStringOrEmpty( SpigotConfig.restartMessage, true ) );
- }
- // 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().getConnection().stop();
+ // Paper start - sync copied from above with minor changes, async added
+ private static void shutdownServer(boolean isRestarting)
+ {
+ if ( MinecraftServer.getServer().isSameThread() )
+ {
+ // Kick all players
+ for ( ServerPlayer p : com.google.common.collect.ImmutableList.copyOf( MinecraftServer.getServer().getPlayerList().players ) )
+ {
+ p.connection.disconnect( CraftChatMessage.fromStringOrEmpty( SpigotConfig.restartMessage, true ) );
+ }
+ // 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().getConnection().stop();
+
+ // 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
+
}