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CS 134 Assignment 2 (Hints (Server -> Time map (Keeps track of last…

- - - - View's number (id)
        Primary and backup network port names
      - Only has backup if possible
    - - Actual Primary
      - Backup of the previous view
        primary --- primary (backup to prev primary)
      - Initial primary
        
        Accepts an server
    - - Can be any server other than the primary
  - - - Servers Send a heartbeat signal
      - ViewService replies with current view
    - - Says I'm alive
      - Server gets current view
      - Server replies with its current view
        
        Tells us if they match
    - - If no reply in PING INTERVALS = dead
    - - If a server restarts
        
        Sends one or more pings = 0 to notify crash
  - - - No pings from from primary AND backup
      - If primary crashes
      - If we have no backup but have an idle server available
        
        NEW BACKUP
    - - The view service may not proceed from view X to view X+1 if it has not received a Ping(X) from the primary of view X
      - If primary never sends we never get new view
  - - - The viewservice monitors whether each available server is alive or dead.
    - - If the current primary or backup becomes dead, the viewservice selects a server to replace it.
      - A client checks with the viewservice to find the current primary.
      - The servers cooperate with the viewservice to ensure that at most one primary is active at a time.
- - - - ensure that the backup's key/value database remains identical to the primary's
  - - - Wait for a reply from backup
    - - It turns out the primary must send Gets as well as Puts to the backup
        
        If backup rejects request indicates split brain
- - - - Primary syncs with backup
        
        The primary will send its complete database to the new backup, and then send subsequent Puts to the backup to ensure that the backup's key/value database remains identical to the primary's.
- - - - Primary = previous primary or backup
      - Backup = any server or empty
        
        Can't have multiple?
- - - - If the primary is empty
      - If the backup is empty but primary is not
      - If primary acks
      - How to handle failure
        
        Tick's responsibilities
    - - Handles