Impala on CDH OCF Connector: Install and Configure

Alation Cloud Service Applies to Alation Cloud Service instances of Alation

Customer Managed Applies to customer-managed instances of Alation


The port numbers listed below are defaults. If you are using non-default ports, then ensure they are open.

  • Open outbound TCP port 21050 to the Impala server

  • Open outbound TCP port 9083 to the metastore

  • Open outbound TCP port 9870 to the WebHDFS server

  • Open outbound TCP port 9871 to the WebHDFS server if the cluster uses TLS

  • Open TCP port 14000 for HTTPFS connection

Extraction of Complex Data Types

Complex data types, such as map, array, and struct are extracted. By default, they will be represented as flat lists.

You can enable tree-structure-like representation of complex data types using alation_conf on the Alation server.


Alation Cloud Service customers can request server configuration changes through Alation Support.

To enable the representation of complex data types as a tree structure:

  • On your Alation instance, set the alation_conf parameter alation.feature_flags.enable_generic_nosql_support to True.

  • Additionally, use the parameter alation.feature_flags.docstore_tree_table_depth to define the depth of the display. By default, three levels are displayed.

For information about using alation_conf, refer to Using alation_conf.


After changing values of these parameters, restart Alation Supervisor from the Alation shell: alation_supervisor restart all.

You can find more information about Alation actions in Alation Actions.

Service Account

Create a service account for Alation prior to adding your Impala data source to the catalog. The service account requires these permissions:

  • SELECT on all schemas which you plan to extract into the catalog.

  • Read and execute permissions for the HDFS location that stores Impala query logs.

  • Read and execute permissions for Impala external tables.

  • Access to the metastore.

Kerberized Impala

Alation recommends creating the service account in the same realm as the realm used by Impala users.

Kerberos Configuration File

In case your Impala data source is kerberized, prepare the krb5.conf file and, if applicable, the keytab file for the service account. They will need to be uploaded to Alation.

Connection Over SSL

If your connection from Alation will go over SSL, prepare the truststore file. The truststore file will need to be uploaded to Alation in the settings of the Impala data source to enable metadata extraction, sampling, and query log ingestion over SSL.

Alation expects the truststore.jks file of the HDFS service. You will also need the truststore password. Consult your Impala administrator about downloading this file.

Usually, you can download the certificate from the HDFS component in Cloudera Manager. To locate and download the certificate:

  1. Open the HDFS service in Cloudera Manager.

  2. Click Configuration, then search for Cluster-Wide Default TLS/SSL Client Truststore Location. You should be able to locate the path to the folder that contains the truststore.jks file.



    The path to the file may be different for your Impala instance.

Configuration in Alation

STEP 1: Install the Connector

Alation On-Premise


Installation of OCF connectors requires Alation Connector Manager to be installed as a prerequisite.

To install an OCF connector:

  1. If this has not been done on your instance, install the Alation Connector Manager: Install Alation Connector Manager.

  2. Ensure that the OCF connector Zip file is available on your local machine.

  3. Install the connector on the Connectors Dashboard page using the steps in Manage Connectors.

Alation Cloud Service


On Alation Cloud Service instances, Alation Connector Manager is available by default.

Depending on your network configuration, you may need to use Alation Agent to connect to databases.

Connection via Alation Agent
  1. Ensure that Alation Agent is enabled on your Alation instance. If necessary, create a Support ticket with Alation for an Alation representative to enable the Alation Agent feature on your instance and to receive the Alation Agent installer.

  2. Install the Alation Agent.

  3. Install the OCF connector on Alation Agent.

Connection Without Agent

To install an OCF connector:

  1. Ensure that the OCF connector Zip file is available on your local machine.

  2. Install the connector on the Connectors Dashboard page using the steps in Manage Connectors.

STEP 2: Create and Configure a New Data Source

In Alation, add a new data source:

  1. Log in to Alation as a Server Admin.

  2. Expand the Apps menu on the right of the main toolbar and select Sources.

  3. On the Sources page, click +Add on the top right of the page and in the list that opens, click Data Source. This will open the Add a Data Source wizard.

  4. On the first screen of the wizard, specify a name for your data source, assign additional Data Source Admins, if necessary, and click the Continue Setup button on the bottom. The Add a Data Source screen will open.

