@Viswa To check Namenode Safe mode status, Login to Namenode host and issue the below command, [user@NNhost1 ~]$ hdfs dfsadmin -safemode get Safe mode is OFF in NNhost1/10.X.X.X:8020 Safe mode is OFF in NNhost2/10.X.X.X:8020 If Safe mode is turned ON, please issue the below command to leave from safemode. [user@NNhost1 ~]$ hdfs dfsadmin -safemode leave ... View more

I believe that statement was referring specifically to the listing operation performed by ListFile, and not the overall state of the primary node. For example, if ListFile ran and listed files 1 and 2, and then the primary node changes and file 3 is available, it won't list files 1 and 2 again, it will start with 3, but if files 1 and 2 were in progress in the rest of the flow on the original primary node when it went down, they are stuck there until that node comes back up. The state tracking is done through the state management API which uses Zookeeper when clustered. I believe in this case it is using timestamps track the last time the processor ran and the timestamp of the most recent file it saw, and then looking for files newer than that on the next execution. Also keep in mind, this whole scenario only makes sense when listing a remote directory that all nodes in the NiFi cluster have access to, otherwise it doesn't make sense when listing a local directory that is only on one node. ... View more

Sunile and I troubleshot this issue further. The first thing we did is we enabled sun.security.krb5.debug=true, this can be done in bootstrap.conf, see this doc. What we found, nifi-bootstap.log, was: INFO [NiFi logging handler] org.apache.nifi.StdOut Found unsupported keytype (18) for smanjee@FIELD Keytype 18 is aes256-cts-hmac-sha1-96 (see this page), and was the cipher used when we created the keytab for the smanjee@FIELD user. We created a new keytab using the cipher des3-cbc-sha1, and this resolved the issue. Note: I am not recommending that weak ciphers be used in Production environments. ... View more

@Sunile Manjee UUIDs are created when a template is add to the canvas. This allows users to instantiate the same template multiple times within a single NiFi. It also insures not conflict of UUID with other existing components already instantiated. There is no way for users to set the UUIDs of any component manually. The only way to maintain UUIDs between NiFi instances is to move the entire flow.xml.gz file from one NIFi to the next rather then using templates. Thanks, Matt ... View more