Class: Sequent::Core::EventStore

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Includes:
ActiveRecord::ConnectionAdapters::Quoting
Defined in:
lib/sequent/core/event_store.rb

Defined Under Namespace

Classes: DeserializeEventError, NoEventTypesCache, OptimisticLockingError

Constant Summary collapse 

->(progress, done, _) do
  if done
    Sequent.logger.debug "Done replaying #{progress} events"
  else
    Sequent.logger.debug "Replayed #{progress} events"
  end
end

Instance Method Summary collapse

Constructor Details

#initialize(cache_event_types: true) ⇒ EventStore

Returns a new instance of EventStore.



38
39
40
41
42
43
44
 
# File 'lib/sequent/core/event_store.rb', line 38

def initialize(cache_event_types: true)
  @event_types = if cache_event_types
                   ThreadSafe::Cache.new
                 else
                   NoEventTypesCache.new
                 end
end

Instance Method Details

#aggregate_query(aggregate_id) ⇒ Object 



126
127
128
129
130
131
132
133
134
135
136
137
138
139
 
# File 'lib/sequent/core/event_store.rb', line 126

def aggregate_query(aggregate_id)
  <<~SQL.chomp
    (
    SELECT event_type, event_json
      FROM #{quote_table_name Sequent.configuration.event_record_class.table_name} AS o
    WHERE aggregate_id = #{quote(aggregate_id)}
    AND sequence_number >= COALESCE((SELECT MAX(sequence_number)
                                     FROM #{quote_table_name Sequent.configuration.event_record_class.table_name} AS i
                                     WHERE event_type = #{quote Sequent.configuration.snapshot_event_class.name}
                                       AND i.aggregate_id = #{quote(aggregate_id)}), 0)
    ORDER BY sequence_number ASC, (CASE event_type WHEN #{quote Sequent.configuration.snapshot_event_class.name} THEN 0 ELSE 1 END) ASC
    )
  SQL
end

#aggregates_that_need_snapshots(last_aggregate_id, limit = 10) ⇒ Object

Returns the ids of aggregates that need a new snapshot.



195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
 
# File 'lib/sequent/core/event_store.rb', line 195

def aggregates_that_need_snapshots(last_aggregate_id, limit = 10)
  stream_table = quote_table_name Sequent.configuration.stream_record_class.table_name
  event_table = quote_table_name Sequent.configuration.event_record_class.table_name
  query = <<~SQL.chomp
    SELECT aggregate_id
      FROM #{stream_table} stream
     WHERE aggregate_id::varchar > COALESCE(#{quote last_aggregate_id}, '')
       AND snapshot_threshold IS NOT NULL
       AND snapshot_threshold <= (
             (SELECT MAX(events.sequence_number) FROM #{event_table} events WHERE events.event_type <> #{quote Sequent.configuration.snapshot_event_class.name} AND stream.aggregate_id = events.aggregate_id) -
             COALESCE((SELECT MAX(snapshots.sequence_number) FROM #{event_table} snapshots WHERE snapshots.event_type = #{quote Sequent.configuration.snapshot_event_class.name} AND stream.aggregate_id = snapshots.aggregate_id), 0))
     ORDER BY aggregate_id
     LIMIT #{quote limit}
     FOR UPDATE
  SQL
  Sequent.configuration.event_record_class.connection.select_all(query).map { |x| x['aggregate_id'] }
end

#commit_events(command, streams_with_events) ⇒ Object

Stores the events in the EventStore and publishes the events to the registered event_handlers.

The events are published according to the order in the tail of the given streams_with_events array pair.

Parameters:

  • command —

    The command that caused the Events

  • streams_with_events —

    is an enumerable of pairs from StreamRecord to arrays ordered uncommitted ‘Event`s.



57
58
59
60
61
62
63
64
 
# File 'lib/sequent/core/event_store.rb', line 57

def commit_events(command, streams_with_events)
  fail ArgumentError, 'command is required' if command.nil?

