Hot Backup

Percona Server for MongoDB includes an integrated open-source hot backup system for the default WiredTiger storage engine. It creates a physical data backup on a running server without notable performance and operating degradation.

Making a backup

To take a hot backup of the database in your current dbpath, do the following:

  • Make sure to provide access to the backup directory for the mongod user

    chown mongod:mongod <backupDir>
    
  • Run the createBackup command as administrator on the admin database and specify the backup directory.

    > use admin
    switched to db admin
    > db.runCommand({createBackup: 1, backupDir: <backup_data_path})
    { "ok" : 1 }
    

If the backup was successful, you should receive an { "ok" : 1 } object. If there was an error, you will receive a failing ok status with the error message, for example:

> db.runCommand({createBackup: 1, backupDir: ""})
{ "ok" : 0, "errmsg" : "Destination path must be absolute" }

Saving a backup to a TAR archive

Implementation details

This feature was implemented in Percona Server for MongoDB 4.2.1-1.

To save a backup in the format of tar archive, use the archive field to specify the destination path:

> use admin
...
> db.runCommand({createBackup: 1, archive: <path_to_archive>.tar })

Streaming hot backups to a remote destination

Percona Server for MongoDB enables uploading hot backups to an Amazon S3 or a compatible storage service, such as MinIO.

This method requires that you provide the bucket field in the s3 object:

> use admin
...
> db.runCommand({createBackup: 1, s3: {bucket: "backup20190510", path: <some_optional_path>} })

In addition to the mandatory bucket field, the s3 object may contain the following fields:

Field Type Description
bucket string The only mandatory field. Names are subject to restrictions described in the Bucket Restrictions and Limitations section of Amazon S3 documentation
path string The virtual path inside the specified bucket where the backup will be created. If the path is not specified then the backup is created in the root of the bucket. If there are any objects under the specified path, the backup will not be created and an error will be reported.
endpoint string The endpoint address and port - mainly for AWS S3 compatible servers such as the MinIO server. For a local MinIO server, this can be “127.0.0.1:9000”. For AWS S3 this field can be omitted.
scheme string “HTTP” or “HTTPS” (default). For a local MinIO server started with the minio server command this should field should contain HTTP.
useVirtualAddressing bool The style of addressing buckets in the URL. By default ‘true’. For MinIO servers, set this field to false. For more information, see Virtual Hosting of Buckets in the Amazon S3 documentation.
region string The name of an AWS region. The default region is US_EAST_1. For more information see AWS Service Endpoints in the Amazon S3 documentation.
profile string The name of a credentials profile in the credentials configuration file. If not specified, the profile named default is used.
accessKeyId string The access key id
secretAccessKey string The secret access key

Credentials

If the user provides the access key id and the secret access key parameters, these are used as credentials.

If the access key id parameter is not specified then the credentials are loaded from the credentials configuration file. By default, it is ~/.aws/credentials.

An example of the credentials file

[default]
aws_access_key_id = ABC123XYZ456QQQAAAFFF
aws_secret_access_key = zuf+secretkey0secretkey1secretkey2
[localminio]
aws_access_key_id = ABCABCABCABC55566678
aws_secret_access_key = secretaccesskey1secretaccesskey2secretaccesskey3

Examples

Backup in root of bucket on local instance of MinIO server

> db.runCommand({createBackup: 1,  s3: {bucket: "backup20190901500",
scheme: "HTTP",
endpoint: "127.0.0.1:9000",
useVirtualAddressing: false,
profile: "localminio"}})

Backup on MinIO testing server with the default credentials profile

The following command creates a backup under the virtual path “year2019/day42” in the backup bucket:

> db.runCommand({createBackup: 1,  s3: {bucket: "backup",
path: "year2019/day42",
endpoint: "sandbox.min.io:9000",
useVirtualAddressing: false}})

Backup on AWS S3 service using default settings

> db.runCommand({createBackup: 1,  s3: {bucket: "backup", path: "year2019/day42"}})

See also

AWS Documentation: Providing AWS Credentials
https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html

Restoring data from backup

Restoring from backup on a standalone server

To restore your database on a standalone server, stop the mongod service, clean out the data directory and copy files from the backup directory to the data directory. The mongod user requires access to those files to start the service. Therefore, make the mongod user the owner of the data directory and all files and subdirectories under it, and restart the mongod service.

Run the following commands as root or by using the sudo command

# Stop the mongod service
$ systemctl stop mongod
# Clean out the data directory
$ rm -rf /var/lib/mongodb/*
# Copy backup files
$ cp -RT <backup_data_path> /var/lib/mongodb/
# Grant permissions to data files for the mongod user
$ chown -R mongod:mongod /var/lib/mongodb/
# Start the mongod service
$ systemctl start mongod

Restoring from backup in a replica set

The recommended way to restore the replica set from a backup is to restore it into a standalone node and then initiate it as the first member of a new replica set.

Note

If you try to restore the node into the existing replica set and there is more recent data, the restored node detects that it is out of date with the other replica set members, deletes the data and makes an initial sync.

Run the following commands as root or by using the sudo command

The restore steps are the following:

  1. Stop the mongod service:

    $ systemctl stop mongod
    
  2. Clean the data directory and then copy the files from the backup directory to your data directory. Assuming that the data directory is /var/lib/mongodb/, use the following commands:

    $ rm -rf /var/lib/mongodb/*
    $ cp -RT <backup_data_path> /var/lib/mongodb/
    
  3. Grant permissions to the data files for the mongod user

    $ chown -R mongod:mongod /var/lib/mongodb/
    
  4. Make sure the replication is disabled in the config file and start the mongod service.

    $ systemctl start mongod
    
  5. Connect to your standalone node via the mongo shell and drop the local database

    > mongo
    > use local
    > db.dropDatabase()
    
  6. Restart the node with the replication enabled

    • Shut down the node.

      $ systemctl stop mongod
      
    • Edit the configuration file and specify the replication.replSetname option

    • Start the mongod node:

      $ systemctl start mongod
      
  7. Initiate a new replica set

    # Start the mongo shell
    > mongo
    # Initiate a new replica set
    > rs.initiate()
    

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