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Large resource manager heap usage reported in ambari when cluster idle?

Expert Contributor

Noticing that on an idle cluster

[root@airflowetl ~]# hadoop versionHadoop 3.1.1.3.1.0.0-78
Source code repository git@github.com:hortonworks/hadoop.git -r e4f82af51faec922b4804d0232a637422ec29e64
Compiled by jenkins on 2018-12-06T12:26Z Compiled with protoc 2.5.0 From source with checksum eab9fa2a6aa38c6362c66d8df75774
This command was run using /usr/hdp/3.1.0.0-78/hadoop/hadoop-common-3.1.1.3.1.0.0-78.jar

I see ambari continually reports RM heap usage gradually growing from ~25% up to ~40-90% then snapping back down to 25%. IMAGE Checking the RM UI, I see no jobs running (nor does the spark history UI show any incomplete jobs)... IMAGE

Anyone know why this would be happening? Any other debugging info I should provide (not very experienced with hadoop admin stuff)? Why does resource manager heap (ambari UI) not match YARN cluster overview dashboard usage percentages?