Purpose of this plugin

The purpose of this plugin is to provide local snapshot functionality, so in case of issues the blockchain can be rebuild locally from own exported data. The plugin provides a cli interface, with the following available commands:

• create (with option to append, or to select --start and --end block height to export)
• import
• verify
• rollback (and backup forged transactions during the process)
• truncate

The commands and their usage is described below.

Installation

yarn add @phantomchain/core-snapshots-cli

Usage

The plugin allows for manipulation, creation and import functionality of various snapshots via the CLI interface

Creating a fresh new snapshot

The following action creates a new snapshot in ./phantom/snapshots/devnet/ folder.

yarn create:devnet

The command will generate snapshot files in your configured folder. By default this folder will be in ~./phantom/snapshots/NETWORK_NAME. Files names are following this pattern: table.codec. For example, command yarn create:devnet will create the following files in the folder: ~./phantom/snapshots/NETWORK_NAME/0-331985/

• blocks.lite
• transactions.lite

The folder 0-331985 indicates that the snapshot includes data between block 0 and block 331985.

A snapshot can also be created by specifying --start and --end options where we can specify start and end block height we want to export.

Selecting codec for export

Snapshot creation supports three different codecs, to work with. Each of them is a balance between speed and size of the local snapshot. Currently we have:

• lite codec: uses basic serialization with minimall storage informations. It is the default choice between size and speed
• phantom codec: uses Phantom's block and transactions serialization/deserialization mechanism to store and import data. It is a bit slower than lite codec, but uses less data.
• msgpack coded: uses msgpack's library default compression, giving us maximum speed, but also maximum disk size usage.

  yarn create:devnet --codec lite

Snapshots created with a selected codec have their corresponding file extensions (lite, phantom and msgpack), when naming files. For example a snapshot file created with lite codec would look like this: blocks.lite.

Append data to an existing snapshot

To enable rolling snapshost and their faster import execution, it is possible to append data to an the existing snapshot. The command is the same as for creating of snapshot with additional parameter for -b or --blocks where we specify the existing snapshot blocks/folder we want to append to. As a --blocks parameter you only provide the 0-331985 blocks number or folder name, for example yarn create:devnet --blocks 0-331985.

When append is completed a new folder is created, while preserving the old snapshost. You must manually delete snapshost folders if needed.

Importing a snapshot

The following action imports a snapshot from .phantom/snapshots/devnet/ folder. Snapshot filename must be specified. You specify only first filename - from the blocks.

Make sure that your node is not running.

yarn import:devnet -b 0-331985

If you want to import from block 1, e.g. empty database first, you should run the yarn truncate:NETWORK_NAME command or add --truncate parameter to the import command.

yarn truncate:devnet

Using the --truncate parameter

yarn import:devnet -b 0-331985 --truncate

Verifiying records during import --signature-verify

If you want to do additional crpto.verify check for each block and transaction a flag --signature-verify can be added to the import command

yarn import:devnet --blocks 0-331985 --truncate --signature-verify

Please not that this will increase the import time drastically.

By default behaviour when snapshot is imported, the block heigth is set to last finished round (blocks are deleted at the end). If you have more snaphshot files following each other, then you can disable this with the --skip-revert-round flag. If this flag is present, block height will not be reverted at the end of import to last completed round.

Verify existing snapshot

If is wise to validate a snapshot. Functionality is simillar to import, just that there is no database interaction - so basic chain validation with crypto. To check your snapshot run the following command.

yarn verify:devnet --blocks 0-331985

You can also just verify the chaining process and skip signature verification with --skip-sign-verify option.

yarn verify:devnet --blocks 0-331985 --skip-sign-verify

Also note that a database verification is performed when the core starts.

Rolling back chain

The command enables you to rollback you local blockhain database. By specifying the end height you can rollback chain to a history state.

yarn rollback:devnet -b 350000

Above command will rollback the chain to block height of 350000.

If the -b or --block-height argument is not set, the command will rollback the chain to the last completed round.

Rollback command also makes a backup of forged transactions. Transactions are stored next to the snapshot files (in ./phantom/snapshots/NETWORK_NAME). File is named rollbackTransactionBackup.startBlockHeight.endBlockHeight.json, for example: rollbackTransactionBackup.53001.54978.json containes transactions from block 53001 to block 54978.

Security

If you discover a security vulnerability within this package, please send an e-mail to [email protected]. All security vulnerabilities will be promptly addressed.

Credits

• Kristjan Košič
• All Contributors

License

MIT © ArkEcosystem