Design questions for Lab 3

Phase 1

• What state do you keep to indicate whether or not you are the leader?
• How do you know you are the leader?

1a

• At what point do Paxos servers know to start looking for heartbeat messages?
• When do you ignore p1a's? When do you act on them? Can you act on them while in phase 2?

1b

• Is it possible to receive 1b messages with a ballot larger than your current ballot? Why or why not?
• When do you ignore p1b's? When do you act on them?
• Are you merging logs "on the fly" or keeping track of logs till you see a majority? Or something else? Justify your design decision.
• When does the leader stop merging logs?
• What data structure are you using to record p1b's? When does this data structure get initialized/cleared?

Phase 2

• When do you know the leader is dead?

2a

• How do you handle 2a's with larger ballot numbers than your ballot number?
• What causes 2a requests to be sent?

2b

• What data structure are you using to keep track of 2b responses?
• How do you know to try progressing slot out?

“Phase 3” (Log propagation and Garbage Collection)

• Does phase 3 happen concurrently with phase 2?
• What messages are you "piggybacking" to share log decisions and garbage collection information?
• What data structure are the nodes going to use to keep track of who has executed what commands?