gem install sq-dbsync

require 'sq/dbsync'

include Sq::Dbsync

# Config will typically differ per environment.
config = {
  sources: {
    db_a: {
      database: 'db_a_production',
      user:     'sqdbsync-ro',
      password: 'password',
      host:     'db-a-host',
      brand:    'mysql',
      port:     3306,
    },
    db_b: {
      database: 'db_b_production',
      user:     'sqdbsync-ro',
      password: 'password',
      host:     'db-b-host',
      brand:    'postgresl',
      port:     5432,
    }
  },
  target: {
    database: 'replica',
    user:     'sqdbsync',
    password: 'password',

    # Only localhost supported, since `LOAD DATA INFILE` is used which
    # requires a shared temp directory.
    host:     'localhost',
    brand:    'mysql',
    port:     3306,
  },

  # Optional configuration
  logger: Loggers::Stream.new,     # A graphite logger is provided, see source.
  clock: ->{ Time.now.utc },       # In test env it can be useful to fix this.
  error_handler: ->(e) { puts(e) } # Notify your exception system
}

# Write plans that specify how data is replicated.
DB_A_PLAN = [{
  table_name: :users,
  columns: [
    # You must replicate the primary key.
    :id,

    # You must replicate a timestamp column, and it should be indexed on the
    # target system.
    :updated_at,

    # Then whatever other columns you require.
    :name,
    :account_type,
    :created_at,

  ],
  indexes: {
    # Indexing it on the source system is optional
    index_users_on_updated_at: {:columns=>[:updated_at], :unique=>false},
  },

  # Basic schema transformations are supported.
  db_types: {
    :account_type => [:enum, %w(
      bronze
      silver
      gold
    )]
  }
},{
  table_name: :account_types,
  source_table_name: :user_account_types,
  columns: :all
}]

plans = [
  [StaticTablePlan.new(DB_A_PLAN), :db_a],
  [AllTablesPlan.new, :db_b]
]

manager = Manager.new(config, plans)

# Run a batch load nightly
manager.batch(ALL_TABLES)

# Run an incremental load continuously
manager.increment

# You can load a subset of tables if necessary
manager.batch([:users])

class IncrementalLoadWithDeletes < Sq::Dbsync::IncrementalLoadAction
  def process_deletes
    if plan.table_name == :audit_logs
      ExampleRecordDestroyer.run(db, registry, :audit_logs, :other_table)
    end
  end
end

CONFIG = {
  # ...
  incremental_action: IncrementalLoadWithDeletes,
}