For each process, we keep a list of
MemberStat { int id; boolean alive; string address; }
MyState { leader, member, non_member }
By default, leader is the process with lowest id number, which starts with 1.
Leader has to be initiated first, the order of each member's initiation does not matter.
When a node initiates, it first identifies whether its leader, if so, it opens a TCP channel and starts to listen
If its not a leader, it identifies the first process as leader and sends a request message to ask for joining the group.
Every 2 seconds, each process will send an I am alive
message to each processes in the alive processes list.
For each process i, if, in the past 4 seconds, there is an
I am alive message received from process k, then we mark
process k to be alive. otherwise we treat it as offline.
1) when a new process join the group, it first establish
a connection with leader.
2) when a connection is established, it sends a join message
to the leader.
3) the leader then broadcast message to all
Every 5 secs, the process will send a heartbeat message to all processes in the address list. Message will only be one int long, which will be the id of the sender.
Each Member struct will have a field 'has_received_heartbeat'; which is initiated as true;
Every 5 secs, the process will check status. if the has_received_hearbeat
is true, set it to false. If it is false, then report the process as offline.