  5. On the Add a Data Source screen, the only field you should populate is Database Type. From the Database Type dropdown, select the connector name. After that you will be navigated to the Settings page of your new data source.


    Agent-based connectors will have the Agent name appended to the connector name.

The connector name is Impala OCF Connector.


Impala supports different types of authentication methods. Use the JDBC URI format that corresponds to the authentication method you are using.


A port number is mandatory for all authentication schemes. Default values will be applied if no port is specified.

Basic Authentication





Kerberized Impala





Connection over SSL




  • SSL

  • Kerberos + SSL


Metastore URI





Metastore Principal Example



On the Access tab, set the data source visibility using these options:

  • Public Data Source—The data source will be visible to all users of the catalog.

  • Private Data Source—The data source will be visible to the users allowed access to the data source by Data Source Admins.

You can add new Data Source Admin users in the Data Source Admins section.

General Settings


This section describes configuring settings for credentials and connection information stored in the Alation database. If your organization has configured Azure KeyVault or AWS Secrets Manager to hold such information, the user interface for the General Settings page will change to include the following icons to the right of most options:


By default, the database icon is selected, as shown. In the vault case, instead of the actual credential information, you enter the ID of the secret. See Configure Secrets for OCF Connector Settings for details.

Perform the configuration on the General Settings tab.

Application Settings

Specify Application Settings if applicable. Click Save to save the changes after providing the information.



BI Connection Info

This parameter is used to generate lineage between the current data source and another source in the catalog, for example a BI source that retrieves data from the underlying database. The parameter accepts host and port information of the corresponding BI data source connection.

Use the following format: host:port

You can provide multiple values as a comma-separated list:,

Find more details in BI Connection Info.

Disable Automatic Lineage Generation

Select this checkbox to disable automatic lineage generation from QLI, MDE, and Compose queries. By default, automatic lineage generation is enabled.

Connector Settings

Data Source Connection

Populate the data source connection information and save the values by clicking Save in this section.




Specify the JDBC URI in the required format. See JDBC URI.

Metastore URI

Specify the metastore URI.


Specify the service account username.


Specify the service account password.

Enable SSL

Enable SSL authentication by selecting the Enable SSL checkbox.

If the Enable SSL checkbox is enabled, upload the SSL certificate using the upload link below.

Truststore password

Specify the password for the SSL certificate.

Note: The password will be deleted if the data source connection is deleted.

Enable Kerberos Authentication

Enable or disable Kerberos authentication by selecting or clearing the Enable Kerberos Authentication checkbox.

If the Kerberos authentication checkbox is enabled, upload the krb5.conf file using the upload link under the checkbox.

Use keytab

To enable Kerberos with Keytab authentication, select the Use Keytab checkbox and upload the keytab file for the service account using the upload link under the checkbox.

Metastore Principal

Specify the metastore principal.

Logging Configuration

Select the logging level for the connector logs and save the values by clicking Save in this section. The available log levels are based on the Log4j framework.



Log level

Select the log level to generate logs. The available options are INFO, DEBUG, WARN, TRACE, ERROR, FATAL, ALL.

You can view the connector logs in Admin Settings > Manage Connectors > Impala OCF Connector.

Obfuscate Literals

Obfuscate Literals—Enable this toggle to hide actual values in the query statements that are ingested during query log ingestion or executed in Compose. This toggle is disabled by default.

Test Connection

After specifying the connector settings, under Test Connection, click Test to validate network connectivity.

Metadata Extraction

The Impala OCF Connector supports default extraction—This type of MDE is based on Impala API calls that are built in the connector code.

Custom query-based MDE is not supported.


Complex data types are extracted. See Extraction of Complex Data Types for information on how to enable their representation in the Alation user interface.

You can configure metadata extraction (MDE) for an OCF data source on the Metadata Extraction tab of the Settings page. Refer to Configure Metadata Extraction for OCF Data Sources for information about the available configuration options.


For details about configuring the Compose tab of the Settings, refer to Configure Compose for OCF Data Sources.


Compose is not available on Alation Cloud Service instances when the data source is connected through Alation Agent. For this data source, Compose with Kerberos and SSL authentication is currently not supported.

