Use Data Lake Storage Gen1 with Azure HDInsight clusters

Note

Deploy new HDInsight clusters using Azure Data Lake Storage Gen2 for improved performance and new features.

To analyze data in HDInsight cluster, you can store the data either in Azure Blob storage, Azure Data Lake Storage Gen1, or Azure Data Lake Storage Gen2. All storage options enable you to safely delete HDInsight clusters that are used for computation without losing user data.

In this article, you learn how Data Lake Storage Gen1 works with HDInsight clusters. To learn how Azure Blob storage works with HDInsight clusters, see Use Azure Blob storage with Azure HDInsight clusters. For more information about creating an HDInsight cluster, see Create Apache Hadoop clusters in HDInsight.

Note

Data Lake Storage Gen1 is always accessed through a secure channel, so there is no adls filesystem scheme name. You always use adl.

Note

This article has been updated to use the new Azure PowerShell Az module. You can still use the AzureRM module, which will continue to receive bug fixes until at least December 2020. To learn more about the new Az module and AzureRM compatibility, see Introducing the new Azure PowerShell Az module. For Az module installation instructions, see Install Azure PowerShell.

Availability for HDInsight clusters

Apache Hadoop supports a notion of the default file system. The default file system implies a default scheme and authority. It can also be used to resolve relative paths. During the HDInsight cluster creation process, specify a blob container in Azure Storage as the default file system. Or with HDInsight 3.5 and newer versions, you can select either Azure Blob storage or Azure Data Lake Storage Gen1 as the default files system with a few exceptions. The cluster and the storage account must be hosted in the same region.

HDInsight clusters can use Data Lake Storage Gen1 in two ways:

  • As the default storage
  • As additional storage, with Azure Blob storage as default storage.

Currently, only some of the HDInsight cluster types/versions support using Data Lake Storage Gen1 as default storage and additional storage accounts:

HDInsight cluster type Data Lake Storage Gen1 as default storage Data Lake Storage Gen1 as additional storage Notes
HDInsight version 4.0 No No ADLS Gen1 isn't supported with HDInsight 4.0
HDInsight version 3.6 Yes Yes Except HBase
HDInsight version 3.5 Yes Yes Except HBase
HDInsight version 3.4 No Yes
HDInsight version 3.3 No No
HDInsight version 3.2 No Yes
Storm You can use Data Lake Storage Gen1 to write data from a Storm topology. You can also use Data Lake Storage Gen1 for reference data that can then be read by a Storm topology.

Warning

HDInsight HBase is not supported with Azure Data Lake Storage Gen1

Using Data Lake Storage Gen1 as an additional storage account doesn't affect performance. Or the ability to read or write to Azure blob storage from the cluster.

Use Data Lake Storage Gen1 as default storage

When HDInsight is deployed with Data Lake Storage Gen1 as default storage, the cluster-related files are stored in adl://mydatalakestore/<cluster_root_path>/, where <cluster_root_path> is the name of a folder you create in Data Lake Storage. By specifying a root path for each cluster, you can use the same Data Lake Storage account for more than one cluster. So, you can have a setup where:

  • Cluster1 can use the path adl://mydatalakestore/cluster1storage
  • Cluster2 can use the path adl://mydatalakestore/cluster2storage

Notice that both the clusters use the same Data Lake Storage Gen1 account mydatalakestore. Each cluster has access to its own root filesystem in Data Lake Storage. The Azure portal deployment experience prompts you to use a folder name such as /clusters/<clustername> for the root path.

To use Data Lake Storage Gen1 as default storage, you must grant the service principal access to the following paths:

  • The Data Lake Storage Gen1 account root. For example: adl://mydatalakestore/.
  • The folder for all cluster folders. For example: adl://mydatalakestore/clusters.
  • The folder for the cluster. For example: adl://mydatalakestore/clusters/cluster1storage.

For more information for creating service principal and grant access, see Configure Data Lake Storage access.

Extracting a certificate from Azure Keyvault for use in cluster creation

If the certificate for your service principal is stored in Azure Key Vault, you must convert the certificate to the correct format. The following code snippets show how to do the conversion.

First, download the certificate from Key Vault and extract the SecretValueText.

$certPassword = Read-Host "Enter Certificate Password"
$cert = (Get-AzureKeyVaultSecret -VaultName 'MY-KEY-VAULT' -Name 'MY-SECRET-NAME')
$certValue = [System.Convert]::FromBase64String($cert.SecretValueText)

Next, convert the SecretValueText to a certificate.

