Database Snapshotting

Paima will periodically generate local snapshots of the database. This is useful for two main cases:

1. Restoring the database in case a bug causes it to get into a bad state
2. Bootstrapping new deployments of a game quickly

Snapshots Storage & Scheduling

Paima Engine Runtime will automatically create/use a snapshots folder. On startup, the runtime will check the snapshots folder and note the block height when the last snapshot was taken (by reading the file names, which are following the paima-snapshot-X standard, where X is the block height that the snapshot was taken at). If no snapshot exists, then a snapshot is created at that point.

Snapshots are made based on the latest block height stored in the game's state machine. Notably, snapshots are made every 21600 blocks AFTER the state machine has been updated for that block number.

Creating The Snapshot

We will be using pg_dump to create the snapshots because "it makes consistent backups even if the database is being used concurrently."

You can find a pretty straightforward set of instructions for initiating the snapshots by following this guide all the way up until "compressing the archive" (we will want to do compression).

Snapshot Deletion

Only 2 snapshots should be kept, thus when a new snapshot is created the runtime should check how many snapshots exist in the folder. If there are 3, then the oldest snapshot must be deleted.