  Sequent.logger.debug("[EventStore] Committing events for command #{command.class}")

  store_events(command, streams_with_events)
  publish_events(streams_with_events.flat_map { |_, events| events })
end

#events_exists?(aggregate_id) ⇒ Boolean

Returns:



145
146
147
 
# File 'lib/sequent/core/event_store.rb', line 145

def events_exists?(aggregate_id)
  Sequent.configuration.event_record_class.exists?(aggregate_id: aggregate_id)
end

#find_event_stream(aggregate_id) ⇒ Object 



213
214
215
216
 
# File 'lib/sequent/core/event_store.rb', line 213

def find_event_stream(aggregate_id)
  record = Sequent.configuration.stream_record_class.where(aggregate_id: aggregate_id).first
  record&.event_stream
end

#load_events(aggregate_id) ⇒ Object

Returns all events for the aggregate ordered by sequence_number, loading them from the latest snapshot event onwards, if a snapshot is present



100
101
102
 
# File 'lib/sequent/core/event_store.rb', line 100

def load_events(aggregate_id)
  load_events_for_aggregates([aggregate_id])[0]
end

#load_events_for_aggregates(aggregate_ids) ⇒ Object 



104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
 
# File 'lib/sequent/core/event_store.rb', line 104

def load_events_for_aggregates(aggregate_ids)
  return [] if aggregate_ids.none?

  streams = Sequent.configuration.stream_record_class.where(aggregate_id: aggregate_ids)

  query = aggregate_ids.uniq.map { |aggregate_id| aggregate_query(aggregate_id) }.join(' UNION ALL ')
  events = Sequent.configuration.event_record_class.connection.select_all(query).map do |event_hash|
    deserialize_event(event_hash)
  end

  events
    .group_by(&:aggregate_id)
    .map do |aggregate_id, es|
    [
      streams.find do |stream_record|
        stream_record.aggregate_id == aggregate_id
      end.event_stream,
      es,
    ]
  end
end

#replay_events ⇒ Object

Replays all events in the event store to the registered event_handlers.

DEPRECATED: use replay_events_from_cursor instead.

Parameters:

  • block —

    that returns the events.



153
154
155
156
157
 
# File 'lib/sequent/core/event_store.rb', line 153

def replay_events
  warn '[DEPRECATION] `replay_events` is deprecated in favor of `replay_events_from_cursor`'
  events = yield.map { |event_hash| deserialize_event(event_hash) }
  publish_events(events)
end

#replay_events_from_cursor(get_events:, block_size: 2000, on_progress: PRINT_PROGRESS) ⇒ Object

Replays all events on an EventRecord cursor from the given block.

Prefer this replay method if your db adapter supports cursors.

Parameters:

  • get_events —

    lambda that returns the events cursor

  • on_progress (defaults to: PRINT_PROGRESS) —

    lambda that gets called on substantial progress



166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
 
# File 'lib/sequent/core/event_store.rb', line 166

def replay_events_from_cursor(get_events:, block_size: 2000,
                              on_progress: PRINT_PROGRESS)
  progress = 0
  cursor = get_events.call
  ids_replayed = []
  cursor.each_row(block_size: block_size).each do |record|
    event = deserialize_event(record)
    publish_events([event])
    progress += 1
    ids_replayed << record['id']
    if progress % block_size == 0
      on_progress[progress, false, ids_replayed]
      ids_replayed.clear
    end
  end
  on_progress[progress, true, ids_replayed]
end

#stream_events_for_aggregate(aggregate_id, load_until: nil, &block) ⇒ Object

Returns all events for the AggregateRoot ordered by sequence_number, disregarding snapshot events.

This streaming is done in batches to prevent loading many events in memory all at once. A usecase for ignoring the snapshots is when events of a nested AggregateRoot need to be loaded up until a certain moment in time.

Parameters:

  • aggregate_id —

    Aggregate id of the AggregateRoot

  • load_until (defaults to: nil) —

    The timestamp up until which you want to built the aggregate. Optional.

  • &block —

    Block that should be passed to handle the batches returned from this method



75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
 
# File 'lib/sequent/core/event_store.rb', line 75

def stream_events_for_aggregate(aggregate_id, load_until: nil, &block)
  stream = find_event_stream(aggregate_id)
  fail ArgumentError, 'no stream found for this aggregate' if stream.blank?

  q = Sequent
    .configuration
    .event_record_class
    .where(aggregate_id: aggregate_id)
    .where.not(event_type: Sequent.configuration.snapshot_event_class.name)
    .order(:sequence_number)
  q = q.where('created_at < ?', load_until) if load_until.present?
  has_events = false

  q.select('event_type, event_json').each_row do |event_hash|
    has_events = true
    event = deserialize_event(event_hash)
    block.call([stream, event])
  end
  fail ArgumentError, 'no events for this aggregate' unless has_events
end

#stream_exists?(aggregate_id) ⇒ Boolean

Returns:



141
142
143
 
# File 'lib/sequent/core/event_store.rb', line 141

def stream_exists?(aggregate_id)
  Sequent.configuration.stream_record_class.exists?(aggregate_id: aggregate_id)
end