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https://issues.apache.org/jira/browse/NIFI-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17209395#comment-17209395
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Hsin-Ying Lee commented on NIFI-7866:
-------------------------------------
Hi Mark
Can we catch NPE and throw ConnectionException from loadFromConnectionResponse
method?
> When cluster coordinator dies, other nodes may have trouble rejoining cluster
> -----------------------------------------------------------------------------
>
> Key: NIFI-7866
> URL: https://issues.apache.org/jira/browse/NIFI-7866
> Project: Apache NiFi
> Issue Type: Bug
> Components: Core Framework
> Reporter: Mark Payne
> Priority: Major
>
> When the cluster coordinator is lost, the nodes must now begin communicating
> with a newly elected Cluster Coordinator. This is handled through the
> StandardFlowService.
> When the `handleReconnectionRequest` method is called and the request
> provided does not contain the dataflow, the node is to connect to the cluster
> coordinator and request the dataflow:
> {code:java}
> private void handleReconnectionRequest(final ReconnectionRequestMessage
> request) {
> try {
> logger.info("Processing reconnection request from cluster
> coordinator.");
> // reconnect
> ConnectionResponse connectionResponse = new
> ConnectionResponse(getNodeId(), request.getDataFlow(),
> request.getInstanceId(), request.getNodeConnectionStatuses(),
> request.getComponentRevisions());
> if (connectionResponse.getDataFlow() == null) {
> logger.info("Received a Reconnection Request that contained no
> DataFlow. Will attempt to connect to cluster using local flow.");
> connectionResponse = connect(false, false,
> createDataFlowFromController());
> }
> loadFromConnectionResponse(connectionResponse);
> ... {code}
> However, if the call above to `connect(false, false,
> createDataFlowFromController()` returns false (which is a valid case), that
> null value is passed along to the loadFromConnectionResponse. This method
> expects a non-null connectionResponse and throws a NullPointerException,
> resulting in the following stack trace (stack trace based on nifi 1.11.4):
> {code:java}
> 2020-09-29 10:18:53,324 ERROR [Reconnect to Cluster]
> o.a.nifi.controller.StandardFlowService Handling reconnection request failed
> due to: org.apache.nifi.cluster.ConnectionException: Failed to connect node
> to cluster due to:
> java.lang.NullPointerExceptionorg.apache.nifi.cluster.ConnectionException:
> Failed to connect node to cluster due to: java.lang.NullPointerExceptionat
> org.apache.nifi.controller.StandardFlowService.loadFromConnectionResponse(StandardFlowService.java:1035)at
>
> org.apache.nifi.controller.StandardFlowService.handleReconnectionRequest(StandardFlowService.java:668)at
>
> org.apache.nifi.controller.StandardFlowService.access$200(StandardFlowService.java:109)at
>
> org.apache.nifi.controller.StandardFlowService$1.run(StandardFlowService.java:415)at
> java.lang.Thread.run(Thread.java:748)Caused by:
> java.lang.NullPointerException: nullat
> org.apache.nifi.controller.StandardFlowService.loadFromConnectionResponse(StandardFlowService.java:989)...
> 4 common frames omitted {code}
> This results in the node not reconnecting to the cluster.
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