学习快照算法

• 17 December 2017

Chandy & Lamport Snapshot Algorithm 是在分布式系统中获取全局状态的算法。伪代码如下：

• Marker receiving rule:

When I receive a marker on channel c    
	If (I am not yet taking part in this snapshot) {    
		Record my state now (count # of each commodity in hand only)     
		Do Marker sending rule    
		Record that the state of channel c is empty    
		Begin keeping track of state all other incoming channels (except c):    
	} else if this marker is coming in from a new channel c {    
		Record that the state of channel c is all messages it has received since it began keeping track. (No more coming.)    
		Stop recording any further messages on channel c (they are now post-shapshot)    
		If (this is last channel to receive marker on) send records to Monitor process     
}    

• Marker sending rule:

For (each outgoing channel c) {    
	Send one marker message over c     
}    

（未完待续...）