Mark Payne created NIFI-7866:
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Summary: 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
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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