HDFS replication policy definition JSON file

The policy definition JSON file contains all the parameters required to create an HDFS replication policy. When you edit the file to define an HDFS replication policy, remove the parameters that are not required for the replication policy.

Parameters in HDFS replication policy definition JSON file

The following table lists the parameters in the policy definition JSON file that are required for an HDFS replication policy:


Parameter	Description
`clusterCrn`	Provide the source cluster CRN for the HDFS replication policy. Replication Manager saves the replication policy in the specified cluster CRN.
`policyName`	Provide a unique name for the replication policy.
`name`	Provide the unique name for the policy.
`type`	Provide `FS` to create an HDFS replication policy.
`path`	Provide the HDFS file path in the source cluster.
`mapReduceService`	Provide the MapReduce or YARN service for the replication policy to use.
`logPath`	Provide an alternate path for the logs, if required.
`replicationStrategy`	Provide one of the following options to determine whether the file replication tasks must be distributed among the mappers statically or dynamically: `STATIC` - Static replication distributes file replication tasks among the mappers up front to achieve an uniform distribution based on the file sizes. `DYNAMIC` - Dynamic replication distributes the file replication tasks in small sets to the mappers, and as each mapper completes its tasks, it dynamically acquires and processes the next unallocated set of tasks. Default is `DYNAMIC`.
`skipChecksumChecks`	Provide `true` to skip checksum checks. Default is `true`. Checksums are used to perform the following tasks: To skip replication of files that have already been copied. When set to `true`, the replication job skips copying a file if the file lengths and modification times are identical between the source and destination clusters. Otherwise, the job copies the file from the source to the destination. To redundantly verify the integrity of data. However, checksums are not required to guarantee accurate transfers between clusters. HDFS data transfers are protected by checksums during transfer and storage hardware also uses checksums to ensure that data is accurately stored. These two mechanisms work together to validate the integrity of the copied data.
`skipListingChecksumChecks`	Provide `true` to skip checksum check while comparing two files to determine whether they are the same or not. Otherwise, the file size and last modified time are used to determine if files are the same or not. Skipping the check improves performance during the mapper phase. note If you set `skipChecksumChecks` to `false`, the `skipListingChecksumChecks` is also set to `false` by default.
`abortOnError`	Provide `true` to stop the policy job when an error occurs. This ensures that the files copied up to that point remain on the destination, but no additional files are copied. Default is `false`.
`abortOnSnapshtDiffFailures`	Provide `true` to stop the replication job if a snapshot diff fails during replication.
`preserve`	Provide `true` to preserve the block size, replication count, permissions (including ACLs), and extended attributes (XAttrs) as they exist on the source file system. `blockSize` `replicationCount` `permissions` `extendedAtrributes` Provide `false` to use the settings as configured on the destination file system. By default, the source system settings are preserved. In an HDFS replication policy: when the permissions parameter is set to `true` and both the source and destination clusters support ACLs, replication preserves ACLs. Otherwise, ACLs are not replicated. when `extendedAtrributes` is set to `true` and both the source and destination clusters support extended attributes, the replication process preserves them. when you select one or more of the `Preserve` options, and you are replicating to S3 or ADLS, the values of all of these options are saved in metadata files on S3 or ADLS. When you replicate from S3 or ADLS to HDFS, you can set the options you want to preserve.
`deletePolicy`	Provide one of the following options: `KEEP_DELETED_FILES` - Retains the destination files even when they no longer exist at the source. `DELETE_TO_TRASH` - Moves files to the trash folder if the HDFS trash is enabled. (Not supported when replicating to S3 or ADLS.) `DELETE_PERMANENTLY` - Uses the least amount of space; use with caution. Default is `KEEP_DELETED_FILES`.
`alerts`	Configure the following parameters as required: `onFailure` - Provide `true` to generate alerts when the replication job fails. `onStart` - Provide `true` to generate alerts when the replication job starts. `onSuccess` - Provide `true` to generate alerts when the replication job completes successfully. `onAbort` - Provide `true` to generate alerts when the replication job is aborted.
`exclusionFilters`	Provide one or more directory paths to exclude from replication.
`frequencyInSec`	Auto-populated after the policy runs successfully. Shows the time duration between two replication jobs in seconds.
`targetDataset`	Auto-populated after the policy runs successfully. Shows the target location where the replicated files are available on the target cluster.
`cloudCredentials`	Provide the cloud credentials.
`sourceCluster`	Shows the source cluster name.
`targetCluster`	Shows the target cluster name in the `dataCProvideName$cluster` name format. For example, "DC-US$My Destination 17".
`startTime`	Shows the start time of the replication job in the `YYYY-MM-DDTHH:MM:SSZ` format.
`endTime`	Shows the end time of the replication job in the `YYYY-MM-DDTHH:MM:SSZ` format.
`distcpMaxMaps`	Provide the maximum map slots to limit the number of map slots per mapper. Default is `20`.
`distcpMapBandwidth`	Provide the maximum bandwidth to limit the bandwidth per mapper. Default is `100 MB`.
`queueName`	Provide a YARN queue name, if necessary. Default queue name is `Default`.
`tdeSameKey`	Provide `true` if the source and destination are encrypted with the same TDE key.
`description`	Provide a description for the policy.
`enableSnapshotBasedReplication`	Provide `true` to enable snapshot-based replication.
`cloudEncryptionAlgorithm`	Provide the cloud encryption algorithm.
`cloudEncryptionKey`	Provide the cloud encryption key.
`plugins`	Provide the plugins to deploy on all the nodes in the cluster if you have multiple repositories configured in your environment.
`cmPolicySubmitUser`	Provide the following options: `userName` - Provide the user name that you are using to run the policy. `sourceUser` - Provide the source cluster username, if any.

