Then the service will be unavailable until you recover at least one of them. ... View more

@Big-dAta ,   A quorum in a ZooKeeper ensemble is a group of servers with more than half of the total number of servers in the ensemble. So for an ensemble of 5 servers, the quorum is 3 servers.   As long as there are 3 servers available an election can always be carried out. So, in your example, the 4 remaining servers will talk to each other and decide who will be the new leader.   Cheers, André   ... View more

@RB764 ,   Ok, I see. In the case of running JS code on the browser client, it makes sense to see the errors that you are seeing. That's exactly what CORS restrictions are designed for.   Are you loading this script from a file locally on your computer or is this part from a web application that you have running on a server?   If this is local to your computer, I would recommend that you use some other language to interact with NiFi, since running this locally on a browser has limitations. In Python, for example, you can use the nipyapi module, which makes it really easy to interact with the NiFi API:   from nipyapi import config, security from nipyapi.nifi.apis.flow_api import FlowApi config.nifi_config.host = 'https://<<server host:port>>/nifi-api' security.set_service_ssl_context(service='nifi', ca_file='<</path/to/truststore.pem>>') security.service_login(service='nifi', username='<<user>>', password='<<pwd>>') api = FlowApi() summary = api.get_cluster_summary()   If what you are trying to do is part of a web application, the interaction between application and NiFi should happen on the server side instead of the browser. This would also eliminate any sort of CORS issues.   Cheers, André   ... View more