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154556eec6
Queries that run only against in-memory system tables are currently subject to the same admission control process as all other queries. Since these queries do not use any resources on executors, admission control does not need to consider the state of executors when deciding to admit these queries. This change adds a boolean configuration option 'onlyCoordinators' to the fair-scheduler.xml file for specifying a request pool only applies to the coordinators. When a query is submitted to a coordinator only request pool, then no executors are required to be running. Instead, all fragment instances are executed exclusively on the coordinators. A new member was added to the ClusterMembershipMgr::Snapshot struct to hold the ExecutorGroup of all coordinators. This object is kept up to date by processing statestore messages and is used when executing queries that either require the coordinators (such as queries against sys.impala_query_live) or that use an only coordinators request pool. Testing was accomplished by: 1. Adding cluster membership manager ctests to assert cluster membership manager correctly builds the list of non-quiescing coordinators. 2. RequestPoolService JUnit tests to assert the new optional <onlyCoords> config in the fair scheduler xml file is correctly parsed. 3. ExecutorGroup ctests modified to assert the new function. 4. Custom cluster admission controller tests to assert queries with a coordinator only request pool only run on the active coordinators. Change-Id: I5e0e64db92bdbf80f8b5bd85d001ffe4c8c9ffda Reviewed-on: http://gerrit.cloudera.org:8080/22249 Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com> Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>