Azure Data Lake Storage Gen1

This topic describes Azure ADLS Gen1 and Dremio configuration information.

Azure Data Lake Storage Gen1 is an optimized storage for big data analytics workloads and supports Data Lake Gen1 file systems.

[info] Azure Data Lake Storage Gen2

For information about Dremio support for Azure Data Lake Storage Gen2, see Azure Storage.

Azure Configuration

Dremio connects to Azure Data Lake Store using a pre-generated authentication key.

[info] Reading Parquet Files

Dremio supports offheap memory buffers for reading Parquet files from Azure Data Lake Store (ADLS), as of Dremio version 3.1.3.

Registering application with Azure Active Directory

  1. Go to Azure Portal and select Azure Active Directory from the left navigation bar. Then select App Registrations.

  2. Click on Endpoints and note down OAUTH 2.0 TOKEN ENDPOINT. This will be the OAuth 2.0 Token Endpoint for your Azure Data Lake Store source in Dremio.

  3. Click New application registration. Select a Name, choose Web app / API as type and enter a Sign-on URL. This URL can be a valid arbitrary URL.

  4. Once created, click on the registered app and note down Application ID. This will be the Application ID for your Azure Data Lake Store source in Dremio.

  5. While in the registered app, select Keys under API Access. Then enter a Description and select an expiration. Click Save and note down Value. This will be the Password for your Azure Data Lake Store source in Dremio.

Granting Azure Data Lake Store access

  1. Go to your desired Data Lake Store resource. Note down the name of the Data Lake Store. This will be the Resource Name for your Azure Data Lake Store source in Dremio.

  2. Click on Access control (IAM) and click Add. Select Owner as the Role and find the name of the application you registered above. Click Save.

  3. For the same Data Lake Store resource, go to Data explorer, then navigate to the top level directory that'll be used by Dremio. Click Access and add Read, Execute and Write (if using as distributed store) permissions to the application registered above.

Dremio Configuration

General

Dremio Field Azure Property
Resource Name Name of the resource
Application ID Application ID of the registered application under Azure Active Directory
OAuth 2.0 Token Endpoint Azure Active Directory OAuth 2.0 Token Endpoint for registered applications
Access key value Generated password value for the registered application

REQUIRED: After a successful first connection in Dremio, do the following:

  1. Ensure that the source is successfully created and tested.
  2. Add and set the fs.adl.impl.disable.cache connection property to false.
    This property is set to optimize performance. Do not set this property before the source is created and tested; it impacts credential usage and can cause issues if you are reconfiguring the connection.
  3. Restart your cluster after saving the source with this property.

Advanced Options

Advanced options include:

  • Enable asynchronous access when possible (default)
  • Enable exports into the source (CTAS and DROP).
  • Root Path -- Root path for the source.
  • Connection Properties -- A list of additional connection properties.

Advanced Options

Reflection Refresh

  • Never refresh -- Specifies how often to refresh based on hours, days, weeks, or never.
  • Never expire -- Specifies how often to expire based on hours, days, weeks, or never.

    Metadata

Dataset Handling

  • Remove dataset definitions if underlying data is unavailable (Default).
    If this box is not checked and the underlying files under a folder are removed or the folder/source is not accessible, Dremio does not remove the dataset definitions. This option is useful in cases when files are temporarily deleted and put back in place with new sets of files.
  • Automatically format files into physical datasets when users issue queries. If this box is checked and a query runs against the un-promoted PDS/folder, Dremio automatically promotes using default options. If you have CSV files, especially with non-default options, it might be useful to not check this box.

Metadata Refresh

  • Dataset Discovery -- Refresh interval for top-level source object names such as names of DBs and tables.
    • Fetch every -- Specify fetch time based on minutes, hours, days, or weeks. Default: 1 hour
  • Dataset Details -- The metadata that Dremio needs for query planning such as information needed for fields, types, shards, statistics, and locality.
    • Fetch mode -- Specify either Only Queried Datasets, All Datasets, or As Needed. Default: Only Queried Datasets
      • Only Queried Datasets -- Dremio updates details for previously queried objects in a source.
        This mode increases query performance because less work is needed at query time for these datasets.
      • All Datasets -- Dremio updates details for all datasets in a source. This mode increases query performance because less work is needed at query time.
      • As Needed -- Dremio updates details for a dataset at query time. This mode minimized metadata queries on a source when not used, but might lead to longer planning times.
    • Fetch every -- Specify fetch time based on minutes, hours, days, or weeks. Default: 1 hour
    • Expire after -- Specify expiration time based on minutes, hours, days, or weeks. Default: 3 hours

      Sharing

You can specify which users can edit. Options include:

  • All users can edit.
  • Specific users can edit.

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