private void updateRegionTransition(ServerStateNode serverNode, TransitionCode state,
    RegionInfo regionInfo, long seqId, long procId) throws IOException {
    checkMetaLoaded(regionInfo);

    RegionStateNode regionNode = regionStates.getRegionStateNode(regionInfo);
    if (regionNode == null) {
      // the table/region is gone. maybe a delete, split, merge
      throw new UnexpectedStateException(String.format(
        "Server %s was trying to transition region %s to %s. but Region is not known.",
        serverNode.getServerName(), regionInfo, state));
    }
    LOG.trace("Update region transition serverName={} region={} regionState={}",
      serverNode.getServerName(), regionNode, state);

    regionNode.lock();
    try {
      if (!reportTransition(regionNode, serverNode, state, seqId, procId)) {
        // Don't log WARN if shutting down cluster; during shutdown. Avoid the below messages:
        // 2018-08-13 10:45:10,551 WARN ...AssignmentManager: No matching procedure found for
        // rit=OPEN, location=ve0538.halxg.cloudera.com,16020,1533493000958,
        // table=IntegrationTestBigLinkedList, region=65ab289e2fc1530df65f6c3d7cde7aa5 transition
        // to CLOSED
        // These happen because on cluster shutdown, we currently let the RegionServers close
        // regions. This is the only time that region close is not run by the Master (so cluster
        // goes down fast). Consider changing it so Master runs all shutdowns.
        if (
          this.master.getServerManager().isClusterShutdown() && state.equals(TransitionCode.CLOSED)
        ) {
          LOG.info("RegionServer {} {}", state, regionNode.getRegionInfo().getEncodedName());
        } else {
          LOG.warn("No matching procedure found for {} transition on {} to {}",
            serverNode.getServerName(), regionNode, state);
        }
      }
    } finally {
      regionNode.unlock();
    }
  }
Delete the region states. This is called by "DeleteTable"
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignmentManager.java