public void startPool(HiveConf conf, final WMFullResourcePlan resourcePlan) throws Exception {
    if (restrictedConfig == null) { // Sanity check; restrictedConfig is always set in setup.
      throw new AssertionError("setupPool or setupNonPool needs to be called first");
    }
    if (defaultSessionPool != null) {
      defaultSessionPool.start();
    }
    if (expirationTracker != null) {
      expirationTracker.start();
    }
    initTriggers(conf);
    if (resourcePlan != null) {
      Collection<String> appliedTriggers = updateTriggers(resourcePlan);
      LOG.info("Updated tez session pool manager with triggers {} from active resource plan: {}",
          appliedTriggers, resourcePlan.getPlan().getName());
    }
    metrics.start(conf);
  }
Note: this is not thread-safe.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/TezSessionPoolManager.java