Class: Sequent::Core::AggregateRepository

Inherits:
Object
  • Object
show all
Defined in:
lib/sequent/core/aggregate_repository.rb

Overview

Repository for aggregates.

Implements the Unit-Of-Work and Identity-Map patterns to ensure each aggregate is only loaded once per transaction and that you always get the same aggregate instance back.

On commit all aggregates associated with the Unit-Of-Work are queried for uncommitted events. After persisting these events the uncommitted events are cleared from the aggregate.

The repository keeps track of the Unit-Of-Work per thread, so can be shared between threads.

Defined Under Namespace

Classes: AggregateNotFound, HasUncommittedEvents, NonUniqueAggregateId

Constant Summary collapse

AGGREGATES_KEY =

Key used in thread local

'Sequent::Core::AggregateRepository::aggregates'.to_sym

Instance Method Summary collapse

Instance Method Details

#add_aggregate(aggregate) ⇒ Object

Adds the given aggregate to the repository (or unit of work).

Only when commit is called all aggregates in the unit of work are ‘processed’ and all uncammited_events are stored in the event_store



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# File 'lib/sequent/core/aggregate_repository.rb', line 40

def add_aggregate(aggregate)
  existing = aggregates[aggregate.id]
  if existing && !existing.equal?(aggregate)
    fail NonUniqueAggregateId.new(aggregate, aggregates[aggregate.id])
  else
    aggregates[aggregate.id] = aggregate
  end
end

#clear ⇒ Object

Clears the Unit of Work.



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# File 'lib/sequent/core/aggregate_repository.rb', line 133

def clear
  Thread.current[AGGREGATES_KEY] = nil
end

#clear! ⇒ Object

Clears the Unit of Work.

A HasUncommittedEvents is raised when there are uncommitted_events in the Unit of Work.



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# File 'lib/sequent/core/aggregate_repository.rb', line 140

def clear!
  fail HasUncommittedEvents if aggregates.values.any? { |x| !x.uncommitted_events.empty? }

  clear
end

#commit(command) ⇒ Object

Gets all uncommitted_events from the ‘registered’ aggregates and stores them in the event store.

The events given to the EventStore are ordered in loading order of the different AggregateRoot’s. So Events are stored (and therefore published) in order in which they are ‘apply`-ed per AggregateRoot.

The command is ‘attached’ for traceability purpose so we can see which command resulted in which events.

This is all abstracted away if you use the Sequent::Core::CommandService



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# File 'lib/sequent/core/aggregate_repository.rb', line 121

def commit(command)
  updated_aggregates = aggregates.values.reject { |x| x.uncommitted_events.empty? }
  return if updated_aggregates.empty?

  streams_with_events = updated_aggregates.map do |aggregate|
    [aggregate.event_stream, aggregate.uncommitted_events]
  end
  updated_aggregates.each(&:clear_events)
  store_events command, streams_with_events
end

#contains_aggregate?(aggregate_id) ⇒ Boolean

Returns whether the event store has an aggregate with the given id

Returns:



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# File 'lib/sequent/core/aggregate_repository.rb', line 104

def contains_aggregate?(aggregate_id)
  Sequent.configuration.event_store.stream_exists?(aggregate_id) &&
    Sequent.configuration.event_store.events_exists?(aggregate_id)
end

#ensure_exists(aggregate_id, clazz) ⇒ Object

Throws exception if not exists.



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# File 'lib/sequent/core/aggregate_repository.rb', line 50

def ensure_exists(aggregate_id, clazz)
  !load_aggregate(aggregate_id, clazz).nil?
end

#load_aggregate(aggregate_id, clazz = nil) ⇒ Object

Loads aggregate by given id and class Returns the one in the current Unit Of Work otherwise loads it from history.



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# File 'lib/sequent/core/aggregate_repository.rb', line 56

def load_aggregate(aggregate_id, clazz = nil)
  load_aggregates([aggregate_id], clazz)[0]
end

#load_aggregates(aggregate_ids, clazz = nil) ⇒ Object

Loads multiple aggregates at once. Returns the ones in the current Unit Of Work otherwise loads it from history.

Note: This will load all the aggregates in memory, so querying 100s of aggregates with 100s of events could cause memory issues.

Returns all aggregates or raises AggregateNotFound If clazz is given and one of the aggregates is not of the correct type a TypeError is raised.

aggregate_ids The ids of the aggregates to be loaded clazz Optional argument that checks if all aggregates are of type clazz



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# File 'lib/sequent/core/aggregate_repository.rb', line 73

def load_aggregates(aggregate_ids, clazz = nil)
  fail ArgumentError, 'aggregate_ids is required' unless aggregate_ids
  return [] if aggregate_ids.empty?

  unique_ids = aggregate_ids.uniq
  result = aggregates.values_at(*unique_ids).compact
  query_ids = unique_ids - result.map(&:id)

  result += Sequent.configuration.event_store.load_events_for_aggregates(query_ids).map do |stream, events|
    aggregate_class = Class.const_get(stream.aggregate_type)
    aggregate_class.load_from_history(stream, events)
  end

  if result.count != unique_ids.count
    missing_aggregate_ids = unique_ids - result.map(&:id)
    fail AggregateNotFound, missing_aggregate_ids
  end

  if clazz
    result.each do |aggregate|
      fail TypeError, "#{aggregate.class} is not a #{clazz}" unless aggregate.class <= clazz
    end
  end

  result.map do |aggregate|
    aggregates[aggregate.id] = aggregate
  end
end