Chronicle.Events.EventContext (cratis_chronicle v3.16.1)

The context of an event handed to reactors and reducers.

It carries the same information as the .NET client's EventContext, so a handler can see who caused an event, how it is correlated and where it sits in the event sequence.

A struct is a map: handlers can keep pattern matching on keys (def handle(event, %{event_source_id: id})) or use context.caused_by.

:event_type — %{id: String.t(), generation: non_neg_integer()}
:event_source_type, :event_source_id, :event_source (the registered event source name, or nil), :event_stream_type, :event_stream_id
:sequence_number, :occurred
:event_store, :namespace, :event_sequence_id (when known)
:correlation_id — string
:caused_by — Chronicle.Identity (including on_behalf_of), or nil
:causation — list of Chronicle.Auditing.CausationEntry
:tags — list of tag strings; :named_tags — map of name to value
:hash, :subject
:appended_generation — the generation that was actually appended, regardless of which generation the handler is written against. 0 means unknown: an older kernel that doesn't send this field, or an event appended outside a registered event source.
:observation_state — the observation state; :replaying? is true while the observer is replaying
:delivery_id — reactors only; see delivery_id/1

Summary

Functions

delivery_id(context, reactor_id)

The stable identity of one delivery of an event to a reactor.

from_wire(ctx, opts \\ [])

Builds an event context from the wire EventContext of a reactor or reducer observation.

Types

t()

@type t() :: %Chronicle.Events.EventContext{
  appended_generation: term(),
  causation: term(),
  caused_by: term(),
  correlation_id: term(),
  delivery_id: term(),
  event_sequence_id: term(),
  event_source: term(),
  event_source_id: term(),
  event_source_type: term(),
  event_store: term(),
  event_stream_id: term(),
  event_stream_type: term(),
  event_type: term(),
  hash: term(),
  named_tags: term(),
  namespace: term(),
  observation_state: term(),
  occurred: term(),
  replaying?: term(),
  sequence_number: term(),
  subject: term(),
  tags: term()
}

Functions

delivery_id(context, reactor_id)

@spec delivery_id(t(), String.t()) :: String.t()

The stable identity of one delivery of an event to a reactor.

Derived exactly like the .NET ReactorDelivery.Id: the reactor id, event store, namespace, event sequence id, event source id and sequence number joined with #. Use it as the key of whatever records that a side effect completed.

from_wire(ctx, opts \\ [])

@spec from_wire(map(), keyword()) :: t()

Builds an event context from the wire EventContext of a reactor or reducer observation.

Options: :event_sequence_id and :reactor_id (when given, a :delivery_id is derived).