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Backup plugin for Tutor

This is a plugin for Tutor that provides backup and restore functionality for MySQL, MongoDB, and Caddy services in both local and Kubernetes Tutor deployments.

In a local deployment, you can run the backup from the command line. The backups are stored as a single compressed tar file, named backup.YYYY-MM-DD.tar.xz, in $(tutor config printroot)/env/backup/. You can then copy the Tutor config root folder to a new host and restore your Open edX environment with the restore command.

In Kubernetes, the plugin runs the backup job as a CronJob by default. You can also run the backup job from the command line. In both cases the backup tar file, named backup.YYYY-MM-DD.tar.xz, is stored in an S3 bucket. Then, in a new Kubernetes deployment, you can use the restore command to restore your Open edX environment. You can even schedule the restore as a CronJob to periodically download the latest backup and restore your environment. This can, for example, be useful if you want to maintain a standby site for disaster recovery purposes.

Version compatibility matrix

You must install a supported release of this plugin to match the Open edX and Tutor version you are deploying. If you are installing this plugin from a branch in this Git repository, you must select the appropriate one:

Open edX release Tutor version Plugin branch Plugin release
Lilac >=12.0, <13 Not supported Not supported
Maple >=13.2, <141 maple 0.3.x
Nutmeg >=14.0, <15 nutmeg 1.x.x
Olive >=15.0, <16 olive 2.x.x
Palm >=16.0, <17 quince >=2.1.0, <4
Quince >=17.0, <18 quince >=3.1.0, <4
Redwood2 >=18.0, <19 main >=4

Installation

pip install git+https://github.com/hastexo/tutor-contrib-backup@v4.0.0

Usage

To enable this plugin, run:

tutor plugins enable backup

Then, run the following command to add the plugin's configuration parameters to your Tutor environment:

tutor config save

Building the image

In order to build and push the local image, you will need to point your Docker image build process to a local registry.

You can do this in one of two ways:

  1. You already set the Tutor DOCKER_REGISTRY option. In this case, this plugin will push the backup image to your previously configured registry.
  2. You override just the BACKUP_DOCKER_IMAGE configuration value, for example: 
    tutor config save --set BACKUP_DOCKER_IMAGE=localhost:5000/backup:v4.0.0
    Substitute the correct registry prefix if, rather than using a local instance of the Distribution Registry, you are using a container registry provided by GitHub, GitLab, Harbor, etc.

Then, build the Docker image:

tutor images build backup

And finally, push it to your local registry:

tutor images push backup

In a Tutor local deployment:

To run a backup in a local Tutor deployment:

tutor local backup

This creates a tar file containing a dump of the MySQL database, a dump of the MongoDB database, and a copy of the Caddy data directory.

You can find the tar file under $(tutor config printroot)/env/backup/.

To restore MySQL, MongoDB, and Caddy from a previously-made backup tar file:

tutor local restore

This will look for the tar file under $(tutor config printroot)/env/backup/, extracts the tar file, and restore the services from the backup files.

You can also exclude specific data from the restore. For example, if you want to restore only MySQL data, and leave the state of MongoDB and Caddy untouched, run:

tutor local restore --exclude=caddy --exclude=mongodb

In a Tutor k8s deployment:

By default, the backup job runs as a scheduled CronJobs once a day at midnight. You can change the schedule by changing the BACKUP_K8S_CRONJOB_BACKUP_SCHEDULE configuration parameter. To suspend the scheduled backup job, set BACKUP_K8S_CRONJOB_BACKUP_ENABLE to false. Note that you need to restart your Kubernetes deployment with tutor k8s quickstart for this change to take effect.

If you need to run the backup job outside the schedule, use:

tutor k8s backup

The backup job backs up MySQL, MongoDB, and the Caddy data directory, creates a tar file with a date stamp, and uploads it to an S3 storage bucket as set by the BACKUP_S3_* configuration parameters. Note that if you want to run multiple backups in a day, you might want to enable object versioning in your bucket. Otherwise, only the last backup taken on any day survives.

You might also consider applying a lifecyle expiration rule to your storage bucket if you want to retain your backups for a limited time, and discard backups beyond a certain age.

If you are running Kubernetes in a production environment, you might need to store the dump and tar files in a generic ephemeral volume instead of the default local node storage (requires Kubernetes 1.23 or higher). To accomplish this, set BACKUP_K8S_USE_EPHEMERAL_VOLUMES to True. Optionally you can change the volume size using the BACKUP_K8S_EPHEMERAL_VOLUME_SIZE variable, which is 10Gi by default.

