Howto/MrPlowDataMigration

Mr Plow Data Migration

From RocksDB to Atomic File DB.

Overview

Before 2021, MrPlow was suggested to run with ConfigOption/db_type of rocksdb. RocksDB has great performance and is generally fairly reliable, but it does occasionally break in various ways. For a node, that is not a big problem. You can always delete a node DB and then resync.

However, for things that need to be persisted, it isn't good enough. So there is a new DB type of 'atomic_file' which uses one file per record. For things like MrPlow that has a small number of records but the records are very important, that is a better fit.

This guide is for how to switch a mining pool from RocksDB to Atomic File while maintaining the share state.

Steps

Stop Pool

Stop Pool. The RocksDB database must be closed.

Run Data Migration

The data migration tool is in the source. A bazel build :all will create it.

The command is MrPlowDataMigrate and takes two parameters, the path to the existing RocksDB data and the path to the new Atomic File DB. The Atomic File DB path doesn't need to exist, it will be created.

$ bazel-bin/MrPlowDataMigrate /home/nerd/plow.db /home/nerd/plow.file.db
Migrating data from rocksdb: /home/nerd/plow.db
Migrating data to atomic file db: /home/nerd/plow.file.db
Dec 31, 2020 10:10:19 PM snowblossom.lib.db.rocksdb.JRocksDB <init>
INFO: Loading RocksDB with path /home/nerd/plow.db
Dec 31, 2020 10:10:19 PM snowblossom.lib.db.atomicfile.AtomicFileDB <init>
INFO: Loading AtomicFileDB with path /home/nerd/plow.file.db
Dec 31, 2020 10:10:19 PM snowblossom.miner.plow.DataMigrate main
INFO: Have source PPLNS state with 270 entries
Dec 31, 2020 10:10:30 PM snowblossom.miner.plow.DataMigrate main
INFO: Saved found block list: 68049
Dec 31, 2020 10:10:30 PM snowblossom.miner.plow.DataMigrate main
INFO: PPLNS state saved
Dec 31, 2020 10:10:30 PM snowblossom.miner.plow.DataMigrate main
INFO: Migration complete
Dec 31, 2020 10:10:30 PM snowblossom.lib.db.rocksdb.JRocksDB close
INFO: RocksDB flush started
Dec 31, 2020 10:10:30 PM snowblossom.lib.db.rocksdb.JRocksDB close
INFO: RocksDB flush completed

The migration does sanity checks. It will only proceed if the source does have a PPLNS state and the destination does not.

Update Config

Update your plow config. Set:

db_type=atomic_file

and db_path=<new path> to be the new location you created in the migration step.

Restart Pool

You should be good to go.