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Posted to issues@nifi.apache.org by GitBox <gi...@apache.org> on 2020/10/13 15:55:35 UTC
[GitHub] [nifi] markap14 opened a new pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
markap14 opened a new pull request #4602:
URL: https://github.com/apache/nifi/pull/4602
…ct, ensure that it relinquishes role of Cluster Coordinator and Primary Node
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[GitHub] [nifi] markap14 commented on pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
Posted by GitBox <gi...@apache.org>.
markap14 commented on pull request #4602:
URL: https://github.com/apache/nifi/pull/4602#issuecomment-732200676
To provide a clearer explanation of what this change is doing (since looking at the code change doesn't make it clear that anything related to component revisions changed)...
When a node is disconnected from the cluster because it fails to make an update, it will immediately attempt to reconnect. If that reconnection is successful, then the node can remain part of the cluster. This is done because there are some changes that can happen that our fingerprinting logic says is okay. For example, if the position of a component moves, or if a component is stopped. Upon cluster reconnect, the joining node will simply update that component to match the cluster. For other changes, such as a processor property change, fingerprinting logic will prevent the node from joining, and the node will then transition to a DISCONNECTED state.
When that change initially happens, because the node will immediately attempt to connect to the cluster again, it transitions from CONNECTED to CONNECTING (not DISCONNECTED). As a result, it does not relinquish any roles that it holds as Primary Node / Cluster Coordinator. This results in an issue where the Cluster Coordinator may fail to update a component and as such has an old Revision number and then attempts to connect to the Cluster. The node is allowed to join and downloads the list of Component Revisions from the Cluster Coordinator. BUT, in this situation, the Cluster Coordinator is the node with the outdated Component Revisions, so it never gets the list that the rest of the cluster has.
This fix addresses the issue by making the node relinquish any roles that it holds (Cluster Coordinator, Primary Node) so that another node will pick up the roles. This causes the old Cluster Coordinator to then get the list of Component Revisions from a newly elected Cluster Coordinator, so that the revisions are up to date.
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[GitHub] [nifi] exceptionfactory commented on pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
Posted by GitBox <gi...@apache.org>.
exceptionfactory commented on pull request #4602:
URL: https://github.com/apache/nifi/pull/4602#issuecomment-711109965
This seems like an important correction, how feasible is it to unit test the solution?
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[GitHub] [nifi] markap14 commented on pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
Posted by GitBox <gi...@apache.org>.
markap14 commented on pull request #4602:
URL: https://github.com/apache/nifi/pull/4602#issuecomment-717443793
Thanks for reviewing @tpalfy and @exceptionfactory.
@exceptionfactory I don't think we can really unit test this. I mean, we could write a test that verifies that if connected to a cluster, that `controller.onClusterDisconnect()` gets called. But it's pretty clear that it does given the code snippet:
```
if (controller.isConnected()) {
controller.onClusterDisconnect();
}
```
I don't think an integration test would really be any more help. A system-level test could potentially be written. I may consider that as a follow-on. But given that it's easy to verify the fix manually and @tpalfy and I have, I don't think it's worth holding up the PR for that.
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[GitHub] [nifi] markap14 commented on pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
Posted by GitBox <gi...@apache.org>.
markap14 commented on pull request #4602:
URL: https://github.com/apache/nifi/pull/4602#issuecomment-717444273
Merging based on @tpalfy +1
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[GitHub] [nifi] markap14 merged pull request #4602: NIFI-7920: When node that is connected to cluster is asked to reconne…
Posted by GitBox <gi...@apache.org>.
markap14 merged pull request #4602:
URL: https://github.com/apache/nifi/pull/4602
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