To restore from the latest version of the backup made today:

tutor k8s restore

To restore from the latest version of the backup made on a particular date:

tutor k8s restore --date={YYYY-MM-DD}

To restore from a particular version of the backup, you first need its version ID. You can either look this up by interacting with your S3 bucket through your S3 provider's CLI or web UI; or you can use the command below to list the version ID and the corresponding timestamp of the last 20 backups:

tutor k8s restore --list-versions

You can change the number of versions shown by passing an integer to the list-versions argument. For example, --list-versions=10. This will start a Kubernetes Job. So the output will be in the corresponding pod's log.

Use the ID of the desired backup version to restore services:

tutor k8s restore --version={version-id}

If you run multiple backups each day and want to restore from a specific version of a backup on a particular day, use --version in combination with --date.

The restore command will start a job that downloads the specified version of the backup from the S3 storage bucket and restores MySQL, MongoDB, and Caddy from it.

You can also exclude specific data from the restore. For example, if you want to restore MySQL and MongoDB data, but not certificate data for Caddy, run:

tutor k8s restore --exclude=caddy

If you want to restore your environment periodically, set the BACKUP_K8S_CRONJOB_RESTORE_ENABLE configuration parameter to true and provide the desired schedule by setting the BACKUP_K8S_CRONJOB_RESTORE_SCHEDULE (by default it is set to once a day at 30 mins past midnight). This will always download the latest version of the backup from the S3 bucket. Note that you need to restart your Kubernetes deployment with tutor k8s quickstart for these changes to take effect.

You can also tweak the history limits for the CronJobs using the BACKUP_K8S_CRONJOB_HISTORYLIMIT_* configuration parameters.

A note on manual restores

The plugin does not stop services while restoring them. Before doing a manual (that is, not CronJob scheduled) restore, you might consider stopping the Caddy service or taking your site offline by other means. When the restore process is complete, remember to bring the Caddy service (or external load balancer or proxy) back online. This prevents your users from encountering errors during the restore process.

Configuration

General options

  • BACKUP_DOCKER_IMAGE (default: <DOCKER_REGISTRY>backup:v4.0.0, relative to DOCKER_REGISTRY as defined by the global Tutor option)

Kubernetes options

  • BACKUP_K8S_CRONJOB_HISTORYLIMIT_FAILURE (default: 1)
  • BACKUP_K8S_CRONJOB_HISTORYLIMIT_SUCCESS (default: 3)
  • BACKUP_K8S_CRONJOB_STARTING_DEADLINE_SECONDS (default: 900)
  • BACKUP_K8S_CRONJOB_BACKUP_ENABLE (default: true, periodic backup is enabled.)
  • BACKUP_K8S_CRONJOB_BACKUP_SCHEDULE (default: "0 0 * * *", once a day at midnight)
  • BACKUP_K8S_CRONJOB_RESTORE_ENABLE (default: false, periodic restore is disabled.)
  • BACKUP_K8S_CRONJOB_RESTORE_SCHEDULE (default: "30 0 * * *", once a day at 30 mins past midnight)
  • BACKUP_K8S_CRONJOB_CONCURRENCYPOLICY (default: "Forbid", see the Kubernetes documentation for other available options)
  • BACKUP_K8S_USE_EPHEMERAL_VOLUMES (default: false)
  • BACKUP_K8S_EPHEMERAL_VOLUME_SIZE (default: 10Gi)

Make sure the periodic backup job always runs before the restore job during the day.

Options related to S3 storage

The following parameters will be pre-populated if the tutor-contrib-s3 plugin is enabled in your Tutor deployment. If you don't have that plugin enabled, or you prefer to use a different S3 service or setting for your backup storage, change these configuration parameters:

  • BACKUP_S3_HOST (default: None) - set only if using any other service than AWS S3
  • BACKUP_S3_PORT (default: None) - set only if using any other service than AWS S3
  • BACKUP_S3_REGION (default: "")
  • BACKUP_S3_SIGNATURE_VERSION (default: "s3v4")
  • BACKUP_S3_ADDRESSING_STYLE (default: "auto")
  • BACKUP_S3_USE_SSL (default: true)
  • BACKUP_S3_ACCESS_KEY (default: "{{ OPENEDX_AWS_ACCESS_KEY }}")
  • BACKUP_S3_SECRET_ACCESS_KEY (default: "{{ OPENEDX_AWS_SECRET_ACCESS_KEY }}")
  • BACKUP_S3_BUCKET_NAME (default: "backups")

These values can be modified with tutor config save --set PARAM_NAME=VALUE commands.

