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State Snapshot

As the size of the blockchain itself and the number of transactions and other data on the chain increases, the time required to sync the full chain increases. At epoch 266 it was about 18 hours. The other issue is that most major upgrades also update the database schema meaning the database needs to be synced from scatch.

To overcome these issues, we are providing a cardano-db-sync state snapshot, which should drastically reduce the time required to get db-sync back up and running after the database is dropped and recreated. This snapshot is compatible with both cardano-db-sync and cardano-db-sync with --no-epoch-table (which doesn't maintain the extra epoch table).

Note: It is not possible to create a snapshot from one version of the database schema and restore it so it can be used with a db-sync that uses another version of the schema.

All of the following assumes that the executable cardano-db-tool and the script postgresql-setup.sh is available on the machine where the snapshot is being created or restored.

Currently (at epoch 269), creating a snapshot takes about 15 minutes and restoring one takes about 45 minutes.

Things to note:

  • Snapshots (because they depend on the database schema) are not portable across db-sync versions.
  • Snapshots (because they include a snapshot of the ledger state) are not portable across CPU architectures (ie it is not possible to create a snapshot on x86_64 and expect it to work correctly on say arm64).
  • Creating and restoring snapshots requires significant amounts of free disk space (at epoch 269 it required about 10G). If there is insufficient disk space, gzip can give some odd error messages.
  • node tip should be ahead of the snapshot point during restoration otherwise cardano-db-sync will roll back to genesis

Creating a Snapshot

To create a snapshot, the cardano-db-sync executable should be stopped. Taking a snapshot is then a two step process:

PGPASSFILE=config/pgpass-mainnet cardano-db-tool prepare-snapshot --state-dir ledger-state/mainnet/

which will then print out the command (combining the database schema version with the block number in the database with the slot number used by the ledger state and the ) required to generated the snapshot:

PGPASSFILE=config/pgpass-mainnet scripts/postgresql-setup.sh --create-snapshot \
    db-sync-snapshot-schema-9-block-5796064-x86_64 ledger-state/mainnet/31021676-f3873e4bec.lstate

Restoring from a Snapshot

Restoring the state from a snapsot will drop the current database, recreate the tables and then populate them. It can be done as simply as:

PGPASSFILE=config/pgpass-mainnet scripts/postgresql-setup.sh --restore-snapshot \
	db-sync-snapshot-schema-9-block-5796064-x86_64 ledger-state/mainnet

Once the script has completed successfully, db-sync can be restarted and it should continue syncing from the block number listed in the state snapshot file name.

Mainnet Snapshots Location

Mainnet snapshots can be found here. They are also linked from the cardano-db-sync releases page