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.

1 files changed, 44 insertions, 0 deletions

diff --git a/patches/server/0329-Remote-Connections-shouldn-t-hold-up-shutdown.patch b/patches/server/0329-Remote-Connections-shouldn-t-hold-up-shutdown.patch
new file mode 100644
index 0000000000..fb2f7c6706
--- /dev/null
+++ b/patches/server/0329-Remote-Connections-shouldn-t-hold-up-shutdown.patch
@@ -0,0 +1,44 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <[email protected]>
+Date: Tue, 31 Mar 2020 03:50:42 -0400
+Subject: [PATCH] Remote Connections shouldn't hold up shutdown
+
+Bugs in the connection logic appears to leave stale connections even, preventing shutdown
+
+diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+index b15cee6f21ff300b596922a8eed35a5f8a89fe22..d6dc8c983d26ce89f17a990be4284fdc78ad164b 100644
+--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
++++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+@@ -416,11 +416,11 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
+         }
+ 
+         if (this.rconThread != null) {
+-            this.rconThread.stop();
++            this.rconThread.stopNonBlocking(); // Paper - don't wait for remote connections
+         }
+ 
+         if (this.queryThreadGs4 != null) {
+-            this.queryThreadGs4.stop();
++            // this.remoteStatusListener.stop(); // Paper - don't wait for remote connections
+         }
+ 
+         System.exit(0); // CraftBukkit
+diff --git a/src/main/java/net/minecraft/server/rcon/thread/RconThread.java b/src/main/java/net/minecraft/server/rcon/thread/RconThread.java
+index 594fbb033b63b8c9fb8752b1fcc78f8e9f7a2a83..c12d7db2b048a327c0e8f398848cd3a9bce0ebce 100644
+--- a/src/main/java/net/minecraft/server/rcon/thread/RconThread.java
++++ b/src/main/java/net/minecraft/server/rcon/thread/RconThread.java
+@@ -104,6 +104,14 @@ public class RconThread extends GenericThread {
+ 
+         this.clients.clear();
+     }
++    // Paper start - don't wait for remote connections
++    public void stopNonBlocking() {
++        this.running = false;
++        for (RconClient client : this.clients) {
++            client.running = false;
++        }
++    }
++    // Paper end - don't wait for remote connections
+ 
+     private void closeSocket(ServerSocket socket) {
+         LOGGER.debug("closeSocket: {}", socket);