Depending on the nature and configuration of your S3-compatible service, some of these values may be required to set.

  • If using AWS S3, you will need to set BACKUP_S3_REGION to a non-empty value. And make sure BACKUP_S3_ADDRESSING_STYLE is set to "auto".
  • If you want to use an alternative S3-compatible service, you need to set the BACKUP_S3_HOST and BACKUP_S3_PORT parameters.
  • For a Ceph Object Gateway that doesn’t set rgw_dns_name, you will need BACKUP_S3_ADDRESSING_STYLE: path.
  • When dealing with very large databases, restoring MongoDB may consume more memory than available and the process may break. In this situation, you can set BACKUP_MONGORESTORE_ADDITIONAL_OPTIONS to -j 1 to limit the number of collections that are restored in parallel in order to save memory.

Selecting databases to backup

By default, all MySQL and MongoDB databases will be included in the backup. This is the desired behavior in most cases.

However, in some situations it may be necessary to explicitly choose which databases must be included in the backup. For example, when the same database cluster is used for other purposes and holds logical databases for other services, you might not want to backup all databases. In addition, if you are using a cloud provider database as a service, the cluster may include internal databases that the LMS user might not be allowed to access, thus throwing an error during the backup process.3

In such cases, you can specify the MySQL databases you would like to back up, using the BACKUP_MYSQL_DATABASES option. This option takes a list of strings with the names of the databases, such as:

BACKUP_MYSQL_DATABASES:
  - openedx
  - notes
  - ecommerce
  - discovery

Remember to include all databases used by edx-platform, as well as those created by any plugins installed.

You may or may not choose to include the internal mysql database in this list. If you have made sure that all your database users and privileges are managed by Tutor (as you should), and none have been created manually, then it should be safe to not include mysql in the BACKUP_MYSQL_DATABASES list. However, if you omit BACKUP_MYSQL_DATABASES from your configuration altogether, then the plugin does include the mysql database in the backup.

For MongoDB databases, the corresponding configuration option is:

BACKUP_MONGODB_DATABASES:
  - openedx
  - cs_comments_service

If your MongoDB instance uses an authentication database name other than admin, make sure you provide that with BACKUP_MONGODB_AUTHENTICATION_DATABASE.

Opting out of single-transaction backups and flushing logs

In certain cloud MySQL services, like AWS Aurora, it might be forbidden (even for the root user) to lock the database. In these cases you might get errors like Couldn't execute 'FLUSH TABLES WITH READ LOCK': Access denied for user. This is caused by using the single-transaction option in MySQL dumps, and flushing logs after restoring.

To overcome these issues, you can set BACKUP_MYSQL_SINGLE_TRANSACTION and BACKUP_MYSQL_FLUSH_LOGS to false. Both values are true by default. BACKUP_MYSQL_SINGLE_TRANSACTION controls the use of --single-transaction option in the mysqldump command, while BACKUP_MYSQL_FLUSH_LOGS enables or disables issuing mysqladmin flush-logs after restoring the database.

Please note that doing this will cause the MySQL database to be dumped without locking the tables, which might result in inconsistent backup archives. If you set BACKUP_MYSQL_FLUSH_LOGS to false, we recommend to stop all services before starting the backup process.

Using this plugin with service version upgrades

In general, you should be able to use this plugin even when you are upgrading to a new MySQL, MongoDB, or Caddy version. This is something that commonly happens as a result of a new Open edX/Tutor major release.

However, you need to make sure that after restoring a backup from a prior version, you run tutor local init or tutor k8s init in order to ensure that any required in-place data modifications also rerun.

Changelog

For a detailed breakdown of features and fixes in each release, please see the changelog.

License

This software is licensed under the terms of the AGPLv3.

Footnotes

  1. For Open edX Maple and Tutor 13, you must run version 13.3.0 or later. That is because this plugin uses the Tutor v1 plugin API, which was introduced with that release. ↩

  2. Tutor 18 and Open edX Redwood included a leap in MongoDB releases (from 4.4 to 7.0). As a result of this change, the amount of disk space required by MongoDB during a database restore increased substantially (to about 3 times the size of the database). When upgrading to Tutor 18, you may need to expand your MongoDB container's database storage volume. ↩

  3. There is a known limitation in certain configurations of AWS Aurora in which an attempt to back up the internal mysql database will result in an error: mysqldump: Couldn't execute 'SHOW CREATE PROCEDURE rds_import_binlog_ssl_material': Failed to load routine mysql.rds_import_binlog_ssl_material. The table mysql.proc is missing, corrupt, or contains bad data. ↩