Class: RubyEventStore::ROM::UnitOfWork

Inherits:
Object
  • Object
show all
Defined in:
lib/ruby_event_store/rom/unit_of_work.rb

Instance Method Summary collapse

Constructor Details

#initialize(gateway) ⇒ UnitOfWork

Returns a new instance of UnitOfWork.



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# File 'lib/ruby_event_store/rom/unit_of_work.rb', line 6

def initialize(gateway)
  @gateway = gateway
end

Instance Method Details

#call {|changesets = []| ... } ⇒ Object

Yields:

  • (changesets = []) 


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# File 'lib/ruby_event_store/rom/unit_of_work.rb', line 10

def call
  yield(changesets = [])
  @gateway.transaction(
    savepoint: true,
    # See: https://github.com/jeremyevans/sequel/blob/master/doc/transactions.rdoc
    #
    # Committing changesets concurrently causes MySQL deadlocks
    # which are not caught and retried by Sequel's built-in
    # :retry_on option. This appears to be a result of how ROM
    # handles exceptions which don't bubble up so that Sequel
    # can retry transactions with the :retry_on option when there's
    # a deadlock.
    #
    # This is exacerbated by the fact that changesets insert multiple
    # tuples with individual INSERT statements because ROM specifies
    # to Sequel to return a list of primary keys created. The likelihood
    # of a deadlock is reduced with batched INSERT statements.
    #
    # For this reason we need to manually insert changeset records to avoid
    # MySQL deadlocks or to allow Sequel to retry transactions
    # when the :retry_on option is specified.
    retry_on: Sequel::SerializationFailure,
    before_retry:
      lambda do |_num, ex|
        env.logger.warn("RETRY TRANSACTION [#{self.class.name} => #{ex.class.name}] #{ex.message}")
      end
  ) { changesets.each(&:commit) }
end