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Backup Restore

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Tadaya Tsuyukubo edited this page Jun 9, 2017 · 5 revisions

The HostManagementService provides an asynchronous API for backup/restore the document index, through internal document index service requests.

Backup

Send a PATCH BackupRequest request to /core/management.

BackupRequest:

  • kind: specify com:vmware:xenon:services:common:ServiceHostManagementService:BackupRequest
  • destination: URI with http/https scheme or file scheme with local file or directory are supported. When http/https is specified, destination is expected to accept PUT request with range header. The PUT request contains a zip file that contains files used by document index service.
  • backupType: ZIP, DIRECTORY, and STREAM is supported.
    ZIP is default and generates a zipped backup local file.
    DIRECTORY is supported for a local directory and performs incremental backup.
    STREAM is for http/https destination. zipped content will be sent to the destination as PUT requests.

In the request body, kind and destination are required parameters.

NOTE:
For backward compatibility, currently backupType parameter is optional and default to ZIP if not specified. However, it is recommended to always explicitly specify this parameter since it may become required parameter in future.

Sample:

> curl -X PATCH -H "Content-Type: application/json" -d '
{
  "kind": "com:vmware:xenon:services:common:ServiceHostManagementService:BackupRequest",
  "destination": "file:/var/backup/xenon-backup.zip",
  "backupType": "ZIP"
}
' http://localhost:8000/core/management

Incremental Backup

When backupType=DIRECTORY and local directory is specified in destination, it will perform incremental backup.
Incremental backup only copies new files and deletes unused index files in new snapshot to the destination directory.
Each incremental backup operation updates the contents of the directory to reflect the most recent state of the index.

For example, when backup is performed first time, it will simply add all index files into the destination directory. Since index files are immutable, when next backup is performed pointing to the directory that contains previous backup files, it will copy ONLY newly created index files and remove unused files.

Sample:

curl -X PATCH -H "Content-Type: application/json" -d '
{
  "kind": "com:vmware:xenon:services:common:ServiceHostManagementService:BackupRequest",
  "destination": "file:/var/xenon-backup/",
  "backupType": "DIRECTORY"
}
' http://localhost:8010/core/management

Example Scenario

Here is an example scenario to perform incremental backup.

  • Once a day, take a full backup
  • Every X minutes/hour, take incremental backup
  • Store backup files in remote host (e.g.: S3, different server, etc)

In my backup script:

  • Use /backup local directory as a workspace for backup
  • Clear /backup if it is a daily full backup
  • List existing files from last backup, and keep the list
    • e.g: ls /backup
  • Perform incremental backup specifying /backup as destination
    • When /backup is empty, incremental backup will essentially a full backup (daily backup)
  • Compare file names in /backup against the list from last backup
    • Backup files are immutable, thus checking only file names is sufficient.
  • Take newly created files to your backup store location (e.g.: upload to S3, etc)

Restore

Send a PATCH RestoreRequest request to /core/management.
NOTE: you MUST restart the service host that processed the restore request.

RestoreRequest:

  • kind: specify com:vmware:xenon:services:common:ServiceHostManagementService:RestoreRequest
  • destination: URI with http/https scheme or file scheme with local file or directory are supported. When http/https is specified, it is expected to accept GET requests from target xenon host with range header, and return a zip file that contains files used by document index service.

Sample:

> curl -X PATCH -H "Content-Type: application/json" -d '
{
  "kind": "com:vmware:xenon:services:common:ServiceHostManagementService:RestoreRequest",
  "destination": "file:/var/backup/xenon-backup.zip"
}
' http://localhost:8000/core/management

Time Snapshot Boundary

When timeSnapshotBoundaryMicros parameter is specified in restore request, recovered data will not have documents updated after the specified time. This will make point in time recovery available from the backup.

Restore and HostID

When documents are restored on new node, they still keep old hostId as their documentOwnerId. This, in general, doesn't cause any issues, however, it will have a problem for migration.
Detail is documented here.

To prevent skipping documents due to owner mismatch at migration, we recommend setting same hostId on the new node. (e.g: --id=<old node id> for host startup argument)

In-memory document index

InMemoryLuceneDocumentIndexService is an opt-in service to store document index in memory.
LuceneDocumentIndexBackupService works for both file-based and in-memory based document index services.

To perform backup/restore to in-memory document index service, backup service needs to be initialized with in-memory index service, and register it to the host. (In example below, it uses ServiceUriPaths.CORE_IN_MEMORY_DOCUMENT_INDEX_BACKUP for convenience, but not limited to)

Starting in-memory related services

host.addPrivilegedService(InMemoryLuceneDocumentIndexService.class);

InMemoryLuceneDocumentIndexService inMemoryIndexService = new InMemoryLuceneDocumentIndexService();
LuceneDocumentIndexBackupService inMemoryIndexBackupService = new LuceneDocumentIndexBackupService(inMemoryIndexService);

host.startService(Operation.createPost(host, ServiceUriPaths.CORE_IN_MEMORY_DOCUMENT_INDEX), inMemoryIndexService);
host.startService(Operation.createPost(host, ServiceUriPaths.CORE_IN_MEMORY_DOCUMENT_INDEX_BACKUP), inMemoryIndexBackupService);

Backup

When requesting a backup, specify backupServiceLink in request.

> curl -X PATCH -H "Content-Type: application/json" -d '
{
  "kind": "com:vmware:xenon:services:common:ServiceHostManagementService:BackupRequest",
  "destination": "file:/var/backup/xenon-backup.zip",
  "backupType": "ZIP",
  "backupServiceLink": "/core/in-memory-document-index-backup"
}
' http://localhost:8000/core/management

Restore

To restore, specify backupServiceLink in request.

> curl -X PATCH -H "Content-Type: application/json" -d '
{
  "kind": "com:vmware:xenon:services:common:ServiceHostManagementService:RestoreRequest",
  "destination": "file:/var/backup/xenon-backup.zip",
  "backupServiceLink": "/core/in-memory-document-index-backup"
}
' http://localhost:8000/core/management

When it is restoring to the in-memory index service, host restart is not required.
If you restart the host, in-memory data will be cleared.

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