Migrating an HDFS Yandex Data Processing cluster to a different availability zone

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Updated at October 14, 2024

Create a cluster via import in Terraform
Copy the data to the new cluster
Delete the initial cluster

Subclusters of each Yandex Data Processing cluster reside in the same cloud network and availability zone. You can migrate a cluster to a different availability zone. The migration process depends on the cluster type:

The following describes how to migrate HDFS clusters.
For information on migrating lightweight clusters, follow the tutorial.

Note

The Intel Broadwell platform is not available for clusters with hosts residing in the ru-central1-d availability zone.

To migrate an HDFS cluster:

Before you begin, create a subnet in the availability zone to which you are migrating the cluster.

Create a cluster via import in Terraform

To create a Yandex Data Processing cluster in a different availability zone with the same configuration as the initial cluster, import the initial cluster's configuration into Terraform:

Terraform

If you do not have Terraform yet, install it.
Get the authentication credentials. You can add them to environment variables or specify them later in the provider configuration file.
Configure and initialize a provider. There is no need to create a provider configuration file manually, you can download it.
Place the configuration file in a separate working directory and specify the parameter values. If you did not add the authentication credentials to environment variables, specify them in the configuration file.
In the same working directory, place a .tf file with the following contents:
```
resource "yandex_dataproc_cluster" "old" { }
```
Write the initial cluster ID to the environment variable:
```
export DATAPROC_CLUSTER_ID=<cluster_ID>
```
You can request the ID with a list of clusters in the folder.

Import the initial cluster settings into the Terraform configuration:

terraform import yandex_dataproc_cluster.old ${DATAPROC_CLUSTER_ID}

Get the imported configuration:
```
terraform show
```
Copy it from the terminal and paste it into the .tf file.
Place the file in the new imported-cluster directory.
Modify the copied configuration so that you can create a new cluster from it:
- Specify the new cluster name in the resource string and the name parameter.
- Delete the created_at, host_group_ids, id, and subcluster_spec.id parameters.
- Change the availability zone in the zone_id parameter.
- In the subnet_id parameters of the subcluster_spec sections, specify the ID of the new subnet created in the required availability zone.
- Change the SSH key format in the ssh_public_keys parameter. Source format:
```
ssh_public_keys = [
  <<-EOT
    <key>
  EOT,
]
```
  Required format:
```
ssh_public_keys = [
  "<key>"
]
```
Get the authentication credentials in the imported-cluster directory.
In the same directory, configure and initialize a provider. There is no need to create a provider configuration file manually, you can download it.
Place the configuration file in the imported-cluster directory and specify the parameter values. If you did not add the authentication credentials to environment variables, specify them in the configuration file.
Make sure the Terraform configuration files are correct using this command:
```
terraform validate
```
If there are any errors in the configuration files, Terraform will point them out.
Create the required infrastructure:
1. Run the command to view planned changes:
```
terraform plan
```
  If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.
2. If you are happy with the planned changes, apply them:
  1. Run the command:
```
terraform apply
```
  2. Confirm the update of resources.
  3. Wait for the operation to complete.
All the required resources will be created in the specified folder. You can check resource availability and their settings in the management console.

Copy the data to the new cluster

Make sure no operations or jobs are being performed on the HDFS files and directories you want to copy.

To see a list of running operations and jobs:
1. In the management console, select Yandex Data Processing.
2. Click the initial cluster name and select the Operations tab, then select Jobs.
Note

Until you have completed the migration, do not run any operations or jobs modifying the HDFS files and directories you are copying.
Connect via SSH to the master host of the initial cluster.
Get a list of directories and files to be copied to the new cluster:
```
hdfs dfs -ls /
```
Instead of the / symbol, you can specify the directory you need.
To test copying data to the new Yandex Data Processing cluster, create test directories:
```
hdfs dfs -mkdir /user/foo &&\
hdfs dfs -mkdir /user/test
```
In the example below, only the /user/foo and /user/test test directories are copied for demonstration purposes.
Connect via SSH to the master host of the new cluster.
Create a file named srclist:
```
nano srclist
```
Add to it a list of directories intended for migration:
```
hdfs://<initial_cluster_FQDN>:8020/user/foo
hdfs://<initial_cluster_FQDN>:8020/user/test
```
In the command, specify the FQDN of the master host of the initial cluster. For information on how to obtain an FQDN, read the tutorial.
Put the srclist file into the /user HDFS directory:
```
hdfs dfs -put srclist /user
```
Create a directory to copy the data to. In the example, it is the copy directory, nested in /user.
```
hdfs dfs -mkdir /user/copy
```
Copy the data between clusters using DistCp:
```
hadoop distcp -f hdfs://<new_cluster_FQDN>:8020/user/srclist \
hdfs://<new_cluster_FQDN>:8020/user/copy
```
In the command, specify the FQDN of the master host of the new cluster.

As a result, all directories and files specified in the srclist will be copied to the /user/copy directory.

If copying a large volume of data, use the -m <maximum_simultaneous_copies> flag in the command to limit network bandwidth consumption. For more information, see the DistCp documentation.

You can view the data volume you copy in the HDFS web interface. To open it:
1. In the management console, select Yandex Data Processing.
2. Click the initial cluster name.
3. On its page, in the UI Proxy section, click the HDFS Namenode UI link.
The DFS Used field states the initial cluster's data volume in HDFS.
Make sure the data is copied:
```
hdfs dfs -ls /user/copy
```

This way you can copy all the data you need. To do this, specify the required directories and files in srclist.

Delete the initial cluster

To do it, follow this guide.

Migrating an HDFS Yandex Data Processing cluster to a different availability zone

Create a cluster via import in TerraformCreate a cluster via import in Terraform

Copy the data to the new clusterCopy the data to the new cluster

Delete the initial clusterDelete the initial cluster

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Create a cluster via import in Terraform

Copy the data to the new cluster

Delete the initial cluster