$certObject = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 -ArgumentList $certValue,$null,"Exportable, PersistKeySet"
$certBytes = $certObject.Export([System.Security.Cryptography.X509Certificates.X509ContentType]::Pkcs12, $certPassword.SecretValueText);
$identityCertificate = [System.Convert]::ToBase64String($certBytes)

Then you can use the $identityCertificate to deploy a new cluster as in the following snippet:

New-AzResourceGroupDeployment `
    -ResourceGroupName $resourceGroupName `
    -TemplateFile $pathToArmTemplate `
    -identityCertificate $identityCertificate `
    -identityCertificatePassword $certPassword.SecretValueText `
    -clusterName  $clusterName `
    -clusterLoginPassword $SSHpassword `
    -sshPassword $SSHpassword `
    -servicePrincipalApplicationId $application.ApplicationId

Use Data Lake Storage Gen1 as additional storage

You can use Data Lake Storage Gen1 as additional storage for the cluster as well. In such cases, the cluster default storage can either be an Azure Blob storage or a Azure Data Lake Storage Gen1 account. When running HDInsight jobs against the data stored in Azure Data Lake Storage Gen1 as additional storage, use the fully qualified path. For example:

adl://mydatalakestore.azuredatalakestore.net/<file_path>

There's no cluster_root_path in the URL now. That's because Data Lake Storage isn't a default storage in this case. So all you need to do is provide the path to the files.

To use a Data Lake Storage Gen1 as additional storage, grant the service principal access to the paths where your files are stored. For example:

adl://mydatalakestore.azuredatalakestore.net/<file_path>

For more information for creating service principal and grant access, see Configure Data Lake Storage access.

Use more than one Data Lake Storage Gen1 account

Adding a Data Lake Storage account as additional and adding more than one Data Lake Storage accounts can be done. Give the HDInsight cluster permission on data in one or more Data Lake Storage accounts. See Configure Data Lake Storage Gen1 access below.

Configure Data Lake Storage Gen1 access

To configure Azure Data Lake Storage Gen1 access from your HDInsight cluster, you must have an Azure Active directory (Azure AD) service principal. Only an Azure AD administrator can create a service principal. The service principal must be created with a certificate. For more information, see Quickstart: Set up clusters in HDInsight, and Create service principal with self-signed-certificate.

Note

If you are going to use Azure Data Lake Storage Gen1 as additional storage for HDInsight cluster, we strongly recommend that you do this while you create the cluster as described in this article. Adding Azure Data Lake Storage Gen1 as additional storage to an existing HDInsight cluster is not a supported scenario.

For more information on the access control model, see Access control in Azure Data Lake Storage Gen1.

Access files from the cluster

There are several ways you can access the files in Data Lake Storage from an HDInsight cluster.

  • Using the fully qualified name. With this approach, you provide the full path to the file that you want to access.

    adl://<data_lake_account>.azuredatalakestore.net/<cluster_root_path>/<file_path>
    
  • Using the shortened path format. With this approach, you replace the path up to the cluster root with:

    adl:///<file path>
    
  • Using the relative path. With this approach, you only provide the relative path to the file that you want to access.

    /<file.path>/
    

Data access examples

Examples are based on an ssh connection to the head node of the cluster. The examples use all three URI schemes. Replace DATALAKEACCOUNT and CLUSTERNAME with the relevant values.

A few hdfs commands

  1. Create a file on local storage.

    touch testFile.txt
    
  2. Create directories on cluster storage.

    hdfs dfs -mkdir adl://DATALAKEACCOUNT.azuredatalakestore.net/clusters/CLUSTERNAME/sampledata1/
    hdfs dfs -mkdir adl:///sampledata2/
    hdfs dfs -mkdir /sampledata3/
    
  3. Copy data from local storage to cluster storage.

    hdfs dfs -copyFromLocal testFile.txt adl://DATALAKEACCOUNT.azuredatalakestore.net/clusters/CLUSTERNAME/sampledata1/
    hdfs dfs -copyFromLocal testFile.txt adl:///sampledata2/
    hdfs dfs -copyFromLocal testFile.txt /sampledata3/
    
  4. List directory contents on cluster storage.

    hdfs dfs -ls adl://DATALAKEACCOUNT.azuredatalakestore.net/clusters/CLUSTERNAME/sampledata1/
    hdfs dfs -ls adl:///sampledata2/
    hdfs dfs -ls /sampledata3/
    

Creating a Hive table

Three file locations are shown for illustrative purposes. For actual execution, use only one of the LOCATION entries.