Sample HDFS replication policy definition JSON file

The following snippet shows the contents of the HDFS replication policy definition JSON file.

{
	"name": "string",
	"type": "FS"|"HIVE",
	"sourceDataset": {
		"hdfsArguments": {
			"path": "string",
                     "mapReduceService": "string",
                     "logPath": "string",
			"replicationStrategy": "DYNAMIC"|"STATIC",
			"errorHandling": {
				"skipChecksumChecks": true|false,
				"skipListingChecksumChecks": true|false,
				"abortOnError": true|false,
				"abortOnSnapshotDiffFailures": true|false
			},
			"preserve": {
				"blockSize": true|false,
				"replicationCount": true|false
				"permissions": true|false,
				"extendedAttributes": true|false
			},
			"deletePolicy": "KEEP_DELETED_FILES"|"DELETE_TO_TRASH"|"DELETE_PERMANENTLY",
			"alerts": {
				"onFailure": true|false,
				"onStart": true|false,
				"onSuccess": true|false,
				"onAbort": true|false
			},
			"exclusionFilters": ["string", ...]
			},
			"hiveArguments": {
				"databasesAndTables": [
					{
						"database": "string",
						"tablesIncludeRegex": "string",
						"tablesExcludeRegex": "string",
					}
					...
				],
				"sentryPermissions": "INCLUDE"|"EXCLUDE",
				"skipUrlPermissions": true|false,
				"numThreads": integer
			}
		},
		"frequencyInSec": integer,
		"targetDataset": "string",
		"cloudCredentials": "string",
		"sourceCluster": "string",
		"targetCluster": "string",
		"startTime": "string",
		"endTime": "string",
		"distcpMaxMaps": integer,
		"distcpMapBandwidth": integer,
		"queueName": "string",
		"tdeSameKey": true|false,
		"description": "string",
		"enableSnapshotBasedReplication": true|false
		"cloudEncryptionAlgorithm": "string",
		"cloudEncryptionKey": "string",
		"plugins": ["string", ...],
		"hiveExternalTableBaseDirectory": "string",
		"cmPolicySubmitUser": {
			"userName": "string",
			"sourceUser": "string"
		}
	}