Consider
1) n1, n2, n3, n4, n5
2) n2 and n3 are both down
3) start n6 to replace n2
4) start n7 to replace n3
We want to replace the dead nodes n2 and n3 to fix the cluster to have 5
running nodes.
Replace operation in step 3 will fail because n3 is down.
We would see errors like below:
replace[25edeec0-57d4-11ec-be6b-7085c2409b2d]: Nodes={127.0.0.3} needed
for replace operation are down. It is highly recommended to fix the down
nodes and try again.
In the above example, currently, there is no way to replace any of the
dead nodes.
Users can either fix one of the dead nodes and run replace or run
removenode operation to remove one of the dead nodes then run replace
and run bootstrap to add another node.
Fixing dead nodes is always the best solution but it might not be
possible. Running removenode operation is not better than running
replace operation (with best effort by ignoring the other dead node) in
terms of data consistency. In addition, users have to run bootstrap
operation to add back the removed node. So, allowing replacing in such
case is a clear win.
This patch adds the --ignore-dead-nodes-for-replace option to allow run
replace operation with best effort mode. Please note, use this option
only if the dead nodes are completely broken and down, and there is no
way to fix the node and bring it back. This also means the user has to
make sure the ignored dead nodes specified are really down to avoid any
data consistency issue.
Fixes#9757Closes#9758
eba4a4fba4