如何在分散的事件源数据库中处理共识？(How to handle consensus in a decentralized event sourced database?)

 假设我有一个X服务器的动态网络（不是随时间修复的），只有附加数据库中的所有事件的相同副本。 现在，我想支持在这10台服务器中的任何一台上创建新事件，并让它们达成共识，复制事件，并且所有事件都会产生完全相同的事件顺序。 我知道这是一个常见的问题，并且有一些算法应该处理这样的事情。 但我并没有完全掌握它们，而且我对有关事件采购的共识有几个问题。 
 
 我认为服务器永远不能完全确定它认为已经达成共识的价值真的最终是“正确的”价值吗？ 我的基础是，新服务器可以随时加入网络，并提供平衡以支持其他价值。 这可能会在很晚的时候发生。 但在这种情况下，服务器应如何处理新的“正确”值？ 在事件采购中，附加补偿事件以进行更正是正常的，但是这些补偿事件是否必须同时复制到所有服务器？ 确保所有服务器都具有完全相同的事件。 
 
 如果不添加补偿事件，而只是“弹出”已经提交的事件，我们不必复制这些我猜，但后来我们会遇到其他问题。 如果（错误地）提交的事件在事件总线上发送，以便其他服务可以对它们作出反应，我们不能只是从我们的事件数据库中弹出它们而不会弄乱它们。 
 
 或者，如果在一小段时间内达成共识后真正致力于价值，那会更好吗？ 然后用冷手对待所有新/迟到的服务器？ 让他们接受结果呢？ 如果新服务器连接到比第一个更大的自己的网络并且他们都已经达成了对另一个值的共识，该怎么办？ 

Lets say I have dynamic network of X servers (not fixed over time) with a identical copy of all events in a append only database. Now I'd like to support creating new events on any of these 10 servers and have them reach consensus, replicate the events and all result in the exact same event order. I understand this is a common problem and that there are algorithms that are supposed to handle things like this. But I don't fully grasp them and I have a few questions regarding consensus in relation to event sourcing in particular.
 
I assume that a server never can be completely sure that the value it think it has reached consensus about is really what ends up being the "correct" value? I base this on the fact that new servers can join to the network at any time and tip the balance to favor another value. This could potentially happen much later as well. But in this case, how should a server handle a new "correct" value? In event sourcing it is normal to append compensating events to make corrections but shouldn't these compensating event have to be replicated to all servers as well then? To make sure that all servers have the exact same events I mean.
 
If not adding compensating event but instead just "popping" already committed events we wouldn't have to replicate these I guess but then we would run into other problems instead. If the (wrongly) committed events are sent out on a event bus so that other services can react to them we can't just pop them from our event db without messing things up.
 
Or is it better to just really commit to a value once consensus have been reached within a small timeframe? And then treat all new/late servers with a cold hand? Make them accept the result anyway? What if the new server is connected to it's own network that is larger then the first one and they all have reached consensus on another value?

原文：https://stackoverflow.com/questions/47391523