So at my top level I have my nput port, common fetch process group and multiple list process groups: I set my input port to support 10 concurrent tasks which I though might help but I’m not really sure. Each list process group contains the following which includes the remote process group: I’ve tried both RAW and HTTP, RAW seem to be a little better on recovery be not perfect. My common fetch process group contains the following: No real issues here if the remote process group can find the the iinput port everything works as expected. In my nifi-app.log file I see things like this: 2018-10-23 15:19:46,403 INFO [main] o.apache.nifi.controller.FlowController Started 3 Remote Group Ports transmitting 2018-10-23 15:19:46,403 INFO [main] o.a.n.w.c.ApplicationStartupContextListener Flow Controller started successfully. 2018-10-23 15:19:46,650 WARN [Remote Process Group 763b0492-57ec-3bdb-71c0-b6c607183d9c Thread-1] o.a.n.r.util.SiteToSiteRestApiClient Failed to get controller from http://localhost:6080/nifi-api due to org.apache.http.conn.HttpHostConnectException: Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect 2018-10-23 15:19:46,653 WARN [Remote Process Group 763b0492-57ec-3bdb-71c0-b6c607183d9c Thread-1] o.a.n.remote.StandardRemoteProcessGroup Unable to communicate with remote instance RemoteProcessGroup[http://localhost:6080/nifi] org.apache.nifi.controller.exception.CommunicationsException: org.apache.nifi.controller.exception.CommunicationsException: Unable to communicate with Remote NiFi at URI http://localhost:6080/nifi due to: Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect at org.apache.nifi.remote.StandardRemoteProcessGroup.refreshFlowContents(StandardRemoteProcessGroup.java:883) at org.apache.nifi.remote.StandardRemoteProcessGroup.lambda$initialize$0(StandardRemoteProcessGroup.java:193) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Caused by: org.apache.nifi.controller.exception.CommunicationsException: Unable to communicate with Remote NiFi at URI http://localhost:6080/nifi due to: Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect at org.apache.nifi.remote.StandardRemoteProcessGroup.refreshFlowContents(StandardRemoteProcessGroup.java:845) ... 8 common frames omitted 2018-10-23 15:19:47,664 WARN [NiFi Site-to-Site Connection Pool Maintenance] o.a.n.r.util.SiteToSiteRestApiClient Failed to get controller from http://localhost:6080/nifi-api due to org.apache.http.conn.HttpHostConnectException: Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect 2018-10-23 15:19:47,665 WARN [NiFi Site-to-Site Connection Pool Maintenance] o.apache.nifi.remote.client.PeerSelector org.apache.nifi.remote.client.PeerSelector@31c739e8 Unable to refresh Remote Group's peers due to Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect 2018-10-23 15:19:48,654 INFO [main] o.e.jetty.server.handler.ContextHandler Started o.e.j.w.WebAppContext@2c952e6{/nifi-api,file:///C:/Dev/aim_project_repos/nifi-1.7.1/work/jetty/nifi-web-api-1.7.1.war/webapp/,AVAILABLE}{.\work\nar\framework\nifi-framework-nar-1.7.1.nar-unpacked\META-INF\bundled-dependencies\nifi-web-api-1.7.1.war} 2018-10-23 15:19:48,668 WARN [NiFi Site-to-Site Connection Pool Maintenance] o.a.n.r.util.SiteToSiteRestApiClient Failed to get controller from http://localhost:6080/nifi-api due to org.apache.http.conn.HttpHostConnectException: Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect 2018-10-23 15:19:48,668 WARN [NiFi Site-to-Site Connection Pool Maintenance] o.apache.nifi.remote.client.PeerSelector org.apache.nifi.remote.client.PeerSelector@750d934c Unable to refresh Remote Group's peers due to Connect to localhost:6080 [localhost/127.0.0.1] failed: Connection refused: connect Restarting sometimes clears the issue. ... View more