If you manage your cluster through Cloudera Manager, configure the settings for all the Impala-related daemons by navigating to this page: Clusters > Impala > Configuration > View and Edit. See the Cloudera Manager documentation for instructions about how to configure Impala through Cloudera Manager: Impala information for Cloudera Manager 5, Impala information for Cloudera Manager 4.

If the Cloudera Manager interface does not yet have a form field for a newly added option, or if you need to use special options for debugging and troubleshooting, the Advanced option page for each daemon includes one or more fields where you can enter option names directly. In Cloudera Manager 4, these fields are labelled Safety Valve; in Cloudera Manager 5, they are called Advanced Configuration Snippet. There is also a free-form field for query options, on the top-level Impala Daemon options page.

When you run Impala in a non-Cloudera Manager environment, the Impala server, statestore, and catalog services start up using values provided in a defaults file, /etc/default/impala.

This file includes information about many resources used by Impala. Most of the defaults included in this file should be effective in most cases. For example, typically you would not change the definition of the CLASSPATH variable, but you would always set the address used by the statestore server. Some of the content you might modify includes:

IMPALA_STATE_STORE_HOST=127.0.0.1
IMPALA_STATE_STORE_PORT=24000
IMPALA_BACKEND_PORT=22000
IMPALA_LOG_DIR=/var/log/impala
IMPALA_CATALOG_SERVICE_HOST=...
IMPALA_STATE_STORE_HOST=...

export IMPALA_STATE_STORE_ARGS=${IMPALA_STATE_STORE_ARGS:- \
    -log_dir=${IMPALA_LOG_DIR} -state_store_port=${IMPALA_STATE_STORE_PORT}}
IMPALA_SERVER_ARGS=" \
-log_dir=${IMPALA_LOG_DIR} \
-catalog_service_host=${IMPALA_CATALOG_SERVICE_HOST} \
-state_store_port=${IMPALA_STATE_STORE_PORT} \
-use_statestore \
-state_store_host=${IMPALA_STATE_STORE_HOST} \
-be_port=${IMPALA_BACKEND_PORT}"
export ENABLE_CORE_DUMPS=${ENABLE_COREDUMPS:-false}

To use alternate values, edit the defaults file, then restart all the Impala-related services so that the changes take effect. Restart the Impala server using the following commands:

$ sudo service impala-server restart
Stopping Impala Server:                                    [  OK  ]
Starting Impala Server:                                    [  OK  ]

Restart the Impala statestore using the following commands:

$ sudo service impala-state-store restart
Stopping Impala State Store Server:                        [  OK  ]
Starting Impala State Store Server:                        [  OK  ]

Restart the Impala catalog service using the following commands:

$ sudo service impala-catalog restart
Stopping Impala Catalog Server:                            [  OK  ]
Starting Impala Catalog Server:                            [  OK  ]

Some common settings to change include:

• Statestore address. Cloudera recommends the statestore be on a separate host not running the impalad daemon. In that recommended configuration, the impalad daemon cannot refer to the statestore server using the loopback address. If the statestore is hosted on a machine with an IP address of 192.168.0.27, change:

  IMPALA_STATE_STORE_HOST=127.0.0.1

  to:

  IMPALA_STATE_STORE_HOST=192.168.0.27

• Catalog server address (including both the hostname and the port number). Update the value of the IMPALA_CATALOG_SERVICE_HOST variable. Cloudera recommends the catalog server be on the same host as the statestore. In that recommended configuration, the impalad daemon cannot refer to the catalog server using the loopback address. If the catalog service is hosted on a machine with an IP address of 192.168.0.27, add the following line:

  IMPALA_CATALOG_SERVICE_HOST=192.168.0.27:26000

  The /etc/default/impala defaults file currently does not define an IMPALA_CATALOG_ARGS environment variable, but if you add one it will be recognized by the service startup/shutdown script. Add a definition for this variable to /etc/default/impala and add the option -catalog_service_host=hostname. If the port is different than the default 26000, also add the option -catalog_service_port=port.

