docs: add backup concept, guide, and configuration (#98)

docs/docs/concepts/overview.md

@@ -457,7 +457,13 @@ After passing the validation, Replay will clear task instances of the requested
 up and run. Replay will frequently check the status of each task from the scheduler (every 5 minutes) to track if 
 each task is still in progress, failed, or succeeded.
 
-Optimus also provides Replay Dry Run to simulate all the impacted tasks without actually re-running the tasks.
+Optimus also provides Backup to duplicate a resource that can be perfectly used before running Replay. Optimus accepts 
+which datastore and resource that needs to be backed up and users have a choice to also back up the downstream resources 
+within the same project. Where the backup result will be located, and the expiry detail can be configured in the project 
+configuration.
+
+Both Replay and Backup are provided with Dry Run to simulate all the impacted tasks or resources without actually re-running 
+the tasks or backing up the resources.
 
 ## Monitoring & Alerting
 

docs/docs/getting-started/configuration.md

@@ -19,6 +19,8 @@ datastore:
   type: bigquery
   # path where resource spec for BQ are stored
   path: "bq"
+  # backup configurations of a datastore
+  backup: {}
 
 # project variables usable in specifications
 config:

docs/docs/guides/backup.md

@@ -0,0 +1,66 @@
+---
+id: backup
+title: Backup Resources
+---
+
+Backup is a common prerequisite step to be done before re-running or modifying a resource. Currently, Optimus supports 
+backup for BigQuery tables and provides dependency resolution, so backup can be also done to all the downstream tables 
+as long as it is registered in Optimus and within the same project.
+
+## Configuring backup details
+
+Several configurations can be set to have the backup result in your project as your preference. Here are the 
+available configurations for BigQuery datastore.
+
+Configuration key | Description                              | Default        |
+------------------|------------------------------------------|----------------|
+ttl               | Time to live in duration                 | 720h           |
+prefix            | Prefix of the result table name          | backup         |
+dataset           | Where the table result should be located | optimus_backup |
+
+These values can be set in the project [configuration](../getting-started/configuration.md).
+
+
+## Run a backup
+
+To start a backup, run the following command:
+
+```shell
+$ optimus backup resource --project sample-project --namespace sample-namespace
+```
+
+After you run the command, prompts will be shown. You will need to answer the questions.
+
+```
+$ optimus backup resource --project sample-project --namespace sample-namespace
+? Select supported datastore? bigquery
+? Why is this backup needed? backfill due to business logic change
+? Backup downstream? Yes
+```
+
+You will be shown a list of resources that will be backed up, including the downstream resources (if you chose to do so).
+You can confirm to proceed if the list is as expected, and please wait until the backup is finished.
+
+Once the backup is finished, the list of backup results along with where it is located will be shown.
+
+
+## Get list of backups
+
+List of recent backups of a project can be checked using this sub command:
+
+```shell
+$ optimus backup list --project sample-project
+```
+
+Recent backup ID including the resource, when it was created, what is the description or purpose of the backup will be 
+shown. Backup ID is used as a postfix in backup result name, thus you can find those results in the datastore 
+(for example BigQuery) using the backup ID. However, keep in mind that these backup results have expiry time set.
+
+## Run a backup dry run
+
+A dry run is also available to simulate all the resources that can be backed up without actually doing it. Example of dry 
+run usage:
+
+```shell
+$ optimus backup resource --project sample-project --namespace sample-namespace --dry-run
+```

docs/sidebars.js

@@ -37,6 +37,7 @@ module.exports = {
         "guides/organising-specifications",
         "guides/optimus-serve",
         "guides/task-bq2bq",
+        "guides/backup",
         "guides/replay"
       ],
     },