Sampling and Profiling

Alation supports a number of ways to retrieve data samples and column profiles. For details, see Configure Sampling and Profiling for OCF Data Sources.

Query Log Ingestion

On the Query Log Ingestion tab, you can select the QLI options for your data source and schedule the QLI job if necessary.

For Impala on CDH, Alation supports QLI from query log files stored on HDFS.

Prerequisites for QLI

In order to run Query Log Ingestion for an Impala data source, perform the following pre-configuration on your instance of Impala:

  • Enable audit log in Impala. For specific details refer to documentation for your CDH version, for example: Impala Auditing.

    • Enable auditing by including the option -audit_event_log_dir=directory_path in your impalad startup options. The path refers to a local directory on the server, not an HDFS directory.

    • Decide how many queries will be represented in each log file. By default, Impala starts a new log file every 5,000 queries. To specify a different number, include the option -max_audit_event_log_file_size=number_of_queries in the impalad startup options. Limiting the size manages disk space by archiving older logs and reduces the amount of text to process when analyzing activity for a particular period.

  • Periodically retrieve audit logs from Impala coordinator nodes to HDFS.

    • By default, the audit logs are located in /var/log/impalad/audit/ inside Impala coordinator nodes. Users can also configure the place of audit logs.

    • To periodically retrieve logs, you can write a script and run it as a cron job to pull the audit logs from impala coordinator nodes to HDFS every day. See an example in Appendix 8 A.8 Impala QLI Script.

    • Create a directory for storing all Impala audit logs in HDFS.

    • The audit log files from each Impala coordinator node should only stay in an HDFS subdirectory of the audit log directory. The subdirectory should be named by the ID of the Impala coordinator node, for example, IP address, or any unique identifier.

After all the steps are completed, you can configure and perform Query Log Ingestion (QLI) for Impala in Alation.

Place Query Logs on HDFS

Impala supports query log extraction from files located on an HDFS server. To set up QLI:

  1. SSH into the CDH instance.

  2. Log in as the root user.

  3. While logged in as the root user, change the current directory to /var/log/impalad/audit.

  4. In the audit directory, make sure there’s an Impala audit event log file. The file has the format: impala_audit_event_log_1.0-*.

  5. After confirming the file exists, create a directory in the /user/history/done directory on HDFS, for example:

    sudo -u hdfs hadoop fs -mkdir -p /user/history/done/log_1

    The name of the directory can be anything you want. We named it log_1 in this example.

  6. After creating the log_1 directory, recursively modify the permission of the /done directory and its sub-directories with the following command:

    sudo -u hdfs hadoop fs -chmod -R 777 /user/history/done
  7. Copy the impala_audit_event_log_1.0-*file into the log_1 directory with the following command:

    hadoop fs -put impala_audit_event_log_1.0-* /user/history/done/log_1

As an alternative to the above steps that manually copy the log file to a directory, you can use this script to periodically copy the log file to the HDFS.

Configure QLI in Alation

You can configure QLI on the Query Log Ingestion tab of the data source settings page.

  1. Open the Query Log Ingestion tab of the settings page.

  2. Under Connector Settings > Query Extraction, provide the required information and click Save:



    Logs Directory


    WebHDFS Server

    Hostname of the WebHDFS server

    WebHDFS Port

    Specify the HDFS port number for your environment. The default is 9870 or or 9871 in case of TLS). If you are using a different port, clear the Use Default checkbox under the HDFS Port field.

    Use Default

    Leave selected if you are using the default port.

    Clear this checkbox if you are using a port number other than the default.

    WebHDFS User


Perform QLI

You can either perform QLI manually on demand or enable automated QLI:

  1. To perform manual QLI, under the Automated and Manual Query Log Ingestion section of the Query Log Ingestion tab, ensure that the Enable Automated Query Log Ingestion toggle is disabled.


    Metadata extraction must be completed first before running QLI.

  2. Click Preview to get a sample of the query history data to be ingested.

  3. Click the Import button to perform QLI on demand.

  4. To schedule QLI, enable the Enable Automated Query Log Ingestion toggle.

  5. Set a schedule under Automated Query Log Ingestion Time by specifying values in the week, day, and time fields. The next QLI job will run on the schedule you have specified.


    The hourly schedule for automated QLI is not supported.