[corosync] Why we send downlist and joinlist separately?

Yunkai Zhang qiushu.zyk at taobao.com
Thu Nov 3 06:18:52 GMT 2011


Hi Angus:

I found that corosync sends downlist(​​alias leftlist in CPG) and
joinlist separately to CPG client after a new ring established.

When a node lefts from or joins into a ring, only downlist or joinlist
contain content, this behavior seems not strange.

But suppose there are two ring: Ring(A,B), Ring(C,D,E,F) that are
forming into a new ring, and these nodes: B,E,F dropped in the GATHER
state, then only these nodes: A,C,D will form the new Ring(A,C,D). And
corosync will send downlist(B) and joinlist(C,D) as two confchg events
to the CPG client of node A. This will make CPG client confused.

The correct way is that send _Only_ one confchg event containing both
downlist and joinlist to the CPG client. In this case,
1) The CPG client of A should receive only one confchg as following:
memb:A,C,D       left:B         join:C,D

2) The CPG client of C,D should receive only one confchg as following:
memb:A,C,D       left:E,F       join:A

Angus, what is your opinion?

If you agree with me, I would summit patch to fix it.

-- 
Yunkai Zhang
Work at Taobao


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