this was caused by a bad fix for switching. we can't consider zero-damage attacks as cancelled because zero-damage might have been the result of things like consuming absorption hearts, so the aftereffects need to be processed even when the net damage is zero.
while this is slightly less bandwidth efficient (1 in 92 datagrams not full vs 1 in 733), this is significantly less memory-hard.
I made this decision looking at the memory pressures that 1MB chunks exert - especially on RakNet. Client-side, these resource pack chunks all hang around in RakNet memory until the whole thing is received, and it's a lot more costly to receive 733 datagrams than it is to receive 92, especially since it's much more likely that some of the 733 will disappear along the way.
If, for example, the first couple of hundred KB split parts arrived out of 1MB, and then one of the parts got lost, all the already-received parts would hang around in memory not getting processed. With smaller chunks this is much less of a problem.
I explored taking the chunk size all the way down to 1KB to reduce the bandwidth waste caused by split packets (split headers), but this made resource pack downloading unbearably slow, so it wasn't acceptable.
the old limit was made in the php5 days when performance was far worse and it was much more costly to generate chunks that weren't needed. Now it's significantly less and having a higher limit allows terrain to be sent more quickly in new worlds and to fast-moving players.
This limit really ought to go away completely but considering the technical barriers in the way it'll have to stay for now.
Introduction
This PR is a second attempt at improving movement processing to fix#1215 , #2730 and more.
This is significantly less complex than the previous attempt #2646 -- it gets rid of the movement buffering system entirely and instead relies on a simple rate limit counter to restrict on-the-fly movement processing.
Movement is rate limited to a max average of 2 per tick. It allows up to 5 seconds' backlog to accommodate network lag. The rate limit counter is increased by 2 per tick and decreased once for every movement processed. This prevents movement processing being abused for denial of service attacks.
Changes
API changes
This PR, while obviously highly beneficial for most current users, poses some BC-breaking issues because of changes to the internal Player API.
Player->processMovement() (protected) has been removed. This is a BC concern for custom player classes which overrode it and called it as a parent. In addition, child implementations won't be called every tick any more, which could break some custom movement processing systems.
Player->newPosition (protected) has been removed. This internal field may have been accessed by custom movement implementations.
Player->isTeleporting (protected) has been removed. BC concern is same as previous point.
Player->getNextPosition() (public) has been @deprecated.
Added the following protected Player class members:
int $moveRateLimit
?Vector3 $forceMoveSync
handleMovement()
processMostRecentMovements()
revertMovement()
Behavioural changes
Player movement is now subject to less rubberbanding and has more reliable behaviour.