DROP TABLE myTable;
CREATE EXTERNAL TABLE myTable (
    t1 string,
    t2 string,
    t3 string,
    t4 string,
    t5 string,
    t6 string,
    t7 string)
ROW FORMAT DELIMITED FIELDS TERMINATED BY ' '
STORED AS TEXTFILE
LOCATION 'adl://DATALAKEACCOUNT.azuredatalakestore.net/clusters/CLUSTERNAME/example/data/';
LOCATION 'adl:///example/data/';
LOCATION '/example/data/';

Identify storage path from Ambari

To identify the complete path to the configured default store, navigate to HDFS > Configs and enter fs.defaultFS in the filter input box.

Create HDInsight clusters with access to Data Lake Storage Gen1

Use the following links for detailed instructions on how to create HDInsight clusters with access to Data Lake Storage Gen1.

Refresh the HDInsight certificate for Data Lake Storage Gen1 access

The following example PowerShell code reads a certificate from a local file or Azure Key Vault, and updates your HDInsight cluster with the new certificate to access Azure Data Lake Storage Gen1. Provide your own HDInsight cluster name, resource group name, subscription ID, app ID, local path to the certificate. Type in the password when prompted.

$clusterName = '<clustername>'
$resourceGroupName = '<resourcegroupname>'
$subscriptionId = '01234567-8a6c-43bc-83d3-6b318c6c7305'
$appId = '01234567-e100-4118-8ba6-c25834f4e938'
$addNewCertKeyCredential = $true
$certFilePath = 'C:\localfolder\adls.pfx'
$KeyVaultName = "my-key-vault-name"
$KeyVaultSecretName = "my-key-vault-secret-name"
$certPassword = Read-Host "Enter Certificate Password"
# certSource
# 0 - create self signed cert
# 1 - read cert from file path
# 2 - read cert from key vault
$certSource = 0

Login-AzAccount
Select-AzSubscription -SubscriptionId $subscriptionId

if($certSource -eq 0)
{
    Write-Host "Generating new SelfSigned certificate"

    $cert = New-SelfSignedCertificate -CertStoreLocation "cert:\CurrentUser\My" -Subject "CN=hdinsightAdlsCert" -KeySpec KeyExchange
    $certBytes = $cert.Export([System.Security.Cryptography.X509Certificates.X509ContentType]::Pkcs12, $certPassword);
    $certString = [System.Convert]::ToBase64String($certBytes)
}
elseif($certSource -eq 1)
{

    Write-Host "Reading the cert file from path $certFilePath"

    $cert = new-object System.Security.Cryptography.X509Certificates.X509Certificate2($certFilePath, $certPassword)
    $certString = [System.Convert]::ToBase64String([System.IO.File]::ReadAllBytes($certFilePath))
}
elseif($certSource -eq 2)
{

    Write-Host "Reading the cert file from Azure Key Vault $KeyVaultName"

    $cert = (Get-AzureKeyVaultSecret -VaultName $KeyVaultName -Name $KeyVaultSecretName)
    $certValue = [System.Convert]::FromBase64String($cert.SecretValueText)
    $certObject = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 -ArgumentList $certValue, $null,"Exportable, PersistKeySet"

    $certBytes = $certObject.Export([System.Security.Cryptography.X509Certificates.X509ContentType]::Pkcs12, $certPassword.SecretValueText);

    $certString =[System.Convert]::ToBase64String($certBytes)
}

if($addNewCertKeyCredential)
{
    Write-Host "Creating new KeyCredential for the app"
    $keyValue = [System.Convert]::ToBase64String($cert.GetRawCertData())
    New-AzADAppCredential -ApplicationId $appId -CertValue $keyValue -EndDate $cert.NotAfter -StartDate $cert.NotBefore
    Write-Host "Waiting for 7 minutes for the permissions to get propagated"
    Start-Sleep -s 420 #7 minutes
}

Write-Host "Updating the certificate on HDInsight cluster..."

Invoke-AzResourceAction `
    -ResourceGroupName $resourceGroupName `
    -ResourceType 'Microsoft.HDInsight/clusters' `
    -ResourceName $clusterName `
    -ApiVersion '2015-03-01-preview' `
    -Action 'updateclusteridentitycertificate' `
    -Parameters @{ ApplicationId = $appId; Certificate = $certString; CertificatePassword = $certPassword.ToString() } `
    -Force

Next steps

In this article, you learned how to use HDFS-compatible Azure Data Lake Storage Gen1 with HDInsight. This storage allows you to build adaptable, long-term, archiving data acquisition solutions. And use HDInsight to unlock the information inside the stored structured and unstructured data.

For more information, see: