Also a little curious as to what triggered this bug.
Can you explain a bit?
I can indeed explain a bit.
Each Battlegrounds game is actually multiple Hearthstone game simulations running in parallel, communicating through a shared coordinator. Before each combat round, your randomness seed value is synchronized with your opponent's, so combat should play out with random numbers rolling the same values. After combat, you each get a new random seed so your simulations will diverge again.
A desync occurs when two opposing players' game simulations diverge in combat. This can happen for several reasons. On launch day of the Galakrond's Awakening patch (16.2) there was an issue with initial synchronization, resulting in many combat rounds never actually getting synchronized in the first place. That issue was fixed and patched the same day.
This current issue is a result of an error during the minion copy step. In Battlegrounds everything happens from left to right, so if two triggers fire off the same action then the minion on the left should trigger first. This was working correctly on your opponent's side of the board, but not on your side of the board. This can occur with Soul Jugglers and Deathrattle demons. It can also happen if two or more Deathrattle minions die to a cleave effect at the same time. The Soul Juggler situation is much more common, especially in the current meta and with the introduction of Imprisoner and Fiendish Servant.
Hopefully this fix will be the last of the desyncs for a while. Don't worry, we've got plenty of metrics to let us know immediately if any combat is desynced, so if new ones show up we'll be able to track them down, too.
Thanks so much for this replay. I've been trying to figure out the root cause of this for weeks now and that taunted Fiendish Servant on the right side of Lich King's board lead me to the heart of the problem. Hopefully I've completely solved the issue this time.
syah_hs
I can indeed explain a bit.
Each Battlegrounds game is actually multiple Hearthstone game simulations running in parallel, communicating through a shared coordinator. Before each combat round, your randomness seed value is synchronized with your opponent's, so combat should play out with random numbers rolling the same values. After combat, you each get a new random seed so your simulations will diverge again.
A desync occurs when two opposing players' game simulations diverge in combat. This can happen for several reasons. On launch day of the Galakrond's Awakening patch (16.2) there was an issue with initial synchronization, resulting in many combat rounds never actually getting synchronized in the first place. That issue was fixed and patched the same day.
This current issue is a result of an error during the minion copy step. In Battlegrounds everything happens from left to right, so if two triggers fire off the same action then the minion on the left should trigger first. This was working correctly on your opponent's side of the board, but not on your side of the board. This can occur with Soul Jugglers and Deathrattle demons. It can also happen if two or more Deathrattle minions die to a cleave effect at the same time. The Soul Juggler situation is much more common, especially in the current meta and with the introduction of Imprisoner and Fiendish Servant.
Hopefully this fix will be the last of the desyncs for a while. Don't worry, we've got plenty of metrics to let us know immediately if any combat is desynced, so if new ones show up we'll be able to track them down, too.
syah_hs
Thanks so much for this replay. I've been trying to figure out the root cause of this for weeks now and that taunted Fiendish Servant on the right side of Lich King's board lead me to the heart of the problem. Hopefully I've completely solved the issue this time.