Managing Impala Admission Control

Minimum Required Role: Configurator (also provided by Cluster Administrator, Full Administrator)

Admission control is an Impala feature that imposes limits on concurrent SQL queries, to avoid resource usage spikes and out-of-memory conditions on busy CDH clusters. It is a form of "throttling". New queries are accepted and executed until certain conditions are met, such as too many queries or too much total memory used across the cluster. When one of these thresholds is reached, incoming queries wait to begin execution. These queries are queued and are admitted (that is, begin executing) when the resources become available.

For further information on Impala admission control, see Admission Control and Query Queuing.

Enabling and Disabling Impala Admission Control Using Cloudera Manager

You perform this task when you have determined that the Impala workload is heavy enough to cause capacity problems on the cluster. The capacity issues could be because of a high volume of concurrent queries, because of heavy-duty join and aggregation queries that require large amounts of memory, or because Impala is being used alongside other Hadoop data management components and the resource usage of Impala must be constrained to work well in a multitenant deployment.

  1. Go to the Impala service.
  2. Click the Configuration tab.
  3. Select Category > Admission Control.
  4. Select or clear both the Enable Impala Admission Control checkbox and the Enable Dynamic Resource Pools checkbox.
  5. Click Save Changes to commit the changes.
  6. Restart the Impala service.

After completing this task, for further configuration settings, customize the configuration settings for the dynamic resource pools, as described in Creating an Impala Dynamic Resource Pool and Editing Dynamic Resource Pools.

Configuring Impala Admission Control Using Cloudera Manager

In CDH 5.7 / Impala 2.5 and higher, Cloudera recommends configuring admission control at a granular level, using the dynamic resource pools feature, rather than using the cluster-wide settings.

  • In the Admission Control configuration group for Impala, ignore all the settings below the checkboxes to enable or disable admission control and dynamic resource pools.
  • Whether you are creating a new pool or editing the settings of an existing one, follow the decision process in Choosing Settings for an Impala Dynamic Resource Pool.
  • If you are subdividing your workload and do not already have a dynamic resource pool set up for it, follow the procedure in Creating an Impala Dynamic Resource Pool.
  • To edit the properties of an existing dynamic resource pool, follow the procedure in Editing Dynamic Resource Pools.