Chandy–Lamport algorithm
The Chandy–Lamport algorithm is a snapshot algorithm that is used in distributed systems for recording a consistent global state of an asynchronous system. It was developed by and named after Leslie Lamport and K. Mani Chandy. History. According to Leslie Lamport's website, “The distributed snapshot algorithm described here came about when I visited Chandy, who was then at the University of Texas in Austin. He posed the problem to me over dinner, but we had both had too much wine to think about it right then. The next morning, in the shower, I came up  with the solution. When I arrived at Chandy's office, he was waiting for me with the same solution.” Definition. The assumptions of the algorithm are as follows: The algorithm works using marker messages. Each process that wants to initiate a snapshot records its local state and sends a marker on each of its outgoing channels. All the other processes, upon receiving a marker, record their local state, the state of the channel from which the marker just came as empty, and send marker messages on all of their outgoing channels. If a process receives a marker after having recorded  its local state, it records the state of the incoming channel from which the marker came as carrying all the messages received since it first recorded its local state. Some of the assumptions of the algorithm can be facilitated using a more reliable communication protocol such as TCP/IP. The algorithm can be adapted so that there could be multiple snapshots occurring simultaneously. Algorithm. The Chandy–Lamport algorithm works like this: From this, the observer builds up a complete snapshot: a saved state for each process and all messages “in the ether” are saved.