• Memory limits. You can limit the amount of memory available to Impala. For example, to allow Impala to use no more than 70% of system memory, change:

  export IMPALA_SERVER_ARGS=${IMPALA_SERVER_ARGS:- \
      -log_dir=${IMPALA_LOG_DIR} \
      -state_store_port=${IMPALA_STATE_STORE_PORT} \
      -use_statestore -state_store_host=${IMPALA_STATE_STORE_HOST} \
      -be_port=${IMPALA_BACKEND_PORT}}

  to:

  export IMPALA_SERVER_ARGS=${IMPALA_SERVER_ARGS:- \
      -log_dir=${IMPALA_LOG_DIR} -state_store_port=${IMPALA_STATE_STORE_PORT} \
      -use_statestore -state_store_host=${IMPALA_STATE_STORE_HOST} \
      -be_port=${IMPALA_BACKEND_PORT} -mem_limit=70%}

  You can specify the memory limit using absolute notation such as 500m or 2G, or as a percentage of physical memory such as 60%.

    Note: Queries that exceed the specified memory limit are aborted. Percentage limits are based on the physical memory of the machine and do not consider cgroups.

• Core dump enablement. To enable core dumps on systems not managed by Cloudera Manager, change:

  export ENABLE_CORE_DUMPS=${ENABLE_COREDUMPS:-false}

  to:

  export ENABLE_CORE_DUMPS=${ENABLE_COREDUMPS:-true}

  On systems managed by Cloudera Manager, enable the Enable Core Dump setting for the Impala service.

    Note:

  • The location of core dump files may vary according to your operating system configuration.

  • Other security settings may prevent Impala from writing core dumps even when this option is enabled.

  • On systems managed by Cloudera Manager, the default location for core dumps is on a temporary filesystem, which can lead to out-of-space issues if the core dumps are large, frequent, or not removed promptly. To specify an alternative location for the core dumps, filter the Impala configuration settings to find the core_dump_dir option, which is available in Cloudera Manager 5.4.3 and higher. This option lets you specify a different directory for core dumps for each of the Impala-related daemons.

• Authorization using the open source Sentry plugin. Specify the -server_name and -authorization_policy_file options as part of the IMPALA_SERVER_ARGS and IMPALA_STATE_STORE_ARGS settings to enable the core Impala support for authentication. See Starting the impalad Daemon with Sentry Authorization Enabled for details.

• Auditing for successful or blocked Impala queries, another aspect of security. Specify the -audit_event_log_dir=directory_path option and optionally the -max_audit_event_log_file_size=number_of_queries and -abort_on_failed_audit_event options as part of the IMPALA_SERVER_ARGS settings, for each Impala node, to enable and customize auditing. See Auditing Impala Operations for details.

• Password protection for the Impala web UI, which listens on port 25000 by default. This feature involves adding some or all of the --webserver_password_file, --webserver_authentication_domain, and --webserver_certificate_file options to the IMPALA_SERVER_ARGS and IMPALA_STATE_STORE_ARGS settings. See Security Guidelines for Impala for details.

• Another setting you might add to IMPALA_SERVER_ARGS is a comma-separated list of query options and values:

  -default_query_options='option=value,option=value,...'
  

  These options control the behavior of queries performed by this impalad instance. The option values you specify here override the default values for Impala query options, as shown by the SET statement in impala-shell.

• During troubleshooting, Cloudera Support might direct you to change other values, particularly for IMPALA_SERVER_ARGS, to work around issues or gather debugging information.

  Note:

These startup options for the impalad daemon are different from the command-line options for the impala-shell command. For the impala-shell options, see impala-shell Configuration Options.

You can check the current runtime value of all these settings through the Impala web interface, available by default at http://impala_hostname:25000/varz for the impalad daemon, http://impala_hostname:25010/varz for the statestored daemon, or http://impala_hostname:25020/varz for the catalogd daemon. In the Cloudera Manager interface, you can see the link to the appropriate service_name Web UI page when you look at the status page for a specific daemon on a specific host.

The impalad daemon implements the main Impala service, which performs query processing and reads and writes the data files.

The statestored daemon implements the Impala statestore service, which monitors the availability of Impala services across the cluster, and handles situations such as nodes becoming unavailable or becoming available again.

The catalogd daemon implements the Impala catalog service, which broadcasts metadata changes to all the Impala nodes when Impala creates a table, inserts data, or performs other kinds of DDL and DML operations.

By default, the metadata loading and caching on startup happens asynchronously, so Impala can begin accepting requests promptly. To enable the original behavior, where Impala waited until all metadata was loaded before accepting any requests, set the catalogd configuration option --load_catalog_in_background=false.