STABLE
======

Author: Bela Ban
Date: May 29 2007

Goal: to purge messages delivered by all members


Vars
----
- digest: used to reconcile all STABLE messages, re-initialized on STABILITY message (with digest from NAKACK)
- votes: list of members from whom we have received STABLE messages. Reset on STABILITY message

Initialization
--------------
- Set digest from NAKACK

When the timer expires or max_bytes have been received
------------------------------------------------------
- Send STABLE message

Sending of STABLE message
-------------------------
- Get the current digest (from NAKACK) using the GET_DIGEST_STABLE event
- Send the STABLE message to group

On reception of STABLE message from P
-------------------------------------
- If P already present in votes: discard
- Else:
  - Update digest
  - Add P to votes
  - If votes from all members:
    - Send STABILITY message

On reception of STABILITY message
---------------------------------
- Pass STABLE event down to NAKACK to purge messages on which every member agreed that they have been delivered
- Set digest from NAKACK
- Clear votes


View change
-----------
- Set digest from NAKACK
- Clear votes