| 2013-08-27 07:26:39 |
Teemu Ollakka |
description |
Sometimes when two out of three nodes leave the cluster almost simultaneously, the remaining node may end up in non-PC even if the nodes left gracefully.
Here is what happens:
1) Node 1 leaves the cluster, nodes 2 and 3 get the notification from EVS layer that node 1 left
2) Nodes 2 and 3 exchange states to form new PC view, but node 2 decides to leave just before message exchange is complete
3) Because forming new PC view was interrupted, node 3 loses the information that node 1 left gracefully, so final quorum computation for singleton view results non-PC
Expected behavior would be that the status of node 1 leaving gracefully would be preserved over intermediate view changes. |
Sometimes when two out of three nodes leave the cluster almost simultaneously, the remaining node may end up in non-PC even if the nodes left gracefully.
Here is what happens:
1) Node 1 leaves the cluster, nodes 2 and 3 get the notification from EVS layer that node 1 left
2) Nodes 2 and 3 exchange states to form new PC view, but node 2 decides to leave just before message exchange is complete
3) Because forming new PC view was interrupted, node 3 loses the information that node 1 left gracefully, so final quorum computation for singleton view results non-PC
Expected behavior would be that the status of node 1 leaving gracefully would be preserved over intermediate view changes.
Note that if nodes 1 and 2 leave cluster so simultaneously that node 3 gets the notification of it in single view change or if nodes 2 and 3 finish the message exchange for new PC view before node 2 leaves, the outcome is that node 3 ends up in PC as expected. |
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