The Impala Service

The Impala Service is the Cloudera Manager representation of the three daemons that make up the Impala interactive SQL engine. Through the Impala Service page, you can monitor, start and stop, and configure all the related daemons from a central page.

For general information about Impala and how to use it, especially for writing Impala SQL queries, see Apache Impala - Interactive SQL.

For information on features that support Impala resource management see Admission Control and Query Queuing.

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Installing Impala and Creating the Service

You can install Impala through the Cloudera Manager installation wizard, using either parcels or packages, and have the service created and started as part of the Installation wizard. See Cloudera Installation Guide.

If you elect not to include the Impala service using the Installation wizard, you can use the Add Service wizard to perform the installation. The wizard will automatically configure and start the dependent services and the Impala service. See Adding a Service for instructions.

Configuring the Impala Service

There are several types of configuration settings you may need to apply, depending on your situation.

Configuring Table Statistics

Configuring table statistics is highly recommended when using Impala. It allows Impala to make optimizations that can result in significant (over 10x) performance improvement for some joins. If these are not available, Impala will still function, but at lower performance.

The Impala implementation to compute table statistics is available in CDH 5.0.0 or higher and in Impala version 1.2.2 or higher. The Impala implementation of COMPUTE STATS requires no setup steps and is preferred over the Hive implementation. See Overview of Table Statistics. If you are running an older version of Impala, follow the procedure in Accessing Apache Hive Table Statistics in CDH.

Using a Load Balancer with Impala

To configure a load balancer:
  1. Go to the Impala service.
  2. Click the Configuration tab.
  3. Select Scope > Impala Daemon
  4. Select Category > All
  5. Enter the hostname and port number of the load balancer in the Impala Daemons Load Balancer property in the format hostname:port number.
  6. Enter a Reason for change, and then click Save Changes to commit the changes.

Impala Web Servers

Enabling and Disabling Access to Impala Web Servers

Each of the Impala-related daemons includes a built-in web server that lets an administrator diagnose issues with each daemon on a particular host, or perform other administrative actions such as cancelling a running query. By default, these web servers are enabled. You might turn them off in a high-security configuration where it is not appropriate for users to have access to this kind of monitoring information through a web interface. (To leave the web servers enabled but control who can access their web pages, consult the Configuring Secure Access for Impala Web Servers later in this section.)

  • Impala Daemon
    1. Go to the Impala service.
    2. Click the Configuration tab.
    3. Select Scope > Impala Daemon
    4. Select Category > Ports and Addresses.
    5. Select or clear Enable Impala Daemon Web Server.
    6. Enter a Reason for change, and then click Save Changes to commit the changes.
    7. Restart the Impala service.
  • Impala StateStore
    1. Go to the Impala service.
    2. Click the Configuration tab.
    3. Select Scope > Impala StateStore.
    4. Select Category > All
    5. Select or clear Enable StateStore Web Server.
    6. Enter a Reason for change, and then click Save Changes to commit the changes.
    7. Restart the Impala service.
  • Impala Catalog Server
    1. Go to the Impala service.
    2. Click the Configuration tab.
    3. Select Scope > Impala Catalog Server.
    4. Select Category > All
    5. Check or uncheck Enable Catalog Server Web Server.
    6. Enter a Reason for change, and then click Save Changes to commit the changes.
    7. Restart the Impala service.

Opening Impala Web Server UIs

  • Impala StateStore
    1. Go to the Impala service.
    2. Select Web UI > Impala StateStore Web UI.
  • Impala Daemon
    1. Go to the Impala service.
    2. Click the Instances tab.
    3. Click an Impala Daemon instance.
    4. Click Impala Daemon Web UI.
  • Impala Catalog Server
    1. Go to the Impala service.
    2. Select Web UI > Impala Catalog Web UI.
  • Impala Llama ApplicationMaster
    1. Go to the Impala service.
    2. Click the Instances tab.
    3. Click a Impala Llama ApplicationMaster instance.
    4. Click Llama Web UI.

Configuring Secure Access for Impala Web Servers

Cloudera Manager supports two methods of authentication for secure access to the Impala Catalog Server, Daemon, and StateStoreweb servers: password-based authentication and TLS/SSL certificate authentication. Both of these can be configured through properties of the Impala Catalog Server, Daemon, and StateStore. Authentication for the three types of daemons can be configured independently.

Configuring Password Authentication

  1. Go to the Impala service.
  2. Click the Configuration tab.
  3. Search for "password" using the Search box within the Configuration page. This should display the password-related properties (Username and Password properties) for the Impala Catalog Server, Daemon, and StateStore. If there are multiple role groups configured for Impala Daemon instances, the search should display all of them.
  4. Enter a username and password into these fields.
  5. Enter a Reason for change, and then click Save Changes to commit the changes.
  6. Restart the Impala service.

Now when you access the Web UI for the Impala Catalog Server, Daemon, and StateStore, you are asked to log in before access is granted.

Configuring TLS/SSL Certificate Authentication

  1. Create or obtain an TLS/SSL certificate.
  2. Place the certificate, in .pem format, on the hosts where the Impala Catalog Server and StateStore are running, and on each host where an Impala Daemon is running. It can be placed in any location (path) you choose. If all the Impala Daemons are members of the same role group, then the .pem file must have the same path on every host.
  3. Go to the Impala service page.
  4. Click the Configuration tab.
  5. Search for "certificate" using the Search box within the Configuration page. This should display the certificate file location properties for the Impala Catalog Server, Daemon, and StateStore. If there are multiple role groups configured for Impala Daemon instances, the search should display all of them.
  6. In the property fields, enter the full path name to the certificate file.
  7. Enter a Reason for change, and then click Save Changes to commit the changes.
  8. Restart the Impala service.

When you access the Web UI for the Impala Catalog Server, Daemon, and StateStore, https will be used.