Cloudera Docs

Impala Tab

The Impala tab displays CPU and memory utilization for Impala queries using three tabs: Queries, Peak Memory Usage and Spilled Memory tab.

Queries Tab

The Overview tab displays information about Impala queries.

The top part of the page displays summary information about Impala queries for the entire cluster. The table in the lower part displays the same information by tenant. Both sections display the following:
  • Total – Total number of queries.

    Click the link with the total to view details and charts about the queries.

  • Avg Wait Time in Queue – Average time, in milliseconds, spent by a query in an Impala pool while waiting for resources. If this number is high, consider increasing the resources allocated to the pool. If this number is high for several pools, consider increasing the number of hosts in the cluster.
  • Successful – The number and percentage of queries that finished successfully.

    Click the link with the total to view details and charts about the queries.

  • Memory Limit Exceeded – Number and percentage of queries that failed due to insufficient memory. If there are such queries, consider increasing the memory allocated to the pool. If there are several pools with such queries, consider increasing the number of hosts in the cluster.
  • Timed Out in Queue – Number of queries that timed out while waiting for resources in a pool. If there are such queries, consider increasing the maximum number of running queries allowed for the pool. If there are several pools with such queries, consider increasing the number of hosts in the cluster.
  • Rejected – Number of queries that were rejected by Impala because the pool was full. If this number is high, consider increasing the maximum number of queued queries allowed for the pool.
Click the column header to sort the table by that column.

Peak Memory Usage Tab

This report shows how Impala consumes memory at peak utilization. If utilization is high for a pool, consider adding resources to the pool. If utilization is high for several pools, consider adding more hosts to the cluster.

The Summary section of this page displays aggregated peak memory usage information for the entire cluster and the Utilization by Tenant section displays peak memory usage by tenant. Both sections display the following:
  • Max Allocated
    • Peak Allocation Time – The time when Impala reserved the maximum amount of memory for queries.

      Click the drop-down list next to the date and time and select View Impala Queries Running at the Time to see details about the queries.

    • Max Allocated – The maximum memory that was reserved by Impala for executing queries. If the percentage is high, consider increasing the number of hosts in the cluster.
    • Utilized at the Time – The amount of memory used by Impala for running queries at the time when maximum memory was reserved.

      Click View Time Series Chart to view a chart of peak memory allocations.

    • Histogram of Allocated Memory at Peak Allocation Time – Distribution of memory reserved per Impala daemon for executing queries at the time Impala reserved the maximum memory. If some Impala daemons have reserved memory close to the configured limit, consider adding more physical memory to the hosts.
  • Max Utilized
    • Peak Usage Time – The time when Impala used the maximum amount of memory for queries.

      Click the drop-down list next to the date and time and select View Impala Queries Running at the Time to see details about the queries.

    • Max Utilized – The maximum memory that was used by Impala for executing queries. If the percentage is high, consider increasing the number of hosts in the cluster.
    • Reserved at the Time – The amount of memory reserved by Impala at the time when it was using the maximum memory for executing queries.

      Click View Time Series Chart to view a chart of peak memory utilization.

    • Histogram of Utilized Memory at Peak Usage Time – Distribution of memory used per Impala daemon for executing queries at the time Impala used the maximum memory. If some Impala daemons are using memory close to the configured limit, consider adding more physical memory to the hosts.

Spilled Memory Tab

The Spilled Memory tab displays information about Impala spilled memory. These disk spills can deteriorate the performance of Impala queries significantly. This report shows the amount of disk spills for Impala queries by tenant. If disk spill is high for a pool, consider adding resources to the pool. If disk spill is high for several pools, consider adding more hosts to the cluster.

For each tenant, the following are displayed:
  • Average Spill – Average spill per query
  • Maximum Spill – Maximum memory spilled per hour