DRILL-6090: While connecting to drill-bits using JDBC Driver through Zookeeper, a lot of "Curator-Framework-0" threads are created if connec…
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DRILL-6090: While connecting to drill-bits using JDBC Driver through Zookeeper, a lot of "Curator-Framework-0" threads are created if connection to drill-bit is not successful(no drill-bits are up/reachable)I am using Drill JDBC driver 1.12.0 to connect to MapR-DB. I am finding the available drill-bits using Zookeepers. When drill-bits are not up or not reachable, the connection is failed with exception: "Failure in connecting to Drill: oadd.org.apache.drill.exec.rpc.RpcException: Failure setting up ZK for client", which is expected, but number of threads created by ZKClusterCoordinator just keeps on increasing.Steps to reproduce the issueSetup a connection with a drill-bit using Apache Drill JDBC driver 1.12.0 through Zookeeper hosts(port 5181)Now stop the drill-bit services or block the drill-bit IPs using iptable rulesTruncate catalina logsTry to connect to the drill-bit/hit a code path that requires connection to drill-bits.Take thread dump using kill -QUIT <java process id>grep -c "Curator-Framework-0" catalina.outObserve that the curator framework thread just keep on accumulatingRCA:ZKClusterCoordinator creates curator threads in the constructorZKClusterCoordinator is instantiated by DrillClient.connectDrillClient.connect is called in DrillConnectionImpl constructorFix:Call DrillConnectionImpl .cleanup() from all the catch blocks in the DrillConnectionImpl constructor.close apache/drill#1094
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