Virtual Net: A Decentralized Architecture for Interaction in Mobile Virtual Worlds

Algorithm 8

Group reconfiguration.

1. On any replica:

2. Upon R ∖ G ≠ ∅  ∧ R ≠ G_T  ∧ LE = false

3.  G_T ← R

4.  GR← true

5.  If r_L = self, then

6.   cid ← cid + 1

7.   GR_QUERY ← (epoch, cid)

8.   Reliably broadcast GR_QUERY to G_T  ∩R

9.

10.

11. Upon GR_QUERY(epoch’, cid’) from r_L  ∧ epoch’ ≥          // Use cid to discard messages from a

   epoch ∧ cid’ > cid ∧ LE = false                 previous unfinished GR;

12.  GR ← true                        // epoch’ ≥ epoch: for new members

13.  cid ← cid’                       // cid’ > cid: because the new cid has not

14.  If epoch = 0, then                     been received

15.   epoch ← epoch’

16.  GE_STATE ← (Q_d, E, cid, epoch)

17.  Reliably send GE _STATE to r_L

18.

19. Upon LOAD_CONFIG(Q_d’, E’, epoch’, cid’, G_T, Init)

   from r_L  ∧ epoch’ = epoch ∧ cid’ = cid ∧ LE = false

20.  (Q_d, E) ← (Q_d’, E’)

21.  G ← G_T

22.  LE ← false

23.  If newReplica = true, then

24.   Initialize(Init)

25.   newReplica←false

26.  For each r∈G∩R,

27.   r.age ← r.age + 1

28.

29.

30. Upon GE _STATE(Q_d,i, E_i, cid_i, epoch_i) from r_i  ∧ epoch_i

   = epoch ∧ cid_i = cid ∧ LE = false

31.  Events←Events∪  

32.  Decisions←Decision∪  

33.  Senders←Senders∪  

34.

35. Upon G_T  ∩R⊆Senders

36.  Q_d ← Longest(Events)

37.  E ← Merge(Decisions)

38.  Init ← (t₀,  , (λ_c, state),      // state: current application state

   ,S)

39.  LOAD_ CONFIG ← (Q_d, E, epoch, cid, G_T, Init)

40.  Reliably broadcast LOAD_ CONFIG to G_T  ∩R

41.  Broadcast G_T to S

42.  G_T ← ∅